WO2023127330A1

WO2023127330A1 - Bandpass filter

Info

Publication number: WO2023127330A1
Application number: PCT/JP2022/042256
Authority: WO
Inventors: Atsuhiro Yamamoto; Takehiro Kishida
Original assignee: Furuno Electric Co., Ltd.
Priority date: 2021-12-27
Filing date: 2022-11-14
Publication date: 2023-07-06
Also published as: JP2023096199A

Abstract

The bandpass filter (10, 10A or 10B) has a first post-wall waveguide, a second post-wall waveguide, a connected waveguide, and a first, second and third via conductor (51, 52 and 50). The first and the second post-wall waveguide are arranged in order in the first direction and transmit high frequency signals in opposite directions to each other. The connected waveguide is placed on the second direction side, which is the transmission direction of the first post-wall waveguide, and connects to the one end of the first and the second post-wall waveguide. The first and second via conductor (51, 52) are located within the respective post-wall waveguide at a distance (L1) from the one end of the respective post-wall waveguide. The third via conductor (50) is located within the connected waveguide at a distance (L2) from the one end of the first and the second post-wall waveguide.

Description

BANDPASS FILTER

The present disclosure generally relates to a bandpass filter and, more particularly relates, to a bandpass filter that filters high frequency signals.

Background

A bandpass filter is an electronic device or circuit that allows signals (such as electric signals) with frequencies within a certain range to pass through it and rejects (or attenuates) signals with frequencies outside the certain range. In particular, a bandpass filter passes electromagnetic waves of a certain passband and blocks electromagnetic waves outside the passband. The ‘passband’ refers to the range of frequencies or wavelengths that can pass through a filter. The bandpass filter operating in the millimeter wave band is called a waveguide.

A conventional bandpass filter disclosed in the Japanese Patent Application No. JP 6633117 B2, filed by Fujikura Ltd, describes a bandpass filter formed by a post-wall waveguide. The post-wall waveguide of the bandpass filter is formed on one plane. The post-wall waveguide has multiple resonators connected in series by multiple short walls formed at prescribed intervals along the transmission direction of the high frequency signal. The bandpass filter functions as a bandpass filter by adjusting the resonant frequencies of multiple resonators. However, in this configuration of the bandpass filter, the plane area becomes larger.

Therefore, there exists a need for a bandpass filter that suppresses or reduces the plane area using a post-wall waveguide.

Summary

In order to solve the foregoing problem and to provide other advantages, one aspect of the present disclosure is to provide a bandpass filter that includes a first post-wall waveguide, a second post-wall waveguide, which are arranged in order in first direction, conveys high frequency signal in the first post-wall waveguide and the second post-wall waveguide in opposite direction to each other. The first post-wall waveguide and the second post-wall waveguide are arranged in the order of a first direction and transmit high frequency signals in opposite directions to each other. A connected waveguide which is located on an end of a second direction, wherein the second direction is a conveying direction of the first post-wall waveguide, connects to one end of the first post-wall waveguide and the second post-wall waveguide. A first via conductor is located within the first post-wall waveguide and at a position at a first distance from the one end of the first post-wall waveguide. A second via conductor is located within the second post-wall waveguide and at a second distance from the one end of the second post-wall waveguide. A third via conductor is located within the connected waveguide and at a position at a third distance from the one end.

In an aspect, the bandpass filter includes a first addition distance obtained by adding the first distance and the third distance and the second addition distance obtained by adding the second distance and the third distance.

In an aspect, the first and second addition distance are set based on wavelength of the high frequency signal, and the third distance is set based on coupling factor of the first post-wall waveguide and the second post-wall waveguide.

In an aspect, the first post-wall waveguide of the bandpass filter further includes, a first conductor layer, a second conductor layer running parallel to first conductor layer along the second direction and having a length of the second direction shorter than that of the first conductor layer, and a plurality of fourth via conductors connecting the first conductor layer and the second conductor layer. The bandpass filter further includes the second post-wall waveguide including the second conductor layer, and a third conductor layer located the first direction side relative to the second conductor layer and running parallel to the second conductor layer along the second direction and having a length of the second direction longer than the second conductor layer, and a plurality of fifth via conductors connecting the second conductor layer and the third conductor layer.

The bandpass filter further includes the connected waveguide including the first conductor layer, the third conductor layer and a plurality of sixth via conductors located in one end of the second conductor layer to the first post-wall waveguide and the second post-wall waveguide and to the opposite side in the second direction, connecting the first conductor layer to the third conductor layer. The first via conductor located within an area bounded by the first conductor layer, the second conductor layer and the plurality of the fourth via conductors, the second via conductor located within an area bounded by the second conductor layer, the third conductor layer and a plurality of fifth via conductors, and the third via conductor arranged in an area bounded by the first conductor layer, the third conductor layer and the plurality of sixth via conductor.

In an aspect, the first via conductor, the third via conductor, the plurality of sixth via conductors, and the plurality of fourth via conductors are formed in a first dielectric layer of a dielectric.

In an aspect, the second via conductor, the third via conductor, the plurality of sixth via conductors, and the plurality of fifth via conductors are formed in a second dielectric layer of the dielectric.

In an aspect, the first conductor layer has a slit positioned perpendicular to an end of the second conductor layer that meets the face of the first conductor layer.

In an aspect, the distance between the first conductor layer and the second conductor layer in the first direction is shorter than the distance between the second conductor layer and the third conductor layer.

In an aspect, the thickness of the first dielectric layer is smaller than the thickness of the second dielectric layer.

In an aspect, the first via conductor and the second via conductor are positioned such that the positions of second direction overlap and line up with first direction.

In an aspect, the first via conductor and the second via conductor are positioned to extending to the first direction.

In an aspect, a third dielectric layer is arranged between the first dielectric layer and the second dielectric layer.

In an aspect, a sixth via conductor is formed in the third dielectric layer.

In an aspect, a high frequency signal amplification circuit includes the bandpass filter of present disclosure and one or more amplifiers.

An advantage of various embodiments of the present disclosure is to provide a bandpass filter that filters high frequency signals. It should be noted that in the bandpass filter of the present disclosure, the first and second post-wall waveguides are not placed side by side on one side, but are stacked on top of each other, thereby reducing the plane area. Thus, the plane area of the bandpass filter is suppressed using the post-wall waveguide.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

In the present disclosure, the first and second post-wall waveguides are not placed side by side on one side but are stacked on top of each other. In this way, a smaller plane area is realized. Furthermore, the region between the first via conductor and the third via conductor along with the region between the second via conductor and the third via conductor acts as a resonator with a given resonant frequency. Thus, the area where the first post-wall waveguide, the connected waveguide, and the second post-wall waveguide are contiguous, acts as a bandpass filter.

The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate an exemplary embodiment of the present disclosure and, together with the description, serve to explain the principles of the present disclosure. It should be noted that in the accompanying drawings, like or same reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the disclosed embodiments and, together with the detailed description of the disclosure, serve to explain the principles of the disclosed embodiments.

The diagrams are for illustration only, which thus is not a limitation of the present disclosure. Moreover, those skilled in the art will understand that the drawings are not to scale.
FIG. 1 illustrates a perspective view of a bandpass filter, in accordance with an embodiment of the present disclosure; FIG. 2 illustrates an exploded view of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure; FIG. 3A illustrates a first plan view of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure;FIG. 3B illustrates a second plan view of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure; FIG. 4A, FIG. 4B, and FIG. 4C illustrate side section views of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure; FIG. 5 is a graph showing characteristics of an S-parameter of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure; FIG. 6 is a table comparing the in-band loss and plane size between the bandpass filter of FIG. 1 and the conventional post-wall waveguide bandpass filter (comparative example) and microstrip line; FIG. 7A illustrates a first plan view of the bandpass filter, in accordance with another embodiment of the present disclosure;FIG. 7B illustrates a second plan view of the bandpass filter of FIG. 7A, in accordance with another embodiment of the present disclosure; FIG. 8 illustrates a side section view of the bandpass filter of FIG. 7A, in accordance with another embodiment of the present disclosure; FIG. 9 illustrates a side section view of the bandpass filter, in accordance with another embodiment of the present disclosure; and FIG. 10 illustrates a schematic diagram of an exemplary high frequency signal amplification circuit to which the bandpass filter of the present disclosure is applied.

DETAILED DESCRIPTION

The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the present disclosure as defined by the appended claims.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present disclosure. It will be apparent to those skilled in the art that embodiments of the present disclosure may be practiced without some of these specific details. It should be understood that the particular values and configurations discussed in the following non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof.

The present disclosure particularly relates to a bandpass filter that filters high frequency signals. Compared to the conventional techniques, in the present disclosure, the first and second post-wall waveguides are not placed side by side on one side but are stacked on top of each other. Thus, the plane area of a bandpass filter is suppressed using the post-wall waveguide.

A bandpass filter according to an embodiment of the present disclosure will be described with reference to FIG. 1 to FIG. 6. FIG. 1 illustrates a perspective view of a bandpass filter, in accordance with an embodiment of the present disclosure. FIG. 2 illustrates an exploded view of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure. FIG. 3A illustrates a first plan view of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure. FIG. 3B illustrates a second plan view of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure. FIG. 4A, FIG. 4B and FIG. 4C illustrates side section views of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure. As shown in FIGS. 1 to FIG. 4C, the bandpass filter 10 includes at least a dielectric 20, a first conductor layer 31, a second conductor layer 32, a third conductor layer 33, a first via conductor 51, a second via conductor 52, a third via conductor 50, a plurality of fourth via

conductors

411 and 421, a plurality of fifth via

conductors

412 and 422, and a plurality of sixth via

conductors

401 and 402. The z-axial direction shown in FIG. 1 corresponds to a first direction, and the x-axial direction corresponds to a second direction.

The dielectric 20 has a first dielectric layer 21 and a second dielectric layer 22. The first and second dielectric layers 21 and 22 are flat plates extending in x-axial and y-axial directions perpendicular to each other. The first and second dielectric layers 21 and 22 are stacked in a z-axial direction. In this configuration, the side of the first dielectric layer 21 in the dielectric 20 (the side perpendicular to the lamination direction) is a first principal side 201 of the dielectric 20. The side of the second dielectric layer 22 in the dielectric 20 (the side perpendicular to the lamination direction) is a second principal side 202 of the dielectric 20.

In an embodiment, the first conductor layer 31, the second conductor layer 32, and the third conductor layer 33 are flat films. The first conductor layer 31 is placed on the first principal side 201 in the dielectric 20. The second conductor layer 32 is placed at the contact surface between the first dielectric layer 21 and the second dielectric layer 22 in the dielectric 20. The third conductor layer 33 is placed on the second principal side 202 in the dielectric 20.

The length of the x-axial direction of the second conductor layer 32 is shorter than the length of the x-axial direction of the first and third conductor layers 31 and 33. In other words, the one end 320 of the x-axial direction 210 of the second conductor layer 32 is located between the first conductor layer 31 and the third conductor layer 33. This forms a region in the x-axial direction of dielectric 20 where the first conductor layer 31, the second conductor layer 32, and the third conductor layer 33 are placed side by side in the z-axial direction, and a region where the first conductor layer 31 and the third conductor layer 33 are placed side by side in the z-axial direction (a region that does not have the second conductor layer 32).

The plurality of fourth via

conductors

411 and 421 is formed in the region where the second conductor layer 32 is placed. The plurality of fourth via

conductors

411 and 421 is columnar and is formed in the first dielectric layer 21, such that it penetrates the first dielectric layer 21 in the z-axial direction.

Further, the plurality of fourth via

conductors

411 and 421 is each spaced at a predetermined interval along the x-axial direction. The rows of the plurality of fourth via

conductors

411 and 421 run side by side along the x-axial direction at a prescribed distance to the y-axial direction.

Along a columnar axial direction, one end of the plurality of fourth via conductors 411 and one end of the plurality of fourth via conductors 421 is connected to the first conductor layer 31. Similarly, along the columnar axial direction, the other end of the plurality of fourth via conductor 411 and other end of the plurality of fourth via conductor 421 is connected to the second conductor layer 32.

Thus, the parts placed in the first dielectric layer 21 are surrounded by the first conductor layer 31, the second conductor layer 32, and the plurality of fourth via

conductors

411 and 421, and form a first post-wall waveguide. Further, the first post-wall waveguide takes the direction parallel to the x-axial direction as the transmission direction of the high frequency signal. Further, it should be noted that because of this structure, the one end of the transmission direction of the high frequency signal of the first post-wall waveguide is the one end 320 of the second conductor layer 32.

The plurality of fifth via

conductors

412 and 422 is formed in the region where the second conductor layer 32 is placed. The plurality of fifth via

conductors

412 and 422 is columnar and is formed in the second dielectric layer 22 such that it penetrates the second dielectric layer 22 in a z-axial direction. The plurality of fifth via

conductors

412 and 422 are each spaced at a predetermined interval along the x-axial direction. The rows of the plurality of fifth via

conductors

412 and 422 run side by side along the x-axial direction at a prescribed distance to the y-axial direction. One end of the columnar axial direction in the plurality of fifth via

conductors

412 and 422 connects to the second conductor layer 32. The other end of the columnar axial direction in the plurality of fifth via

conductors

412 and 422 connects to the third conductor layer 33.

Thus, the parts placed in the second dielectric layer 22 and surrounded by the second conductor layer 32, the third conductor layer 33, and the plurality of the fifth via

conductors

412 and 422, form a second post-wall waveguide. The second post-wall waveguide then takes the direction parallel to the x-axial direction as the transmission direction of the high frequency signal. Also, because of this structure, the one end of the transmission direction of the high frequency signal of the second post-wall waveguide is the one end 320 of the second conductor layer 32. Furthermore, the columns of the via

conductor

411 and 412 and the columns of the via

conductor

421 and 422 are aligned in the z-axial direction.

Thus, the first and second post-wall waveguides are aligned in the z-axial direction. Then, the position of the first post-wall waveguide and the position of the second post-wall waveguide in the x-axial and y-axial directions are almost the same. Thus, the plane area (the area seen in the z-axial direction) is reduced by about half, compared with the continuous formation of the first and second post-wall waveguides on one side. The plurality of sixth via

conductors

401 and 402 is formed in areas where the second conductor layer 32 is not located. The plurality of sixth via

conductors

401 and 402 is columnar and is formed in the first dielectric layer 21 and the second dielectric layer 22, such that it penetrates the first and second dielectric layers 21 and 22 continuously in a z-axial direction. In other words, the plurality of sixth via

conductors

401 and 402 penetrates the dielectric 20 into a z-axial direction.

The plurality of sixth via conductors 401 and the plurality of sixth via conductor 402 are spaced side by side, at a predetermined interval along the x-axial direction. The plurality of sixth via conductor 401 is arranged in a continuous line with the plurality of fourth via conductors 411 and the plurality of fifth via conductors 412 in the x-axial direction. The plurality of sixth via conductors 402 is arranged in a continuous line with the plurality of fourth via conductors 421 and the plurality of fifth via conductors 422 in the x-axial direction. One end of columnar axial direction in the plurality of sixth via

conductors

401 and 402 connects to the first conductor layer 31. The other end of the columnar axial direction in the plurality of sixth via

conductors

401 and 402 connects to the third conductor layer 33.

The third via conductor 50 is positioned at a distance (third distance) L2 away from the one end 320 of the second conductor layer 32 in the x-axial direction 210. The third via conductor 50 is positioned on the opposite side with the first post-wall waveguide and the second post-wall waveguide with respect to the one end 320 of the second conductor layer 32. That is, the third via conductor 50 is placed in an area where the second conductor layer 32 is not formed. In other words, the third via conductor 50 is located within an area bounded by the first conductor layer 31, the third conductor layer 33, and the plurality of the sixth via

conductors

401 and 402.

The third via conductor 50 is positioned approximately midway between the columns of the plurality of sixth via

conductors

401 and 402 in the y-axial direction. The third via conductor 50 is formed in the first dielectric layer 21 and the second dielectric layer 22. The third via conductor 50 is columnar and penetrates the first and second dielectric layers 21 and 22 in a z-axial direction continuously. In other words, the third via conductor 50 penetrates the dielectric 20 into a z-axial direction. The one end of the columnar axial direction in third via conductor 50 connects to the first conductor layer 31. The other end of the columnar axial direction in the third via conductor 50 connects to the third conductor layer 33.

The parts enclosed by or placed in the first conductor layer 31, the third conductor layer 33, the plurality of sixth via

conductors

401 and 402, the third via conductor 50, and the dielectric 20 form a connected waveguide. Further, in this configuration, the connected waveguide connects the first post-wall waveguide and the second post-wall waveguide. Thus, for example, as shown in FIG. 4A, the high frequency signal is transmitted from the first post-wall waveguide to the second post-wall waveguide through the connected waveguide. Alternatively, the high frequency signal is transmitted from the second post-wall waveguide through the connected waveguide to the first post-wall waveguide.

The first via conductor 51 is positioned at a distance (first distance) L1 away from the one end 320 of the second conductor layer 32 in the x-axial direction. The first via conductor 51 is placed in an area bounded by the first conductor layer 31, the second conductor layer 32, and the plurality of fourth via

conductors

411 and 421. In other words, first via conductor 51 is placed within the first post-wall waveguide. The first via conductor 51 is positioned closer to the row of the fourth via conductor 411 than to the row of the plurality of fourth via conductors 421 in the y-axial direction. In other words, the distance W1 between the plurality of fourth via conductors 411 and the first via conductor 51 in the y-axial direction is less than half the width of the first post-wall waveguide.

The first via conductor 51 is formed in the first dielectric layer 21. The first via conductor 51 is columnar and penetrates the first dielectric layer 21 in a z-axial direction. The one end of the columnar axial direction in first via conductor 51 connects to the first conductor layer 31. The other end of the columnar axial direction in the first via conductor 51 connects to the second conductor layer 32. The distance between the third via conductor 50 and the first via conductor 51 in the x-axial direction (first addition distance (L1 + L2)) is 1/2 of the wavelength of the high frequency signal passed by the bandpass filter 10. Thus, the region between the third via conductor 50 and first via conductor 51 acts as a resonator resonating at the frequency of the high frequency signal passed by the bandpass filter 10.

The second via conductor 52 is positioned at a distance (second distance) L1 away from the one end 320 of the second conductor layer 32 in the x-axial direction. The second via conductor 52 is placed in an area bounded by the second conductor layer 32, the third conductor layer 33, and the plurality of fifth via

conductors

412 and 422. In other words, the second via conductor 52 is placed within the second post-wall waveguide. The second via conductor 52 is positioned closer to the row of the plurality of fifth via conductors 412 than to the row of the plurality of fifth via conductors 422 in the y-axial direction. In other words, the distance W2 between the plurality of fifth via conductors 412 and the second via conductor 52 in the y-axial direction is less than half the width of the second post-wall waveguide. The second via conductor 52 is formed in the second dielectric layer 22. The second via conductor 52 is columnar and penetrates the second dielectric layer 22 in a z-axial direction. The one end of the columnar axial direction in the second via conductor 52 connects to the second conductor layer 32. The other end of the columnar axial direction in the second via conductor 52 connects to the third conductor layer 33.

The distance between third via conductor 50 and the second via conductor 52 in the x-axial direction (second addition distance (L1 + L2)) is 1/2 of the wavelength of the high frequency signal passed by the bandpass filter 10. Thus, the region between the third via conductor 50 and the second via conductor 52 acts as a resonator resonating at the frequency of the high frequency signal passed by the bandpass filter 10. Therefore, by providing the above configuration, the bandpass filter 10 can realize a filter that passes the desired frequency band and attenuates other frequency bands. Furthermore, as mentioned above, the first and second post-wall waveguides overlap in the z-axial direction, so that the plane area of the bandpass filter 10 can be reduced.

In particular, post-wall waveguides and filters that transmit X-band high frequency signals tend to have larger plane areas because of the wavelength of the high frequency signal. However, by having this configuration, the bandpass filter 10 can reduce the plane area even when applied to the X-band high frequency signal, and this effect is more effective.

FIG. 5 is a graph showing characteristics of an S-parameter of the bandpass filter of FIG. 1, in accordance with the embodiment of the present disclosure. In FIG. 5, the solid line indicates S21 (passing characteristics) and the dashed line indicates S11 (reflective properties). As shown in FIG. 5, the bandpass filter 10 can pass the desired frequency band and attenuate the others. FIG. 6 is a table comparing the in-band loss and plane size of the bandpass filter of FIG. 1 with the conventional post-wall waveguide bandpass filter (comparative example) and microstrip line. The conventional post-wall waveguide in FIG. 6 forms a first post-wall waveguide and a second post-wall waveguide on one side, and this structure has a filter function. As shown in FIG. 6, the bandpass filter 10 of FIG. 1, in accordance with the embodiment, can reduce in-band loss to the same extent as the conventional bandpass filter with post-wall waveguide and bandpass filter with microstrip line. On that basis, the bandpass filter 10 in accordance with the embodiment, can significantly reduce the plane size (plane area) compared to the conventional bandpass filter with post-wall waveguide and bandpass filter with microstrip line.

It should be noted that, the bandpass filter 10 can co-ordinately set the distance L2 with one end 320 and the third via conductor 50 of the second conductor layer 32 while keeping the distance between the first via conductor 51 and the second via conductor 52 and the third via conductor 50, constant. By setting the distance L2, the bandpass filter 10 can set the coupling factor (degree of coupling) between the first and second post-wall waveguides. The bandpass filter 10 can set the pass bandwidth correspondingly by setting the coupling factor (degree of coupling). This enables the bandpass filter 10 to achieve a filter with the desired pass bandwidth.

In addition, the positions of the first via conductor 51 and the second via conductor 52 (as viewed in the z-axial direction) need not necessarily be the same. However, by aligning the first via conductor 51 and second via conductor 52, the configuration of the bandpass filter 10 is simplified and easier to manufacture. Furthermore, for example, the first via conductor 51 and the second via conductor 52 can be realized by third via conductor 50 penetrating both the first dielectric layer 21 and the second dielectric layer 22. This will further simplify the manufacturing of the first via conductor 51 and second via conductor 52.

FIG. 7A illustrates a first plan view of the bandpass filter, in accordance with another embodiment of the present disclosure. FIG. 7B illustrates a second plan view of the bandpass filter of FIG. 7A, in accordance with another embodiment of the present disclosure. FIG. 8 illustrates a side section view of the bandpass filter of FIG. 7A, in accordance with another embodiment of the present disclosure. As shown in FIG. 7A, FIG. 7B and FIG. 8, the bandpass filter 10A, in accordance with another embodiment of the disclosure, differs from the bandpass filter 10 for FIG. 1, in that, it has a dielectric 20A and a slit 310. The other configuration of the bandpass filter 10A is the same as that of the bandpass filter 10, and a description of similar parts is omitted. The dielectric 20A is a laminate of a first dielectric layer 21A and the second dielectric layer 22. The thickness D1 of the first dielectric layer 21A is smaller than the thickness D2 of the second dielectric layer 22. With such a configuration, the thickness of the dielectric 20A can be reduced. This allows the bandpass filter 10A to have a smaller plane area and a smaller thickness.

The first conductor layer 31 has the slit 310 to include the position of the foot of the perpendicular line lowered from one end 320 (end) of the second conductor layer 32 to the first conductor layer 31. The slit 310 is the conductor free portion (conductor non-forming portion) of the flat plate conductor. The slit 310 is rectangular in the z-axial direction, for example, and has a length Ls in the x-axial direction and a length Ws in the y-axial direction. Further, the slit 310 contains the one end 320 of the second conductor layer 32 and is formed from the one end 320 to the first post-wall waveguide side. By providing the slit 310, even if the first dielectric layer 21A is thinner than the second dielectric layer 22, the capacitive components of the first conductor layer 31 and the second conductor layer 32 can be suppressed, and impedance matching between the first post-wall waveguide and the second post-wall waveguide can be achieved. Thus, the bandpass filter 10A can achieve excellent passing characteristics while reducing plane area and thickness. It should be noted that, the length Ls and the length Ws of the slit 310 can be set correspondingly, to achieve desired characteristics. This allows the bandpass filter 10A to achieve better impedance matching.

FIG. 9 illustrates a side section view of the bandpass filter, in accordance with one another embodiment of the present disclosure. FIG. 9 shows a cross-section in a position similar to that of FIG. 4C. As shown in FIG. 9, the bandpass filter 10B differs from the bandpass filter 10 of FIG. 1, in that it has a dielectric 20B, a fourth and fifth conductor layers 321 and 322, and a sixth via conductor 329. The other configuration of the bandpass filter 10B is the same as that of the bandpass filter 10 of FIG. 1, and the description of similar parts is omitted. The bandpass filter 10B has the dielectric 20B. The dielectric 20B is a laminate of multiple

dielectric layers

21, 22 and 23 (also referred as, first, second and third dielectric layer). The third dielectric layer 23 is arranged between the first and second dielectric layers 21 and 22.

The bandpass filter 10B has a fourth conductor layer 321, a fifth conductor layer 322, and sixth via conductor 329. The fourth conductor layer 321 is arranged at the contact surface between the first dielectric layer 21 and the third dielectric layer 23. The fifth conductor layer 322 is arranged at the contact surface between the third dielectric layer 23 and the second dielectric layer 22. The length of the x-axial direction of fourth conductor layer 321 and the fifth conductor layer 322 is shorter than that of first conductor layer 31 and the third conductor layer 33. That is, one end 3210 of the fourth conductor layer 321 and one end 3220 of fifth conductor layer 322 are placed between the first conductor layer 31 and the third conductor layer 33. The sixth via conductor 329 is formed in the third dielectric layer 23. The sixth via conductor 329 connects the fourth conductor layer 321 near one end 3210 and the fifth conductor layer 322 near one end 3220. The sixth via conductor 329 is placed in multiple positions, and the sixth via conductor 329 is placed side by side in the y-axial direction at prescribed intervals.

With such a configuration, a part consisting of the fourth conductor layer 321, the fifth conductor layer 322, and the sixth via conductor 329 achieves the same functionality as the second conductor layer 32 of the bandpass filter 10. The bandpass filter 10B, like the bandpass filter 10, can achieve the desired filter characteristics and reduce the plane area. In addition, the bandpass filter 10B can adjust the position of the first and second post-wall waveguides in the z-axial direction accordingly. For example, bandpass filter 10B can achieve the desired filter characteristics and reduce the plane area even if the first and second post-wall waveguides are separated in the z-axial direction. It should be noted that the third via conductor 50 of FIG. 4C or FIG. 8 is referred as a third via conductor 50B in FIG. 9.

The bandpass filters 10, 10A and 10B including the above configuration can be applied, for example, to a high frequency signal amplification circuit as shown below. FIG. 10 is a schematic diagram showing one example of a high frequency signal amplification circuit to which the bandpass filter of the present disclosure is applied.

As shown in FIG. 10, a high frequency signal amplification circuit 80 includes a first amplifier 811, a second amplifier 812, a third amplifier 813, a set of amplifiers 814, a bandpass filter 82, a distributor 83, a synthesizer 84, and a first waveguide 85. The high frequency signal amplification circuit 80 also has an input port 801 and an output port 802. The input port 801 is connected to the first amplifier 811. Then, the first amplifier 811, the bandpass filter 82, the second amplifier 812, the first waveguide 85, and the third amplifier 813 are connected in series. The third amplifier 813 is connected to the distributor 83. The distributor 83 (for example, divider) is then connected to the set of amplifiers 814. The set of amplifiers 814 connects to the synthesizer 84. The synthesizer 84 is connected to output port 802.

The high frequency signal amplification circuit 80 inputs the high frequency signal from the input port 801. The high frequency signal entered at input port 801 is output to first amplifier 811. The first amplifier 811 amplifies the high frequency signal and outputs it to the bandpass filter 82. The bandpass filter 82 passes the input high frequency signal through the frequency band, which is output as the high frequency signal amplification circuit 80, and performs filtering that attenuates the other frequency bands. The bandpass filter 82 outputs the filtered high frequency signal to the second amplifier 812. The second amplifier 812 amplifies the high frequency signal from the bandpass filter 82 and outputs it to the first waveguide 85. The first waveguide 85 transmits a high frequency signal to the third amplifier 813. The third amplifier 813 amplifies the high frequency signal from the first waveguide 85 and outputs it to the distributor 83.

The distributor 83 (or divider see, DIV in FIG. 10) distributes the input high frequency signals and outputs them to the set of amplifiers 814. The set of amplifiers 814, each amplifies the input high frequency signal and output it to the synthesizer 84. The synthesizer 84 synthesizes the high frequency signals (of Cosmic Microwave Background (CMB)) from the set of amplifiers 814 and outputs them to the output port 802. Thus, the high frequency signal amplification circuit 80 constitutes a four-stage amplification circuit in the transmission direction of the high frequency signal. This allows the high frequency signal amplification circuit 80 to amplify the high frequency signal at high gain as a whole, thus constituting a so-called high power amplifier.

In this example, the high frequency signal amplification circuit 80 is composed of four stages of the amplification circuit. However, the number of stages constituting the high frequency signal amplification circuit 80 is not limited to the four stages. The number of amplifiers connected in parallel to each stage is not limited to the configuration described above. In such a configuration, the bandpass filter 82 applies the configurations of the bandpass filters 10, 10A, and 10B described above. Thus, the high frequency signal amplification circuit 80 can amplify the high frequency signal of the desired frequency with high power, suppress the undesired radiation to the outside in the bandpass filter 82, and reduce the plane area.

It will be appreciated that variations of the above disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.

Claims

A bandpass filter (10, 10A or 10B), comprising:
　　　　a first post-wall waveguide and a second post-wall waveguide, which are arranged in order in first direction, configured to convey high frequency signal in the first post-wall waveguide and the second post-wall waveguide in opposite direction to each other;
　　　　a connected waveguide, which is located on an end of a second direction, wherein the second direction is a conveying direction of the first post-wall waveguide, configured to connect to one end of the first post-wall waveguide and the second post-wall waveguide;
　　　　a first via conductor (51) located within the first post-wall waveguide and at a position at a first distance (L1) from the one end of the first post-wall waveguide;
　　　　a second via conductor (52) located within the second post-wall waveguide and at a second distance (L1) from the one end of the second post-wall waveguide; and
　　　　a third via conductor (50) located within the connected waveguide and at a position at a third distance (L2) from the one end.
The bandpass filter according to claim 1, wherein a first addition distance is obtained by adding the first distance (L1) and the third distance (L2), and a second addition distance obtained by adding the second distance (L1) and the third distance (L2).
The bandpass filter according to claim 2, wherein the first and second addition distances are set based on wavelength of the high frequency signal.
The bandpass filter according to claims 1 or 2, wherein the third distance (L2) is set based on coupling factor of the first post-wall waveguide and the second post-wall waveguide.
The bandpass filter according to any of claims 1 to 4, wherein
　　　　the first post-wall waveguide further comprises:
　　　　　　　　a first conductor layer (31);
　　　　　　　　a second conductor layer (32) running parallel to the first conductor layer (31) along the second direction and having a length of the second direction shorter than that of the first conductor layer (31); and
　　　　　　　　a plurality of fourth via conductors (411, 421) connecting the first conductor layer (31) and the second conductor layer (32);
　　　　the second post-wall waveguide further comprising:
　　　　　　　　the second conductor layer (32);
　　　　　　　　a third conductor layer (33) located at first direction side relative to the second conductor layer (32) and running parallel to the second conductor layer (32) along the second direction and having a length of the second direction longer than the second conductor layer (32); and
　　　　　　　　a plurality of fifth via conductors (412, 422) connecting the second conductor layer (32) and the third conductor layer (33);
　　　　the connected waveguide comprising:
　　　　　　　　the first conductor layer (31);
　　　　　　　　the third conductor layer (33); and
　　　　　　　　a plurality of sixth via conductors (401, 402) connecting the first conductor layer (31) to the third conductor layer (33);
　　　　the first via conductor (51) is located within an area bounded by the first conductor layer (31), the second conductor layer (32) and the plurality of fourth via conductors (411, 421),
　　　　the second via conductor (52) is located within an area bounded by the second conductor layer (32), the third conductor layer (33) and the plurality of fifth via conductors (412, 422), and
　　　　the third via conductor (50) is arranged in the area bounded by the first conductor layer (31), the third conductor layer (33) and the plurality of sixth via conductor (401, 402).
The bandpass filter according to claim 5, wherein the first via conductor (51), the third via conductor (50), the plurality of sixth via conductors (401, 402), and the plurality of fourth via conductors (411, 421) are formed in a first dielectric layer (21) of a dielectric (20).
The bandpass filter according to claim 5, wherein the second via conductor (52), the third via conductor (50), the plurality of sixth via conductors (401, 402), and the plurality of fifth via conductors (412, 422) are formed in a second dielectric layer (22) of a dielectric (20).
The bandpass filter according to any of the claims 6 to 7, wherein the first conductor layer (31) has a slit (310) positioned perpendicular to an end of the second conductor layer (32) that meets the face of the first conductor layer (31).
The bandpass filter according to claim 8, wherein the distance between the first conductor layer (31) and the second conductor layer (32) in the first direction is shorter than the distance between the second conductor layer (32) and the third conductor layer (33).
The bandpass filter according to any of the claims 1 to 9, wherein thickness of a first dielectric layer (21A) is smaller than thickness of the second dielectric layer (22).
The bandpass filter according to any of the claims 1 to 10, wherein the first via conductor (51) and the second via conductor (52) are positioned such that positions of second direction overlap and line up with the first direction.
The bandpass filter according to any of the claims 1 to 11, wherein the first via conductor (51) and the second via conductor (52) are positioned to extending to the first direction.
The bandpass filter according to any of claims 1 to 12, wherein a third dielectric layer (23) is arranged between the first dielectric layer (21) and the second dielectric layer (22).
The bandpass filter according to claim 13, wherein a sixth via conductor (329) is formed in the third dielectric layer (23).
A high frequency signal amplification circuit (80), comprising:
　　　　the bandpass filter according to any of claims 1 to 14; and
　　　　an amplifier (811, 812, 813 or 814).