Filter device and filter

A filter device including a filter and waveguide tubes broadens a band in which return loss is small. A filter device (1) includes: a filter (11) including wide walls (13, 14) and narrow walls (16); and first and second waveguide tubes (21, 31). The filter 11 includes first and second columnar conductors (pins 18 and 19) each passing through an opening (13a1 or 13a2) which is provided in the wide wall (conductor layer 13) and having one end portion (181, 191) located inside the substrate (12). The first and second waveguide tubes (21, 31) are placed such that each of the first and second columnar conductors (pin 18, 19) passes through an opening (22a, 23a) and such that another end portion (182, 192) of each of the columnar conductors (pin 18, 19) is located inside the waveguide tube (21, 31).

TECHNICAL FIELD

The present invention relates to a filter device in which a filter and two waveguide tubes are coupled to each other. The present invention also relates to a filter capable of being coupled to the waveguide tubes.

BACKGROUND ART

As filters used in millimeter wave band, filters using a waveguide tube made of a metal are widely known. FIG. 8 in Non-Patent Literature 1 illustrates a filter which can be coupled to a rectangular waveguide tube being rectangular in cross section at opposite ends thereof. This filter includes a plurality of resonators that are formed by cutting a metal block. At a boundary between the adjacent resonators is provided a coupling window for electromagnetically coupling the resonators to each other. Such a filter constructed by coupling a plurality of resonators to each other is called a resonator coupled filter.

The properties of this filter depend on a resonance frequency of each resonator and a coupling coefficient between the resonators. The resonance frequency is a physical quantity which is determined by the size of each resonator, and the coupling coefficient is a physical quantity which is determined by the size of the coupling window. Accordingly, the properties of the filter disclosed in Non-Patent Literature 1 strongly depend on the size of the filter itself.

Thus, in a case where the temperature of an external environment changes, the properties of the filter disclosed in Non-Patent Literature 1 vary according to the temperature change. In other words, the filter disclosed in Non-Patent Literature 1 is a highly temperature dependent filter. Variation of the properties of the filter will cause transmission of electromagnetic waves included in a band that are supposed to be reflected. Thus, the filter disclosed in Non-Patent Literature 1 is not suitable for use in an environment in which the temperature changes dramatically.

Examples of a filter having properties that are less temperature dependent include a filter disclosed in Non-Patent Literature 2. The filter disclosed in Non-Patent Literature 2 is a resonator-coupled constituted by a post-wall waveguide (PWW). In the PWW included in this filter, a region which is rectangular in cross-sectional shape and is surrounded by a pair of conductor layers provided on respective opposite surfaces of a substrate made of a dielectric and by a post wall constituted by a plurality of conductor posts which are placed in the substrate in a fence-like manner, functions as a propagation region through which electromagnetic waves propagate.

Note that since the substrate which is a constituent member of the PWW is small in thickness, the width of the pair of conductor layers in a cross section of the propagation region is greater than the height of the post wall (equal to the thickness of the substrate) in the cross section. Thus, in the PWW, the pair of conductor layers is also called a pair of wide walls, and the post wall is also called narrow walls. In a case where directions parallel to a normal to the pair of wide walls are referred to as upper and lower directions, directions parallel to a direction of propagation of electromagnetic waves are referred to as anterior and posterior directions, directions orthogonal to the upper and lower directions and to the anterior and posterior directions are referred to as left and right directions, the pair of wide walls surrounds the propagation region from the upper and lower directions, the narrow walls surround the propagation region from the anterior and posterior directions and from the left and right directions. Note that, of all the narrow walls, narrow walls surrounding the propagation region from the left and right directions are also referred to as side walls, and narrow walls surrounding the propagation region from the anterior and posterior directions are also referred to as short walls.

The filter disclosed in Non-Patent Literature 2 employs quartz glass as a dielectric material constituting the substrate. Quartz glass has a small linear expansion coefficient in comparison with metal. Thus, in a case where the temperature of the external environment greatly changes (in a case where the temperature of the external environment changes in a range of, for example, not less than −25° C. and not more than 100° C.), the amount of change in size of the filter itself is small, as compared to the filter disclosed in Non-Patent Literature 1. Therefore, the properties of this filter have low temperature dependence, as compared to the filter disclosed in Non-Patent Literature 1.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

A filter is a passive device that limits a center frequency and bandwidth of electromagnetic waves to be transmitted. However, the coupling section between the filter and the waveguide tube is required to reduce return loss over a wide band. This is because the filter must limit a band of electromagnetic waves, and it is not preferable that the bandwidth is limited by the coupling section between the filter and the waveguide tube.

Unfortunately, the filter disclosed in Non-Patent Literature 2, when connected with a waveguide tube, tends to have large return loss, and it is thus difficult to broaden a bandwidth in which reflection loss is small. This problem will be described below.

Patent Literatures 1 to 3 each disclose, as described below, transmission lines in which a waveguide tube is coupled to one end portion of the PWW. These transmission lines can be used as a structure for coupling the filer and waveguide tube disclosed in Non-Patent Literature 2 to each other.

In the transmission line illustrated in FIGS. 1 to 4 of Patent Literature 1 (in Patent Literature 1, the transmission line is described as “connection structure”), a coupling window is provided by omitting a short wall of the PWW, and part of the short wall of the waveguide tube is opened (in Patent Literature 1, the short wall is described as “closure structure”). In this transmission line, the open part of the short wall in the waveguide tube faces the coupling window of the PWW so that the PWW and the waveguide tube are coupled to each other.

In the transmission line illustrated in FIGS. 1 to 3 of Patent Literature 2 (in Patent Literature 2, the transmission line is described as “transmission mode converting device”), the PWW and the waveguide tube are placed in such a manner that they share a conductor layer provided on one surface of the substrate. This conductor layer functions as one wide wall of the PWW and also functions as one wide wall of the waveguide tube (see FIG. 3). To the wide wall shared by the PWW and the waveguide tube are provided four rectangular coupling windows. In this transmission line, the PWW and the waveguide tube are coupled to each other via these four coupling windows.

In the transmission line illustrated in FIGS. 1 and 2 of Patent Literature 3, a coupling window is provided in one wide wall of the PWW, and a short wall of the waveguide tube is opened. In this transmission line, a part of the wide wall where the coupling window is provided in the PWW faces an open cross section of the short wall of the waveguide tube so that the PWW and the waveguide tube are coupled to each other.

Further, the transmission lines disclosed in Patent Literatures 1 to 3 employ a microstrip line (MSL) as a planar transmission path to be coupled to an end portion of the PWW on a side away from another end portion thereof on a side to which the waveguide tube is connected, wherein the MSL includes a signal line and a ground layer. Those transmission lines include a columnar conductor (for example, in Patent Literature 3, the columnar conductor is described as a power feeding pin) that converts a mode of propagating through the inside of the PWW into a mode of propagating through the inside of the MSL. This columnar conductor couples the PWW and the waveguide tube.

The above-described transmission lines as disclosed in Patent Literatures 1 to 3, in a case where they are used as a transmission line in which a filter and a waveguide tube are coupled to each other, are required to have small return loss (e.g., return loss of −15 dB or less) over a wide band (e.g., in the case of operation in the E-band, not less than 71 GHz to not more than 86 GHz).

For example, in a case where −15 dB is set as a threshold value against which to judge return loss, the bandwidths of all of the transmission lines disclosed in Patent Literatures 1 to 3 are less than 10 GHz (see FIG. 9 of Patent Literature 1, FIG. 13 of Patent Literature 2, and FIG. 4 of Patent Literature 3). These bandwidths are not sufficient for transmission lines in which a filter and waveguide tubes are coupled to each other, and the conventional transmission lines have room for broadening of the band.

The present invention has been made in view of the above problem, and it is an object of the present invention to broaden a band in which return loss is small in a filter device including (i) a filter using a PWW and (ii) waveguide tubes coupled to the filter.

Solution to Problem

In order to solve the above problem, a filter device in accordance with an aspect of the present invention is a filter device, including: a filter comprising a substrate made of a dielectric, a pair of wide walls being constituted by a first conductor layer and a second conductor layer, respectively, and covering respective opposite surfaces of the substrate, and narrow walls being constituted by post walls which are provided inside the substrate; and a first waveguide tube and a second waveguide tube each including a tube wall made of a conductor and being placed along the substrate.

The filter further includes: a first columnar conductor passing through a first opening which is provided in the first conductor layer, the first columnar conductor having one end portion located inside the substrate; and a second columnar conductor passing through a second opening which is provided in the first conductor layer or the second conductor layer, the second columnar conductor having one end portion located inside the substrate.

The first waveguide tube is placed such that the first columnar conductor passes through an opening which is provided in the tube wall of the first waveguide tube and such that another end portion of the first columnar conductor is located inside the first waveguide tube, and the second waveguide tube is placed such that the second columnar conductor passes through an opening which is provided in the tube wall of the second waveguide tube and such that another end portion of the second columnar conductor is located inside the second waveguide tube.

In order to solve the above problem, a filter in accordance with an aspect of the present invention is a filter including: a substrate made of a dielectric; a pair of wide walls being constituted by a first conductor layer and a second conductor layer, respectively, and covering respective opposite surfaces of the substrate; and narrow walls being constituted by post walls which are provided inside the substrate, the filter further including: a first columnar conductor passing through a first opening which is provided in the first conductor layer, the first columnar conductor having one end portion located inside the substrate; and a second columnar conductor passing through a second opening which is provided in the first conductor layer or the second conductor layer, the second columnar conductor having one end portion located inside the substrate.

Advantageous Effects of Invention

A filter device and a filter in accordance with an aspect of the present invention can broaden a band in which return loss is small.

DESCRIPTION OF EMBODIMENTS

A filter device in accordance with an aspect of the present invention is a filter device obtained by coupling (i) a filter constituted by a post-wall waveguide (PWW) and (ii) two waveguide tubes (first waveguide tube and second waveguide tube). In the filter device in accordance with an aspect of the present invention, the filter is provided between the first waveguide tube and the second waveguide tube.

A filter device in accordance with an aspect of the present invention is designed to be operated in the E-band (band of not less than 70 GHz to not more than 90 GHz). Further, a filter device in accordance with an aspect of the present invention is designed to be operated in an external environment with a temperature of not less than −25° C. and not more than 100° C.

A filter device in accordance with Embodiment 1 of the present invention will be described with reference toFIGS. 1 and 2.FIG. 1is an exploded perspective view illustrating a filter device1in accordance with Embodiment 1.FIG. 2is a cross-sectional view illustrating a PWW-waveguide tube converting section included in the filter device1.

In the filter device1, a filter11, a waveguide tube21, and a waveguide tube31are placed such that directions of propagation of electromagnetic waves in the filter11, the waveguide tube21, and the waveguide tube31are in line with each other (preferably become parallel to each other). In orthogonal coordinate systems illustrated inFIGS. 1 and 2, a y-axis is set to the directions of propagation of electromagnetic waves in the filter11, the waveguide tube21, and the waveguide tube31, a z-axis is set to a direction normal to a surface of a substrate12, and an x-axis is set to a direction orthogonal to the y-axis and the z-axis.

Note that, in the present specification, in accordance with the orientation of the filter device1arranged as illustrated inFIG. 1, a z-axis positive (negative) direction is referred to as an upper (lower) direction, an x-axis positive (negative) direction is referred to as a left (right) direction, and a y-axis positive (negative) direction is referred to as an anterior (posterior) direction. Further, in a case where no specification of whether a positive direction or a negative direction is made, a z-axis direction is referred to as upper and lower directions, an x-axis direction is referred to as left and right directions, and a y-axis direction is referred to as anterior and posterior directions.

As illustrated inFIG. 1, the filter device1includes the filter11constituted by a PWW, the waveguide tube21, and the waveguide tube31. The waveguide tube21and the waveguide tube31are a first waveguide tube and a second waveguide tube, respectively, recited in the claims.

The filter11is a laminate substrate in which a conductor layer13and a conductor layer14are provided on opposite sides of a substrate12made of a dielectric (made of quartz glass in Embodiment 1). The conductor layer13and the conductor layer14are, respectively, a first conductor layer and a second conductor layer recited in the claims. Note that the substrate12need only be made of a dielectric, and the dielectric which constitutes the substrate12may be selected as appropriate in consideration of at least one of a relative dielectric constant, processability, and the like.

The filter11has a first region R1provided in advance in the vicinity of an opening13a1(described later). In the first region R1, part of a tube wall of the waveguide tube21can be placed. Further, the filter11has a second region provided in advance in the vicinity of an opening13a2(described later). In the second region, part of a tube wall of the waveguide tube31can be placed. The opening13a1and the opening13a2are a first opening and a second opening recited in the claims.

Inside the substrate12are provided post walls obtained by arranging a plurality of conductor posts161i,162i,163j, and164j(where i and j are any positive integers) in a fence-like manner (seeFIG. 1).

The plurality of conductor posts161i,162i,163j, and164jare obtained by charging a conductor such as a metal into vias, which are formed so as to pass through the substrate12from the front surface to the rear surface of the substrate12, or by depositing the conductor on internal surfaces of the vias. All of the plurality of conductor posts161i,162i,163j, and164jelectrically connect the conductor layer13and the conductor layer14. Note that a diameter of the conductor posts161i,162i,163j, and164jmay be set as appropriate according to the operation band. In Embodiment 1, the diameter of the conductor posts161i,162i,163j, and164jis 100 μm. Further, an interval between adjacent ones of the conductor posts161i, an interval between adjacent ones of the conductor posts162i, an interval between adjacent ones of the conductor posts163j, and an interval between adjacent ones of the conductor posts164jare each 100 μm, which is equal to the diameter of the conductor posts161i,162i,163j, and164j.

A side wall161, which is a post wall obtained by arranging the plurality of conductor posts161iat a predetermined spatial period in a fence-like manner, functions as a kind of conductor wall that reflects electromagnetic waves in a band corresponding to the spatial period.

Similarly, a post wall obtained by the plurality of conductor posts162iconstitutes a side wall162, a post wall obtained by the plurality of conductor posts163jconstitutes a short wall163, and a post wall obtained by the plurality of conductor posts164jconstitutes a short wall164. Further, the side walls161and162and the short walls163and164are collectively referred to as narrow walls16. Individual plane surfaces represented by imaginary lines (two-dot chain lines) illustrated inFIG. 1are imaginary plane surfaces each including corresponding ones of central axes of the plurality of conductor posts161i,162i,163j, and164j, and are plane surfaces each schematically representing a conductor wall which is imaginarily realized by a corresponding one of the side walls161and162and the short walls163and164.

Note thatFIG. 1omits some of the conductor posts161i, some of the conductor posts162i, some of the conductor posts163j, and some of the conductor posts164j, for ease of viewing of the configuration of the PWW-waveguide tube converting section (described later).

As illustrated inFIG. 1, the narrow walls16surround a rectangular parallelepiped-shaped region from the anterior and posterior directions and from the left and right directions. Further, the conductor layer13and the conductor layer14, which are a pair of wide walls, surround the rectangular parallelepiped-shaped region from the upper and lower directions, respectively. Electromagnetic waves propagate through a propagation region, i.e. the rectangular parallelepiped-shaped region, in the y-axis direction of the propagation region. Thus, the PWW is constituted by a pair of wide walls and narrow walls.

In Embodiment 1, the above-described rectangular parallelepiped-shaped propagation region is divided into a resonator11a, a resonator11b, a resonator11c, and a resonator11dby partition walls171,172, and173. Note that, as with the narrow walls16, the partition walls171,172, and173are constituted by post walls.

Although the partition wall171is constituted by the conductor posts, no conductor posts are provided in and near a center of the partition wall171. Thus, the conductor posts are not provided in some area of the post walls, and such an area functions as a coupling window171athrough which the resonator11aand the resonator11b, adjacent to each other, are electromagnet coupled.

Similarly, through a coupling window172aprovided in and near the center of the partition wall172, the resonator11band the resonator11care coupled. Through a coupling window173aprovided in and near the center of the partition wall173, the resonator11cand the resonator11dare coupled.

The filter11configured by electromagnetically coupling the resonators11ato11din this manner is a resonator-coupled filter.

The waveguide tube21is made of a conductor (in Embodiment 1, a brass surfaced with gold plating). As illustrated inFIG. 1, the waveguide tube21includes a tube wall22, which is rectangular in cross section, and a short wall23. The short wall23seals an end portion (end portion on a y-axis negative direction side) of the tube wall22. That is, the waveguide tube21is a rectangular waveguide tube. The tube wall22has a wide wall221and a wide wall222, which are a pair of wide walls, and a narrow wall223and a narrow wall224, which are a pair of narrow walls.

Out of the pair of wide walls, the wide wall222located on a filter11side (on a z-axis negative direction side) has an opening22a, which is larger in diameter than a pin18(described later).

To couple the filter11and the waveguide tube21, the waveguide tube21is brought close to the filter11in the z-axis negative direction from a disassembled state illustrated inFIG. 1, and the waveguide tube21is placed on the filter11in such a manner that the pin18passes through the opening22a, and a lower surface of the wide wall222comes into close contact with an upper surface of the conductor layer13without any gap between them.

In the filter device1configured as described above, the waveguide tube21is electromagnetically coupled to the filter11via the pin18. Thus, the pin18is a PWW-waveguide tube converting section through which the filter11, which is constituted by PWW, and the waveguide tube are coupled. The PWW-waveguide tube converting section will be described in detail later with reference toFIG. 2.

In Embodiment 1, an end portion (end portion on a y-axis positive direction side) of the waveguide tube21on a side facing away from the short wall23is trimmed off so as to be flush with an end face of the substrate12on the y-axis positive direction side. However, the end portion of the waveguide tube21on the y-axis positive direction side may further extend toward the y-axis positive direction side, without being trimmed off. Further, as described later with reference toFIG. 7, the end portion of the waveguide tube21on the y-axis positive direction side may be coupled to a device, such as an antenna, which is suitable to be coupled with use of a waveguide tube.

Note that, in Embodiment 1, the waveguide tube21is left hollow inside. Instead of having such a hollow structure, the waveguide tube21may be configured such that dielectric particles for adjusting a relative dielectric constant are charged into the waveguide tube21.

The waveguide tube31has the same configuration as that of the waveguide tube21. That is, the waveguide tube31is constituted by a tube wall32and a short wall33. The tube wall32has a wide wall321and a wide wall322, which are a pair of wide walls, and a narrow wall323and a narrow wall324, which are a pair of narrow walls. Further, the wide wall322has an opening32athat is larger in diameter than a pin19(described later).

In the waveguide tube21, the short wall23is placed on the filter11so as to be located on the y-axis negative direction side. In contrast, in the waveguide tube31, the short wall33is placed on the filter11so as to face in the direction opposite to the direction in which the waveguide tube21faces, that is, so as to be located on the y-axis positive direction side.

The waveguide tube31is electromagnetically coupled to the filter11via the pin19. Thus, as in the case of the pin18, the pin19is a PWW-waveguide tube converting section. The PWW-waveguide tube converting section will be described in detail later with reference toFIG. 2.

The filter device1includes a first PWW-waveguide tube converting section, in which the filter11and the waveguide tube21are coupled to each other, and a second PWW-waveguide tube converting section, in which the filter11and the waveguide tube31are coupled to each other. The first PWW-waveguide tube converting section and the second PWW-waveguide tube converting section have the same configuration. Thus, in Embodiment 1, the PWW-waveguide tube converting section included in the filter device1will be described by taking the first PWW-waveguide tube converting section as an example.

A cross-sectional view of a cross section taken along line A-A′ inFIG. 1(a cross section along a y-z plane surface) is illustrated inFIG. 2.FIG. 2is a cross-sectional view illustrating the vicinity of the pin18.

As illustrated inFIG. 2, a portion of the conductor layer13is cut out in the shape of a ring in the vicinity of the conductor posts163j(conductor posts constituting the short wall163) in the propagation region of the filter11. As a result, the conductor layer13is provided with an opening13a1. Inside the opening13a1is provided a land131(not illustrated inFIG. 1) which is concentric with the opening13a1. Further, a circular opening is provided in and near the center of the land131(preferably in the center of the land131), and the substrate12has a cylindrical pore which communicates with the circular opening and extends from a surface of the substrate12(the surface on a z-axis positive direction side) to the inside of the substrate12. As illustrated inFIG. 2, the pore is a non-through-hole.

The pin18(first columnar conductor recited in the claims) made of a metal is secured to the substrate12by being inserted into the opening and pore of the land131described above. The pin18being inserted into the substrate12in this way passes through the opening13a1, and a lower end portion181of the pin18(one end portion recited in the claims) is located inside the substrate12, i.e. in the propagation region of the filter11. Further, an upper end portion182(another end portion recited in the claims) of the pin18being secured in this way is located inside the waveguide tube21, i.e. in the propagation region of the waveguide tube21.

The diameter of the pin18, the length of the pin18(length along the z-axis direction), the length of a portion of the pin18inserted into the substrate12, and the length of a portion of the pin18protruding through the surface of the substrate12can be used as design parameters for optimizing return loss. For example, in Embodiment 1, 180 μm is employed as the diameter of the pin18.

Note that the end portion182of the pin18is not in electrical communication with the wide wall221. The length of the portion of the pin18protruding through the substrate can be adjusted within the bounds of the end portion182not contacting the wide wall221.

In a case where electromagnetic waves propagating through the propagation region of the filter11in the y-axis positive direction are present, the portion of the pin18inserted into the substrate12draws the electromagnetic waves which have propagated through the propagation region of the filter11, and the portion of the pin18protruding through the substrate12radiates the electromagnetic waves into the propagation region of the waveguide tube21. Similarly, in a case where electromagnetic waves propagating through the propagation region of the waveguide tube21in the y-axis negative direction are present, the portion of the pin18protruding through the substrate12draws the electromagnetic waves from the propagation region of the waveguide tube21, and the portion of the pin18inserted into the substrate12radiates the electromagnetic waves into the propagation region of the filter11. Thus, the pin18functions as the PWW-waveguide tube converting section.

As described above, the pin18electromagnetically couples a mode of propagating through the propagation region of the filter11and a mode of propagating through the propagation region of the waveguide tube21. The coupling between the filter11and the waveguide tube21via the pin18is provided over a wide band, in comparison to coupling with use of the conventional coupling window. Thus, the filter device1including the pin18can reduce return loss at a coupling section between the filter11and the waveguide tube21over a wide band, in comparison to the conventional transmission device. Thus, the filter device1can broaden a band in which return loss is small, in comparison to the conventional transmission line.

Note that, as described earlier, the filter11illustrated inFIGS. 1 and 2can be easily coupled to the waveguide tube21and the waveguide tube31with use of (i) the waveguide tube21having the tube wall22with the opening22aand (ii) the waveguide tube31having the tube wall32with the opening32a. Specifically, it is possible to couple the filter11and the waveguide tube21by passing the pin18through the opening22aprovided in the waveguide tube21and by placing the waveguide tube21such that the end portion182of the pin18is located inside the waveguide tube21. The same applies to coupling of the filter11and the waveguide tube31

A coupling section, provided in this way, between the filter11and the waveguide tube21can reduce return loss over a wide band. Similarly, a coupling section, provided in this way, between the filter11and the waveguide tube31can reduce return loss over a wide band. Thus, the filter11is also included in the technical scope of the present invention.

A pin118, which is a variation of the pin18, will be described with reference toFIG. 3. (a) ofFIG. 3is a cross-sectional view illustrating a filter device1including the pin118. (b) ofFIG. 3is an enlarged cross-sectional view illustrating the pin118. Note that, in Embodiment 1, a variation is described by taking the pin118as an example. However, as a matter of course, it is also possible to employ, as a variation of the pin19, the structure of the pin118obtained by deforming the pin18. In a case where the pin118is employed as the first PWW-waveguide tube converting section included in the filter device1, it is preferable to employ a variation of the pin19as the second PWW-waveguide tube converting section.

In the filter device1illustrated inFIG. 3, the pin18included in the filter device1illustrated inFIGS. 1 and 2is replaced by the pin118, and the waveguide tube21included in the filter device1illustrated inFIGS. 1 and 2is replaced by a waveguide tube121. In the present variation, only different features of the filter device1illustrated inFIG. 3, as compared with the features of the filter device1illustrated inFIGS. 1 and 2, will be described.

The pin118is divided into a blind via118a, which is a first part, and a blind via118b, which is a second part.

The blind via118ais configured as below. An opening13a1is provided in the vicinity of the conductor post163jin the propagation region of the filter11. Inside the opening13a1, a land131is provided. Further, a cylindrical pore is provided in and near the center of the land131(preferably in the center of the land131). The pore is a non-through-hole. The blind via118ais obtained by charging a conductor such as a metal into the non-through-hole or by depositing the conductor on an internal surface of the non-through-hole. The blind via118ahas a lower end portion (one end portion recited in the claims) located inside the substrate12, i.e. in the propagation region of the filter11. Further, the blind via118ahas an upper end portion (another end portion recited in the claims) which is in electrical communication with the land131.

The blind via118bis embedded in a block119made of a dielectric (made of quartz glass in Embodiment 1), an upper end portion118b1(end portion on the z-axis positive direction side) is located inside the block119, and a lower end portion118b2(end portion on the z-axis negative direction side) reaches the surface of the block119.

The blind via118bcan be produced as follows: A substrate used as the block119is a substrate (i) having a thickness smaller than a distance between the wide walls1221and1222of the waveguide tube121, (ii) being made of a dielectric (made of quartz glass in Embodiment 1), and (iii) having a conductor layer120formed on one surface (surface on the z-axis negative direction side inFIG. 3) of the substrate. A plurality of blind vias are formed in a matrix manner on the substrate having the conductor layer120formed thereon. Then, by cutting the substrate having the plurality of blind vias formed thereon into cubes, the block119having the blind via118bformed thereon is obtained. Then, by cutting out a portion of the conductor layer120in a ring shape, (i) a land1201which is in electrical communication with the blind via118band (ii) the conductor layer120surrounding the land1201while being spaced away from the land1201are formed on the surface of the block119.

As illustrated in (b) ofFIG. 3, the land1201is connected to the land131with use of a bump B1. The conductor layer120is connected to the conductor layer13with use of bumps B2and B3. The bumps B1to B3, which are an aspect of an electrically conductive connecting member, are each obtained by forming a solder layer on a surface of a metallic spherical member. In this manner, the blind via118bis connected and secured to the blind via118a.

Here, to reduce return loss as much as possible, it is preferable that a central axis of the blind via118abe coaxial (coincide) with a central axis of the blind via118b.

The electrically conductive connecting member may be a solder, an electrically conductive adhesive (e.g., silver paste), or the like as an alternative to the bumps. However, by employing the bumps B1to B3having a uniform diameter as the electrically conductive connecting member, it is possible to easily enhance parallelism between the surface of the substrate12on which the conductor layer13is formed and the surface of the block119on which the conductor layer120is formed. Thus, it is easy to connect the blind via118aand the blind via118bin a state in which the central axis of the blind via118aand the central axis of the blind via118bare parallel to each other.

In the case of the pin18, a cylindrical pore having a predetermined diameter (e.g., 180 μm) is provided in advance on the substrate12at a predetermined position, and the pin18is inserted into the pore so that the pin18is secured to the substrate12. In this case, the diameter of the pore needs to be precisely formed. The predetermined diameter is defined with a certain margin (tolerance). However, in a case where the diameter of a provided pore is smaller than the predetermined diameter, the pin18cannot be inserted into the substrate. In a case where the diameter of a provided pore is larger than the predetermined diameter, the pin18cannot be firmly secured to the substrate.

Further, the pin18, which is a very thin columnar conductor, tends to bend when inserted into the pore. Therefore, the operation of inserting the pin18into the substrate12need to be done with a high degree of precision, regardless of whether when a person carries out the operation by hand or when a manipulator controlled by a machine is used to carry out the operation.

On the contrary, in the case of the pin118, the blind via118aand the blind via118bcan be connected easily and accurately with use of the electrically conductive connecting member such as the bumps B1to B3. Thus, the filter device1with the pin118can be easily produced in comparison with the filter device1with the pin18.

Further, the configuration in which the blind via118b, which is the second part, is embedded in the block119provides ease of handling in comparison with a configuration in which the second part is merely a columnar conductor (a configuration in which the blind via118bis not embedded in the block119). Thus, the filter device1with the pin118can be produced more easily.

With the pin118embedded in the block119, a size of an opening122a(see (a) ofFIG. 3) provided on the wide wall1222of the waveguide tube121is larger than the opening22a(seeFIG. 2). Specifically, when the filter device1is viewed in a plan view, the size of the opening122ais increased so as to encompass the block119. With such a configuration, the waveguide tube21can be placed easily at a predetermined position even when the pin118is embedded in the block119.

EXAMPLES

As Example 1 of the present invention, reflection characteristics and transmission characteristics were calculated with use of the configuration of the PWW-waveguide tube converting section included in the filter device1illustrated inFIG. 2. In Example 1, the pin18is employed as the PWW-waveguide tube converting section. In Example 1, design parameters of the pin18were determined as follows:Diameter: 180 μmLength of the portion inserted into the substrate12: 420 μmLength of the portion protruding through the substrate12: 700 μm

As Example 2 of the present invention, reflection characteristics and transmission characteristics were calculated with use of the configuration of the PWW-waveguide tube converting section included in the filter device1illustrated inFIG. 3. In Example 2, the pin118is employed as the PWW-waveguide tube converting section.

Note that the design parameters common to both Example 1 and Example 2 were determined as follows:

Thickness of the substrate12: 520 μmDielectric constant of the substrate12: 3.89
Waveguide tube21Distance between the wide wall221and the wide wall222: 1149 μmDistance between the narrow wall223and the narrow wall224: 2500 μm.

(Reflection Characteristics and Transmission Characteristics)

(a) ofFIG. 4is a graph showing reflection characteristics (frequency dependence of S11) and transmission characteristics (frequency dependence of A21) in Example 1. (b) ofFIG. 4is a graph showing reflection characteristics (frequency dependence of S11) and transmission characteristics (frequency dependence of S parameter S21) in Example 2. In both (a) ofFIG. 4and (b) ofFIG. 4, the symbol “S11” is given to a plot of the reflection characteristic, and the symbol “S21” is given to a plot of the transmission characteristics.

Referring to (a) ofFIG. 4, the reflection characteristics, S11, in Example 1 is not more than −15 dB in a band of approximately not less than 71 GHz to not more than 88 GHz.

Referring to (b) ofFIG. 4, the reflection characteristics, S11, in Example 2 is not more than −15 dB in a band of approximately not less than 73 GHz to not more than 90 GHz.

As described above, the transmission lines in Examples 1 and 2 achieved reduction of return loss over a wide band, in comparison to the transmission line provided with the conventional PWW-waveguide tube converting section with use of a coupling window.

Further, both Example 1 and Example 2, with return loss reduced over a wide band, exhibit favorable transmission characteristics over a wide band.

The second PWW-waveguide tube converting section has the same configuration as that of the first PWW-waveguide tube converting section. Thus, the second PWW-waveguide tube converting section shows the same results as those shown in the Examples described above.

A filter device in accordance with Embodiment 2 of the present invention will be described with reference toFIG. 5. (a) and (b) ofFIG. 5are each a cross-sectional view illustrating a filter device401in accordance with Embodiment 2. (a) ofFIG. 5illustrates a cross-sectional view taking along a plane surface (y-z plane surface) that (i) includes a central axis of a pin418, which is a columnar conductor constituting the PWW-waveguide tube converting section, and (ii) extends along a direction (y-axis direction) of propagation of electromagnetic waves. (b) ofFIG. 5illustrates cross-sectional view taken along a plane surface (z-x plane surface) that (i) includes the central axis of the pin418and (ii) intersects the direction (y-axis direction) of propagation of electromagnetic waves.

As illustrated inFIG. 5, the filter device401includes a filter411, a housing441, and a resin substrate451.

The filter411has the same configuration as that of the filter11illustrated inFIGS. 1 and 2. Corresponding constituent members of the filter411have reference symbols which are obtained by putting “4” in front of reference symbols of the constituent members of the filter11. In Embodiment 2, descriptions of those constituent members will be omitted.

The housing441illustrated inFIG. 5is made by forming, in a rectangular parallelepiped-shaped metal block, tubular spaces4211and4311rectangular in cross section and a recess4411for accommodating the filter411. The tubular space4211and the tubular space4311correspond to the first tubular space and the second tubular space recited in the claims, respectively.

InFIG. 5, the housing441is placed on a resin substrate451(described later) such that a lengthwise direction of the metal block coincides with a y-axis direction of an orthogonal coordinate system illustrated inFIG. 5, and a height direction of the metal block coincides with a z-axis direction of the orthogonal coordinate system illustrated inFIG. 5.

Out of six side wall surfaces constituting the metal block, a z-x plane surface on a y-axis positive direction side has the rectangular parallelepiped-shaped tubular space4211which is dug in the y-axis negative direction. Further, out of the six side wall surfaces constituting the metal block, a z-x plane surface on a y-axis negative direction side has the rectangular parallelepiped-shaped tubular space4311which is dug in the y-axis positive direction. These tubular spaces4211and4311function as waveguide tubes421and431that guide electromagnetic waves in the y-axis direction, respectively, in the same manner as the waveguide tubes21and31illustrated inFIGS. 1 and 2.

In other words, as illustrated in (a) and (b) ofFIG. 5, an upper wall4221, a lower wall4222, a right wall4223, and a left wall4224, all of which surround the sides of the tubular space4211, constitute a tube wall422of the waveguide tube421. Out of the walls defining the tubular space4211, the wall along the z-x plane surface constitutes a short wall423of the waveguide tube421. Thus, the upper wall4221and the lower wall4222form a wide wall of the waveguide tube421. The right wall4223, the left wall4224, and the short wall423form a narrow wall of the waveguide tube421.

The tubular space4311is constituted in the same manner as the tubular space4211and is defined by a tube wall432and a short wall433. The tube wall432is constituted by an upper wall4321and a lower wall4322, which are a pair of wide walls, and a right wall4323and a left wall4324, which are a pair of narrow walls. In the state illustrated in (a) ofFIG. 5, the tubular space4311is provided so as to be mirror symmetric to the tubular space4211about a symmetry axis (axis parallel to a z-axis). A distance between the short wall423and the short wall433is set according to a distance between the pin418and the pin419. Then, the tubular space4311is provided such that the above-described symmetry axis coincides with an imaginary line which is a set of points equidistant from the pin418and the pin419.

Out of six side wall surfaces constituting the metal block, an x-y plane surface on a z-axis negative direction side has the rectangular parallelepiped-shaped recess4411which is dug in the z-axis positive direction. The shape of an opening of the recess4411corresponds to the shape of the substrate412of the filter411. To allow the recess4411to accommodate the filter411, the filter411is pushed into the recess4411through the opening of the recess4411in the z-axis positive direction. Note that the recess4411is provided at a position so as to be mirror symmetric about a symmetry axis (axis parallel to the z-axis). The symmetry axis about which the recess4411is mirror symmetric coincides with the symmetry axis about which the tubular space4211and the tubular space4311are mirror symmetric.

Note that a rim of the housing441around the recess4411is referred to as a skirt4412. To reliably accommodate the filter411, the depth of the recess4411, i.e. the height of the skirt4412, is set to be greater than the thickness of the filter411(total thickness of the substrate412, the conductor layer413, and the conductor layer414).

As illustrated in (a) and (b) ofFIG. 5, an opening421ais provided at a boundary between a region of the tubular space4211on the y-axis negative direction side of the lower wall4222, which is one of the members defining the tubular space4211, and a region of the bottom surface of the recess4411on the y-axis positive direction side. The tubular space4211and the recess4411communicate with each other via the opening421a.

Similarly, an opening431ais provided at the boundary between the tubular space4311and the recess4411. The tubular space4311and the recess4411communicate with each other via the opening431a.

The filter411is placed inside the recess4411such that (1) an end portion of the pin418, which is the first PWW-waveguide tube converting section, on the z-axis positive direction side is located inside the tubular space4211, and the conductor layer413seals the opening421aand such that (2) an end portion of the pin419, which is the second PWW-waveguide tube converting section, on the z-axis positive direction side is located inside the tubular space4311, and the conductor layer413seals the opening431a. Thus, in the region in which the opening421ais provided, a portion of the conductor layer413that seals the opening421afunctions as a portion of the lower wall4222of the waveguide tube421. Further, in the region in which the opening431ais provided, a portion of the conductor layer413that seals the opening431afunctions as a portion of the lower wall4322of the waveguide tube431.

According to this configuration, the pin418can electromagnetically couple a mode of propagating through the waveguide tube421and a mode of propagating through the filter411. Since the opening421ais sealed by the conductor layer413, loss does not increase. Similarly, the pin419can electromagnetically couple a mode of propagating through the waveguide tube431and a mode of propagating through the filter411. Since the opening431ais sealed by the conductor layer413, loss does not increase.

Further, the housing441is configured such that the whole of the filter411is accommodated inside the recess4411. Therefore, the housing441can reliably protect the filter411(in particular, substrate412) against an external impact.

Note that as illustrated inFIG. 5, the waveguide tube421may be coupled to another waveguide tube, i.e. a waveguide tube461, on an open end side of the waveguide tube421. The waveguide tube431may be coupled to another waveguide tube, i.e. a waveguide tube471, on an open end side of the waveguide tube431. In Embodiment 2, a flange442is provided on the open end side of the waveguide tube421. Further, a flange463is provided at the end portion of the waveguide tube461on the waveguide tube421side. The flange442and the flange463are secured with use of a bolt481and a nut482, so that the waveguide tube421and the waveguide tube461are coupled to each other. The same applies to a flange443, which is provided on an open end side of the waveguide tube431, and a flange473, which is included in the waveguide tube471.

The resin substrate451is configured such that the resin substrate451is capable of holding the filter411in a state in which the filter411is sandwiched between the resin substrate451and the housing441. As illustrated in (b) ofFIG. 5, the housing441and the resin substrate451are secured with use of bolts483and485and nuts484and486. A combination of the bolt483and the nut484and a combination of the bolt485and the nut486are each an aspect of a pressure applying member recited in the claims. The pressure applying member is not limited to a combination of a bolt and a nut.

The resin substrate451is made of resin (made of glass epoxy resin in Embodiment 2). A resin material constituting the resin substrate451can be selected as appropriate in view of thermal expansion properties, processability, and the like.

On a surface of the resin substrate451on a side facing the filter411(on the z-axis positive direction side), is provided a protrusion in a shape corresponding to the recess4411(in a shape corresponding to a skirt4412). This protrusion pushes the filter411toward the housing441(to the z-axis positive direction side).

At this time, the height of the skirt4412of the housing441is so set that the skirt4412and the resin substrate451are spaced away from each other.

According to the above configuration, the protrusion of the resin substrate451pushes the conductor layer414of the filter411in the z-axis positive direction. As a result, the conductor layer413of the filter411is pushed onto the bottom surface of the recess4411of the housing441. That is, the surface of the conductor layer413and the bottom surface of the recess4411are in close contact with each other, and thus prevent generation of an air gap in an interface IF.

Thus, the housing441and the resin substrate451are secured in a state in which the surface of the conductor layer413and the bottom surface of the recess4411are in close contact with each other without any gap between them.

With the above configuration, the filter411is sandwiched between the housing441and the resin substrate451. This prevents the filter411from being displaced inside the recess4411. In this way, the filter411and the waveguide tube421can be reliably held in proper positions in relation to each other, and the filter411and the waveguide tube431can be reliably held in proper positions in relation to each other. Thus, it is possible to prevent fluctuation of return loss that can occur at a coupling section between the filter411and the waveguide tube421and at a coupling section between the filter411and the waveguide tube431. Thus, the filter device401can reliably broaden a band in which return loss is small, in comparison to the conventional transmission line.

Further, since it is possible to prevent generation of an air gap in the interface IF, it is possible to prevent electromagnetic waves propagating through the waveguide tube421and electromagnetic waves propagating through the waveguide tube431from entering the interface IF. Thus, it is possible to further reduce loss that can occur at the coupling section between the filter411and the waveguide tube421and at the coupling section between the filter411and the waveguide tube431.

Further, according to the above configuration, the waveguide tube421is integrally molded with the housing441, and the filter411is firmly secured to the recess4411of the housing441. Thus, the filter device401allows the waveguide tube421and the waveguide tube431to be firmly coupled to the filter411.

A filter device501, which is Variation 1 of the filter device401, will be described with reference toFIG. 6. Corresponding constituent members of the filter device501in common with the filter device401have reference symbols which are obtained by replacing the initial number “4” of reference symbols for the filter device401(seeFIG. 5) by “5”. In the present variation, only different features of the filter device501, as compared with the features of the filter device401, will be described, and the other features will be omitted.

As illustrated inFIG. 6, a resin substrate551included in the filter device501has no protrusion provided thereon, although the resin substrate451has the protrusion provided thereon. That is, a surface of the resin substrate551on the side facing the housing541is constituted by a flat surface.

A skirt5412is configured such that the height of the skirt5419is greater than the thickness of the filter511(total thickness of a substrate512, a conductor layer513, and a conductor layer514). This allows the conductor layer514and the resin substrate551to be spaced away from each other. That is, the conductor layer514and the resin substrate551have an air gap between them. In this way, the filter device501has an air gap between the conductor layer514and the resin substrate551. Thus, in an area where the air gap is present, a protrusion (protrusion of the resin substrate451) may be provided on the surface of the resin substrate551on a side facing the housing541

In the present embodiment, a resin material is filled in the air gap. Examples of the resin material include an adhesive, a resin mold, and the like. These resin materials are viscous fluids when filled, and then cures into a solid after a lapse of a predetermined time period.

For example, assume that a resin material in an amount exceeding the volume of the above-described air gap is filled in the air gap. In this case, the resin material thus filled is raised above the air gap by surface tension. In this state, the curing reaction of the resin material is proceeded. Then, at a point in time when the resin material becomes semi-cured, the resin substrate551is secured to the housing541. According to this configuration, the resin material having a volume which exceeds the volume of the air gap causes a pressure for pushing the filter511toward the housing541(to the z-axis positive direction). Thus, according to this configuration, it is possible to prevent generation of an air gap in an interface IF between the surface of the conductor layer513and the bottom surface of the recess5411, with use of a simple configuration.

A filter device601, which is Variation 2 of the filter device401, will be described with reference toFIG. 7. Corresponding constituent members of the filter device601in common with the filter device401have reference symbols which are obtained by replacing the initial number “4” of reference symbols for the filter device401(seeFIG. 5) by “6”. In the present variation, only different features of the filter device601, as compared with the features of the filter device401, will be described, and the other features will be omitted.

As illustrated inFIG. 7, a resin substrate651included in the filter device601has a protrusion which is provided on the resin substrate451. On the surface of the protrusion, a conductor layer652is provided.

A skirt6412is configured such that the height of the skirt6412is less than a sum of (a) the thickness of a filter611(total thickness of a substrate612, a conductor layer613, and a conductor layer614), (b) the height of the resin substrate651, and (c) the thickness of the conductor layer652. This allows the skirt6412and the resin substrate651to be spaced away from each other. That is, the skirt6412and the resin substrate651have an air gap between them. Thus, as long as the skirt6412and the resin substrate651have the air gap between them, the surface of the resin substrate651on a side facing the housing641may be flat.

Besides, the conductor layer614of the filter611is connected to the conductor layer652by use of a plurality of bumps DB. The bumps DB are an aspect of the connecting members recited in the claims, each of the bumps DB connects the conductor layer652and the conductor layer614with each other in its dot-like narrow region.

In this way, the filter611and the resin substrate651may be connected to each other by use of a plurality of connecting members. According to such a configuration, it is possible to firmly secure the filter611to the resin substrate651.

A filter device (1,401,501,601) in accordance with an embodiment of the present invention is a filter device (1,401,501,601), including: a filter (11,411,511,611) including a substrate (12,412,512,612) made of a dielectric, a pair of wide walls being constituted by a first conductor layer (13,413,513,613) and a second conductor layer (14,414,514,614), respectively, and covering respective opposite surfaces of the substrate (12,412,512,612), and narrow walls being constituted by post walls which are provided inside the substrate (12,412,512,612); and a first waveguide tube (21,121,421,521,621) and a second waveguide tube (31,431) each including a tube wall (22,32,122,422,432,522,622) made of a conductor and being placed along the substrate (12,412,512,612).

The filter (11,411,511,611) further includes: a first columnar conductor (18,118,418,518,618) passing through a first opening (13a1) which is provided in the first conductor layer (13,413,513,613), the first columnar conductor (18,118,418,518,618) having one end portion (181,118a1) located inside the substrate (12,412,512,612); and a second columnar conductor (19,419) passing through a second opening (13a2) which is provided in the first conductor layer (13,413,513,613) or the second conductor layer (14,414,514,614), the second columnar conductor (19,419) having one end portion (191) located inside the substrate (12,412,512,619).

The first waveguide tube (21,121,421,521,621) is placed such that the first columnar conductor (18,118,418,518,618) passes through an opening (22a,122a) which is provided in the tube wall (22,122,422,522,622) of the first waveguide tube (21,121,421,521,621) and such that another end portion (182,118b1) of the first columnar conductor (18,118,418,518,618) is located inside the first waveguide tube (21,121,421,521,621), and the second waveguide tube (31,431) is placed such that the second columnar conductor (19,419) passes through an opening (32a) which is provided in the tube wall (32,432) of the second waveguide tube (31,431) and such that another end portion (192) of the second columnar conductor (19,419) is located inside the second waveguide tube (31,431).

According to the above configuration, the filter and the first waveguide tube are electromagnetically coupled to each other via the first columnar conductor passing through the first opening which is provided in the first conductor layer. Similarly, the filter and the second waveguide tube are electromagnetically coupled to each other via the second columnar conductor passing through the second opening which is provided in the first conductor layer or the second conductor layer.

The first columnar conductor and the second columnar conductor can reduce return loss at a coupling section between the filter and the waveguide tube over a wide band, in comparison to a coupling window which couples a filter and a waveguide tube in the conventional transmission device. Thus, the filter device in accordance with an embodiment of the present invention can broaden a band in which return loss is small, in comparison to a case where a filter and a waveguide tube are coupled to each other with use of the conventional transmission line.

Further, a filter device (1,401,501,601) in accordance with an embodiment of the present invention is preferably configured such that the filter (11,411,511,611) further includes one or more partition walls (171,172,173) being constituted by post walls provided inside the substrate (12,412,512,612) and dividing a region surrounded by the pair of wide walls (13,14,413,414,513,514,613,614) and the narrow walls into a plurality of resonators (11ato11d), the one or more partition walls (171,172,173) having respective coupling windows (171a,172a,173a).

Further, a filter device (1) in accordance with an embodiment of the present invention is preferably configured such that the first columnar conductor (118) and the second columnar conductor are each divided into a first part (118a) and a second part (118b), the first part (118a) being embedded in the substrate (12) and having one end portion (118a2) which reaches a surface of the substrate (12), the second part (118b) protruding through the substrate (12), and the first part (118a) and the second part (118b) are connected to each other by an electrically conductive connecting member (B1).

Each of the columnar conductors of the transmission line in accordance with an embodiment of the present invention is divided into the first part and the second part, as described above. The first part, which is embedded in the substrate and has one end portion exposed to the surface of the substrate, can be formed by a method similar to a method of forming the post wall. Then, by connecting the second part to the first part with use of the electrically conductive connecting member, each of the columnar conductors is formed.

A transmission line in accordance with an embodiment of the present invention can be produced by such a production method. Thus, the transmission line in accordance with an embodiment of the present invention can be produced easily, in comparison with a transmission line including a columnar conductor which is constituted by a single member.

Further, a filter device (1) in accordance with an embodiment of the present invention is preferably configured such that the second part (118b) of each of the first columnar conductor (118) and the second columnar conductor is embedded in a block (119) made of a dielectric, and an end portion (118b2) of the second part on a side facing the first part (118a) reaches a surface of the block (119).

The above configuration allows the second part to be easily handled in connecting the second part to the first part. Thus, the transmission line in accordance with an embodiment of the present invention can be produced more easily, in comparison with a transmission line in which the second part is not embedded in the block.

Further, a filter device (401,501,601) in accordance with an embodiment of the present invention further includes: a housing (441,541,641) made of a metal, the housing including a first tubular space (4211), a second tubular space (4311), and a recess (4411,5411,6411), the first tubular space (4211) functioning as a propagation region of the first waveguide tube (421,521,621), the second tubular space (4311) functioning as a propagation region of the second waveguide tube (431), the recess (4411,5411,6411) accommodating the filter (411,511,611); and a resin substrate (451,551,651) holding the filter (411,511,611) in a state in which the filter (411,511,611) is sandwiched between the resin substrate (451,551,651) and the housing (441,541,641).

In the filter (411,511,611), the second opening provided in the first conductor layer (413,513,613) or the second conductor layer (414,514,614) is provided in the first conductor layer (413,513,613).

The recess (4411,5411,6411) and the first tubular space (4211) communicate with each other via a first opening which is provided at a boundary between the recess (4411,5411,6411) and the first tubular space (4211), and the recess (4411,5411,6411) and the second tubular space (4311) communicate with each other via a second opening which is provided at a boundary between the recess (4411,5411,6411) and the second tubular space (4311).

The filter (411,511,611) is preferably placed such that the another end portion of the first columnar conductor (418,518,618) and the another end portion of the second columnar conductor (419) are located inside the first tubular space (4211) and the second tubular space (4311), respectively, and such that the first conductor layer (413,513,613) seals the first opening and the second opening which are provided at the boundaries.

According the above configuration, the filter is sandwiched with use of the housing and the resin substrate. Thus, the filter and the waveguide tube can be reliably held in positions in relation to each other. Thus, it is possible to prevent fluctuation of return loss that can occur at a coupling section between the filter and the waveguide tube. Thus, the filter device in accordance with an embodiment of the present invention can reliably broaden a band in which return loss is small, in comparison to a case where a filter and a waveguide tube are coupled to each other with use of the conventional transmission line.

Further, a filter device (401,601) in accordance with an embodiment of the present invention further includes a pressure applying member (483,484,485,486,683,684,685,686) which applies pressure to a skirt (4412,6412), which is a rim of the housing (441,641) around the recess (4411,6411), and to the resin substrate (451,651) in such a direction that the filter (411,611) is sandwiched between the skirt (4412,6412) and the resin substrate (451,651).

It is preferable that a height of the skirt (4412,6412) is so set that the skirt (4412,6412) and the resin substrate (451,651) are spaced away from each other.

According the above configuration, in connecting the resin substrate and the housing to each other, pressure is applied to the resin substrate and the housing in such a direction that the filter is sandwiched between the resin substrate and the housing. By so setting the height of the skirt that the skirt and the resin substrate are spaced away from each other, the filter is pushed in such a direction that the filter approaches the housing. Thus, it is possible to prevent generation of an air gap in between the first conductor layer of the filter and the recess of the housing.

Further, a filter device (501) in accordance with an embodiment of the present invention further includes a pressure applying member (583,584,585,586) which applies pressure to a skirt (5412), which is a rim of the housing (541) around the recess (5411), and to the resin substrate (551) in such a direction that the filter (511) is sandwiched between the skirt (5412) and the resin substrate (551).

It is preferable that a height of the skirt (5412) is so set that the second conductor layer (514) of the filter (511) and the resin substrate (551) are spaced away from each other, and a resin material is filled in an air gap between the second conductor layer (514) and the resin substrate (551).

By filling the resin substrate in the air gap between the second conductor layer of the filter and the resin substrate, the resin material pushes the filter in such a direction that the filter approaches the housing. Thus, it is possible to prevent generation of an air gap in between the first conductor layer of the filter and the recess of the housing.

Further, a filter device (601) in accordance with an embodiment of the present invention further includes a pressure applying member (683,684,685,686) which applies pressure to a skirt (6412), which is a rim of the housing (641) around the recess (6411), and to the resin substrate (651) in such a direction that the filter (611) is sandwiched between the skirt (6412) and the resin substrate (651).

It is preferable that a height of the skirt (6412) is so set that the second conductor layer (614) of the filter (611) and the resin substrate (651) are spaced away from each other, and the second conductor layer (614) is connected to the resin substrate (651) by a plurality of connecting members DB).

In this way, the filter and the resin substrate may be connected to each other by a plurality of connecting members. According to such a configuration, it is possible to firmly secure the filter to the resin substrate.

A filter (11,411,511,611) in accordance with an embodiment of the present invention is a filter including: a substrate (12,412,512,612) made of a dielectric; a pair of wide walls (13,14,413,414,513,514,613,614) being constituted by a first conductor layer (13,413,513,613) and a second conductor layer (14,414,514,614), respectively, and covering respective opposite surfaces of the substrate (12,412,512,612) and narrow all being constituted by post walls which are provided inside the substrate (12,412,512,612), the filter (11,411,511,611) further including: a first columnar conductor (18,118,418,518,618) passing through a first opening (13a1) which is provided in the first conductor layer (13,413,513,613), the first columnar conductor (18,118,418,518,618) having one end portion (181,118a1) located inside the substrate (12,412,512,612); and a second columnar conductor (19,419) passing through a second opening (13a2) which is provided in the first conductor layer (13,413,513,613) or the second conductor layer (14,414,514,614), the second columnar conductor (19,419) having one end portion (191) located inside the substrate (12,412,512,612).

According to the above configuration, with use of the first waveguide tube and the second waveguide tube each having the tube wall provided with the opening, it is possible to easily couple the filter and these waveguide tubes to each other. Specifically, it is possible to easily couple the filter and the first and second waveguide tubes to each other by (1) placing the first waveguide tube such that the first columnar conductor passes through the first opening which is provided in the tube wall of the first waveguide tube and such that another end portion of the first columnar conductor is located inside the first waveguide tube and by (2) placing the second waveguide tube such that the second columnar conductor passes through the second opening which is provided in the tube wall of the second waveguide tube and such that another end portion of the second columnar conductor is located inside the second waveguide tube.

The coupling sections, provided in this way, between the filter and the waveguide tubes can reduce return loss over a wide bandwidth, as in the case of the filter device in accordance with an embodiment of the present invention.

Further, a filter (11,411,511,611) in accordance with an embodiment of the present invention is preferably configured such that the first conductor layer (13,413,513,613) has a first region (R1) provided in advance in a vicinity of the first opening (13a1), the first region (R1) allowing part of the tube wall (22,122,422,522,622) of the first waveguide tube (21,121,421,521,621) to be placed in the first region (R1), and the first conductor layer (13,413,513,613) or the second conductor layer (14,414,514,614) has a second region provided in advance in a vicinity of the second opening (13a2), the second region allowing part of the tube wall (32,432) of the second waveguide tube (31,431) to be placed in the second region.

Further, it is preferable that a filter (11,411,511,611) in accordance with an embodiment of the present invention further includes one or more partition walls (171,172,173) being constituted by post walls provided inside the substrate (12,412,512,612) and dividing a region surrounded by the pair of wide walls (13,14,413,414,513,514,613,614) and the narrow walls into a plurality of resonators (11ato11d), the one or more partition walls (171,172,173) having respective coupling windows (171a,172a,173a).

Note that in the above section starting with “Aspects of the present invention can also be expressed as follows:”, only members whose reference symbols are indicated inFIGS. 1 to 7out of the members corresponding to the constituent components recited in the claims, are followed by their reference symbols in parentheses.

REFERENCE SIGNS LIST