JP2015050492A - Waveguide filter, transmission circuit, microwave output device and radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a band-pass filter suppressing the leakage of an electromagnetic wave, while achieving a planar disposition with a small length in a tube axis direction.SOLUTION: In a resonator 301, a length in a direction orthogonal to the tube axis direction is approximately 1/2 of the guide wavelength of a fundamental wave, and a length in the tube axis direction is approximately 1/4 of the guide wavelength of the fundamental wave. Therefore, the resonance direction is a direction orthogonal to the tube axis direction, and an electric field direction in the resonator 301 is in parallel to the tube axis direction. Thus, a connection surface between an upper plate 11 and a lower plate 12 becomes in parallel to the electric field direction in the resonator 301, so that the electromagnetic wave leakage can be suppressed.

Description

  The present invention relates to a waveguide type filter that allows microwaves in a desired frequency band to pass therethrough.

  Conventionally, structures as shown in FIGS. 8A and 8B are known as waveguide type filters. 8A and 8B has a structure in which an iris 32 is disposed in a rectangular waveguide 31 and a plurality of resonators coupled by the iris 32 are provided.

  If the length of one side is about ½λ of the guide wavelength, the resonator enters a resonance state at a frequency corresponding to the guide wavelength. The iris 32 is sized to obtain the desired coupling characteristics.

  Such a waveguide type filter is configured by connecting two metal blocks. The connection surfaces of the two metal blocks are parallel to the magnetic field direction (H plane) in the resonator as shown in FIG. 8A, and in the resonator as shown in FIG. 8B. There are two types, that is, parallel to the electric field direction (E plane).

  If there is a gap in the direction of blocking the current path in the waveguide, electromagnetic wave leakage increases. In particular, electromagnetic field energy is concentrated in the resonator, so that even a slight gap increases loss due to electromagnetic wave leakage.

  In the resonator, since current flows from the center of the upper surface to the center of the lower surface, when the connection surface is parallel to the H surface, the connection surface is in a direction blocking the current path, and thus electromagnetic wave leakage is likely to occur.

  Therefore, when the connection surface is parallel to the H surface, a large amount of screws, brazing, or the like is required so that the two metal blocks are completely in close contact with each other.

  On the other hand, when the connection surface is parallel to the E surface, the connection surface is parallel to the current path, so that electromagnetic wave leakage can be suppressed relatively easily.

  However, in the structure as shown in FIG. 8B, the length in the tube axis direction increases as the number of resonators increases. Therefore, for example, as shown in Patent Document 1, a method for reducing the size of the filter by bending the waveguide in the middle has been proposed.

JP 2005-341350 A

  In the structure in which the waveguide is bent as in Patent Document 1, when the connection surface is parallel to the E plane, the height of the input waveguide and the output waveguide connected to the filter (the direction parallel to the electric field direction) The position will be different. Therefore, the transmission circuit including the waveguide is not arranged in a planar manner and becomes a complicated structure.

  Accordingly, an object of the present invention is to provide a band-pass filter that is short in the tube axis direction and suppresses electromagnetic wave leakage while realizing a planar arrangement.

  The waveguide type filter according to the present invention is a waveguide type filter in which a metal plate composed of upper and lower parts is joined to form a waveguide and one or more resonators, and the waveguide has a tube axis. The dimension in the direction orthogonal to the direction is longer than the dimension parallel to the tube axis direction, and the resonator has a dimension in the direction orthogonal to the tube axis direction shorter than the dimension parallel to the tube axis direction. And

  The waveguide type filter of the present invention is a waveguide type filter in which a waveguide and one or a plurality of resonators are formed by joining upper and lower metal plates, and the waveguide includes: The length in the width direction of the cross section orthogonal to the tube axis direction is longer than the length in the height direction, and the resonator has a dimension in a direction orthogonal to the tube axis direction longer than a dimension parallel to the tube axis direction. It is characterized by that.

  Thus, the resonator has a long direction perpendicular to the tube axis direction and a short length in the tube axis direction, so the resonance direction is a direction orthogonal to the tube axis direction, and the electric field direction in the resonator is Parallel to the tube axis direction. Therefore, the connection surfaces of the plurality of plates are parallel to the direction of the electric field in the resonator, and electromagnetic wave leakage can be suppressed.

  The resonator preferably has a length in the tube axis direction equal to or less than ¼ of the in-tube wavelength so as not to resonate in the tube axis direction and to shorten the length in the tube axis direction. .

  In addition, the resonator has a coupling hole on the input side and output side that is displaced from the center viewed from the tube axis direction in the short direction of the waveguide so that the resonator is coupled to the waveguide in a region where the magnetic field is stronger than the electric field. Preferably it is formed.

  According to the present invention, electromagnetic wave leakage can be suppressed while the length in the tube axis direction is short and a planar arrangement is realized.

It is a block diagram which shows the structure of the radar apparatus provided with the waveguide type filter of this invention. It is a figure which shows the structure of the waveguide type filter which concerns on 1st Embodiment. It is a figure which shows the structure of the waveguide type filter which concerns on 2nd Embodiment. It is a figure which shows the structure of the waveguide type filter which concerns on 3rd Embodiment. It is a figure which shows the structure of the waveguide type filter which concerns on 4th Embodiment. It is a figure which shows the structure of the transmission circuit containing a circulator. It is a cross-sectional view of the place where the stub for adjustment is inserted. It is a figure which shows the structure of the conventional waveguide type filter.

  FIG. 1 is a block diagram showing a configuration of a radar apparatus 71 provided with a waveguide filter of the present invention. The radar device 71 includes a microwave output device 72, a rotary joint 56, an antenna 57, a limiter 58, and a receiving circuit 59. The microwave output device 72 includes a magnetron 51, a drive circuit 52, a transmission circuit 81, and a terminator 54. The transmission circuit 81 includes a circulator 53, the waveguide filter 1, and a circulator 55.

  The magnetron 51 is a microwave generator that generates, for example, a 9.4 GHz microwave as a fundamental wave. The drive circuit 52 drives the magnetron 51 at a predetermined cycle. Microwaves generated by the magnetron 51 are transmitted to the circulator 53 of the transmission circuit 81 through the waveguide.

  The circulator 53 guides the microwave output from the magnetron 51 to the waveguide filter 1. The circulator 53 guides the microwave reflected by the waveguide filter 1 to the terminator 54. The terminator 54 absorbs the input microwave.

  The waveguide filter 1 is a filter that allows a desired frequency band to pass and blocks unnecessary frequency bands from passing.

  The circulator 55 guides the microwave output from the waveguide filter 1 to the rotary joint 56. The rotary joint 56 outputs the microwave input from the fixed-side circulator 55 to the rotating-side antenna 57.

  The antenna 57 transmits the microwave output from the rotary joint 56 in the air, receives the microwave reflected by the object, and outputs the microwave to the rotary joint 56. The received microwave is output to the limiter 58 through the rotary joint 56 and the circulator 55.

  The limiter 58 reflects the microwave when a microwave of a predetermined level or higher is input, and protects the receiving circuit 59 in the subsequent stage.

  FIG. 2 is a diagram illustrating a configuration of the waveguide filter 1 according to the first embodiment. 2A is a transparent perspective view, FIG. 2B is a transparent top view, and FIG. 2C is a transparent front view. In FIG. 2, the microwave propagation direction (tube axis direction) is the y direction, the upward direction of the waveguide is the z direction, and the right direction toward the tube axis direction of the waveguide is the x direction.

  The waveguide filter 1 includes a waveguide 201, a coupling window 401A, a resonator 301, a coupling window 401B, and a waveguide 202. The resonator 301 is connected to the waveguide 201 and the waveguide 202 via the coupling window 401A and the coupling window 401B on both sides in the tube axis direction, respectively.

  The waveguide filter 1 is formed by connecting an upper plate 11 and a lower plate 12 made of a conductive metal such as aluminum. Various recesses formed in the upper plate 11 and the lower plate 12 form the above-described waveguide 201, coupling window 401A, resonator 301, coupling window 401B, and waveguide 202.

  Each of the waveguide 201, the coupling window 401A, the resonator 301, the coupling window 401B, and the waveguide 202 has a substantially rectangular cross section. Both the waveguide 201 and the waveguide 202 have a width in the longitudinal direction (length in the x direction) and a cross section so as to transmit a fundamental wave (eg, 9.4 GHz) microwave in the tube axis direction in the TE10 mode. The height in the short direction (length in the z direction) is set. That is, the length in the width direction of the waveguide 201 and the waveguide 202 is set to about ½ of the guide wavelength of the fundamental wave, and the length in the height direction is set to about ¼ of the guide wavelength. . In this case, as shown in FIG. 2B, the electric field direction in the TE10 mode in the waveguide 201 and the waveguide 202 is orthogonal to the tube axis direction.

  The width of the resonator 301 is set to about ½ of the guide wavelength of the fundamental wave. The height of the resonator 301 is set to about ½ of the guide wavelength of the fundamental wave. Therefore, the resonator 301 can resonate at the fundamental frequency in a direction orthogonal to the tube axis direction.

  The coupling window 401A and the coupling window 401B have a shape in which the width (length in the left-right direction) is long and the height (length in the vertical direction) is short in the tube axis direction. However, the width and the height are set shorter than the waveguide 201 and the waveguide 202, respectively. The coupling window 401A is formed at a position where the energy that enters the resonator 301 from the waveguide 201 becomes higher than the magnetic field energy. Similarly, the coupling window 401B is formed at a position where the energy that enters the waveguide 202 from the resonator 301 becomes higher than the magnetic field energy.

  For example, as shown in FIG. 2C, the coupling window 401A and the coupling window 401B are formed at positions shifted upward (or lower) by Δd from the center of the resonator 301 when viewed from the tube axis direction. Yes. Δd is, for example, about 1/40 of the in-tube wavelength of the fundamental wave. Thereby, the waveguide 201 and the resonator 301 are magnetically coupled, and similarly, the waveguide 202 and the resonator 301 are magnetically coupled.

  With the above configuration, as shown in FIG. 2B, the electric field direction in the resonator 301 is parallel to the tube axis direction. Therefore, the electric field direction in the resonator 301 is parallel to the connection surface of the upper plate 11 and the lower plate 12, and the connection surface (second bonding surface of the present invention) is an H surface, so that electromagnetic waves leak. This can be suppressed. Note that, in the waveguide 201 and the waveguide 202, the electric field direction is orthogonal to the connection surface, and the connection surface (the first bonding surface of the present invention) is the E surface, but is electromagnetic compared to the resonator 301. Since the field energy density is low, electromagnetic waves are less likely to leak.

  On the other hand, the resonator 301 does not resonate in the tube axis direction, and in order to shorten the length of the waveguide filter 1 in the tube axis direction, the length in the tube axis direction is within the tube of the fundamental wave. It is about 1/4 to 1/8 of the wavelength. Actually, it is possible to make the wavelength less than 1/8 of the in-tube wavelength, but there is a possibility that the electric field strength becomes high and discharge occurs, and the loss due to the conductor increases. It is desirable.

  The shape of the resonator is not limited to a rectangular shape, and may be other shapes such as a circular shape and a polygonal shape.

  Next, FIG. 3 is a transmission top view showing the configuration of the waveguide filter 1 according to the second embodiment. Also in FIG. 3, the microwave propagation direction (tube axis direction) is the y direction, and the right direction toward the tube axis direction of the waveguide is the x direction. Moreover, about the structure which is common in FIG. 2, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the waveguide filter 1 according to the second embodiment, a plurality (four in this example) of resonators 301 are connected in series along the tube axis direction. The resonators are connected by a coupling window 401C. The coupling window 401C has the same structure as the coupling window 401A and the coupling window 401B, and is set to have a shorter width and a lower height than the waveguide 201 and the waveguide 202, respectively. The resonance window 401C is also formed at a position shifted upward (or lower) by Δd from the center of the resonator 301 so that the resonators 301 are magnetically coupled.

  By increasing the number of resonators 301 in this way, it becomes possible to design a filter having a steep attenuation characteristic, and also in the tube axis direction with respect to the conventional waveguide type filter as shown in FIG. Can be reduced to about ½ to ¼.

  Next, FIG. 4 is a transmission top view showing the configuration of the waveguide filter 1 according to the third embodiment. Also in FIG. 4, the propagation direction (tube axis direction) of the microwave is the y direction, and the right direction toward the tube axis direction of the waveguide is the x direction. Moreover, about the structure which is common in FIG. 3, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the waveguide filter 1 according to the third embodiment, a plurality (four in this example) of resonators 301 are connected as in the second embodiment. They are different in that they are connected in a direction perpendicular to the tube axis direction.

  That is, the first-stage resonator 301 is magnetically coupled to the second-stage resonator 301 via the coupling window 402 provided on the right side in the tube axis direction, and the third-stage resonator 301 is The second embodiment is different from the second embodiment in that it is magnetically coupled to the fourth-stage resonator 301 via a coupling window 402 provided on the left side in the axial direction. The coupling window 402 is also set to magnetically couple between the resonators 301.

  In this case, the length in the tube axis direction can be further shortened as compared with the second embodiment, and the length in the tube axis direction is 1 with respect to the conventional waveguide type filter as shown in FIG. / 4 to about 1/8.

  Further, according to the structure of the third embodiment, microwaves are transmitted in different directions with respect to the tube axis direction, and the connection surfaces of the upper plate and the lower plate are parallel to the electric field direction (E surface). The positions of the input-side waveguide 201 and the output-side waveguide 202 to be connected in the height direction (direction parallel to the electric field direction) are not changed, and a planar arrangement can be maintained as a transmission circuit including the waveguide. it can.

  In the third embodiment, an example is shown in which some resonators are connected in a direction perpendicular to the tube axis direction. However, by changing the position of the coupling window, the resonator can be moved in any direction such as a 45 degree direction. It is possible to connect a resonator.

  Next, FIG. 5 is a transmission top view showing the configuration of the waveguide filter 1 according to the fourth embodiment. Also in FIG. 5, the microwave propagation direction (tube axis direction) is the y direction, and the right direction toward the tube axis direction of the waveguide is the x direction. Moreover, about the structure which is common in FIG. 4, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the waveguide filter 1 according to the fourth embodiment, similarly to the third embodiment, a plurality of (four in this example) resonators 301 are connected, and some of the resonators 301 are in the tube axis direction. Are connected in a direction orthogonal to the first and second resonators 301 and 301 in that an electric field is connected via a coupling window 404.

  In the electric field coupling and the magnetic field coupling, the phases are reversed. Therefore, the first-stage resonator 301 and the third-stage resonator 301 generate energy in opposite phases. In this case, the characteristic of the waveguide filter 1 is an elliptic filter. Accordingly, it is possible to form a filter having a steeper attenuation characteristic.

  In any of the first to fourth embodiments, the corner portion inside the resonator and the corner portion of the coupling window are chamfered to prevent the concentration of electromagnetic field energy and to prevent discharge. It is preferable.

  Next, FIG. 6 is a diagram showing a configuration of the transmission circuit 81 including the circulator 53 and the circulator 55. 6A is an exploded longitudinal sectional view, FIG. 6B is a top view of the upper plate, and FIG. 6C is a top view of the lower plate.

  The transmission circuit 81 including the circulator 53, the circulator 55, and the waveguide filter 1 is integrated by an upper plate 81A and a lower plate 81B. The waveguide filter 1 is formed by a recess 1A provided on the upper plate 81A and a recess 1B provided on the lower plate 81B. Similarly, the circulator 53 is formed by a recess 53A provided in the upper plate 81A and a recess 53B provided in the lower plate 81B, and the circulator 55 is provided in the recess 55A and the lower plate 81B provided in the upper plate 81A. The recess 55B is formed.

  In addition, a dielectric 534A, a ferrite 535, and a dielectric 534B are disposed between the recess 53A and the recess 53B, and a dielectric 554A, a ferrite 555, and a dielectric 554B are provided between the recess 55A and the recess 55B. Is arranged.

  Further, a magnet 533A is arranged on the side (upper surface side) opposite to the side where the concave portion 53A is formed of the upper plate 81A. Magnet 533A is covered with yoke 532A. A magnet 533B is disposed on the side (lower surface side) opposite to the side where the concave portion 53B is formed of the lower plate 81B. Magnet 533B is covered with yoke 532B.

  Similarly, the magnet 553A is disposed on the side (upper surface side) opposite to the side where the concave portion 55A is formed of the upper plate 81A. Magnet 553A is covered with yoke 552A. A magnet 553B is arranged on the side (lower surface side) opposite to the side where the concave portion 55B of the lower plate 81B is formed. Magnet 553B is covered with yoke 552B.

  Moreover, the adjustment stub 151 is inserted into the upper plate 81A from the surface (upper surface) opposite to the side where the recess 1A is formed. Similarly, in the upper plate 81A, the adjustment stub 531 is inserted from the surface opposite to the side where the recess 53A is formed, and the adjustment stub 551 is inserted from the surface opposite to the side where the recess 55A is formed. .

  The adjustment stub 151, the adjustment stub 531, and the adjustment stub 551 protrude into the waveguide filter 1, the circulator 53, and the circulator 55, respectively, and have characteristics by changing the size of the space in the transmission path. Change.

  Thus, since the circulator 53, the circulator 55, and the waveguide filter 1 are integrated in the transmission circuit 81 and a flange or the like is not used, the workability is good and it is not necessary to consider the interaction due to the combination. .

  The adjustment stub 151 is inserted parallel to the magnetic field direction (H plane) in the resonator of the waveguide filter 1, and the adjustment stub 531 and the adjustment stub 551 are the electric field directions of the circulator 53 and the circulator 55. As described above, the resonator 301 of the waveguide filter 1 has a resonance direction orthogonal to the tube axis direction as described above. The adjustment stub 151, the adjustment stub 531 and the adjustment stub 551 are all inserted from the same direction, and workability is improved.

  Further, the positions of the input-side waveguide and the output-side waveguide connected to the transmission circuit 81 in the height direction are not changed, and the planar arrangement of the entire transmission circuit can be maintained.

  As shown in FIG. 7, the portion of the upper plate 81A where the adjustment stub 531 (and adjustment stub 551) is inserted is the same as the surface of the yoke 532A (or yoke 552A), or the yoke 532A (or yoke 532A). It is preferable to provide the convex portion 811 so as to be higher than the surface of 552A). This facilitates adjustment of the adjustment stub.

DESCRIPTION OF SYMBOLS 1 ... Waveguide type filter 11 ... Upper board 12 ... Lower board 51 ... Magnetron 52 ... Drive circuit 53 ... Circulator 54 ... Terminator 55 ... Circulator 56 ... Rotary joint 57 ... Antenna 58 ... Limiter 59 ... Reception circuit 71 ... Radar apparatus 72 ... Microwave output device 81 ... Transmission circuit 201, 202 ... Waveguide 301 ... Resonator 401A, 401B ... Coupling window

Claims (11)

It is a waveguide type filter that has a monolithic structure by joining metal plates made up and down,
A waveguide and one or more resonators formed by joining the upper and lower metal plates;
A first joint surface of the upper and lower metal plates forming the waveguide is an E surface, and a second joint surface of the upper and lower metal plates forming the resonator is an H surface;
The waveguide filter according to claim 1, wherein the first joint surface and the second joint surface are parallel to each other. A waveguide type filter in which a metal plate composed of upper and lower surfaces is joined to form a waveguide and one or more resonators,
In the waveguide, the length in the width direction of the cross section perpendicular to the tube axis direction is longer than the length in the height direction,
The waveguide type filter, wherein the resonator has a dimension in a direction orthogonal to the tube axis direction longer than a dimension parallel to the tube axis direction. A waveguide filter according to claim 1 or 2,
The waveguide-type filter, wherein the coupling hole on the input side and the output side of the resonator is formed at a position shifted from the center of the resonator viewed from the tube axis direction. A waveguide type filter according to any one of claims 1 to 3,
A waveguide filter, wherein a plurality of the resonators are provided. The waveguide filter according to claim 4, wherein
The waveguide type filter, wherein the plurality of resonators are connected in series along the tube axis direction. The waveguide filter according to claim 4, wherein
The plurality of resonators are partially connected in a direction orthogonal to the tube axis direction. A waveguide filter according to any one of claims 1 to 6,
The resonator is characterized in that a length in a direction parallel to the tube axis direction is ¼ or less of a tube wavelength. A transmission circuit formed by integrating the waveguide filter according to claim 1 and a plurality of circulators,
The transmission circuit, wherein the waveguide filter is disposed between a plurality of circulators. The transmission circuit of claim 8,
A transmission circuit, wherein the waveguide type filter and the plurality of circulators each have a characteristic adjustment stub inserted from the same side. A microwave generator for generating microwaves;
A transmission circuit according to claim 8 or claim 9,
A microwave output device comprising: A microwave output device according to claim 10;
An antenna for launching the microwave into the air;
A radar apparatus comprising:

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