1. A transmitter comprising: a first transmission block that generates a first radio wave having an information signal modulated thereon and having a plane of polarization that rotates; and a second transmission block that generates a second radio wave having the information signal modulated thereon and having a plane of polarization that is fixed.

2. The transmitter of claim 1, wherein the first transmission block comprises a first superimposing circuit that causes a first orthogonal code to be superimposed on the first radio wave, the first orthogonal code being a spreading code, and wherein the second transmission block comprises a second superimposing circuit that causes a second orthogonal code to be superimposed on the second radio wave, the second orthogonal code being orthogonal to the first orthogonal code.

3. The transmitter of claim 2, wherein the second transmission block causes a third orthogonal code to be superimposed on the second radio wave, the third orthogonal code being orthogonal to the first orthogonal code and the second orthogonal code.

4. The transmitter of claim 1, further comprising a plurality of 46 transmission antennas whose planes of polarizations are spatially orthogonal to one another, wherein the first transmission block generates the first radio wave via the plurality of transmission antennas, and wherein the second transmission block generates the second radio wave via the plurality of transmission antennas.

5. The transmitter of claim 4, wherein the first transmission block and the second transmission block respectively generate the first radio wave and the second radio wave at the same time.

6. The transmitter of claim 5, wherein the first transmission block uses a plurality of carrier frequencies to generate the first radio wave, such that the first radio wave has a plane of polarization that rotates at a rotational frequency depending on the plurality of carrier frequencies, and wherein the second transmission block uses the plurality of carrier frequencies to generate the second radio wave.

7. The transmitter of claim 1, wherein the first transmission block comprises: a polarization plane rotating oscillator that oscillates at a frequency corresponding to a rotational frequency of the plane of polarization of the first 47 radio wave, and a carrier oscillator that oscillates at a frequency corresponding to a carrier frequency of the first radio wave, and wherein the first radio wave has a component with a frequency equal to the sum of the carrier frequency and the rotational frequency and has a component with a frequency equal to the difference between the carrier frequency and the rotational frequency.

8. The transmitter of claim 1, wherein the first transmission block comprises: a first sine oscillator that generates a sine wave of a first frequency; a first cosine oscillator that generates a cosine wave of the first frequency; a second sine oscillator that generates a sine wave of a second frequency; and a second cosine oscillator that generates a cosine wave of the second frequency, wherein the plane of polarization of the first radio wave rotates at a rotational frequency equal to half the difference between the first and second frequencies, and wherein the second radio wave has a component with a carrier frequency equal to the first frequency and a component with a carrier frequency equal to the second frequency. 48 9 The transmitter of claim 1, further comprising: an information signal generator that generates the information signal; a synchronization signal generating circuit that generates a synchronization signal; and a signal switching circuit that selects one of the information signal and the synchronization signal, and passes the selected signal to the first transmission block and the second transmission block.

10. A receiver comprising: a first receive section that demodulates a first radio wave having an information signal modulated thereon and having a plane of polarization that rotates; and a second receive section that demodulates a second radio wave having the information signal modulated thereon and having a plane of polarization that is fixed, wherein the receiver restores the information signal on the basis of the result of reception by the first receive section and the second receive section.

11. The receiver of claim 10, wherein the first radio wave contains a component of the information signal spread with a first orthogonal code, the first orthogonal code being a spreading code, wherein the second radio wave contains a component of the information signal spread with a second orthogonal code, the second orthogonal code being a 49 spreading code and being orthogonal to the first orthogonal code, and wherein the receiver further comprises: a first despreading section that despreads the result of the demodulation by the first receive section with the first orthogonal code; and a second despreading section that despreads the result of the demodulation by the second receive section with the second orthogonal code.

12. The receiver of claim 11, wherein the second radio wave further contains a component of the information signal spread with a third orthogonal code, the third orthogonal code being a spreading code and being orthogonal to the first orthogonal code and the second orthogonal code, and wherein the receiver further comprises a third despreading section that despreads the result of the demodulation by the second receive section with the third orthogonal code.

13. The receiver of claim 10, further comprising a plurality of reception antennas whose planes of polarization are spatially orthogonal to one another, wherein the first receive section receives the first radio wave via one of the plurality of reception antennas, and wherein the second receive section receives the second radio wave via the one and another of the plurality of reception antennas.

14. The receiver of claim 13, 50 wherein the first receive section and the second receive section receive the first radio wave and the second radio wave at the same time.

15. The receiver of claim 11, further comprising a restoration section that restores the information signal on the basis of the difference between an output signal of the first despreading section and an output signal of the second despreading section.

16. The receiver of claim 10, further comprising: three or more reception antennas whose planes of polarization are spatially orthogonal; and a polarization rotation circuit that applies weighting on reception signals of the three or more reception antennas to output two pseudo reception signals, wherein the first receive section receives one of the two pseudo reception signals as the first radio wave, and wherein the second receive section receives both of the two pseudo reception signals as the second radio wave.

FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“TRANSMITTER AND RECEIVER”
HITACHI, LTD., of 6-6, Marunouchi 1-chome, Chiyoda-ku,
Tokyo 1008280, Japan
The following specification particularly describes the invention and the manner in
which it is to be performed.
2
DESCRIPTION
Title: TRANSMITTER AND RECEIVER
Technical Field
[0001] The present invention relates to a transmitter and a receiver.
Background Art
[0002] When a transmitter and a receiver communicate with each other by radio
communication and a radio wave scatterer that reflects and/or diffracts
electromagnetic waves is present between the transmitter and the receiver, a
plurality of radio propagation paths are formed between the transmitter and the
receiver. When the plurality of radio propagation paths is simply used together,
the radio communication is interrupted when any one of the propagation paths is
altered by being affected naturally or artificially. For this reason, it is desirable
to eliminate the correlation of the plurality of radio propagation paths.
[0003] For example, Patent Literature 1 listed below states that "According to
the present invention, in connection with a demodulation system of
MIMO-OFDM transmission, when performing MIMO-OFDM transmission using
multiple transmission antennas and reception antennas in an outdoor line-of-sight
environment by assigning different polarizations such as orthogonal polarizations
to respective transmission antennas and reception antennas, using a cross
polarization power ratio measured on a receiver in adjusting XPD of transmission
antennas of the transmitter and the receiver efficiently reduces correlation of
propagation paths and inhibits the reduction of the effect of receive diversity,
which is due to the use of polarized waves, to improve the MIMO-OFDM
3
transmission characteristics" (see paragraph 0022).
Prior Art Document
Patent Document
[0004] Patent document 1: Japanese Patent Application Publication No.
2012-49740
Summary of the Invention
Problems to be Solved by the Invention
[0005] According to the technique disclosed in Patent Literature 1, correlation of
a plurality of radio propagation paths can be reduced to a certain degree.
However, in the technique disclosed in Patent Literature 1, as the transmitter and
the receiver use the plurality of propagation paths together, there is limitation in
the ability of inhibiting correlation of the plurality of radio propagation paths, and
appropriate communication is not always achieved. The present invention is
made in view of the above-described circumstances, and it is an object of the
present invention to provide a transmitter and a receiver that achieve appropriate
communication.
Solution to Problem
[0006] To solve the above-described problem, the present invention provides a
transmitter including: a first transmission block that generates a first radio wave
having an information signal modulated thereon and having a plane of
polarization that rotates; and a second transmission block that generates a second
radio wave having the information signal modulated thereon and having a plane of
polarization that is fixed.
4
Effects of Invention
[0007] The present invention achieves appropriate communication between the
transmitter and the receiver.
Brief Description of Drawings
[0008] FIG. 1 is a block diagram of a radio communication system according to
a first embodiment of the present invention.
FIG. 2 is a block diagram of a radio communication system according to
a second embodiment of the present invention.
FIG. 3 is a block diagram of a radio communication system according to
a third embodiment of the present invention.
FIG. 4 is a block diagram of a radio communication system according to
a fourth embodiment of the present invention.
FIG. 5 is a block diagram of a transmitter according to a fifth
embodiment of the present invention.
FIG. 6 is a block diagram of a receiver according to a sixth embodiment
of the present invention.
FIG. 7 is a block diagram of a radio communication system according to
a seventh embodiment of the present invention.
FIG. 8 is a block diagram of a radio communication system according to
an eighth embodiment of the present invention.
FIG. 9 is a block diagram of a radio communication system according to
a ninth embodiment of the present invention.
FIG. 10 is a block diagram (1/2) of a transceiver according to a tenth
5
embodiment of the present invention.
FIG. 11 is a block diagram (2/2) of the transceiver according to the tenth
embodiment of the present invention.
FIG. 12 is a schematic view of an elevator system according to an
eleventh embodiment of the present invention.
FIG. 13 is a schematic view of a substation system according to a twelfth
embodiment of the present invention.
Embodiments for Carrying out the Invention
[0009] [First Embodiment]
FIG. 1 is a block diagram of a radio communication system according to
a first embodiment of the present invention. The radio communication system
according to the present embodiment includes a transmitter 201 and a receiver
301.
[0010]
The transmitter 201 has transmission antennas 1 and 2 which are spatially
orthogonal to each other. For example, when the plane of polarization of the
transmission antenna 1 is vertical (V), the plane of polarization of the
transmission antenna 2 is horizontal (H). The transmitter 201 has an information
signal generator 4, a transmission block 2011 (first transmission block), and a
transmission block 2012 (second transmission block). The information signal
generator 4 outputs an information signal of an angular frequency ωI, which is to
be transmitted to the receiver 301. The transmission blocks 2011 and 2012
modulate the information signal to generate transmission signals in the
6
radio-frequency band, and feed the generated transmission signals to the
transmission antennas 1 and 2.
[0011] In the transmission block 2011, an orthogonal code generating circuit
(denoted OCG in the drawings) 5 outputs an orthogonal code #1 (first orthogonal
code), which is a spreading code, and a multiplier 7 (first superimposing circuit)
multiplies the orthogonal code #1 by the information signal, to spread the
information signal with the orthogonal code #1. Here, a description is given of
the term "rotational polarization", which is used in the description below. As
polarization of electromagnetic wave, linear polarization and circular polarization
are known. A plane defined by the direction of oscillation of the electric field of
an electromagnetic wave and the propagation direction of the electromagnetic
wave is called plane of polarization. Polarization whose plane of polarization is
fixed is called linear polarization. Polarization whose plane of polarization
rotates is called circular polarization. Rotational polarization is a kind of circular
polarization, and specifically means polarization whose plane of polarization
rotates at a rotational frequency lower than the carrier frequency of the
electromagnetic wave.
[0012] When the rotational angular frequency of the plane of polarization of
rotational polarization is ωp (rotational frequency; ωp > ωI), and time is t, a
polarization rotational frequency cosine oscillator 11 (polarization plane rotating
oscillator) outputs cosωpt, and a polarization rotational frequency sine oscillator
12 (polarization plane rotating oscillator) outputs sinωpt. A multiplier 13
multiplies the output signal of the multiplier 7 by cosωpt, and a multiplier 14
7
multiplies the output signal of the multiplier 7 by sinωpt. When the carrier
angular frequency is ωc (carrier frequency; ωc>ωp), a carrier frequency cosine
oscillator 19 (carrier oscillator) outputs cosωct.
[0013] A multiplier 17 multiplies the output signal of the multiplier 13 by cosωct,
and feeds the result of the multiplication to the transmission antenna 1. A
multiplier 18 multiplies the output signal of the multiplier 14 by cosωct, and feeds
the result of the multiplication to the transmission antenna 2. The
electromagnetic wave transmitted from the transmission block 2011 via the
transmission antennas 1 and 2 is a rotationally polarized electromagnetic wave
having the rotational angular frequency ωp, and propagates an information signal
spread with the orthogonal code #1.
[0014] In the transmission block 2012, an orthogonal code generating circuit 6
outputs an orthogonal code #2 (second orthogonal code), which is a spreading
code, and a multiplier 8 (second superimposing circuit) multiplies the orthogonal
code #2 by the information signal. The orthogonal code #1 and the orthogonal
code #2 are orthogonal to each other. A carrier frequency cosine oscillator 21
outputs cos(ωc-ωp)t, and a carrier frequency cosine oscillator 22 outputs
cos(ωc+ωp)t.
[0015] A multiplier 23 multiplies the output signal of the multiplier 8 by
cos(ωc-ωp)t. The result of this multiplication is fed to the transmission antenna 1
as a transmission signal whose carrier angular frequency is ωc-ωp. A multiplier
24 multiplies the output signal of the multiplier 8 by cos(ωc+ωp)t. The result of
this multiplication is fed to the transmission antenna 2 as a transmission signal
8
whose carrier angular frequency is ωc+ωp. The electromagnetic waves
transmitted from the transmission block 2012 via the transmission antennas 1 and
2 are each a linearly polarized electromagnetic wave with a fixed plane of
polarization and each propagate an information signal spread with the orthogonal
code #2.
[0016]
The receiver 301 has spatially orthogonal reception antennas 61 and 62 to
receive the electromagnetic waves transmitted from the transmitter 201. For
example, when the plane of polarization of the reception antenna 61 is vertical (V),
the plane of polarization of the reception antenna 62 is horizontal (H). A
multiplier 73 (first receive section) multiplies the reception signal of the reception
antenna 61 by cosωct outputted from a carrier frequency cosine oscillator 72. A
multiplier 74 (first despreading section) multiplies the orthogonal code #1
outputted from an orthogonal code generating circuit 71 (first despreading
section) by the output signal of the multiplier 73.
[0017] The multiplier 73 demodulate an electromagnetic wave whose carrier
angular frequency is ωc, and the result of the demodulation is despread at the
multiplier 74. Here, the electromagnetic wave whose carrier angular frequency
is ωc is one generated by the transmission block 2011 and rotationally polarized
via the transmission antennas 1 and 2. At timings when the plane of polarization
of the rotationally polarized electromagnetic wave orthogonally crosses the plane
of polarization of the reception antenna 61, the reception antenna 61 cannot
receive the rotationally polarized electromagnetic wave, and thus the signals
9
outputted by the multipliers 73 and 74 become substantially zero. Those timings
arrive in synchronization with the rotation cycle of the rotational polarization, and
thus can each be represented by an "angle of plane of polarization of rotational
polarization". Hereinafter, this angle is referred to as "non-detection angle θz".
The output signal of the multiplier 74 is ideally identical to the original
information signal outputted by the information signal generator 4 in the
transmitter 201, except at the timings of the non-detection angle θz.
[0018] A carrier frequency cosine oscillator 82 outputs cos(ωc-ωp)t, and a
multiplier 83 (second receive section) multiplies cos(ωc-ωp)t by the reception
signal of the reception antenna 61. A multiplier 84 (second despreading section)
multiplies the orthogonal code #2 outputted from an orthogonal code generating
circuit 81 (second despreading section) by the output signal of the multiplier 83.
With this processing, the reception signal received by the reception antenna 61
and having a carrier angular frequency ωc-ωp is demodulated and despreaded via
the multipliers 83 and 84.
[0019] A carrier frequency cosine oscillator 86 outputs cos(ωc+ωp)t, and a
multiplier 87 (second receive section) multiplies cos(ωc+ωp)t by the reception
signal of the reception antenna 62. A multiplier 88 (second despreading section)
multiplies the orthogonal code #2 outputted from the orthogonal code generating
circuit 81 by the output signal of the multiplier 87. With this processing, the
reception signal received by the reception antenna 62 and having a carrier angular
frequency ωc+ωp is demodulated and despreaded via the multipliers 87 and 88.
[0020] An adder 64 combines the signals outputted from the multipliers 84 and
10
88. Accordingly, the combined signal is ideally identical to the information
signal originally outputted by the information signal generator 4 in the transmitter
201. The electromagnetic wave having the carrier angular frequency ωc+ωp and
having a fixed plane of polarization as well as the electromagnetic wave having
the carrier angular frequency ωc-ωp and having a fixed plane of polarization
propagate an identical information signal with different carrier angular
frequencies and different planes of polarization. Accordingly, by separately
demodulating and despreading these electromagnetic waves and then combining
the resultant signals, the adder 64 is able to continue to output the information
signal at a substantially constant strength.
[0021] A subtractor 65 subtracts the output signal of the multiplier 74 from the
output signal of the adder 64, and outputs the result of the subtraction. As
described above, except at the non-detection angle θz, the output signal of the
multiplier 74 is ideally identical to the original information signal. Accordingly,
except at the non-detection angle θz, ideally, the output signal of the subtractor 65
is zero. Meanwhile, at the non-detection angle θz, the output signal of the
multiplier 74 is substantially zero, and thus, ideally, the subtractor 65 outputs the
original information signal at the non-detection angle θz.
[0022] When a baseband block (denoted by "BB Block" in the drawings) 66
receives information signal from the subtractor 65 at the non-detection angle θz,
the baseband block carries out processing on the basis of the information signal.
Note that the non-detection angle θz is not necessarily singular. If a plurality of
radio propagation paths are present, a plurality of non-detection angles θz occurs.
11
Those non-detection angles are denoted by θz1, θz2, ... , θzn. The subtractor 65
outputs information signal at each of the non-detection angles θz1, θz2, ... , and θzn.
In this case, the baseband block 66 extracts information signal correspondingly to
the non-detection angles θz1, θz2, ... , and θzn, and carries out processing on the
basis of the information signal at a particular non-detection angle θzm, where 1 
m n.
[0023]
The electromagnetic wave transmitted from the transmitter 201 is
reflected by various radio wave scatterers before reaching the receiver 301.
Assuming that a surface of a radio wave scatterer obeys Snell's law of reflection,
when an electromagnetic wave is reflected by the surface, the electromagnetic
wave undergoes a shift in polarization vector inherent to a normal vector of the
surface of the radio scatterer and an incident vector of the electromagnetic wave
incident on the surface. The electromagnetic wave reaches the receiver 301
through a plurality of radio propagation paths that cause shifts in polarization
vector.
[0024] Each of the radio propagation paths generally causes a different inherent
polarization shift. The receiver 301 of the present embodiment is capable of
selectively extracting only the signal transmitted via an electromagnetic wave
having particular polarization (i.e., an electromagnetic wave having a particular
non-detection angle θzm). This is equivalent to selectively capturing only an
information signal that has reached the receiver 301 via a particular radio
propagation path.
12
[0025] As described above, the present embodiment is capable of extracting
information signals transmitted via a plurality of radio propagation paths
chronologically according to the non-detection angles θz1, θz2, ... , and θzn, to
capture only an information signal at a particular non-detection angle θzm. That
is, the present embodiment is capable of selecting a particular radio propagation
path from a plurality of radio propagation paths, and transmitting the information
signal through the selected radio propagation path. This enables the present
embodiment to reduce the correlation of the plurality of radio propagation paths
and have strong resistance to obstacles and interferences of the plurality of radio
propagation paths caused by a natural event or an artificial operation.
[0026] [Second Embodiment]
FIG. 2 is a block diagram of a radio communication system according to
a second embodiment of the present invention. Note that, in FIG. 2, elements
corresponding to those shown in FIG. 1 are respectively given the same symbols
and duplicated descriptions thereof may be omitted. The radio communication
system according to the present embodiment includes the transmitter 201 and a
receiver 302. In the present embodiment, the transmitter 201 has the same
configuration of that of the first embodiment (see FIG. 1). Thus, a detailed
description is given of the configuration of the receiver 302.
[0027] The receiver 302 has three reception antennas 61, 62, and 63, which are
spatially orthogonal to each other. Three signals received via the three reception
antennas 61, 62, and 63 are passed to a polarization rotation circuit 60. The
polarization rotation circuit 60 converts the received three signals into two pseudo
13
reception signals (V', H'), which are spatially orthogonal to each other, and
outputs the two pseudo reception signals (V', H').
[0028] In other words, the polarization rotation circuit 60 applies angular
weighting on the three reception signals from the reception antennas 61, 62, and
63, to convert the three reception signals into two pseudo reception signals (V',H').
Angular weighting is, for example, Euler angles such that two linearly polarized
antennas are virtually formed in the three dimensional space by the reception
antennas 61, 62, and 63, which are spatially orthogonal to one another. That is,
the polarization rotation circuit 60 operates so that the receiver 302 virtually forms
two spatially orthogonal antennas oriented in a freely-selected direction.
[0029] The pseudo reception signals (V',H') outputted from the polarization
rotation circuit 60 are passed to the multipliers 73 and 83. The pseudo reception
signal (H') outputted from the polarization rotation circuit 60 is passed to the
multiplier 87.
In the receiver 302, the configuration from the multipliers 73, 83, and 87
to the subtractor 65 is the same as that of the first embodiment (see FIG. 1)
The baseband block 66 extracts information signal correspondingly to the
non-detection angles θz1, θz2, ... , and θzn, and carries out processing on the basis of
the information signal at a particular non-detection angle θzm (1  m  n) in the
same manner as in the first embodiment.
[0030] In addition, the baseband block 66 controls the angular weighting of the
polarization rotation circuit 60 so that, among the information signals outputted
from the subtractor 65, the information signal at the particular non-detection angle
14
θzm exhibits good communication quality. A plurality of rotationally polarized
electromagnetic waves reaches the receiver 302 via a plurality of radio
propagation paths and then are combined. The combined electromagnetic wave
has one propagation direction and elliptically rotates at a frequency identical to
the frequency of the rotational polarization.
[0031] When one of the two antennas virtually formed by the polarization
rotation circuit 60 is oriented in that propagation direction, the reception strength
of the rotationally polarized wave received by the receiver 302 becomes zero.
Meanwhile, when one of the other virtually formed antennas is oriented
orthogonal to that propagation direction, the reception strength of the rotationally
polarized wave received by the receiver 302 is maximized. The baseband block
66 controls the polarization rotation circuit 60 to set the angular weighting so that
a signal with as much intensity as possible (ideally, signal with a maximum
intensity) is received by the two antennas virtually formed.
[0032] As understood from the above description, the receiver 302 according to
the present embodiment is capable of improving receive sensitivity to a particular
radio propagation path, and thus is capable of improving the quality of the
restored information signal compared to the receiver 301 of the first embodiment.
[0033] [Third Embodiment]
FIG. 3 is a block diagram of a radio communication system according to
a third embodiment of the present invention. Note that, in FIG. 3, elements
corresponding to those shown in FIGS. 1 and 2 are respectively given the same
symbols and duplicated descriptions thereof may be omitted.
15
The radio communication system according to the present embodiment
has a transmitter 203 and a receiver 303. The transmitter 203 has two
transmission blocks 2031 and 2032 that each receive information signal passed
from the information signal generator 4 and feed it to the transmission antennas 1
and 2.
[0034]
In the transmission block 2031 of the transmitter 203, the information
signal outputted from the information signal generator 4 is spread by the
multiplier 7 with the orthogonal code #1. A carrier frequency sine oscillator 31
(first sine oscillator) outputs sinω1t, and a carrier frequency sine oscillator 32
(second sine oscillator) outputs sinω2t. Here, the angular frequency ω1 (carrier
frequency; first frequency) and the angular frequency ω2 (carrier frequency;
second frequency) are carrier angular frequencies close to each other (for example,
ω1 is within plus or minus 10% of ω2). A multiplier 33 multiplies the output
signal of the multiplier 7 by sinω1t, and a multiplier 34 multiplies the output
signal of the multiplier 7 by sinω2t. A subtractor 35 subtracts the output signal of
the multiplier 34 from the output signal of the multiplier 33, and feeds the result
of the subtraction to the transmission antenna 1. As a result, the electromagnetic
wave transmitted by the transmission block 2031 via the transmission antenna 1 is
a sine beat wave whose beat angular frequency is half the difference between the
two angular frequencies ω1 and ω2.
[0035] Meanwhile, a carrier frequency cosine oscillator 41 (first cosine
oscillator) outputs cosω1t, and a carrier frequency cosine oscillator 42 (second
16
cosine oscillator) outputs cosω2t. A multiplier 43 multiplies the output signal of
the multiplier 7 by cosω1t, and a multiplier 44 multiplies the output signal of the
multiplier 7 by cosω2t. An adder 45 adds up the output signals of the multipliers
43 and 44, and feeds the result of the addition to the transmission antenna 2. As
a result, the electromagnetic wave transmitted by the transmission block 2031 via
the transmission antenna 2 is a cosine beat wave whose beat angular frequency is
half the difference between the two angular frequencies ω1 and ω2.
[0036] When the electromagnetic waves transmitted by the transmission block
2031 via the transmission antennas 1 and 2 are combined in space, a rotationally
polarized electromagnetic wave having a plane of polarization rotating at the
above-described beat angular frequency is generated. With this rotationally
polarized electromagnetic wave, the information signal spread with the orthogonal
code #1 is transmitted.
[0037] In the transmission block 2032, the information signal outputted from the
information signal generator 4 is spread with the orthogonal code #2 by the
multiplier 8. A multiplier 46 multiplies the output signal of the multiplier 8 by
cosω1t, and feeds the result of the multiplication to the transmission antenna 1.
A multiplier 47 multiplies the output signal of the multiplier 8 by cosω2t, and
feeds the result of the multiplication to the transmission antenna 2. The
electromagnetic waves transmitted from the transmission block 2032 via the
transmission antennas 1 and 2 are each a linearly polarized electromagnetic wave
with a fixed plane of polarization, and each propagate an information signal
spread with the orthogonal code #2.
17
[0038]
A receiver 303 has, similarly to the receiver 302 (see FIG. 2) of the
second embodiment, the three reception antennas 61, 62, and 63 which are
spatially orthogonal to one another; and the polarization rotation circuit 60 that
virtually forms two spatially orthogonal antennas by applying angular weighting
on the three reception signals from the reception antennas 61, 62, and 63, to
convert the three signals into two pseudo reception signals.
[0039] A multiplier 103 multiplies one (V') of the generated two pseudo
reception signals by cosω1t outputted by the carrier frequency cosine oscillator
101. A multiplier 104 multiplies the one (V') of the generated pseudo reception
signals by cosω2t outputted by the carrier frequency cosine oscillator 102. An
adder 105 adds up the results of the multiplications by the multipliers 103 and 104.
A multiplier 74 multiplies the output signal of the adder 105 by the orthogonal
code #1 outputted by the orthogonal code generating circuit 71. With this
processing, the information signal spread with the orthogonal code #1 is
demodulated and despread.
[0040] The two pseudo reception signals outputted from the polarization rotation
circuit 60 are respectively passed to multipliers 106 and 107. The multiplier 106
multiplies one (H') of the two pseudo reception signals by cosω1t. The multiplier
107 multiplies the other one (V') of the two pseudo reception signals by cosω2t.
An adder 108 adds up the output signals of the multipliers 106 and 107, the
multiplier 84 multiplies the result of this addition by the orthogonal code #2
outputted by the orthogonal code generating circuit 81.
18
With this processing, the information signal spread with the orthogonal
code #2 is demodulated and despread.
[0041] The subtractor 65 (restoration section) subtracts the output signal of the
multiplier 84 from the output signal of the multiplier 74. With this processing,
similarly to the first and second embodiments, the subtractor 65 outputs
information signal at each of the non-detection angles θz1, θz2, ... , and θzn. The
baseband block 66 functions in the same manner as that of the second
embodiment. That is, the baseband block 66 extracts information signals
corresponding to the non-detection angles θz1, θz2, ... , and θzn, and carries out
processing on the basis of the information signal at a particular non-detection
angle θzm, where 1  m  n. In addition, the baseband block 66 controls the
angular weighting of the polarization rotation circuit 60 so that the information
signal outputted from the subtractor 65 at a non-detection angle θzm exhibits good
communication quality.
[0042] The present embodiment uses the angular frequencies ω1 and ω2 close to
each other instead of the angular frequencies ωc and ωp used in the second
embodiment (see FIG. 2). This facilitates implementing many elements
contained in the transmitter 203 and receiver 303 by using digital signal
processors (DSP) or the like. This allows the transmitter 203 and the receiver
303 to be reduced in size, and to have reduced changes of circuit elements due to
aging and temperature change, and thus to achieve high reliability and a long life
span of the device.
[0043] [Fourth Embodiment]
19
FIG. 4 is a block diagram of a radio communication system according to
a fourth embodiment of the present invention. Note that, in FIG. 4, elements
corresponding to those shown in FIGS. 1 to 3 are respectively given the same
symbols and duplicated descriptions thereof may be omitted.
The radio communication system according to the present embodiment
has a transmitter 204 and a receiver 304. The transmitter 204 has the two
transmission blocks 2011 and 2042 that feed information signal passed from the
information signal generator 4 to the transmission antennas 1 and 2, respectively.
[0044]
First, the transmission block 2011 is the same as that of the first
embodiment (see FIG. 1). That is, the transmission block 2011 spreads
information signal with the orthogonal code #1 and outputs a rotationally
polarized electromagnetic wave whose carrier angular frequency is ωc and whose
plane of polarization rotates at the rotational angular frequency ωp, via the
transmission antennas 1 and 2. In the transmission block 2042, the information
signal outputted from the information signal generator 4 is spread with the
orthogonal code #2 by the multiplier 8.
[0045] A carrier frequency cosine oscillator 121 outputs cosωct, and a carrier
frequency sine oscillator 122 outputs sinωct. The multiplier 23 multiplies the
output signal of the multiplier 8 by cosωct. The multiplier 24 multiplies the
output signal of the multiplier 8 by sinωct. The output signals of the multipliers
23 and 24 are respectively fed to the transmission antennas 1 and 2. With this
processing, the transmission block 2042 transmits temporally orthogonal
20
electromagnetic waves via the transmission antennas 1 and 2 by using the cosine
wave cosωct and the sine wave sinωct. These electromagnetic waves are each a
linearly polarized electromagnetic wave with a fixed plane of polarization, and
each propagates information signal spread with the orthogonal code #2.
[0046]
Comparing the configuration of the receiver 304 with that of the receiver
302 of the second embodiment (see FIG. 2), a carrier frequency cosine oscillator
182 is provided in place of the carrier frequency cosine oscillator 82, and a carrier
frequency sine oscillator 186 is provided in place of the carrier frequency cosine
oscillator 86. The carrier frequency cosine oscillator 182 outputs cosωct, and
carrier frequency sine oscillator 186 outputs sinωct. Except these, the
configuration of the receiver 304 is the same as that of the receiver 302.
[0047] In the present embodiment, the transmitter 204 transmits, via two
temporally orthogonal electromagnetic waves each having a fixed plane of
polarization, the same information signal to the receiver 304. These two
electromagnetic waves are separately demodulated and despread, and then the
resulted signals are combined into an information signal via the multipliers 84 and
88 and the adder 64, which allows the adder 64 to continue to output the
information signal at a substantially constant strength.
[0048] The multiplier 74 outputs an information signal that becomes zero at
non-detection angles θz1, θz2, ... , and θzn, in the same manner as in the first and
second embodiments. Accordingly, the subtractor 65 outputs the information
signal at each of the non-detection angles θz1, θz2, ... , and θzn. The baseband
21
block 66 carries out processing on the basis of the information signal at a
particular non-detection angle θzm, and controls the angular weighting of the
polarization rotation circuit 60 so that the information signal at the non-detection
angle θzm exhibits good communication quality.
[0049] According to the present embodiment, as the number of used carrier
frequencies is smaller than that in the first to third embodiments, the amount of
spurious signal caused by nonlinearity of parts of the transmitter 204 can be
reduced and thus improvement of radio communication quality can be achieved.
[0050] [Fifth Embodiment]
FIG. 5 is a block diagram of a radio communication system according to
a fifth embodiment of the present invention. Note that, in FIG. 5, elements
corresponding to those shown in FIGS. 1 to 4 are respectively given the same
symbols and duplicated descriptions thereof may be omitted. The radio
communication system according to the present embodiment has a transmitter 205
and a receiver (not shown). The receiver 301 (see FIG. 1) according to the first
embodiment or the receiver 302 (see FIG. 2) according to the second embodiment
may be applicable as the receiver for the present embodiment.
[0051] The transmitter 205 and the transmitter 201 (see FIG. 1) of the first
embodiment are the same in that they have the transmission blocks 2011 and 2012,
the transmission antennas 1 and 2, and the information signal generator 4. The
transmitter 205 further has a synchronization signal generating circuit (denoted by
SCG in the drawings) 9 and a signal switching circuit 27. The synchronization
signal generating circuit 9 outputs a predetermined synchronization signal. The
22
signal switching circuit 27 selects one of the information signal outputted by the
information signal generator 4 and the synchronization signal outputted by the
synchronization signal generating circuit 9, at regular time intervals or at
non-regular time intervals, to pass the selected signal to both the transmission
blocks 2011 and 2012.
[0052] The synchronization signal generated by the synchronization signal
generating circuit 9 has strong correlation. Thus, the transmitter and the receiver
can establish high-accuracy synchronization therebetween by restoring the
synchronization signal in the receiver. In rotational polarization, the polarization
varies with time. And thus, when high-accuracy synchronization is established
between the transmitter and the receiver, the receiver is able to identify the
polarization with high reliability. Each of the plurality of waves reaching the
receiver via a different propagation path has undergone a polarization shift
inherent to the propagation path. According to the present embodiment, the
receiver is able to improve the accuracy of distinguishing between plural waves
reaching the receiver on the basis of the polarization of the waves, and thus
improve the accuracy of distinguishing between the propagation paths between
the transmitter and the receiver. Therefore, the present embodiment improves
the robustness against modifications made to radio propagation paths by an
outsider.
[0053] [Sixth Embodiment]
FIG. 6 is a block diagram of a radio communication system according to
a sixth embodiment of the present invention. Note that, in FIG. 6, elements
23
corresponding to those shown in FIGS. 1 to 5 are respectively given the same
symbols and duplicated descriptions thereof may be omitted. The radio
communication system according to the present embodiment has the transmitter
203 (see FIG. 3) and a receiver 306. In FIG. 6, illustration of the transmitter 203
is omitted.
[0054] The receiver 306 has: the three reception antennas 61, 62, and 63, which
are spatially orthogonal to one another; and three receive blocks 3061, 3062, and
3063 which respectively process the reception signals of the reception antennas 61,
62, and 63. In the receive block 3061, cosine oscillators 141 and 151
respectively output cosω1t and cosω2t, and sine oscillators 145 and 155
respectively output sinω1t and sinω2t. Orthogonal code generating circuits 142
and 146 each output orthogonal code #1, and orthogonal code generating circuits
152 and 156 each output orthogonal code #2.
[0055] The reception signal of the reception antenna 61 is split into four
branches, and multipliers 143, 147, 153, and 157 respectively multiply the four
signals by cosω1t, sinω1t, cosω2t, and sinω2t. Multipliers 144 and 148
respectively multiply the output signals of the multipliers 143 and 147 by the
orthogonal code #1 to restore the information signal. Multipliers 154 and 158
respectively multiply the output signals of the multipliers 153 and 157 by the
orthogonal code #2 to restore the information signal. In this manner, the four
information signals are generated by the multipliers 144, 148, 154, and 158 and
passed to an arithmetic section 50.
[0056] The receive block 3062 has: cosine oscillators 241 and 251; sine
24
oscillators 245 and 255; multipliers 243, 244, 247, 248, 253, 254, 257, and 258;
orthogonal code generating circuits 242 and 246 that each output the orthogonal
code #1; and orthogonal code generating circuits 252 and 256 that each output the
orthogonal code #2. These respectively correspond to the cosine oscillators 141
and 151; the sine oscillators 145 and 155; the multipliers 143, 144, 147, 148, 153,
154, 157, and 158; the orthogonal code generating circuits 142 and 146; and the
orthogonal code generating circuits 152 and 156 in the above-described receive
block 3061. Thus, the receive block 3062 performs the same processing as the
processing of the receive block 3061 on the reception signal of the reception
antenna 62, to pass four information signals to the arithmetic section 50.
[0057] The receive block 3063 has: cosine oscillators 341 and 351; sine
oscillators 345 and 355; multipliers 343, 344, 347, 348, 353, 354, 357, and 358;
orthogonal code generating circuits 342 and 346 which each output the orthogonal
code #1; and orthogonal code generating circuits 352 and 356 which each output
the orthogonal code #2. These correspond to the respective elements of the
above-described receive block 3061. The receive block 3063 performs the same
processing as the processing of the receive block 3061 on the reception signal of
the reception antenna 63, to pass four information signals to the arithmetic section
50.
[0058] The arithmetic section 50 carries out processing like weighting, addition
and subtraction on the 12 (4 × 3) information signals and passes the result of the
processing to the baseband block 66. More specifically, the arithmetic section 50
assumes the functions of the polarization rotation circuit 60, the subtractor 65 and
25
the like in the receiver 303 in the third embodiment (FIG. 3). With this
configuration, similarly to the subtractor 65 of the third embodiment, the
arithmetic section 50 outputs the information signal at each of the non-detection
angles θz1, θz2, ... , and θzn. The baseband block 66 carries out processing on the
basis of the information signal at a particular non-detection angle θzm, and controls
various constants of the arithmetic section 50 so that the information signal at the
non-detection angle θzm exhibits good communication quality.
[0059] FIG. 6 shows 12 pieces of parts each of which has the substantially same
configuration as the part consisting of the cosine oscillator 141, the orthogonal
code generating circuit 142, and the multipliers 143 and 144. This means that,
when constructing the receiver 306 by using a DSP, the receive blocks 3061, 3062,
and 3063 can be implemented by looping predetermined microprogram
instructions 12 times. As understood from the above, according to the present
embodiment, constructing the receiver 306 by using a DSP will reduce the number
of microprogram instructions, and thus reduce the amount of memory for storing
the microprogram instructions as well as the required design man-hours.
[0060] [Seventh Embodiment]
FIG. 7 is a block diagram of a radio communication system according to
a seventh embodiment of the present invention. Note that, in FIG. 7, elements
corresponding to those shown in FIGS. 1 to 6 are respectively given the same
symbols and duplicated descriptions thereof may be omitted. The radio
communication system according to the present embodiment has a transmitter 207
and a receiver 307.
26
[0061]
The transmitter 207 has the information signal generator 4; a BPSK
modulation circuit 28; transmission blocks 2071 and 2072; and the transmission
antennas 1 and 2. In the transmitter 207, the BPSK modulation circuit 28
converts the information signal outputted from the information signal generator 4
into a binary digital signal. The multiplier 7 in the transmission block 2071
multiplies the orthogonal code #1 by the binary digital signal, and outputs the
result of the multiplication. The multipliers 13 and 14 respectively multiply the
result of the multiplication by cosωpt and sinωpt. Note that ωp is, similar to that
of the first embodiment, the rotational angular frequency of the rotational
polarization.
[0062] A clock circuit 219 outputs a clock signal of a carrier frequency fc.
Delta sigma circuits 217 and 218 respectively sample the output signals of the
multipliers 13 and 14 at the carrier frequency fc. Bandpass filters 15 and 16
respectively extract frequency components near the carrier frequency fc out of
(remove harmonic components from) the output signals of the delta sigma circuits
217 and 218, and feed the extracted signals to the transmission antennas 1 and 2.
As a result, the transmission antennas 1 and 2 transmit a rotationally polarized
electromagnetic wave whose plane of polarization rotates at the rotational angular
frequency ωp and whose carrier frequency is fc.
[0063] In a transmission block 2072, the multiplier 8 multiplies the orthogonal
code #2 by the binary digital signal, and outputs the result of the multiplication.
Clock circuits 221 and 222 respectively output clock signals of a carrier frequency
27
fc-fp and a carrier frequency fc+fp. Delta sigma circuits 223 and 224 sample the
output signals of the multiplier 8 respectively at the carrier frequency fc-fp and the
carrier frequency fc+fp. Bandpass filter 25 extracts frequency component near
the carrier frequency fc-fp out of (remove harmonic components from) the output
signal of the delta sigma circuit 223, and feeds the extracted signal to the
transmission antenna 1. Bandpass filter 26 extracts frequency component near
the carrier frequency fc+fp out of (remove harmonic components from) the output
signal of the delta sigma circuit 224, and feeds the extracted signal to the
transmission antenna 2. As a result, the transmission antenna 1 transmits a
linearly polarized electromagnetic wave whose carrier frequency is fc-fp and
whose plane of polarization is fixed, and the transmission antenna 2 transmits a
linearly polarized electromagnetic wave whose carrier frequency is fc+fp and
whose plane of polarization is fixed, to propagate the information signal spread
with the orthogonal code #2.
[0064]
The receiver 307 has, similarly to the receiver 302 (see FIG. 2) of the
second embodiment, the three reception antennas 61, 62, and 63, which are
spatially orthogonal to one another; and the polarization rotation circuit 60 that
virtually forms two spatially orthogonal antennas by applying angular weighting
on the three reception signals from the reception antennas 61, 62, and 63, to
convert the three reception signals into two pseudo reception signals.
[0065] A clock circuit 272 outputs a clock signal of the carrier frequency fc. A
comparator 273 compares the clock signal with the pseudo reception signal (V'),
28
and outputs the result of the comparison. The multiplier 74 multiplies the output
signal of the comparator 273 by the orthogonal code #1 outputted by the
orthogonal code generating circuit 71. With this processing, the information
signal spread with the orthogonal code #1 is demodulated and despread. More
specifically, the multiplier 74 outputs an information signal that becomes zero at
non-detection angles θz1, θz2, ... , and θzn, in the same manner as in the second
embodiments.
[0066] The clock circuits 282 and 287 output clock signals of carrier frequencies
of fc-fp and fc+fp, respectively. A comparator 283 compares the clock signal of
the carrier frequency fc-fp with the pseudo reception signal (V'), and outputs the
result of the comparison. A comparator 286 compares the clock signal of the
carrier frequency fc+fp with the pseudo reception signal (H'), and outputs the result
of the comparison.
The multipliers 84 and 88 respectively multiply the output signals of the
comparators 283 and 286 by the orthogonal code #2 outputted by the orthogonal
code generating circuit 81, and output the respective results of the multiplications,
which are despread information signals.
[0067] The adder 64 combines the information signals outputted from the
multipliers 84 and 88. The information signal outputted from the adder 64 is a
signal which is made by separately demodulating and despreading the two
electromagnetic waves and then combining the despread signals, and thus has
substantially constant strength. Thus, the subtractor 65 outputs the information
signal at each of the non-detection angles θz1, θz2, ... , and θzn, in the same manner
29
as that of the second embodiment (see FIG. 2). The baseband block 66 also
functions in the same manner as that of the second embodiment. The baseband
block 66 carries out processing on the basis of the information signal at a
particular non-detection angle θzm, and controls the angular weighting of the
polarization rotation circuit 60 so that the information signal at the non-detection
angle θzm exhibits good communication quality.
[0068] [Eighth Embodiment]
FIG. 8 is a block diagram of a radio communication system according to
an eighth embodiment of the present invention. Note that, in FIG. 8, elements
corresponding to those shown in FIGS. 1 to 7 are respectively given the same
symbols and duplicated descriptions thereof may be omitted. The radio
communication system according to the present embodiment has a transmitter 208
and a receiver 308.
[0069] The transmitter 208 has the information signal generator 4, a
transmission blocks 2081 and 2082, and the transmission antennas 1 and 2. In
the transmission block 2081, a cyclic code generating circuit (denoted by CCG in
the drawings) 37 outputs a cyclic code #11. The multiplier 7 multiplies the
cyclic code #11 by the information signal, to spread the information signal. The
configuration of the circuits located downstream of the multiplier 7 is the same as
that of the transmission block 2011 (see FIG. 1) in the first embodiment. That is,
the transmission block 2081 spreads the information signal with the cyclic code
#11 and outputs a rotationally polarized electromagnetic wave whose carrier
angular frequency is ωc and whose plane of polarization rotates at the rotational
30
angular frequency ωp, via the transmission antennas 1 and 2.
[0070] In the transmission block 2082, a cyclic code generating circuit 38
outputs a cyclic code #12. The cyclic code #11 and the cyclic code #12 are
orthogonal to each other. The multiplier 8 multiplies the cyclic code #12 by the
information signal, to spread the information signal. The configuration of the
circuits located downstream of the multiplier 8 is the same as that of the
transmission block 2012 in the first embodiment. That is, the transmission block
2082 outputs two linearly polarized electromagnetic waves whose carrier angular
frequencies are respectively ωc-ωp and ωc+ωp and whose planes of polarization are
fixed and orthogonal to each other, via the transmission antennas 1 and 2.
[0071] The receiver 308 has, similarly to the receiver 302 (see FIG. 2) of the
second embodiment, the three reception antennas 61, 62, and 63 which are
spatially orthogonal to one another; and the polarization rotation circuit 60 that
virtually forms two spatially orthogonal antennas by applying angular weighting
on the three reception signals from the reception antennas 61, 62, and 63, to
convert the three reception signals into two pseudo reception signals.
[0072] The multiplier 73 multiplies the pseudo reception signal (V') by cosωct.
That is, a rotationally polarized electromagnetic wave whose carrier angular
frequency is ωc is demodulated by the multiplier 73. However, the reception
strength of the rotationally polarized electromagnetic wave becomes zero at
non-detection angles θz1, θz2, ... , and θzn, which correspond to a plurality of radio
propagation paths. Thus the output signal of the multiplier 73 becomes zero at
timings corresponding to the non-detection angles.
31
[0073] The multiplier 83 multiplies the pseudo reception signal (V') by
cos(ωc-ωp)t. That is, a linearly polarized electromagnetic wave whose carrier
angular frequency is ωc-ωp is demodulated by the multiplier 83. The multiplier
87 multiplies the pseudo reception signal (H') by cos(ωc+ωp)t. That is, a linearly
polarized electromagnetic wave whose carrier angular frequency is ωc+ωp is
demodulated by the multiplier 87.
[0074] A combination circuit 67 combines the signals outputted from the
multipliers 83 and 87. The signal outputted from the combination circuit 67 is a
signal obtained by separately demodulating the two electromagnetic waves and
then combining the demodulated signals, and thus has substantially constant
strength. A multiplier 68 multiplies the output signal of the multiplier 73 by the
output signal of the combination circuit 67. A cyclic code generating circuit 89
outputs the cyclic code #12. A multiplier 69 multiplies the output signal of the
multiplier 68 by the cyclic code #12, and passes the result of the multiplication to
the baseband block 66.
[0075] Except at the timings corresponding to the non-detection angles θz1,
θz2, ... , and θzn, the multiplier 73 outputs the information signal spread with the
cyclic code #11, and the combination circuit 67 outputs the information signal
spread with the cyclic code #12. In those time periods, the output signal of the
multiplier 68 is a signal which is made by spreading the information signal with a
cyclic code (hereinafter referred to as cyclic code #13) that is orthogonal to both
the cyclic code #11 and the cyclic code #12. Thus, the information signal is not
demodulated by the multiplier 69.
32
[0076] Meanwhile, at the timings corresponding to the non-detection angles θz1,
θz2, ... , and θzn, the output signal of the multiplier 73 is zero, and thus the
multiplier 68 outputs a signal made by spreading the information signal with the
cyclic code #12. This signal is demodulated via a multiplier 69, and thus the
multiplier 69 outputs the information signal at the non-detection angles θz1, θz2, ... ,
and θzn. The baseband block 66 carries out processing on the basis of the
information signal at a particular non-detection angle θzm, and controls the angular
weighting of the polarization rotation circuit 60 so that the information signal at
the non-detection angle θzm exhibits good communication quality.
[0077] According to the present embodiment, the number of the code generating
circuits (a total of three of the cyclic code generating circuits 37, 38, and 89) is
smaller than the number of the code generating circuits in the second embodiment
(a total of four of the orthogonal code generating circuits 5, 6, 71, and 81). This
allows the radio communication system to have reduced amount of digital signal
processing in the receiver 308, so that the receiver 308 can be reduced in size and
power consumption.
[0078] [Ninth Embodiment]
FIG. 9 is a block diagram of a radio communication system according to
a ninth embodiment of the present invention. Note that, in FIG. 9, elements
corresponding to those shown in FIGS. 1 to 8 are respectively given the same
symbols and duplicated descriptions thereof may be omitted. The radio
communication system according to the present embodiment has a transmitter 209
and a receiver 309.
33
[0079] The transmitter 209 has the information signal generator 4, the
transmission block 2011, a transmission block 2092, and the transmission
antennas 1 and 2. First, the transmission block 2011 is the same as that of the
first embodiment (see FIG. 1). That is, the transmission block 2011 spreads
information signal with the orthogonal code #1 and outputs a rotationally
polarized electromagnetic wave whose carrier angular frequency is ωc and whose
plane of polarization rotates at the rotational angular frequency ωp, via the
transmission antennas 1 and 2.
[0080] In the transmission block 2092, orthogonal code generating circuits 316
and 317 output the orthogonal code #2 and an orthogonal code #3 (third
orthogonal code) which are orthogonal to each other. The orthogonal codes #2
and #3 are each also orthogonal to the orthogonal code #1. A carrier frequency
cosine oscillator 29 outputs cosωct. The multiplier 318 multiplies the signal
outputted from the information signal generator 4 by the orthogonal code #2, and
outputs the information signal spread with the orthogonal code #2. The
multiplier 319 multiplies the signal outputted from the information signal
generator 4 by the orthogonal code #3, and outputs the information signal spread
with the orthogonal code #3.
[0081] The multiplier 23 multiplies the output signal of the multiplier 318 by
cosωct, and feeds the result of the multiplication to the transmission antenna 1.
The multiplier 24 multiplies the output signal of the multiplier 319 by cosωct, and
feeds the result of the multiplication to the transmission antenna 2. As a result,
the transmission block 2092 outputs two linearly polarized electromagnetic waves
34
whose carrier angular frequencies are ωc and whose planes of polarization are
fixed and orthogonal to each other, via transmission antennas 1 and 2.
[0082] A receiver 309 has, similarly to the receiver 302 (see FIG. 2) of the
second embodiment, the three reception antennas 61, 62, and 63, which are
spatially orthogonal to each other; and the polarization rotation circuit 60 that
virtually forms two spatially orthogonal antennas by applying angular weighting
on the three reception signals from the reception antennas 61, 62, and 63, to
convert the three reception signals into two pseudo reception signals.
[0083] The carrier frequency cosine oscillator 72 outputs cosωct, and the
multiplier 73 multiplies the pseudo reception signal (V') by cosωct. The
multiplier 74 multiplies the orthogonal code #1 outputted from the orthogonal
code generating circuit 71 by the output signal of the multiplier 73. The
multiplier 73 demodulate the electromagnetic waves whose carrier angular
frequency is ωc, and the result of the demodulation is despread with the
orthogonal code #1 at the multiplier 74. Here, the electromagnetic wave spread
with the orthogonal code #1 is one generated by the transmission block 2011 and
rotationally polarized via the transmission antennas 1 and 2. The reception
strength of the rotationally polarized electromagnetic wave spread with
orthogonal code #1 becomes zero at non-detection angles θz1, θz2, ... , and θzn,
which correspond to a plurality of radio propagation paths. Thus, the output
signal of the multiplier 74 becomes zero at timings corresponding to the
non-detection angles.
[0084] A multiplier 384 multiplies the orthogonal code #2 outputted from an
35
orthogonal code generating circuit 381 by the output signal of the multiplier 73.
With this processing, the output signal of the multiplier 73 is despread with the
orthogonal code #2. The carrier frequency cosine oscillator 86 outputs cosωct,
and the multiplier 87 multiplies the pseudo reception signal (H') by cosωct. A
multiplier 388 (third despreading section) multiplies an orthogonal code #3
outputted from an orthogonal code generating circuit 385 by the output signal of
the multiplier 87. The information signal outputted from the adder 64 is a signal
obtained by separately demodulating and despreading the two electromagnetic
waves and then combining the despread signals, and thus has substantially
constant strength.
[0085] Thus, the subtractor 65 outputs the information signal at each of the
non-detection angles θz1, θz2, ... , and θzn, in the same manner as that of the second
embodiment (see FIG. 2). The baseband block 66 also functions in the same
manner as that of the second embodiment. The baseband block 66 carries out
processing on the basis of the information signal at a particular non-detection
angle θzm, and controls the angular weighting of the polarization rotation circuit
60 so that the information signal at the non-detection angle θzm exhibits good
communication quality.
[0086] According to the present embodiment, the number of the oscillators
included in the transmitter 209 is smaller than that in the transmitter 201 (see FIG.
1) of the first and second embodiments.
In FIG. 2, the carrier frequency cosine oscillators 19 and 29 are
illustrated as separate elements. However, because their oscillation frequencies
36
are the same, a single oscillator can be used as the carrier frequency cosine
oscillators 19 and 29. This allows the devices to be reduced in size and power
consumption.
[0087] [Tenth Embodiment]
FIGS. 10 and 11 are block diagrams of a radio communication system
according to a tenth embodiment of the present invention. Note that, in FIGS. 10
and 11, elements corresponding to those shown in FIGS. 1 to 9 are respectively
given the same symbols and duplicated descriptions thereof may be omitted.
The radio communication system according to the present embodiment has two
transceivers that perform bidirectional communication. In FIGS. 10 and 11, only
a transceiver 400, one of the two transceivers, is shown. The transceiver 400 and
the not-shown transceiver on the other end have the same configuration except
that their spreading codes for transmission are different from each other. That is,
the transceiver 400 uses orthogonal codes #1 and #2 as spreading codes for
transmission, and the transceiver on the other end uses orthogonal codes #3 and
#4 as spreading codes for transmission. Note that the orthogonal codes #1 to #4
are orthogonal to one another.
[0088] In FIG. 10, the transceiver 400 has a transmission block 401, circulators
77 and 78, transmission and reception antennas 111 and 112, and a reception
antenna 63. The transmission and reception antennas 111 and 112, and the
reception antenna 63 are spatially orthogonal to one another. The transmission
block 401 has the transmission blocks 2011 and 2012 having the same
configurations as the transmitter 201 (see FIG. 1) of the first embodiment, and has
37
the information signal generator 4. In the present embodiment, the transmission
signals outputted from the transmission blocks 2011 and 2012 are passed to the
circulators 77 and 78.
[0089] The circulators 77 and 78 each rotate the inputted high-frequency signal
in a clockwise direction in a plane corresponding to the drawing plane of FIG. 10.
Thus, the transmission signals passed to the circulators 77 and 78 are transmitted
to the transceiver (not shown) on the other end, respectively via the transmission
and reception antennas 111 and 112. The transmission and reception antennas
111 and 112, and reception antenna 63 receive electromagnetic waves transmitted
from the transceiver on the other end. The electromagnetic waves received by
the transmission and reception antennas 111 and 112 are outputted via the
circulators 77 and 78 as reception signals *1 and *3. The electromagnetic wave
received by the reception antenna 63 is outputted as is as reception signal *2.
[0090] The transceiver 400 has a receive block 402 shown in FIG. 11. The
reception signals *1, *2, and *3 are passed to the receive block 402. The receive
block 402 has the same configuration as that of the receiver 302 (see FIG. 2) of
the second embodiment, except that, in the receive block 402, the orthogonal code
generating circuits 71 and 81 respectively output orthogonal codes #3 and #4, in
tune with the orthogonal codes for transmission of the not-shown transceiver on
the other end.
[0091] The configuration of the second embodiment (see FIG. 2) is one for
unidirectional communication. Thus, in order to perform bidirectional
communication, two sets of the transmitter 201 and the receiver 302 are necessary.
38
Compared with this configuration, the configuration of the present embodiment
requires smaller number of antennas because the transmission and reception
antennas 111 and 112 can be shared between the transmission block 401 and the
receive block 402, so that the device can be reduced in size and produced at a low
cost, and can have a higher degree of freedom for installation location of the
device.
[0092] [Eleventh Embodiment]
Next, FIG. 12 is an schematic view of an elevator system 1100 according
to an eleventh embodiment of the present invention.
The elevator system 1100 of the present embodiment includes a building
1101 and an elevator car 1111 that moves up and down in the building 1101. The
building 1101 is arranged with a base station radio 1103a and an antenna 1102a,
which are disposed on a floor of the building 1101. The building 1101 is
arranged with a base station radio 1103b and an antenna 1102b, which are
disposed on a ceiling of the building 1101.
[0093] Attached to the elevator car 1111 are antennas 1112a and 1112b, a
terminal radio 1113, and a high-frequency cable 1114 connecting the foregoing.
The base station radios 1103a and 1103b, terminal radio 1113, and the antennas
1102a, 1102b, 1112a, and 1112b are, for example, configured similarly to the
transceiver 400 (see FIGS. 10 and 11) in the tenth embodiment. With this
configuration, the terminal radio 1113 bidirectionally transmits and receives
information signals to/from the base station radios 1103a and 1103b, using
linearly polarized electromagnetic waves and rotationally polarized
39
electromagnetic waves.
[0094] In the present embodiment, base station radios 1103a and 1103b and the
terminal radio 1113 communicate with each other through the inside of the
building 1101 serving as radio transmission medium. Thus, inner walls of the
building 1101 and outer walls of the elevator car 1111 present a multi-path
interference environment in which electromagnetic waves are subjected to
multiple reflections. In addition, the propagation paths of the electromagnetic
waves can be altered due to interference by an artificial operation from the outside.
The present embodiment can, similarly to the above-described embodiments,
reduce the correlation of a plurality of radio propagation paths and have strong
resistance to obstacles and interference by the plurality of radio propagation paths
caused by a natural event or an artificial operation, to provide appropriate
communication. Accordingly, the present embodiment allows for eliminating
wired communication means such as cables, to achieve the same transportability
with a smaller building volume or allow the elevator car 1111 to have increased
dimensions for the same building volume, resulting in improving the
transportability.
[0095] [Twelfth Embodiment]
FIG. 13 is an schematic view of a substation facility monitoring system
1200 according to a twelfth embodiment of the present invention.
The substation facility monitoring system 1200 of the present
embodiment includes a plurality of substation facilities 1201 and a plurality of
base station devices 1211. The number of the base station devices 1211 is
40
smaller than the number of the substation facilities 1201.
Each substation facility 1201 is provided with a terminal station radio
1203 and an antenna 1202. Each base station device 1211 has an antenna 1212
and a base station radio 1213.
[0096] The base station radios 1213, the antennas 1212, the terminal station
radios 1203, and the antennas 1202 are, for example, each configured similarly to
the transceiver 400 (see FIGS. 10 and 11) of the tenth embodiment. With this
configuration, each terminal station radio 1203 bidirectionally transmits and
receives information signals to/from any of the base station radios 1213, using
linearly polarized electromagnetic waves and rotationally polarized
electromagnetic waves.
[0097] The substation facilities 1201 each have dimensions of the order of
several meters, which are significantly larger than the wavelengths corresponding
to the frequencies of the electromagnetic waves used by the base station radios
1213 and the terminal station radios 1203, which range from several hundred
MHz to several GHz. Thus, substation facilities 1201 present a multi-path
interference environment in which electromagnetic waves outputted by the
terminal station radios 1203 and the base station radios 1213 are subjected to
multiple reflections.
[0098] In addition, propagation paths of electromagnetic waves can be altered
due to interference by an artificial operation from the outside. The present
embodiment can, similarly to the above-described embodiments, reduce the
correlation of a plurality of radio propagation paths and have strong resistance to
41
obstacles and interference of the plurality of radio propagation paths caused by a
natural event or an artificial operation, to provide appropriate communication.
The present embodiment eliminates problems due to high-voltage induction
power that may occur when wired connecting means such as cables are used, and
eliminates the cost of laying such cables, leading to improving safety and
reducing cost when constructing control and monitor systems of the substation
facilities 1201.
[0099] [Modifications]
The present invention is not limited to the above-described embodiments,
and various modifications are possible. The above-described embodiments are
exemplified to describe the present invention in an easily understandable manner,
and the present invention is not limited to those including all of the described
components. In addition, a part of the configuration of a certain embodiment
may be replaced with a part of the configuration of another embodiment, and the
configuration of a certain embodiment may be added with a configuration of
another embodiment. Further, a part of the configuration in each of the
embodiments may be deleted, added or replaced with other configuration.
Examples of possible modifications of the above-described embodiments include
the following.
[0100] (1) Receivers, transmitters, and transceivers presented in the first to tenth
embodiments may be implemented using DSPs or discrete circuits.
Application specific integrated circuits (ASICs) or field-programmable
gate arrays (FPGAs) may also be used.
42
[0101] (2) Receivers, transmitters, and transceivers presented in the first to tenth
embodiments may be applicable to various systems other than the elevator system
1100 presented in the eleventh embodiment and the substation facility monitoring
system 1200 presented in the twelfth embodiment.
Reference Signs List
[0102]
1, 2 transmission antenna
4 information signal generator
5, 6 orthogonal code generating circuit
7 multiplier (first superimposing circuit)
8 multiplier (second superimposing circuit)
9 synchronization signal generating circuit
11 polarization rotational frequency cosine oscillator (polarization plane rotating
oscillator)
12 polarization rotational frequency sine oscillator (polarization plane rotating
oscillator)
19 carrier frequency cosine oscillator (carrier oscillator)
27 signal switching circuit
31 carrier frequency sine oscillator (first sine oscillator)
32 carrier frequency sine oscillator (second sine oscillator)
41 carrier frequency cosine oscillator (first cosine oscillator)
42 carrier frequency cosine oscillator (second cosine oscillator)
43
61, 62, 63 reception antenna
65 subtractor (restoration section)
71 orthogonal code generating circuit (first despreading section)
73 multiplier (first receive section)
74 multiplier (first despreading section)
81 orthogonal code generating circuit (second despreading section)
83, 87 multiplier (second receive section)
84,88 multiplier (second despreading section)
201, 203, 204, 205, 207, 208, 209 transmitter
301, 302, 303, 304, 306, 307, 308, 309 receiver
385 orthogonal code generating circuit (third despreading section)
388 multiplier (third despreading section)
2011, 2031, 2071, 2081 transmission block (first transmission block)
2012, 2032, 2042, 2072, 2082, 2092 transmission block (second transmission
block)
ω1 angular frequency (carrier frequency, first frequency)
ω2 angular frequency (carrier frequency, second frequency)
ωc carrier angular frequency (carrier frequency)
ωp rotational angular frequency (rotational frequency)
θz1, θz2, ... , θzn non-detection angle
ωI angular frequency
#1 orthogonal code (first orthogonal code)
#2 orthogonal code (second orthogonal code)
44
#3 orthogonal code (third orthogonal code)
V', H' pseudo reception signal
45
WE CLAIM:
1. A transmitter comprising:
a first transmission block that generates a first radio wave having an
information signal modulated thereon and having a plane of polarization that
rotates; and
a second transmission block that generates a second radio wave having
the information signal modulated thereon and having a plane of polarization that
is fixed.
2. The transmitter of claim 1,
wherein the first transmission block comprises a first superimposing
circuit that causes a first orthogonal code to be superimposed on the first radio
wave, the first orthogonal code being a spreading code, and
wherein the second transmission block comprises a second
superimposing circuit that causes a second orthogonal code to be superimposed on
the second radio wave, the second orthogonal code being orthogonal to the first
orthogonal code.
3. The transmitter of claim 2,
wherein the second transmission block causes a third orthogonal code to
be superimposed on the second radio wave, the third orthogonal code being
orthogonal to the first orthogonal code and the second orthogonal code.
4. The transmitter of claim 1, further comprising a plurality of
46
transmission antennas whose planes of polarizations are spatially orthogonal to
one another,
wherein the first transmission block generates the first radio wave via the
plurality of transmission antennas, and
wherein the second transmission block generates the second radio wave
via the plurality of transmission antennas.
5. The transmitter of claim 4,
wherein the first transmission block and the second transmission block
respectively generate the first radio wave and the second radio wave at the same
time.
6. The transmitter of claim 5,
wherein the first transmission block uses a plurality of carrier frequencies
to generate the first radio wave, such that the first radio wave has a plane of
polarization that rotates at a rotational frequency depending on the plurality of
carrier frequencies, and
wherein the second transmission block uses the plurality of carrier
frequencies to generate the second radio wave.
7. The transmitter of claim 1,
wherein the first transmission block comprises:
a polarization plane rotating oscillator that oscillates at a frequency
corresponding to a rotational frequency of the plane of polarization of the first
47
radio wave, and
a carrier oscillator that oscillates at a frequency corresponding to a carrier
frequency of the first radio wave, and
wherein the first radio wave has a component with a frequency equal to
the sum of the carrier frequency and the rotational frequency and has a component
with a frequency equal to the difference between the carrier frequency and the
rotational frequency.
8. The transmitter of claim 1,
wherein the first transmission block comprises:
a first sine oscillator that generates a sine wave of a first frequency;
a first cosine oscillator that generates a cosine wave of the first
frequency;
a second sine oscillator that generates a sine wave of a second frequency;
and
a second cosine oscillator that generates a cosine wave of the second
frequency,
wherein the plane of polarization of the first radio wave rotates at a
rotational frequency equal to half the difference between the first and second
frequencies, and
wherein the second radio wave has a component with a carrier frequency
equal to the first frequency and a component with a carrier frequency equal to the
second frequency.
48
9 The transmitter of claim 1, further comprising:
an information signal generator that generates the information signal;
a synchronization signal generating circuit that generates a
synchronization signal; and
a signal switching circuit that selects one of the information signal and
the synchronization signal, and passes the selected signal to the first transmission
block and the second transmission block.
10. A receiver comprising:
a first receive section that demodulates a first radio wave having an
information signal modulated thereon and having a plane of polarization that
rotates; and
a second receive section that demodulates a second radio wave having
the information signal modulated thereon and having a plane of polarization that
is fixed,
wherein the receiver restores the information signal on the basis of the
result of reception by the first receive section and the second receive section.
11. The receiver of claim 10,
wherein the first radio wave contains a component of the information
signal spread with a first orthogonal code, the first orthogonal code being a
spreading code,
wherein the second radio wave contains a component of the information
signal spread with a second orthogonal code, the second orthogonal code being a
49
spreading code and being orthogonal to the first orthogonal code, and
wherein the receiver further comprises:
a first despreading section that despreads the result of the demodulation
by the first receive section with the first orthogonal code; and
a second despreading section that despreads the result of the
demodulation by the second receive section with the second orthogonal code.
12. The receiver of claim 11,
wherein the second radio wave further contains a component of the
information signal spread with a third orthogonal code, the third orthogonal code
being a spreading code and being orthogonal to the first orthogonal code and the
second orthogonal code, and
wherein the receiver further comprises a third despreading section that
despreads the result of the demodulation by the second receive section with the
third orthogonal code.
13. The receiver of claim 10, further comprising a plurality of reception
antennas whose planes of polarization are spatially orthogonal to one another,
wherein the first receive section receives the first radio wave via one of
the plurality of reception antennas, and
wherein the second receive section receives the second radio wave via the
one and another of the plurality of reception antennas.
14. The receiver of claim 13,
50
wherein the first receive section and the second receive section receive
the first radio wave and the second radio wave at the same time.
15. The receiver of claim 11, further comprising
a restoration section that restores the information signal on the basis of
the difference between an output signal of the first despreading section and an
output signal of the second despreading section.
16. The receiver of claim 10, further comprising:
three or more reception antennas whose planes of polarization are
spatially orthogonal; and
a polarization rotation circuit that applies weighting on reception signals
of the three or more reception antennas to output two pseudo reception signals,
wherein the first receive section receives one of the two pseudo reception
signals as the first radio wave, and
wherein the second receive section receives both of the two pseudo
reception signals as the second radio wave.