The present invention relates to a connection structure connecting a substrate
which mounts a high frequency (RF) circuit and a \.va\!eg~irfe, and a nanufactnring
method for the connection structure.
10 [Background Art]
[0002]
In the case where a substrate provided with an RF circuit is connected to a
waveguide, there arises a problem that reflection, transmission loss, and leakage of an
electromagnetic wave are increased, and various connection structures have been
15 proposed for solving the problem.
[0003]
Patent literature I discloses a connection structure connecting a dielectric
substrate, on the surface of which a signal transmission line is formed, to a waveguide
via an insulating connection member which is provided with a through hole having the
20 same size as the inner diameter of the waveguide. Also patent literature 2 discloses a
structure connecting a high frequency module to a waveguide substrate via a dielectric
substrate and proposes a structure in which electromagnetic wave leakage is
suppressed by means of providing a choke groove around a waveguide hole of the
waveguide substrate and further providing a land around a through hole having the
25 same size as the waveguide hole of the dielectric substrate.
[Citation List]
[Patent Literature]
[0004]
[PTL I ]
Japanese Patent No. 4261 726
[PTL2]
Japanese Patent Laid-Open No. 2007-336299
[Summary]
5 [Technical Problem]
[0005]
In the above patent literatures, however, it is necessary to provide an opening
having substantially the same size as the waveguide in the connection member or the
dielectric substrate which is to be connected to the waveguide, and it is necessary to
10 provide a substrate including an opening having a different size for each of different
frequency bands. That is, depending on the frequency band, it is necessary to change
not only the RF module but also the substrate opening size, causing a complicated
manufacturing process and a high cost.
[0006]
15 Accordingly, an object of the present invention is to provide a new connection
structure connecting a high frequency circuit and a waveguide which allows a substrate
opening size to be made common without causing deterioration of a transmission line
conversion characteristic, and a manufacturing method for the connection structure.
[Solution to Problem]
20 [0007]
A connection structure according to the present invention is a connection
structure for connecting a high frequency circuit and a waveguide and includes a first
substrate on which the high frequency circuit is mounted and a transmission path
conversion means is provided between the high frequency circuit and the waveguide, a
25 waveguide conductor in which the waveguide is formed, and a second substrate which
is provided on the waveguide conductor and includes an opening having a size larger
than an opening size of the waveguide, wherein the first substrate is fixed onto the
second substrate so as to cover the opening of the second substrate, and a choke is
4
formed utilizing a space among the first substrate, the second substrate, and the
waveguide conductor.
A manufacturing method of a connection structure according to the present
invention is a manufacturing method of a connection structure for connecting a high
5 frequency circuit and a waveguide, and includes the steps of providing a first substrate
on which the high frequency circuit is mounted and a transmission path conversion
means is provided between the high frequency circuit and the waveguide; a waveguide
conductor in which the waveguide is formed, and a second substrate inc!c!ding an
opening having a size larger than an opening size of the waveguide, fixing the second
10 substrate onto the waveguide conductor so as to cause opening centers of the
waveguide and the second substrate to coincide with each other, fixing the first
substrate onto the second substrate so as to cover the opening of the second substrate,
and forming a choke among the first substrate, the second substrate, and the
waveguide conductor.
15 [Advantageous Effects of Invention]
[0008]
According to the present invention, it is possible to standardize the opening size
of the second substrate among different frequency bands to be used without causing
deterioration of the transmission path conversion characteristic.
20 [Brief Description of Drawings]
[0009]
[FIG. I]
FIG. 1 is a cross-sectional view of a connection structure connecting an RF module and
a waveguide according to a first exemplary embodiment of the present invention.
25 [FIG. 21
FIG. 2 is a cross-sectional view of a connection structure connecting an RF module and
a waveguide according to a second exemplary embodiment of the present invention.
[FIG. 31
FIG. 3 is a plan view of the connection structure shown in FIG. 2.
[FIG. 41
FIG. 4 is a cross-sectional view of a connection structure connecting an RF module and
a waveguide according to a third exemplary embodiment of the present invention.
[Detailed Description]
5 [OOIO]
A connection structure according to an exemplary embodiment of the present
invention to be explained next includes a first substrate (module substrate) on which an
RF circuit section and a transmission line conversion section are put together, a seconc!
substrate (mother substrate) in which an opening is formed having a size larger than the
10 opening size of a waveguide, and a waveguide conductor in which the waveguide is
formed. The mother substrate is fixed onto the waveguide conductor so as to cause the
opening centers of the waveguide and the mother substrate to coincide with each other
and the module substrate is fixed onto the mother substrate so as to cover the opening
of the mother substrate. A conductor is disposed around the opening of the mother
15 substrate to form a choke shorting face. A choke is formed by utilizing a space among
the module substrate, the mother substrate, and the waveguide so as to keep a
characteristic necessary for an opening of a waveguide.
[OOI I]
In this manner, by means of forming the opening of the mother substrate which
20 is sufficiently larger than the opening size of the waveguide, an actual opening size can
be determined by the conductor of the waveguide, a conductor of the mother substrate,
and a conductor of the module substrate, and the mother substrate can be made
common among the different frequency bands to be used. Moreover, since a choke
structure is formed only by means of mounting a module substrate and a waveguide
25 each having an opening corresponding to a frequency band to be used on the mother
substrate having the large opening, it is possible to perform waveguide connection by a
simple process without causing characteristic deterioration. In the following,
embodiments of the present invention will be explained with reference to the drawings.
[OOI 21
1. First exemplary embodiment
As shown in FIG. 1, in an RF module connection structure according to a first
exemplary embodiment of the present invention, a module substrate 1 is surfacemounted
onto a mother substrate 2, and the mother substrate 2 is fixed with a screw 13
5 to a conductor 8 serving as a tube wall of a waveguide 3. Thereby, the conductor 8 is
fixed so as to function as electrical ground GND for the mother substrate 2 and also not
to cause a gap. However, because of thickness variation of the mother substrate 2, a
so!dering state and warpage of the modu!e substrate 4 , and the !Ike, it is difficult te
cause the conductor 8 also to contact the module substrate 1 which is surface-mounted
10 on the mother substrate 2, without a gap. Conversely, since it is easy to perform design
so as to intentionally cause a gap to be generated between the module substrate 1 and
the conductor 8, by designing this gap as a choke to form a choke flange, it is possible
to perform waveguide connection preferably. In the following, the configuration of each
part will be explained.
15 [0013]
An RF circuit section and a transmission line conversion section are put
together on the module substrate 1. The RF circuit section includes an amplifier, a
matching circuit, and the like, and the circuit size thereof may depend on an apparatus
design. The transmission line conversion section is configured with a back short 7
20 which is formed by means of cutting out a conductor 6 in a part having the same size as
the opening size of the waveguide 3, and a strip conductor 9. Electronic parts 11 are
mounted on the module substrate 1. The electronic parts 11 are RF circuit parts and
include an amplifier, a matching circuit, and the like. In FIG. 1, while a shield of the
back short 7 and the electronic parts 11 is integrally formed by the conductor 6, it is not
25 necessarily integrally formed, and the shield of the electronic parts I 1 may be formed as
needed also for each of the parts.
[0014]
Further, the module substrate 1 is a multi-layered substrate, and is configured
here with conductor layers l a to I d and insulating layers l e to I f therebetween. The
above electronic parts 11 are mounted on the top conductor layer la, and the strip
conductor 9 extended from the electronic parts 11 is formed in a region corresponding
to the opening of the waveguide 3. In each of the other conductor layers I b to Id, a
conductor is not formed in the region corresponding to the opening of the waveguide 3.
5 The module substrate I is attached to the mother substrate 2 in alignment with the
opening of the mother substrate 2 by a method such as soldering. The layers between
the top conductor layer l a and the bottom conductor layer I d are connected electrically
to one other by via-holes or the like, and connected here to the conductor 8 which is
equivalent to GND through via-holes of the mother substrate 2. Note that, the number
10 of the conductor layers of the module substrate I depends on a design requirement and
the conductor layers l a to I d shown in FIG. I are one example.
[00 1 51
An opening for the waveguide connection is formed in the mother substrate 2
with a size larger than the opening size d of the waveguide, and a conductor plating
15 layer 5a is formed on the edge face of the opening of the mother substrate 2 in contact
with a conductor layer 2d. The mother substrate 2 is fixed to the conductor 8 by the
screw 13. Further, electronic parts 12 are mounted on the mother substrate 2. The
electronic parts 12 include a CPU, a power supply circuit, an IF circuit, and the like.
Further, the mother substrate 2 is a multi-layered substrate, and, while a configuration
20 including conductors 2a to 2d and insulating layers 2e to 2f therebetween is illustrated,
the number of the conductor layers depends on a design requirement. Note that each
of the opening of the waveguide 3 and the opening of the mother substrate 2 is
rectangular or circular.
[00 1 61
2 5 The waveguide 3 and an annular groove 4 are integrally formed in the
conductor 8. The mother substrate 2 and the module substrate 1 are fixed so as to
cover the waveguide 3 of the conductor 8, and thereby a choke is configured with the
annular groove 4, the conductor I d of the module substrate 1, the conductor plating
layer 5a and the conductor layer 2d of the mother substrate 2. While preferably the viaholes
10 are formed as close as possible to the opening end face of the mother
substrate 2, the positions thereof are determined by design.
[OOI 71
As described above, the choke is configured with the annular groove 4, the
5 conductor layer I d of the module substrate 1, the conductor plating layer 5a and the
conductor layer 2d of the mother substrate 2. Accordingly, by setting the effective
distance from the wall face of the waveguide 3 to the deepest face 5 of the annular
groove 4 to be ha!f a \vavelength A, (t = A, 12) inside the waveguide, it is possible to
manufacture a connection structure having a small loss or leakage of a high frequency
10 signal in a desired frequency band to be used, in a simple process.
[OO 1 81
Note that the via-hole 10 may be filled with a conductor as a build-up via. In the
case of the build-up via, even if the deepest face 5 of the annular groove 4 is extended
to under the via-hole 10, the choke characteristic is not affected. Accordingly, there is
15 an advantage that design restriction does not exist.
[00 1 91
2. Second exemplary embodiment
In the above first exemplary embodiment, as shown in FIG. 1, the choke is
configured with the annular groove 4, the conductor layer I d of the module substrate 1,
20 and the conductor plating layer 5a and the conductor layer 2d of the mother substrate 2.
However, the present invention is not limited to this configuration. As shown in FIG. 2,
the choke can be also configured using the via-holes 10 instead of the conductor plating
layer 5a. Hereinafter, a second exemplary embodiment of the present invention will be
explained with reference to FIG. 2 and FIG. 3, provided that the configuration except the
25 choke is the same as that of the first exemplary embodiment shown in FIG. 1, and the
same reference number is attached and explanation will be omitted. In the following,
explanation will be provided focusing on a choke configuration.
[0020]
In FIG. 3, the via-holes 10 are provided so as to surround the opening of the
mother substrate 2 at predetermined intervals (preferably at intervals not larger than 114
of a signal wavelength, and, while a better characteristic is obtained as the intervals are
smaller (e.g., 1/40), these intervals depend on a design condition), and these arranged
5 via-holes 10 form a choke shorting face 5b. That is, in FIG. 2, the choke is configured
with the annular groove 4, the conductor layer I d of the module substrate 1, and the
via-holes 10. By appropriately designing the distance from the wall face of the
waveguide 3 to the choke shorting face 5b, it is possible to manufacture 2 connection
structure having a small loss and leakage of a high frequency signal in a desired
10 frequency band to be used, as in the first exemplary embodiment.
[0021]
3. Third exemplary embodiment
In the above first and second exemplary embodiments, as shown in FIG. I and
FIG. 2, the choke is configured by means of forming the annular groove 4 around the
15 waveguide 3 in the conductor 8. However, if a characteristic such as a bandwidth which
is required for the transmission line conversion allows, it is also possible to form the
choke by a simplified annular groove 4a as shown in FIG. 4 and the via-holes 10. When
the configuration is simplified in this manner, it is expected to make the process of the
conductor 8 easy and to obtain yield improvement and cost reduction.
20 [0022]
Specifically, as shown in FIG. 4, in an RF module connection structure
according to the present embodiment, a choke is formed using as an annular groove 4a
a space formed by the waveguide 3, the opening of the mother substrate 2 and the
module substrate 1 thereabove without forming the groove in the conductor 8 in which
25 the waveguide 3 is formed. That is, the choke is configured with the conductor 8, the
conductor layer I d of the module substrate 1, and conductors in the via-holes 10 of the
mother substrate 2. The arrangement of the via-holes 10 is as illustrated in FIG. 3.
[0023]
Further, a conductor 6a configuring the back short 7 may be provided
separately, and a conductor 14 may be formed for shielding the circuit by the electronic
parts 11 and the circuit by the electronic parts 12. Note that, since the other members
are the same as those of the embodiments shown in FIG. 1 and FIG. 2, the same
5 reference numbers are provided and their explanations will be omitted.
[0024]
Also in the present embodiment, by appropriately designing the distance from
the wall face of the waveguide 3 to the choke shorting face 5b, it is possible to
manufacture a connection structure having a small loss and leakage of a high frequency
10 signal in a desired frequency band to be used, in a simple process. At this time, since
the groove is not formed in the conductor 8 in which the waveguide 3 is formed and the
choke is configured using the opening of the mother substrate 2 and the via-holes 10, it
is possible to further simplify the manufacturing process.
[0025]
15 4. Effect
According to the above-mentioned embodiments of the present invention, by
providing the RF circuit and the transmission line conversion section for the module
substrate 1 and providing an opening larger than the opening size of the waveguide for
the mother substrate 2 at a position corresponding to the position where the module
20 substrate 1 is attached, it is possible to reduce frequency-dependent design factors of
the mother substrate 2, and to make the mother substrate 2 common without being
limited to a frequency band to be used.
[Industrial Applicability]
[0026]
2 5 The present invention can be applied generally to a high frequency apparatus
which requires a connection between a wiring substrate and a waveguide.
[Reference Signs List]
[0027]
1 Module substrate
I a to I d Conductor layer
l e to I g Insulating layer
2 Mother substrate
2a to 2d Conductor layer
5 2e to 2g Insulating layer
3 Waveguide
4, 4a Annular groove
5 Deepest part of an annular groove
5a Plating layer
10 5b Choke shorting face
6, 6a Conductor in back short side
7 Back short
8 Conductor in waveguide side
9 Strip conductor
15 10 Via-hole
11 Electronic parts
12 Electronic parts
13 Screw
14 Conductor
2 0

We Claim:
[Claim I ]
A connection structure for connecting a high frequency circuit and a waveguide,
comprising:
5 a first substrate on which the high frequency circuit is mounted and a
transmission line conversion means is provided between the high frequency circuit and
the waveguide;
a waveguide conductor in which the waveguide is formed; and
a second substrate which is provided on the waveguide conductor and has an
10 opening having a size larger than an opening size of the waveguide,
wherein the first substrate is fixed onto the second substrate so as to cover the
opening of the second substrate, and a choke is formed utilizing a space among the first
substrate, the second substrate, and the waveguide conductor.
[Claim 21
15 The connection structure according to claim I, wherein
the choke includes the waveguide conductor, a conductor layer of the first
substrate, and a conductor passing through the second substrate.
[Claim 31
The connection structure according to claim 2, wherein
2 0 a plurality of the conductors passing through the second substrate is disposed
around the opening of the second substrate at predetermined intervals.
[Claim 41
The connection structure according to claim 2 or 3, wherein
a distance between an inner wall of the waveguide and the conductor passing
25 through the second substrate is set to half a wavelength inside the waveguide.
[Claim 51
A manufacturing method of a connection structure for connecting a high
frequency circuit and a waveguide, comprising the steps of:
providing a first substrate on which the high frequency circuit is mounted and a
transmission line conversion means is provided between the high frequency circuit and
the waveguide, a waveguide conductor in which the waveguide is formed, and a second
substrate including an opening having a size larger than an opening size of the
5 waveguide;
fixing the second substrate onto the waveguide conductor so as to cause
opening centers of the waveguide and the second substrate to coincide with each other;
fixing the first substrate onto the second substrate so as to cover ths openiw of
the second substrate; and
10 forming a choke among the first substrate, the second substrate, and the
waveguide conductor.
[Claim 61
The manufacturing method of a connection structure according to claim 5,
wherein
15 the choke includes the waveguide conductor, a conductor layer of the first
substrate, and a conductor passing through the second substrate.
[Claim 7]
The manufacturing method of a connection structure according to claim 6,
wherein
2 0 a plurality of the conductor passing through the second substrate is disposed
around the opening of the second substrate at predetermined intervals.
[Claim 8]
The manufacturing method of a connection structure according to claim 6 or 7,
wherein
2 5 a distance between an inner wall of the waveguide and the conductor passing
through the second substrate is set to half a wavelength inside the waveguide.