[Document Name] DESCRIPTION
[Title of the Invention] MICROWAVE PROCESSING APPARATUS
[Technical Field]
The present invention relates to a microwave processing
apparatus that processes an object using a microwave.
[Background Art]
Examples of apparatuses that process objects using
microwaves include microwave ovens. In the microwave ovens,
microwaves generated from microwave generators are radiated to
heating chambers made of netals. This causes objects arranged
inside the heating chambers to be heated using the microwaves.
Conventionally, magnetrons have been used as the microwave
generation devices in the microwave ovens. In this case, the
microwaves generated by the magnetrons are fed into the heating
chambers through waveguides.
Here, when the electromagnetic wave distributions of the
microwaves inside the heading chambers are non-uniform, the
objects cannot be uniformly neated. Therefore, a microwave oven
that feeds a microwave generated by a magnetron into a heating
chamber through first and second waveguides has been proposed
(see Patent Document 1) .
[Patent Document 1] JP 2004-47322 A
[Disclosure of the Invention]
[Problems to be Solved by the Invention]
The waveguides for feeding the microwaves generated by

the magnetrons into the heating chambers are formed of hollow
metal tubes. Consequently, in the microwave oven disclosed in
Patent Document 1, a plurality of metal tubes for forming the
first and second waveguides are required. This causes the
microwave oven to increase in size.
Furthermore, Patent Document 1 discloses that the
microwave generated by the magnetron is radiated from a plurality
of radiation antennas rotatably provided. In this case, the
microwave oven also increases in size in order to get a rotational
space of each of the radiation antennas.
An object of the pre sent invention is to provide a microwave
processing apparatus that gives a microwave to an object in a
desired electromagnetic wave distribution and is sufficiently
miniaturized.
[Means for Solving the Problems]
(1) According to an aspect of the present invention, a
microwave processing apparatus that processes an object using
a microwave includes a microwave generator that generates a
microwave, and at least fizst and second radiators that radiate
to the object the microwave generated by the microwave generator,
in which a phase difference between microwaves respectively
radiated from the first and second radiators changes.
In the microwave processing apparatus, the microwave
generated by the microwave generator is radiated to the object
from the first and second radiators. This causes the microwave

radiated from the first radiator and the microwave radiated from
the second radiator to interface with each other in the vicinity
of the object.
Here, when the phase difference between the microwaves
respectively radiated from the first and second radiators is
changed, a state where the microwaves respectively radiated from
the first and second radiators interfere with each other changes.
This causes an electromagnetic wave distribution around the object
to change. Consequently, it is possible to feed the microwaves
to the object in a desired electromagnetic wave distribution.
As a result, the object can be uniformly processed, or a desired
portion of the object can be concentrically processed.
In this case, the necessity of a mechanism and a space
for moving the object as; well as the first and second radiators
is eliminated, which causes the microwave processing apparatus
to be sufficiently miniaturized and made low in cost.
(2) According to another aspect of the present invention,
a microwave processing apparatus that processes an object using
a microwave includes a microwave generator that generates a
microwave, first and second radiators that respectively radiate
to the object the microwave generated by the microwave generator,
and a first phase variator that changes a phase difference between
microwaves respectively radiated from the first and second
radiators, in which the ::irst and second radiators are arranged
such that the radiated microwaves interfere with each other.

In the microwave processing apparatus, the microwave
generated by the microwave generator is radiated to the object
from the first and second radiators.
The first and second radiators are arranged such that the
microwaves respectively radiated therefrom interfere with each
other. This causes themicrowave radiated from the first radiator
and the microwave radiated from the second radiator to interface
with each other.
The first phase variator changes a phase difference between
the microwaves respectively radiated from the first and second
radiators. Thus, a state where the microwaves respectively
radiated from the first and second radiators interfere with each
other changes. This causes an electromagnetic wave distribution
around the object to change. Consequently, it is possible to
feed the microwaves to the object in a desired electromagnetic
wave distribution. As a result, the object can be uniformly
processed, or a desired portion of the object can be concentrically
processed.
In this case, the necessity of a mechanism and a space
for moving the object as well as the first and second radiators
is eliminated, which causes the microwave processing apparatus
to be sufficiently miniaturized and made low in cost.
(3) The first and second radiators may be opposite each
other.
In this case, the object is arranged between the first

radiator and the second radiator, which allows the microwaves
to be respectively reliably radiated to the object from the first
and second radiators. Further, the first and second radiators
are opposite each other, so that the microwave radiated from the
first radiator and the microwave rcidiated from the second radiator
reliably interfere with each other.
(4) The microwavs processing apparatus may further
include a detector that det.ects respective reflected powers from
the first and second radiators, and a controller that controls
the microwave generator, in which the controller may cause the
first and second radiators :o radiate the microwaves to the ob j ect
while changing the frequency of the microwave generated by the
microwave generator, determine the frequency of the microwave
for processing the object as a processing frequency on the basis
of a frequency at which the reflected power detected by the detector
take a minimum or minimal value, and causes themicrowave generator
to generate the microwave having the determined processing
frequency.
In this case, the microwaves are respectively radiated
to the object from the first and second radiators while changing
the frequency of the microwave generated by the microwave
generator. At this time, the frequency of the microwave for
processing the object is determined as the processing frequency
on the basis of the frequency at which summation of the reflected
powers from the first and second radiators, which are detected

by the detector respectively, take a minimum or minimal value.
The microwave having the determined processing frequency is
generated by the microwave generator.
Since the microwave having the processing frequency
determined on the basis of the frequency at which summation of
the reflected powers from the first and second radiators
respectively take a minimum or minimal value is used for processing
the object, the reflected powers generated when the object is
processed are reduced. This causes the power conversion
efficiency of the microwave processing apparatus to be improved.
Furthermore, even when the microwave generator generates
heat due to the reflected powers, its heat value is reduced. As
a result, the microwave generator is prevented from being damaged
and failing due to the reflected powers.
(5) The controller may cause the first and second
radiators to radiate the microwaves to the object while changing
the frequency of the microwave generated by the microwave
generator before the object is processed, and determine the
frequency of the microwave for processing the object as a
processing frequency on the basis of the frequency at which the
reflected power detected by the detector take a minimum or minimal
value.
In this case, the microwaves are respectively radiated
to the object from the first and second radiators while changing
the frequency of the microwave generated by the microwave

generator before the object is processed. At this time, the
frequency of the microwave for processing the object is determined
as the processing frequency on the basis of the frequency at which
summation of the reflected powers from the first and second
radiators, which are detected by the detector respectively, take
a minimum or minimal value.
Thus, the microwave generator can generate the microwave
having the determined processing frequency when the processing
of the object is started. This allows the reflected powers
generated when the processing of the object is started to be reduced.
As a result, the microwave generator is prevented from being
damaged and failing due to the reflected powers.
(6) The controller may cause the first and second
radiators to radiate the: microwaves to the object while changing
the frequency of the microwave generated by the microwave
generator while the object is processed, and determine the
frequency of the microwave for processing the object as a
processing frequency on the basis of the frequency at which the
reflected power detected by the detector take a minimum or minimal
value.
In this case, the microwaves are respectively radiated
to the object from the first and second radiators while changing
the frequency of the microwave generated by the microwave
generator while the ooject is processed. At this time, the
frequency of the microwatve for processing the object is determined

as the processing frequency on the basis of the frequency at which
the summation of reflected powers from the first and second
radiators, which are detected by the detector respectively, take
a minimum or minimal value.
Even while the object is processed, therefore, the
microwave having the determined processing frequency is used for
processing the object every time a predetermined time period has
elapsed or when the reflected powers exceed a predetermined
threshold value, for example. Thus, the reflected powers that
change with time as the processing of the object progresses are
inhibited from increasing. This causes the power conversion
efficiency of the microwave processing apparatus to be improved.
Furthermore, even when the microwave generator generates
heat due to the reflected powers, its heat value is reduced. As
a result, the microwave generator is prevented from being damaged
and failing due to the reflected powers.
(7) The first radiator may radiate the microwave along
a first direction, and the second radiator may radiate the
microwave along a second direction opposite to the first direction.
The microwave processing apparatus may further include a third
radiator that radiates the microwave generated by the microwave
generator to the object along a third direction crossing the first
direction.
In this case, the microwave is radiated to the object along
the first direction from the first radiator, and the microwave

is radiated to the object in the second direction opposite to
the first direction from the second radiator. Further, the
microwave is radiated to the ob j ect in the third direction crossing
the first direction from the third radiator.
The microwaves can be thus respectively radiated to the
object along the different first, second, and third directions.
Therefore, the object can be efficiently heated irrespective of
the directivity of the microwaves.
(8) The microwave generator may include first and second
microwave generators, the first, and second radiators may radiate
to the object the microwave generated by the first microwave
generator, and the third radiator may radiate to the object the
microwave generated by the second microwave generator.
In this case, the microwaves generated by the common first
microwave generator are respectively radiated to the object from
the first and second radiators. Therefore, the phase difference
between the microwaves respectively radiated from the first and
second radiators can be easily changed by the first phase variator.
Furthermore, the microwave generated from the second
microwave generator is radiated to the object from the third
radiator. Therefore, the frequency of the microwave radiated
from the third radiator can be controlled independently of the
frequencies of themicrowaves respectively radiated from the first
and second radiators . This allows the reflected powers generated
when the object is processed to be sufficiently reduced. As a

result, the power conversion efficiency of the microwave
processing apparatus is sufficiently improved.
(9) The first radiator may radiate the microwave along
a first direction, and the second radiator may radiate the
microwave along a second direction opposite to the first direction.
The microwave processing apparatus may further include a third
radiator that radiates the microwave generated by the microwave
generator to the object along a third direction crossing the first
direction, and a fourth radiator that radiates the microwave
generated by the microwave generator to the object along a fourth
direction opposite to the third direction, in which the third
and fourth radiators may be opposed to each other.
In this case, the microwave is radiated to the object along
the first direction from the first radiator, and the microwave
is radiated to the object in the second direction opposite to
the first direction from the second radiator. Further, the
microwave is radiated to the object along the third direction
crossing the first direction from the third radiator, and the
microwave is radiated to the object along the fourth direction
opposite to the third direction from the fourth radiator.
The object can be thus radiated along the different first,
second, third, and fourth directions. Therefore, the object can
be more efficiently heated irrespective of the directivity of
the microwaves.
(10) The microwave processing apparatus may further

include a second phase viriator that changes a phase difference
between the microwaves respectively radiated from the third and
fourth radiators.
An electromagnetic wave distribution between the third
radiator and the fourth radiator that are opposite each other
can be changed by changing the phase difference between the
microwaves respectively radiated from the third and fourth
radiators. Consequently, it is possible to feed the microwaves
to the object in a desired electromagnetic wave distribution.
As a result, the object can be uniformly processed, or a desired
portion of the object can be concentrically processed.
In this case, the necessity of a mechanism and a space
for moving the object as well as the first, second, third, and
fourth radiators is eliminated, which causes the microwave
processing apparatus to be miniaturized and made lower in cost.
(11) The microwave generator may include first and second
microwave generators, the first and second radiators may radiate
to the object the microwave generated by the first microwave
generator, and the third and fourth radiators may radiate to the
object the microwave generated by the second microwave generator.
In this case, the: microwaves generated by the common first
microwave generator are respectively radiated to the object from
the first and second radiators. Therefore, the first phase
variator can easily cnange the phase difference between the
microwaves respectively radiated from the first and second

radiators.
Furthermore, the microwaves generated by the common second
microwave generator are respectively radiated to the object from
the third and fourth radiators. Therefore, the second phase
variator can easily change the phase difference between the
microwaves respectively radiated from the third and fourth
radiators.
This allows the frequencies of the microwaves respectively
radiated from the first and second radiators and the frequencies
of the microwaves respectively radiated from the third and fourth
radiators to be independently controlled.
This allows the reflected power generated when the object
is processed to be further sufficiently reduced. As a result,
the power conversion efficiency of the microwave processing
apparatus to be further sufficiently improved.
(12) The object may be processed by heating processing.
The microwave processing apparatus may further include a heating
chamber that accommodates the object for heating. In this case,
the object can be suojected. to the heating processing by
accommodating the object within the heating chamber.
[Effects of the Invention]
According to the: present invention, the electromagnetic
wave distribution between the first radiator and the second
radiator that are opposite each other can be changed by changing
the phase difference between the microwaves respectively radiated

from the first and second radiators. Consequently, it is possible
to feed the microwaves to the object in a desired electromagnetic
wave distribution. As a result, the object can be uniformly
processed, or a desired portion of the object can be concentrically
processed.
In this case, the: necessity of a mechanism and a space
for moving the object as well as the first and second radiators
is eliminated, which causes the microwave processing apparatus
to be miniaturized and nade lower in cost.
[Brief Description of the Drawings]
[FIG. 1] FIG. 1 is a block diagram showing the
configuration of a microwave oven according to a first embodiment.
[FIG. 2] FIG. 2 is a schematic side view of a microwave
generation device constituting the microwave oven shown in Fig.
1.
[FIG. 3] FIG. 3 is a diagram schematically showing the
circuit configuration of a part of the microwave generation device
shown in Fig. 2.
[FIG. 4] Fig. 4 is a flow chart showing the procedure
for control by a microcomputer shown in Fig. 1.
[FIG. 5] Fig. 5 is a flow chart showing the procedure
for control by a microcomputer shown in Fig. 1.
[FIG. 6] FIG. i is a diagram for explaining mutual
interference between microwaves respectively radiated from
antennas shown in Fig. 1.

[FIG. 7] FIG. 7 is a diagram for explaining mutual
interference betweenmicrowaves in a case where a phase difference
between microwaves respectively radiated from antennas shown in
Fig. 1 changes.
[FIG. 8] FIG. 8 is a diagram showing the contents of an
experiment for investigating the relationship between a phase
difference between microwaves respectively radiated from
opposite two antennas and an electromagnetic wave distribution
within a case and the results of the experiment.
[FIG. 9] FIG. 9 is a diagram showing the contents of an
experiment for investigating the relationship between a phase
difference between microwaves respectively radiated from
opposite two antennas and an electromagnetic wave distribution
within a case and the rssults of the experiment.
[FIG. 10] FIG. 10 is a diagram showing the contents of
an experiment for investigating the relationship between a phase
difference between microwaves respectively radiated from
opposite two antennas and an electromagnetic wave distribution
within a case and the results of the experiment.
[FIG. 11] FIG. 11 is a diagram for explaining a specific
example of processing for sweeping and extracting the frequency
of a microwave.
[FIG. 12] FIG. 12 is a block diagram showing the
configuration of a microwave oven according to a second
embodiment.

[FIG. 13] FIG. 13 is a block diagram showing the
configuration of the microwave oven according to the second
embodiment.
[FIG. 14] FIG. 14 is a block diagram showing the
configuration of a microwave oven according to a third embodiment.
[FIG. 15] FIG. 15 is a block diagram showing the
configuration of a microwave oven according to a fourth
embodiment.
[Best Mode for Carrying Out the Invention]
The embodiments of the present invention will be described
in detail referring to the drawings. The embodiments below
describe a microwave processing apparatus . Amicrowave oven will
be described as an example of the microwave processing apparatus.
[1] First Embodiment
(1-1) Outline of configuration and operations of
microwave oven
Fig. 1 is a block diagram showing the configuration of
a microwave oven according to a first embodiment. As shown in
Fig. 1, a microwave oven 1 according to the present embodiment
includes a microwave generation device 100 and a case 501. Three
antennas A1, A2, and A3 are provided in the case 501.
In the present embodiment, the two antennas A1 and A2 out
of the three antennas A!., A2, and A3 within the case 501 are opposite
each other in a horizontal direction.
The microwave generation device 100 includes a voltage

supplier 200, a microwave generator 300, a power distributor 350,
three phase variators 351a, 351b, and 351c having the same
configuration, threemicrcwaveamplifiers 400, 410, and420having
the same configuration, three reflected power detection devices
600, 610, and 620 having the same configuration, and a
microcomputer 700. The microwave generation device 100 is
connected to a commercial power supply through a power supply
plug 10.
In the microwave generation device 100, the voltage
supplier 200 converts an AC voltage supplied from the commercial
power supply into a variable voltage and a DC voltage, and feeds
the variable voltage to thiemicrowave generator 300, while feeding
the DC voltage to the microwave amplifiers 400, 410, and 420.
The microwave generator 300 generates a microwave on the
basis of the variable voltage supplied from the voltage supplier
200. The power distributor 350 almost equally distributes the
microwave generated by the microwave generator 300 among the phase
variators 351a, 351b, and 351c. The power distributor 350 delays
the phase of the microwave inputted to the phase variator 351b
by 180 degrees and decays the phase of the microwave inputted
to the phase variator 351c by 90 degrees when the phase of the
microwave inputted to the phase variator 351a is used as a basis,
for example.
Each of the phase variators 351a, 351b, and 351c includes
a varactor diode (variable-capacitance diode), for example.

Each of the phase variators 351a, 351b, and 351c is controlled
by the microcomputer 700, to adjust the phase of the fed microwave .
Note that each of the phase variators 351a, 351b, and 351c
may include a pin (PIN) diode and a plurality of lines, for example,
in place of the varactor diode.
For example, a phase difference between microwaves
respectively radiated from the opposite two antennas A1 and A2
can be changed by controlling at least one of the phase variators
351a and 351b. The details will be described later.
The microwave amplifiers 400, 410, and 420 are operated
by the DC voltage supplied from the voltage supplier 200, to
respectively amplify microwaves fedfrom the phase variators 351a,
351b, and 351c. The details of the respective configurations
and operations of the voltage supplier 200, the microwave
generator 300, and the microwave amplifiers 400, 410, and 420
will be described later.
The reflected power detection devices 600, 610, and 620
respectively include detector diodes, directional couplers,
terminators, and so on and feed microwaves amplified by the
microwave amplifiers 400, 410, and 420 to the antennas Al, A2,
and A3 provided within the case 501. This causes the microwaves
to be radiated from the antennas A1, A2, and A3 within the case
501.
At this time, reflective powers are respectively applied
to the reflected power detection devices 600, 610, and 620 from

the antennas A1, A2, and A3. The reflected power detection devices
600, 610, and 620 respectively feed reflected power detection
signals corresponding to the applied reflected powers to the
microcomputer 700.
A temperature sensor TS for measuring the temperature of
an object is provided within the case 501. A temperature measured
value of the object by the temperature sensor TS is given to the
microcomputer 700.
The microcomputer 700 controls the voltage supplier 200,
the microwave generator 300, and the phase variators 351a, 351b,
and 351c. The details will be described later.
(1-2) Details of configuration of microwave generation
device
Fig. 2 is a schematic: side view of the microwave generation
device 100 constituting the microwave oven 1 shown in Fig. 1,
and Fig. 3 is a diagram schematically showing the circuit
configuration of a part of the microwave generation device 100
shown in Fig. 2.
The details of each of components constituting the
microwave generation device 100 will be described on the basis
of Figs. 2 and 3. In Figs. 2 and 3, the illustration of the power
distributor 350, the phase variators 351a, 351b, and 351c, the
microwave amplifiers 410 ar.d 420, the reflected power detection
devices 600, 610, and 620, and the microcomputer 700 is omitted.
The voltage supplier 200 shown in Fig. 2 includes a

rectifier circuit 201 (Fig. 3) and a voltage control device 202
(Fig. 3) . The voltage control device 202 includes a transformer
202a and a voltage control circuit 202b. The rectifier circuit
201 and the voltage control device 202 are accommodated in a case
IM1 (Fig. 2) composed of an insulating material such as resin.
The microwave generator 300 shown in Fig. 2 includes a
radiator fin 301 and a circuit board 302. A microwave generator
303 shown in Fig. 3 is formed in the circuit board 302 . The circuit
board 302 is provided on the radiator fin 301. The circuit board
302 and the microwave generator 303 are accommodated in a metal
case IM2 on the radiator fin 301. The microwave generator 303
is composed of a circuit elenent such as a transistor, for example.
The microwave generator 303 is connected to the
microcomputer 700 shown in Fig. 1. This causes the operation
of the microwave generator 303 to be controlled by the
microcomputer 700.
The microwave amplifier 400 shown in Fig. 2 includes a
radiator fin 401 and a circuit board 402. Three amplifiers 403,
404, and 405 shown in Fig. 3 are formed on the circuit board 402.
The circuit board 402 is provided on the radiator fin 401. The
circuit board 402 and the amplifiers 403, 404, and 405 are
accommodated in a metal case IM3 on the radiator fin 401. Each
of the amplifiers 403, 404, and 405 is composed of a high thermal
stability and high pressure- resistant semiconductor device such
as a transistor using GaN (gallium nitride) and SiC (silicon

carbide).
As shown in Fig. 3, an output terminal of the microwave
generator 303 is connected to an input terminal of the amplifier
403 through a line L1 formed in the circuit board 302, the power
distributor 350 and the phase variator 351a shown in Fig. 1 (which
are not illustrated in Fig. 3), a coaxial cable CC1, and a line
L2 formed in the circuit board 402. Note that the coaxial cable
CC1 and the line L2 are connected to each other in an insulating
connector MC.
An output terminal of the amplifier 403 is connected to
an input terminal of a power distributor 406 through a line L3
formed in the circuit board 402. The power distributor 406
distributes a microwave irputted from the amplifier 4 03 through
the line L3 into two.
Two output terminals of the power distributor 406 are
connected to respective input terminals of the amplifiers 404
and 405 through lines L4 and L5 formed in the circuit board 402.
Respective output terminals of the amplifiers 404 and 405
are connected to an input terminal of a power synthesizer 407
through lines L6 and L8 farmed in the circuit board 402. The
power synthesizer 407 synthesizes respective microwaves inputted
thereto. An output terminal of the power synthesizer 407 is
connected to one end of a coaxial cable CC2 through a line L7
formed in the circuit board 402. The reflected power detection
device 600 shown in Fig. 1 is inserted through the coaxial cable

CC2.
The other end of :he coaxial cable CC2 is connected to
the antenna A1 provided in the case 501. The coaxial cable CC2
and the line L7 are conr.ected to each other in an insulating
connector MC.
An AC voltage Vcc is applied from the commercial power supply
PS to a pair of input tern.inals of the rectifier circuit 201 and
a primary winding of the transformer 202a. The AC voltage Vcc
is 100 (V), for example. A power supply line LV1 for a high
potential and a power supply line LV2 for a low potential are
connected to a pair of output terminals of the rectifier circuit
201.
The rectifier circuit 201 rectifies the AC voltage Vcc
supplied from the commercial power supply PS, and applies a DC
voltage VDD between the power supply lines LV1 and LV2. The DC
voltage VDD is 140 (V), for example. Respective power supply
terminals of the amplifiers 403, 404, and 405 are connected to
the power supply line LV1, and respective ground terminals of
the amplifiers 403, 404, and 405 are connected to the power supply
line LV2.
A secondary winding of the transformer 202a is connected
to a pair of input terminals of the voltage control circuit 202b.
The transformer 202a decreases the AC voltage Vcc. The voltage
control circuit 202b feeds a variable voltage VVA optionally
adjustable from the AC voltage decreased by the transformer 202a

to the microwave generator 303. The variable voltage VVA is a
voltage adjustable between 0 (V) and 10 (V), for example.
The microwave generator 303 generates a microwave on the
basis of the variable voltage VVA applied from the voltage control
circuit 202b. The microwave generated by the microwave generator
303 is fed to the amplifier 403 through the line L1 (the power
distributor 350 and the phase variators 351a to 351c in Fig. 1) ,
the coaxial cable CC1, and the line L2.
The amplifier 403 amplifies the power of the microwave
fed from the microwave generator 303. The microwave amplified
by the amplifier 403 is fed to the amplifiers 404 and 405 through
the line L3, the power distributor 406, and the lines L4 and L5.
The amplifiers 404 and 405 amplify the power of the
microwave fed from the amplifier 403. The microwaves amplified
by the amplifiers 404 and 405 are respectively inputted to the
power synthesizer 407 through the lines L6 and L8, and are
synthesized by the power synthesizer 407 . A composite microwave
is outputted from the power synthesizer 407, and is fed to the
antenna Al through the line 17 and the coaxial cable CC2. The
respective microwaves fed to "he antenna Al from the amplifiers
404 and 405 are radiated into the case 501.
(1-3) Procedure for control by microcomputer
Figs. 4 and 5 are flow charts showing the procedure for
control by the microcomputer 7 00 shown in Fig, 1.
The microcomputer 700 shown in Fig. 1 is commanded to heat

an object by a user's operation, to perform microwave processing,
described below.
As shown in Fig. 4, the microcomputer 700 first causes
a self-contained timer to start a measuring operation (stepSll).
The microcomputer 700 controls the microwave generator 300 shown
in Fig. 1, to set a predetermined first output power as the output
power of the microwave oven 1 (step S12) . The first output power
is less than a second output power, described later. A method
of determining the first output power will be described later.
The microcomputer 700 then sweeps the frequency of the
microwave generated by the microwave generator 300 over a full
frequency band of 2400 MHz to 2500 MHz used in the microwave oven
1, and stores the relationship between a reflective power detected
by each of the reflected power detection devices 600, 610, and
620 shown in Fig. 1 and the frequency (step S13) . The frequency
band is referred to as an ISM (Industrial Scientific and Medical)
band.
Note that the microcomputer 7 00 may store only the
relationship between the reflected power and the frequency in
a case where the reflected power takes a minimal value instead
of storing the relationship between the reflected power and the
frequency in the full frequency band when the frequency of the
microwave is swept. In this case, a used area of a storage in
the microcomputer 700 can be reduced.
The microcomputer 700 then performs frequency extraction

processing for extracting a particular frequency from the ISM
band (step S14).
In the frequency extraction processing, the particular
reflected power (e.g., the minimum value) is identified from the
stored reflected powers, ard the frequency at which the reflected
power is obtained is extracted as an actual heating frequency,
for example. This specific example will be described later.
When the microcomputer 700 stores a plurality of sets of
relationships between the reflected power and the frequency only
in a case where the reflected power takes a minimal value, the
particular frequency is extracted out of the stored plurality
of frequencies as an actual heating frequency.
The microcomputer 700 then sets a predetermined second
output power as the output power of the microwave oven 1 (step
S15) .
The second output power is a power for heating an object
arranged within the case 501 shown in Fig. 1, and corresponds
to the maximum output power (rated output power) of the microwave
oven 1. When the rated output power of the microwave oven 1 is
950 W, for example, the second output power is previously
determined as 950 W.
The microcomputer 700 radiates the microwave having the
actual heating frequency into the case 501 from the antennas A1,
A2, and A3 using the seconc output power (step S16) . This causes
the object arranged with:.n the case 501 to be heated (actual

heating).
Here, the microcomputer 700 controls at least one of the
phase variators 351a and 351b shown in Fig. 1, to continuously
or gradually change a phcise difference between the microwaves
respectively radiated from the opposite two antennas A1 and A2
(step S17) .
Thereafter, the microcomputer 700 determines whether or
not the temperature of the object detected by the temperature
sensor TS shown in Fig. 1 reaches a target temperature (e.g.,
70°C) (step S18) . Note that the target temperature may be
previously fixedly set, or may be optionally manually set by a
user.
When the temperature of the obj ect does not reach the target
temperature, the microcomputer 700 determines whether or not the
reflected power detected by the reflected power detection device
600 exceeds a predetermined threshold value (step S19). Amethod
of determining the threshold value will be described later.
When the reflected power does not exceed the previously
determined threshold value, the microcomputer 700 determines
whether or not a predetermined time period (e.g., 10 seconds)
has elapsed since the measuring operation of the timer was started
in the step S11 (step S20).
Unless the predetermined time period has elapsed, the
microcomputer 700 repeats the operations in the steps S18 to S20
while maintaining a state where the microwave having the actual

heating frequency is radiated using the second output power.
When the temperature of the object reaches the target
temperature in the step S18, the microcomputer 700 terminates
microwave processing.
Furthermore, when the reflected power exceeds the
predetermined threshold value in the step S19, the microcomputer
700 is returned to the operation in the step S11.
When a predetermined time period has elapsed in the step
S20, the microcomputer 700 resets the timer as shown in Fig. 5,
and starts the measuring operation of the timer again (step S21) .
Here, the microccmputer 700 controls at least one of the
phase variators 351a and 351b shown in Fig. 1, such that the phase
difference between the microwaves respectively radiated from the
opposite two antennas A1 and A2 is returned to be zero (step S22) .
The microcomputer 700 sets the first output power as the
output power of the microwave oven 1, as in the step S12 (step
S23) .
The microcomputer 700 then sets the actual heating
frequency extracted in the step S16 as a reference frequency,
partially sweeps the frequency of the microwave in a frequency
band in a predetermined range including the reference frequency
(e.g. , a frequency band in a range of ± 5 MHz from the reference
frequency), and stores the relationship between the reflected
power detected by the ceflected power detection device 600 and
the frequency (step S24).

The microcomputer 700 may store only the relationship
between the reflected power and the frequency in a case where
the reflected power takes a minimal value instead of storing the
relationship between the reflected power and the frequency in
the above-mentioned partial frequency band when the frequency
of the microwave is swept.. In this case, the used area of the
storage in the microcomputer 7 00 can be reduced.
The frequency band serving as an object of sweeping in
the step S24 is narrower than the frequency band serving as an
object of sweeping in the step S13, i.e., the ISM band.
Consequently, a time period required for the sweeping in the step
S24 is made shorter, as compared with a time period required for
the sweeping in the step S13.
The microcomputer 700 then performs frequency
re-extraction processing for extracting the particular frequency
again from the frequency band serving as the object of sweeping
in the step S24 (step S25) . The frequency re-extraction
processing is the same as the frequency extraction processing
in the step S14.
Furthermore, the microcomputer 700 sets the
above-mentioned second output power as the output power of the
microwave oven 1 (step S26).
The microcomputer 700 causes the antennas A1, A2 and A3
to radiate the microwave having the actual heating frequency newly
extracted using the second output power into the case 501 (step

S27) .
Here, the microcorrputer 700 controls at least one of the
phase variators 351a and 351b shown in Fig. 1, to continuously
or gradually change the phase difference between the microwaves
respectively radiated from the opposite two antennas Al and A2
(step S28), as in the operation in the step S17.
Thereafter, the microcomputer 700 performs operations in
the steps S29 to S31, as in the foregoing steps S18 to S20. When
the reflected power exceeds a predetermined threshold value in
the step S30, the microcomputer 700 is returned to the operation
in the step S11 shown in Fig. 4 . When a predetermined time period
has elapsed in the step S31, the microcomputer 700 is returned
to the operation in the: step S21.
(1-4) Phase difference between microwaves respectively
radiated from opposite antennas
As described in the foregoing, in the steps S17 and S28,
the microcomputer 700 changes the phase difference between the
microwaves respectively radiated from the opposite two antennas
Al and A2 at the time of actual heating of the object. The reason
why the microcomputer thus carries out control will be described.
The two antennas Al and A2 out of the three antennas A1,
A2, and A3 within the case 501 are opposite each other in the
horizontal direction, as described above . Thus, it is considered
that on an axis connecting the opposite two antennas A1 and A2,
the microwaves respectively radiated from the antennas A1 and

A2 interfere with each ether.
Fig. 6 is a diagram for explaining mutual interference
between the microwaves respectively radiated from the antennas
Al and A2 shown in Fig. 1. Fig. 6 (a) illustrates a state where
the microwaves are respectively radiated in the same phase (a
phase difference of zero degree) from the antennas Al and A2.
As shown in Fig. 6 (a) , the intensities of the microwaves
respectively radiated from the antennas Al and A2 change in a
sinusoidal shape. In Fig. 6 (a), the positions of the antennas
Al and A2 are respectively shifted in a longitudinal direction
in order to clarify the intensities of the microwaves respectively
radiated from the antenras Al and A2.
Figs. 6 (b) , 6 (c) , 6 (d) , and 6 (e) show temporal changes
in the intensities of microwaves at positions xl, x2, x3, and
x4. The positions xl, x2, x3, and x4 are arranged on an axis
ex connecting the antennas Al and A2. In Figs. 6 (b) to 6 (e) ,
the vertical axis indicates the intensity of the microwave, and
the horizontal axis indicates time.
The respective intensities of the microwaves at the
positions xl to x4 are obtained by synthesizing the microwaves
respectively radiated from the antennas Al and A2. Comparing
Figs . 6 (b) to 6 (e) , the amplitude of the intensity of the microwave
takes a maximum value at the position xl, is moderate at the
positions x2 and x4, anci is zero at the position x3.
In the microwave oven 1, the larger the amplitude of the

intensity of the microwave is,, the higher the rise in the
temperature of the object becomes . On the other hand, the smaller
the amplitude of the intensity of the microwave is, the lower
the rise in the temperature of the object becomes.
Consequently, in this example, the temperature of the
object canbemost raisedat thepositionxl, whilebeingmoderately
raised at the positions; x2 and x4. On the other hand, the
temperature of the object can hardly be raised at the position
x3.
Here, suppose a case where the phase difference between
the microwaves respectively radiated from the antennas A1 and
A2 changes. Fig. 7 is a diagram for explaining mutual interference
between the microwaves respectively radiated from the antennas
Al and A2 shown in Fig. 1 in a case where the phase difference
therebetween changes.
When the phase: difference between the microwaves
respectively radiated from the antennas Al and A2 changes, as
shown in Fig. 7 (a), a state of the mutual interference between
the microwaves respectively radiated from the antennas Al and
A2 also changes.
Figs. 7 (b) , 7 (c:) , 7 (d) , and 7 (e) show temporal changes
in the intensities of the microwaves at the positions x1, x2,
x3, and x4. Also in Figs.7 (b) to 7 (e) , the vertical axis indicates
the intensity of the microwave, and the horizontal axis indicates
time.

Comparing Figs. 7 (b) to 7 (e) , the amplitude of the
intensity of the microwave is moderate at the positions x1, x3,
and x4, while being zero at the position x2.
Consequently, in this cases, the temperature of the object
can be moderately raised at the positions x1, x3, and x4. On
the other hand, the temperature of the object can hardly be raised
at the position x2.
From the foregoing, the inventors have considered that
the state of the mutual interference between the microwaves
oppositely radiated can be easily changed by changing the phase
difference between the mic rowaves and as a result, have considered
that the distribution of the intensities of the microwaves (an
electromagnetic wave distribution) within the microwave oven 1
can be easily changed by changing the phase difference between
the microwaves.
Although description was made of the interference between
the microwaves on the axis cx connecting the antennas A1 and A2,
it is considered that the mutual interference between the
microwaves respectively radiated from the antennas Al and A2
occurs in a space around the axis cx connecting the antennas Al
and A2.
The inventors have conducted the following test in order
to confirm that the non-uniformity of the electromagnetic wave
distribution changes depending on the phase difference between
the microwaves respectively radiated from the opposite two

antennas A1 and A2.
Figs. 8 to 10 are diagrams showing the contents of an
experiment for investigating the relationship between the phase
difference between the microwaves respectively radiated from the
opposite two antennas A1 and A2 and the electromagnetic wave
distribution within the case 501 and the results of the experiment.
Fig. 8 (a) is a transverse sectional view of the case 501
shown in Fig. 1. In this experiment, a plurality of cups CU
containing a predetermined amount of water were first arranged
within the case 501.
The microwaves were respectively radiated from the
opposite two antennas A1 and A2. Thereafter, the radiation of
the microwaves was stopped with an elapse of a predetermined time
period, and the rise ir the temperature of water by the radiation
of the microwaves was measured at the center of each of the cups
CU (a point P in Fig, 8 (a)).
A plurality of phase differences were set between the
microwave radiated from the antenna Al and the microwave radiated
from the antenna A2, and the microwaves were radiated a plurality
of times for each of the set phase differences . In this experiment,
the phase difference was set for 40 degrees from zero degree to
320 degrees.
Thus, the inventors have investigated the electromagnetic
wave distribution of the microwaves by measuring the rise in the
temperature of water arranged within a horizontal plane within

the case 501. This experiment makes it possible to determine
that the energy of the electromagnetic wave is high in a region
where the rise in the temperature of water is high, while being
low in a region where the rise in the temperature of water is
low.
Fig. 8 (b) shows the results of the experiment in a case
where the phase difference between the microwaves was set to zero
degree using an isotherm based on the rise in the temperature
of water. Similarly, Figs. 8 (c) to 10 (j) show the results of
the experiment in a case where the phase difference between the
microwaves was set for 40 decrees from 40 degrees to 320 degrees.
Thus, the results of the experiment shown in Figs. 8 (b)
to Fig. 10 (j) have shown that the rise in the temperature of
water greatly varies within the case 501, and the change in the
set phase difference causes the variation in the rise in the
temperature to change.
When the phase difference is set to 120 degrees and 160
degrees, as shown in Figs. 9 (e) and 9 (f), for example, the rise
in the temperature becomes significantly high in a region HR1
close to one side surface of the case 501.
On the other hand, as shown in Figs. 10 (i) and 10 (j),
when the phase difference is set to 280 degrees and 320 degrees,
the rise in the temperature becomes significantly high in a region
HR2 close to the other side surface of the case 501.
This has made the inventors note that the non-uniformity

of the electromagnetic waive distribution within the case 501
changes depending on the phase difference, to find out that it
is possible to uniformly heat the object and to concentrically
heat a particular portior of the object by changing the phase
difference between the microwaves respectively radiated from the
opposite two antennas A1 and A2 at the time of actual heating
of the object.
In the present embodiment, the above-mentioned operations
in the steps S17 and S28 allow the object arranged within the
case 501 to be uniformly heated at the time of actual heating
of the object.
Since the electromagnetic wave distribution within the
case 501 can be changed by changing the phase difference, the
object arranged within the case 501 need not be moved within the
case 501. Furthermore, the necessity of moving the antenna for
radiating the microwave in order to change the electromagnetic
wave distribution is eliminated.
Therefore, the necessity of a mechanism for moving the
object or the antenna as well as the necessity of getting a space
for moving the object or the antenna within the case 501 are
eliminated. As a result, the microwave oven 1 is made lower in
cost and miniaturized.
In the present embodiment, it is assumed that the
microcomputer 700 continuously or gradually changes the phase
difference. When the phase difference is gradually changed,

however, the phase difference may be changed for 40 degrees or
may be changed for 45 degrees, for example. In this case, the
phase difference that is changed per stage is not limited to the
foregoing values. However, it is preferable that the phase
difference is set to a value that is as low as possible. This
allows non-uniform heating of the object to be further reduced.
The period of the change in the phase difference may be
previously fixedly set or may be optionally manually set by the
user.
When fixedly set, the period of the change in the phase
difference may be changed from zero degree to 360 degrees in 30
seconds or may be changed from zero degree to 360 degrees in 10
seconds, for example.
The phase difference need not be necessarily changed from
zero degree to 360 degrees . For example, the relationship between
a plurality of values of the phase difference and electromagnetic
wave distributions corresponding to the values is previously
stored in a self-contained memory in the microcomputer 700.
In this case, the microcomputer 700 can selectively set
the plurality of values of the phase difference depending on a
state where the object is heated.
Specifically, a plurality of temperature sensors TS are
arranged within the case 501. In this case, the temperature of
the object can be measured with respect to a plurality of portions,
so that the temperature distribution of the object can be known.

At this time, the microcomputer 700 sets the phase
difference such that the energy of the electromagnetic wave is
increased in a portion where the temperature of the object is
low on the basis of the relationship between the values of the
phase difference and the electromagnetic wave distributions,
which is stored in the self-contained memory. This allows the
object to be more uniformly heated.
(1-5) Method of determining first output power
As described in the foregoing, in the microwave oven 1
shown in Fig. 1, the frequency of the microwave is swept using
the first output power be Core the: object is heated using the second
output power, to perform the frequency extraction processing.
The reason for this is as follows.
The reflected power generated by the radiation of the
microwave changes depending on the frequency of the microwave.
Here, when circuit elements respectively constituting the
microwave generator 3C0 and the microwave amplifiers 400, 410,
and 420 shown in Fig. 3 generate heat by the reflected power,
the heat is radiated by the radiator fins 301 and 401 shown in
Fig. 2. When the reflected power increases above the heat
radiation capabilities of the radiator fins 301 and 401, the
circuit elements respectively provided on the radiator fins 301
and 401 may be damaged by generating heat.
In the present embodiment, therefore, the first output
power is determined such that the reflected power does not exceed

the heat radiation capabilities of the radiator fins 301 and 401.
(1-6) Frequency extraction processing and frequency
re-extraction processing
(1-6-a)
In the microwave oven 1 according to the present embodiment,
processing for sweeping and extracting the frequency of the
microwave before actual heating of the object (see steps S13 and
14 in Fig. 4).
Fig. 11 is a diagram for explaining a specific example
of processing for sweeping and extracting the frequency of the
microwave.
Fig. 11 (a) graphically shows the change in the reflected
power in a case where the frequency of the microwave is swept.
In Fig. 11 (a) , the vertical, axis indicates the reflected power,
and the horizontal axis indicates the frequency of the microwave.
In this example, only the reflected power in the antenna
A1 shown in Fig. 1 is illustrated in Fig. 11 (a) in order to make
description easy.
As described in the foregoing, in the microwave oven 1
according to the present embodiment, the frequency of the
microwave is swept over a full ISM frequency band before actual
heating of the object (see an arrow SW1) . The microcomputer 700
stores the relationship between the reflected power and the
frequency.
The microcomputer 700 extracts as an actual heating

frequency a frequency f1 at which the reflected power takes a
minimum value, for example, by the frequency extractionprocessing.
Although in this example, only the reflected power in the antenna
Al is explained, all the reflected powers in the antennas A1,
A2, and A3 are actually measured, and the frequency fl at which
the reflected power takes a minimum value is extracted as an actual
heating frequency.
This causes the microwave having the actual heating
frequency fl to be radiated from the antennas Al to the object
within the case 501 using the second output power. As a result,
the object can be heated while reducing the reflected power.
Note that the frequency of the microwave is swept 0.001
seconds per 0.1 MHz, for example. In this case, one second is
required for the sweeping over the full ISM frequency band.
(1-6-b)
The change in the reflected power dependent on the frequency
(hereinafter referred to as frequency characteristics of the
reflected power) depends on the position, the size, the
composition, the temperature, and so on of the object within the
case 501. Consequently, when theobject is heatedby themicrowave
oven 1 and the temperature of the object rises, the frequency
characteristics of the reflected power also change.
Fig. 11 (b) graphically shows the change in the frequency
characteristics of the reflected power by heating of the object.
In Fig. 11 (b) , the vertical axis indicates the reflected power,

and the horizontal axis indicates the frequency of the microwave.
Further, the frequency characteristics of the reflected power
at the time of sweeping before actual heating are indicated by
a solid line, and the frequency characteristics of the reflected
power in a case where the object is heated by actual heating are
indicated by a broken lane.
In the same manner as described above, only the reflected
power in the antenna A1 shown in Fig. 1 is illustrated in Fig.
11 (b) in order to make description easy.
The frequency characteristics of the reflected power
change, so that the frequency at which the reflected power takes
minimum or minimal values changes. In Fig. 11 (b), g1 indicates
the frequency at which the reflected power takes a minimum value
when the object is heated.
Thus, the frequency characteristics of the reflected power
also change depending en the temperature of the object. In the
microwave oven 1 according to the present embodiment, therefore,
processing for sweeping and re-extracting the frequency of the
microwave is performed for each elapse of a predetermined time
period when the object is subjected to actual heating (see steps
S24 and S25 in Fig. 5).
However, the frequency of the microwave is swept at this
time in a frequency band in a range of + 5 MHz with a frequency
f 1 set at the time of actual heating immediately before the sweeping
used as a reference frequency (see an arrow SW2). This causes

the frequency g1 at which the reflected power takes a minimum
value to be extracted again as a new actual heating frequency.
The frequency of the microwave is swept in a partial
frequency band in a predetermined range including the actual
heating frequency set immediately before the sweeping, which
causes a time period required for the sweeping to be shortened.
When the frequency of the microwave is swept 0.001 seconds per
0.1 MHz, for example, a time period required for the sweeping
in the frequency band in a range of ± 5 MHz from the reference
frequency is 0.1 seconds.
Although in the present embodiment, the processing for
sweeping and re-extracting the frequency in the partial frequency
band is performed at predetermined time intervals, it is
preferable that the time intervals are set to 10 seconds, for
example, such that the frequency characteristics of the reflected
power do not greatly change by heating the object.
(1-7) Threshold value of reflected power
In the microwave oven 1 according to the present embodiment,
it is determined whether or not the reflected power exceeds a
predetermined threshold value at the time of actual heating of
the object (see steps S18 in Fig. 4 and step S30 in Fig. 5).
Here, the threshold value is determined to a value obtained
by adding 50 W to the minimum value of the reflected power detected
at the time of the frequency extraction processing, for example.
When the reflected power increases above 50 W from its value at

the start of actual heating, therefore, the microcomputer 700
sweeps the frequency of the microwave over the full ISM frequency
band, to perform the frequency extraction processing.
This can prevent the reflected power from significantly
increasing during actual heating of the object. Even when the
frequency characteristics of the reflected power greatly changes
by heating the object, the frequency of the microwave is swept
over the full ISM frequency band, so that the frequency extraction
processing is performed. This allows the reflected power to be
always reduced.
(1-8) Another example of frequency extraction processing
The frequency extraction processing may be performed in
the following manner. As shown in Fig. 11 (a), the frequency
characteristics of the reflected power may, in some cases, have
a plurality of minimal values, for example. At this time, the
microcomputer 700 may extract the frequencies f1, f2, and f3
respectively corresponding to the plurality of minimal values
may be extracted as actual heating frequencies.
In this case, the microcomputer 700 may switch the actual
heating frequencies f1, f2, and f3 in this order. For example,
the microcomputer 700 switches the actual heating frequencies
f1, f2, and f3 in this order for three seconds from the start
of actual heating of the object.
When a plurality of minimal values at the same level exist
at the time of sweeping by actual heating at the plurality of

frequencies corresponding to the plurality of minimal values,
therefore, the object can oe subjected to actual heating using
the microwave having the frequency corresponding to each of the
minimal values.
(1-9) Effects
(1-9-a)
In the microwave oven 1 according to the present embodiment,
the phase difference between the microwaves respectively radiated
from the opposite two antennas A1 and A2 changes at the time of
actual heating of the object. This causes the object arranged
within the case 501 to be uniformly heated.
Since the electromagnetic wave distribution within the
case 501 can be changed by changing the phase difference, the
object need not be moved within the case 501. Further, the antenna
for radiating the microwave need not be also moved in order to
change the electromagnetic wave distribution.
This eliminates the necessity of a mechanism for moving
the object or the antenna and eliminates the necessity of getting
a space for moving the object or the antenna within the case 501.
As a result, the microwave oven 1 is made lower in cost and
miniaturized.
(1-9-b)
As shown in Fig. 1, the antenna A3 is provided, in addition
to the opposite two antennas Al and A2, with the antenna A3 not
opposite to the antenna Al and A2 within the case 501 in the

microwave oven 1. The reason for this is as follows.
The microwave has directivity. Consequently, the
arrangement state or the shape of the object within the case 501
cannot, in some cases, efficiently heat the object using the
microwaves respectively radiated from the antennas A1 and A2.
Consequently, the antenna A3 that radiates the microwave
vertically upward from below is provided in addition to the
antennas Al and A2 that radiate the microwaves along the horizontal
direction in this example. This allows the object to be
efficiently heated irrespective of the directivity of the
microwave.
(1-9-c)
In the microwave oven 1 according to the present embodiment,
the frequency of the microwave at which the reflected power
generated when the object is heated takes a minimum value is
extracted by frequency extraction processing before the object
is subjected to actual heating. The extracted frequency is used
as the actual heating frequency, which causes the power conversion
efficiency of the microwave oven 1 to be improved.
Furthermore, in the frequency extraction processing, the
output power of the microwave oven 1 is set to the first output
power sufficiently lower than that at the time of the actual heating.
This causes the radiator fins 301 and 401 to sufficiently radiate
heat even when the circuit elements respectively constituting
the microwave oven 300 and the microwave amplifier 400 generate

heat by the reflected power when the frequency of the microwave
is swept.
As a result, the circuit elements respectively provided
on the radiator fins 301 and 401 are reliably prevented from being
damaged by the reflected power.
(1-9-d)
In the present enbodiment, the two antennas A1 and A2
opposite each other along the horizontal direction are provided
slightly below the center in the vertical direction of the case
501, as shown in Fig. 1. This allows the object arranged in a
lower part of the case 501 to be efficiently heated when the
microwave oven 1 is employed.
(1-10) Modification
Although in the first embodiment, the microcomputer 700
changes the phase difference between the microwaves respectively
radiated from the opposite antennas Al and A2 for each start of
the actual heating using the second output power (see step S17
in Fig. 4), and the phase difference between the microwaves is
returned to zero every time the actual heating is stopped (see
step S22 in Fig. 5) , the phase difference need not be necessarily
returned to zero. The microcomputer 700 may set the phase
difference to a predet.ermined value in the step S22.
Although in the present embodiment, description was made
of an example in which the phase difference between the microwaves
at the time of actual he ating of the object is changed to uniformly

heat the object, the relationship between the phase difference
and the electromagnetic wave distributionmay be previously stored
in the self-contained memory in the microcomputer 700, to change
the phase difference 01 the basis of the relationship to
concentrically heat a desired portion of the object.
For example, the phase difference is so set that the
electromagnetic field is intense at a substantially central part
of a portion where the object is placed within the case 501. In
this case, even a small object can be efficiently heated.
Although the second output power is taken as the maximum
output power of the microwave oven 1, the second output power
may be optionally manually set by the user.
Although in the present embodiment, the microcomputer 700
determines that the microwave processing is terminated on the
basis of a measured value of the temperature of the object, which
is measured by the teirperature sensor TS shown in Fig. 1, the
microwave processing may be terminated on the basis of its
termination time manually set by the user.
In themicrowave oven 1 according to the present embodiment,
if the mutual interference occurs between the microwaves
respectively radiated from the antennas A1 and A2, the antennas
A1 and A2 need not necessarily be opposite each other.
Fig. 12 is a diagram showing other examples of the
arrangement of the artennas A1 and A2 shown in Fig. 1. In the
example shown in Fig. 12 (a), the antenna A1 is horizontally

arranged on an upper part, of one side surface of the case 501,
and the antenna A2 is horizontally arranged on a substantially
central part of the other side surface of the case 501.
In the example shown in Fig. 12 (b), the antenna A1 is
arranged on an upper part of the one side surface of the case
501 so as to be directed toward a substantially central part of
a lower surface of the case 501, and the antenna A2 is horizontally
arranged on a substantially central part of the other side surface
of the case 501.
In the example shown in Fig. 12 (c), the antenna A1 is
arranged on a substantially central part of the lower surface
of the case 501 so as to be inclined toward the other side surface
of the case 501, and the antenna A2 is horizontally arranged on
a substantially central part of the other side surface of the
case 501.
In these cases, the microwaves are also respectively
radiated from the antennas A1 and A2, so that the mutual
interference occurs between both the microwaves. As a result,
the electromagnetic wave distribution within the case 501 changes
by changing the phase difference between both the microwaves.
[2] Second Embodiment
A microwave oven according to a second embodiment differs
from the microwave oven 1 according to the first embodiment in
the following points .
(2-1) Outline of configuration and operations of

microwave oven
Fig. 13 is a block diagram showing the configuration of
the microwave oven according to the second embodiment. As shown
in Fig. 13, a microwave oven 1 according to the second embodiment
differs from the microwave oven 1 (Fig. 1) according to the first
embodiment in the configuration of a microwave generation device
100.
In the microwave oven 1 according to the present embodiment,
the microwave generation device 100 includes a voltage supplier
200, two microwave generators 300 and 310 having the same
configuration, a power distributor 360, two phase variators 351a
and 351b having the same configuration, three microwave amplifiers
400, 410, and 420 having the same configuration, three reflected
power detection devices 600, 610, and 620 having the same
configuration, and a microcomputer 700.
Here, the configuration of the microwave generator 310
is the same as that of the microwave generator 300 described in
the first embodiment.
A power supply ;?lug 10 is connected to a commercial power
supply, so that an AC voltage is supplied to the voltage supplier
200.
The voltage supplier 200 converts the AC voltage supplied
from the commercial power supply into a variable voltage and a
DC voltage, and feecs the variable voltage to the microwave
generators 300 and 210, while feeding the DC voltage to the

microwave amplifiers 400, 410, and 420.
The microwave generator 300 generates a microwave on the
basis of the variable voltage supplied from the voltage supplier
200. The power distributor 360 almost equally distributes the
microwave generated by the microwave generator 300 between the
phase variators 351a and 351b.
Each of the phase variators 351a and 351b is controlled
by the microcomputer 700, to adjust the phase of the fed microwave.
The adjustment of the phase of the microwave by each of the phase
variators 351a and 351b is the same as that in the first embodiment.
The microwave amplifiers 400 and 410 are operated by the
DC voltage supplied from the voltage supplier 200, to respectively
amplify microwaves fed from the phase variators 351a and 351b.
The amplified microwaves are respectively fed to antennas A1 and
A2 opposite each other along a horizontal direction within a case
501 through the reflected power detection devices 600 and 610.
The microwave generator 310 also generates a microwave
on the basis of the variable voltage supplied from the voltage
supplier 200 . The microwave generated by the microwave generator
310 is fed to the microwave amplifier 420.
The microwave amplifier 420 is operated by the DC voltage
supplied from the voltage supplier 200, to amplify the microwave
generated by the microwave generator 300. The amplified
microwave is supplied to an antenna A3 in the case 501 through
the reflected power detection device 620.

(2-2) Effects
As described in the foregoing, in the present embodiment,
a generation source (the iricrowave generator 310) of a microwave
radiated from the antenna A3 differs from a generation source
(themicrowave generator 330) ofmicrowaves respectively radiated
from the opposite antennas A1 and A2.
This allows the frequency of the microwave radiated from
the antenna A3 to be controlled to a frequency different from
the frequencies of the microwaves respectively radiated from the
other antennas A1 and A2. This allows the power conversion
efficiency to be further improved.
The configurations of a power distributor and a phase
variator need not be provided in a transmission path of the
microwave radiated frorr the antenna A3. This causes the
configuration of the microwave oven 1 to be simplified, so that
the microwave oven 1 is made lower in cost and miniaturized.
[3] Third Embodiment
A microwave oven according to a third embodiment differs
from the microwave oven 1 according to the first embodiment in
the following points.
(3-1) Outline of configuration and operations of
microwave oven
Fig. 14 is a block diagram showing the configuration of
the microwave oven according to the third embodiment. As shown
in Fig. 14, a microwave oven 1 according to the third embodiment

differs from the microwave oven 1 (Fig. 1) according to the first
embodiment in the conf iguration of a microwave generation device
100.
In the microwave oven 1 according to the present embodiment,
the microwave generation device 100 includes a voltage supplier
200, a microwave generator 300, three power distributors 350A,
350B, and 350C having the same conf iguration, four phase variators
351a, 351b, 351c, and 351d having the same configuration, four
microwave amplifiers 400, 410, 420, and 430 having the same
configuration, four reflected power detection devices 600, 610,
620, and 630 having the same configuration, and a microcomputer
700.
A power supply plug 10 is connected to a commercial power
supply, to supply an AC voltage to the voltage supplier 200.
The voltage supplier 200 converts the AC voltage supplied
from the commercial power supply into a variable voltage and a
DC voltage, and feeds the variable voltage to the microwave
generator 300, while feeding the DC voltage to the microwave
amplifiers 400, 410, 420, and 430.
The microwave generator 300 generates a microwave on the
basis of the variable voltage supplied from the voltage supplier
200, and feeds the microwave to the power distributor 350A.
The power distributor 350A almost equally distributes the
fed microwave between the power distributors 350B and 350C. The
power distributor 350B almost equally distributes the fed

microwave between the phase variators 351a and 351b. The power
distributor 350C almost equally distributes the fed microwave
between the phase variators 351c and 351d.
Each of the phase variators 351a, 351b, 351c, and 351d
is controlled by the microcomputer 700, to adjust the phase of
the fed microwave. The details will be described later.
The microwave amplifiers 400 and 410 are operated by the
DC voltage supplied from the voltage supplier 200, to respectively
amplify microwaves fed from the phase variators 351a and 351b.
The amplified microwaves are respectively fed to antennas A1 and
A2 opposite each other along a horizontal direction within a case
501 through the reflected power detection devices 600 and 610.
Furthermore, the microwave amplifiers 420 and 430 are also
operated by the DC voltage supplied from the voltage supplier
200, to respectively amplify microwaves fed from the phase
variators 351c and 2 51d. The amplified microwaves are
respectively fed to antennas A3 and A4 opposed to each other along
a vertical direction within the case 501 through the reflected
power detection devices 620 and 630.
(3-2) Adjustment of phase of microwave
As shown in Fig. 14, in the case 501, the antennas A1 and
A2 are opposite each other along the horizontal direction, and
the antennas A3 and A4 are opposite each other along the vertical
direction.
Here, a transmission path of a microwave radiated from

the antenna A1 is provided with the phase variator 351a, and a
transmission path of a microwave radiated from the antenna A2
is provided with the phase variator 351b.
Furthermore, a transmission path of a microwave radiated
from the antenna A3 is provided with the phase variator 351c,
and a transmission path of a microwave radiated from the antenna
A4 is provided with the phase variator 351d.
Thus, in the present embodiment, the microcomputer 7 00
performs the same processing as that in the first embodiment with
respect to the two phase variators 351a and 351b respectively
corresponding to the opposite antennas A1 and A2. That is, the
microcomputer 700 chances a phase difference between the
microwaves respectively radiated from the opposite two antennas
A1 and A2 at the time of actual heating of an object.
Furthermore, the nicrocomputer 700 performs the same
processing as that in the first embodiment with respect to the
two phase variators 351c and 351d respectively corresponding to
the opposite antennas A3 and A4. That is, the microcomputer 700
changes a phase difference between the microwaves respectively
radiated from the opposite two antennas A3 and A4 at the time
of actual heating of the cbject.
(3-3) Effects
In the present embodiment, the phase difference between
the microwaves respectively radiated from the antennas A1 and
A2 opposite each other along r.he horizontal direction is changed,

and the phase difference between the microwaves respectively
radiated from the antennas A3 and A4 opposite each other along
the vertical direction is also changed. Thus, an electromagnetic
wave distribution within the case 501 is sufficiently changed,
which causes the object arranged within the case 501 to be more
uniformly heated.
In the present embodiment, the object arranged within the
case 501 is heated by the microwaves respectively radiated from
the antennas A1 and A2 opposite each other along the horizontal
direction, and is heated by the microwaves respectively radiated
from the antennas A3 and A4 opposite each other along the vertical
direction. This allows the object to be sufficiently efficiently
heated irrespective of the directivity of the microwaves.
[4] Fourth Embociment
A microwave oven according to a fourth embodiment differs
from the microwave oven 1 according to the first embodiment in
the following points.
(4-1) Outline of configuration and operations of
microwave oven
Fig. 15 is a block diagram showing the configuration of
the microwave oven according to the fourth embodiment. As shown
in Fig. 15, a microwave oven 1 according to the fourth embodiment
differs from the microwave oven 1 (Fig. 1) according to the first
embodiment in the configuration of a microwave generation device
100.

In the microwave oven 1 according to the present embodiment,
the microwave generation c.evice 100 includes a voltage supplier
200, microwave generators 300 and 310, two power distributors
370 and 380 having the same configuration, four phase variators
351a, 351b, 351c, and 351d having the same configuration, four
microwave amplifiers 400, 410, 420, and 430 having the same
configuration, four reflected power detection devices 600, 610,
620, and 630 having the same configuration, and a microcomputer
700.
A power supply plug 10 is connected to a commercial power
supply, to supply an AC voltage to the voltage supplier 200.
The voltage supplier 200 converts the AC voltage supplied
from the commercial power supply into a variable voltage and a
DC voltage, and feeds the variable voltage to the microwave
generators 300 and 310, while feeding the DC voltage to the
microwave amplifiers 400, 410, 420, and 430.
The microwave generator 300 generates a microwave on the
basis of the variable voltage supplied from the voltage supplier
200, and feeds the microwave to the power distributor 370. The
power distributor 370 almost equally distributes a microwave
generated by the microwave generator 300 between the phase
variators 351a and 351b.
The microwave generator 310 generates a microwave on the
basis of the variable vcltage supplied from the voltage supplier
200, and feeds the microwave to the power distributor 380. The

power distributor 380 aln.ost equally distributes a microwave
generated by the microwave generator 310 between the phase
variators 351c and 351d.
Each of the phase variators 351a, 351b, 351c, and 351d
is controlled by the micrDcomputer 700, to adjust the phase of
the fed microwave.
Here, the adjustment of the phase of the microwave by each
of the phase variators 351a, 351b, 351c, and 351d is the same
as that in the third embodiment.
The microwave amplifiers 400 and 410 are operated by the
DC voltage supplied f rom the voltage supplier 200, to respectively
amplify microwaves respectively fed from the phase variators 351a
and 351b. The amplified microwaves are respectively fed to
antennas A1 and A2 opposite each other along a horizontal direction
within a case 501 through the reflected power detection devices
600 and 610.
Furthermore, the microwave amplifiers 420 and 430 are also
operated by the DC voltage supplied from the voltage supplier
200, to respectively amplify microwaves fed from the phase
variators 351c and 3 31d. The amplified microwaves are
respectively fed to antennas A3 and A4 opposite each other along
a vertical direction wibhin the case 501 through the reflected
power detection devices 620 and 630.
(4-2) Effects
Even in the present embodiment, a phase difference between

the microwaves respectively radiated from the antennas A1 and
A2 opposite each other along the horizontal direction is changed,
and a phase difference between the microwaves respectively
radiated from the antennas A3 and A4 opposite each other along
the vertical direction is also changed. Thus, an electromagnetic
wave distribution within the case 501 is sufficiently changed,
which causes an object arranged within the case 501 to be more
uniformly heated. This allows the object to be sufficiently
efficiently heated irrespective of the directivity of the
microwaves.
In the present embodiment, a generation source (the
microwave generator 300) of the microwaves respectively radiated
from the antenna A1 and A2 differs from a generation source (the
microwave generator 310) of the microwaves respectively radiated
from the antennas A3 ar.d A4.
This allows the frequencies of the microwaves respectively
radiated from the antennas A1 and A2 to be controlled to frequencies
different from the frequencies of the microwaves respectively
radiated from the other antennas A3 and A4 . This allows the power
conversion efficiency to be further improved.
[5] Correspondences between elements in the claims and
parts in embodiments
In the following paragraphs, non-limiting examples of
correspondences between various elements recited in the claims
below and those described above with respect to various preferred

embodiments of the present invention are explained.
In the first to fourth embodiments described above, the
microwave oven 1 is an example of a microwave processing apparatus,
the microwave generators 300 and 310 are examples of a microwave
generator, the antenna A1 is an example of a first radiator, and
the antenna A2 is an example of a second radiator.
The phase variators 351a and 351b are examples of a first
phase variator, the reflected power detection devices 600, 610,
620, and 630 are examples of a detector, and the microcomputer
700 is an example of a controller.
Furthermore, the antenna A3 is an example of a third
radiator, the microwave generator 300 is an example of a first
microwave generator, the microwave generator 310 is an example
of a second microwave generator, the antenna A4 is an example
of a fourth radiator, and the phase variators 351c and 351d are
examples of a second phase variator.
[Industrial Applicability]
The present invention is applicable to processing
apparatuses that generate microwaves, for example, a microwave
oven, a plasma generation apparatus, a drying apparatus, and an
apparatus for promoting an oxygen reaction.

[Document Name] CLAIMS
1. A microwave processing apparatus that processes an
object using a microwave, comprising:
a microwave generator that generates a microwave; and
at least first and second radiators that radiate to the
object the microwave generated by said microwave generator,
wherein a phase difference between microwaves
respectively radiated from said first and second radiators
changes.
2. A microwave processing apparatus that processes an
object using a microwave, comprising:
a microwave generator that generates a microwave;
first and second radiators that respectively radiate to
the object the microwave generated by said microwave generator;
and
a first phase variator that changes a phase difference
between microwaves respectively radiated from said first and
second radiators,
wherein said first and second radiators are arranged such
that the radiated microwaves interfere with each other.
3 . The microwave processing apparatus according to claim
1, wherein said first and second radiators are opposite each other.
4 . The microwave; processing apparatus according to claim
1, further comprising:
a detector that detects respective reflected powers from

said first and second radiators, and
a controller that controls said microwave generator,
wherein said controller causes said first and second
radiators to radiate the microwaves to the object while changing
the frequency of the microwave generated by said microwave
generator, determines the frequency of the microwave for
processing the object as a processing frequency on the basis of
a frequency at which the re flected power detected by said detector
take a minimum or minimal value, and causes said microwave
generator to generate the microwave having the determined
processing frequency.
5 . The microwave processing apparatus according to claim
4, wherein said controller causes said first and second radiators
to radiate the microwaves to the object while changing the
frequency of the microwave generated by said microwave generator
before the object is processed, and determines the frequency of
the microwave for processing the object as a processing frequency
on the basis of the frequency at which the reflected power detected
by said detector take a minimum or minimal value.
6. The microwave processing apparatus according to claim
4, wherein said controller causes said first and second radiators
to radiate the microwaves to the object while changing the
frequency of the microwave generated by said microwave generator
while the object is processed, and determines the frequency of
the microwave for processing the object as a processing frequency

on the basis of the frequency at which the reflected power detected
by said detector take a minimum or minimal value.
7 . The microwave processing apparatus according to claim
1, wherein said first radiator radiates the microwave along a
first direction, and said second radiator radiates the microwave
along a second direction opposite to said first direction, further
comprising:
a third radiator that radiates the microwave generated
by said microwave generator to the object along a third direction
crossing said first direction.
8 . The microwave processing apparatus according to claim
7, wherein
said microwave generator includes first and second
microwave generators,
said first and second radiators radiate to the object the
microwave generated by said first microwave generator, and
said third radiator radiates to the object the microwave
generated by said second microwave generator.
9. The microwave processing apparatus according to claim
1, wherein
said first radiator radiates the microwave along a first
direction, and said second radiator radiates the microwave along
a second direction opposite to said first direction, further
comprising:
a third radiator that radiates the microwave generated

by said microwave generator to the object along a third direction
crossing said first direction, and
a fourth radiator that radiates the microwave generated
by saidmicrowave generator to the object along a fourth direction
opposite to said third direction,
wherein said third and fourth radiators are opposite each
other.
10. Themicrowaveprocessing apparatus according to claim
9, further comprising a second phase variator that changes a phase
difference between the microwaves respectively radiated from said
third and fourth radiators.
11. Themicrowave processing apparatus according to claim
10, wherein
said microwave generator includes first and second
microwave generators,
said first and second radiators radiate to the object the
microwave generated by said first microwave generator, and
said third and fourth radiators radiate to the object the
microwave generated by sa;.d second microwave generator.
12 . Themicrowave processing apparatus according to claim
1, wherein the object is processed by heating processing, further
comprising :
a heating chamber that accommodates the ob j ect for heating.

A microwave oven includes a microwave generating device and a case. In the case, three antennas are arranged. The two antennas are arranged to face each other in the horizontal direction. In the microwave generating device, microwaves generated by a microwave generating section are distributed substantially equally to phase changers by a power distributer. Each of the phase changers adjusts the phase of the given microwave. Thus, a phase difference between the microwaves radiated from the two facing antennas is changed, and the microwaves are radiated.