WO2024048465A1

WO2024048465A1 - Filter apparatus, transmitter, and radar

Info

Publication number: WO2024048465A1
Application number: PCT/JP2023/030789
Authority: WO
Inventors: Kenichi Iio
Original assignee: Furuno Electric Co., Ltd.
Priority date: 2022-08-29
Filing date: 2023-08-25
Publication date: 2024-03-07
Also published as: JP2024032077A

Abstract

A filter apparatus is provided. The filter apparatus comprises a resonator with adjustment, an adjustment section, a first propagation path, and a second propagation path. The resonator with adjustment propagates a fundamental wave and harmonics of the fundamental wave. The adjustment section is provided in the resonator with adjustment for adjusting a phase of the harmonics of the fundamental wave to an opposite phase. The first propagation path is formed via the resonator with adjustment, and the second propagation path is formed not via the resonator with adjustment. The harmonics of the fundamental wave adjusted to the opposite phase propagating through the first propagation path, and the harmonics of the fundamental wave propagating through the second propagation path are synthesized. Selection Diagram: Figure 2

Description

FILTER APPARATUS, TRANSMITTER, AND RADAR

The present disclosure relates to a filter apparatus, a transmitter, and a radar.

BACKGROUND TECHNOLOGY

Generally, in filter apparatus, not only a fundamental wave but also its harmonics resonate, and therefore, to suppress the harmonics, a low-pass filter that attenuates components of frequencies higher than the fundamental wave is often used together (e.g., Patent Document 1).
Patent document 1: Japanese Laid-Open Patent Publication No. S59-8401

However, in the method of using the low-pass filter in combination, there are problems of increasing the loss due to the lengthening of the path and increasing the size of the apparatus.

The present disclosure has been made in view of the above problems, and its main purpose is to provide a filter apparatus capable of suppressing harmonics, and a transmitter, and a radar equipped with the filter apparatus.

Summary

In order to solve the above problems, a filter apparatus according to one aspect of the present disclosure comprises a resonator with adjustment, an adjustment section, a first propagation path, and a second propagation path. The resonator with adjustment propagates a fundamental wave and harmonics of the fundamental wave. The adjustment section is provided in the resonator with adjustment for adjusting a phase of the harmonics of the fundamental wave to an opposite phase. The first propagation path is formed via the resonator with adjustment, and the second propagation path is formed not via the resonator with adjustment. The harmonics of the fundamental wave adjusted to the opposite phase propagating through the first propagation path, and the harmonics of the fundamental wave propagating through the second propagation path are synthesized. This makes it possible to suppress the harmonics.

In the above aspect, the filter apparatus further comprises an upstream resonator arranged upstream of the resonator with adjustment and a downstream resonator arranged downstream of the resonator with adjustment, wherein the second propagation path may include a coupling path that couples the upstream resonator and the downstream resonator. This makes it possible to suppress the harmonics while obtaining steep pass-through characteristics for the fundamental wave by jump coupling between the resonators.

In the above aspect, the resonator with adjustment, the upstream resonator, and the downstream resonator may be a waveguide resonator that causes the fundamental wave to resonate in a TE mode. This makes it possible to suppress the harmonics in the waveguide resonator while obtaining steep passing characteristics for the fundamental wave.

In the above aspect, the filter apparatus may be equipped with two resonators with adjustment separated by a partition wall that forms an E-plane, and a coupling window formed in the partition wall may propagate a part of the harmonics of the fundamental wave adjusted to the opposite phase. This makes it possible to adjust the propagation amount of the harmonics adjusted to the opposite phase in the first propagation path.

In the above aspect, the upstream resonator and the downstream resonator may be separated by a partition wall that forms an E-plane, and a coupling window as the coupling path formed in the partition wall may propagate a part of the harmonics. This makes it possible to adjust the propagation amount of the harmonics in the second propagation path.

In the above aspect, the filter apparatus further comprises other resonators arranged upstream or downstream of the resonator with adjustment, wherein the second propagation path may be formed independently of a filter section including the resonator with adjustment and the other resonators. According to this, harmonics can be suppressed by the second propagation path independent of the filter section.

In the above aspect, the second propagation path may propagate only the harmonics of the fundamental wave and harmonics supplied from a waveguide line for an input. This makes it possible to suppress the harmonics by propagating only the harmonics.

In addition, the transmitter of another aspect of the present disclosure comprises the filter apparatus described above. According to this, it becomes possible to equip the filter apparatus which realizes suppression of harmonics.

In addition, the radar of another aspect of the present disclosure comprises the filter apparatus described above. According to this, it becomes possible to equip the filter apparatus which realizes suppression of harmonics.

Figure 1 shows an example of a configuration of a radar.

Figure 2 shows an example of a configuration of a filter apparatus.

Figure 3 shows an example of a configuration of a filter apparatus.

Figure 4 shows an example of a configuration of a filter apparatus.

Figure 5 shows an example of a configuration of a filter apparatus.

Figure 6 shows an example of a configuration of a filter apparatus.

Figure 7 shows an example of a configuration of a filter apparatus.

Figure 8 shows an example of a configuration of a filter apparatus.

Figure 9 shows a reference example of a filter apparatus.

MODE(S) FOR CARRYING OUT THE DISCLOSURE

Embodiments of the present disclosure will be described below with reference to the drawings.

Figure 1 is a block diagram showing a configuration example of a radar (100) according to the embodiment. The radar (100) is an example of a transmitter according to the embodiment and is a microwave transmitter/receiver that transmits and receives microwaves. The radar (100) is equipped with a waveguide filter (1) as an example of a filter apparatus according to the embodiment.

In addition to the waveguide filter (1), the radar (100) is equipped with a magnetron (91), a pulse drive circuit (92), a circulator (93), a terminator (94), a circulator (95), a rotary joint (96), an antenna (97), a limiter circuit (98), and a receiving circuit (99).

The magnetron (91) is a microwave generator that oscillates, for example, 9.4 GHz microwaves as a fundamental wave. The pulse drive circuit (92) intermittently drives the magnetron (91) at a predetermined period to generate a pulsed transmission signal. The circulator (93) switches the output destination of the pulsed transmission signal outputted from the magnetron (91).

The waveguide filter (1) is interposed between the magnetron (91) and the antenna (97). In this embodiment, the waveguide filter (1) is configured as a bandpass filter to allow the passage of the fundamental waves and suppress the passage of harmonics relative to the fundamental waves. The suppressed harmonics are consumed by a terminator (94) connected to the circulator (93).

The circulator (95) outputs the transmitted signal from the waveguide filter (1) to the antenna (97) and outputs the received signal from the antenna (97) to the receiving circuit (99). The rotary joint (96) is interposed between the antenna (97) and the circulator (95) to electrically connect the rotating system and the stationary system.

The antenna (97), while being rotated by a motor (not shown), transmits the transmitted signal as a radio wave pulse and converts the received reflected wave into a received signal. The limiter circuit (98) suppresses the received signal of a high level immediately after the start of reception. The receiving circuit (99) acquires the received signal from the antenna (97).

The path from the magnetron (91) to the antenna (97) consists of a waveguide. The path from the antenna (97) to the limiter circuit (98) also consists of a waveguide.

Moreover, in this embodiment, the radar (100) to which the waveguide filter (1) is applied is a marine radar that transmits and receives microwaves. However, it is not limited to this and may be, for example, an on-board radar for obstacle detection or collision prevention that transmits and receives millimeter waves.

Figure 2 is an exploded perspective view showing an example of the configuration of the waveguide filter (1). The waveguide filter (1) comprises: two blocks (2) and (3); a partition plate (4) is sandwiched between the two blocks.

Figure 3 is a diagram showing an example of the configuration of the block (2), which is viewed from the partition plate (4) side. Figure 4 is a diagram showing an example of the configuration of the block (3), which is viewed from the partition plate (4) side.

Figure 5 is a diagram showing an example of the configuration of partition plate (4), which is viewed from the block (3) side. Figure 6 is a diagram showing a cross-section when the block (2) is cut by the VI-VI line shown in Figure 3.

A Z direction in the figure represents the thickness direction or lamination direction of the blocks (2), (3), and the partition plate (4). An X direction and a Y direction represent the short-side, longitudinal directions of the blocks (2), (3), and the partition plate (4) in a plane perpendicular to the Z direction, respectively.

The blocks (2) and (3), as well as the partition plate (4), are made of metal. Specifically, the blocks (2) and (3) are made of a conductive metal material, such as aluminum, for example. Similarly, the partition plate (4) is also made of a conductive metal material, such as aluminum alloy, for example.

The blocks (2) and (3) sandwich the partition plate (4), an opposing side (29) of the block (2) contacts one principal surface of the partition plate (4), and an opposing side (39) of the block (3) contacts the other principal surface of the partition plate (4). The blocks (2), (3), and the partition plate (4) are fastened by fastening members such as screws (not shown).

As shown in Figure 3, a recess (20) for radio wave propagation is formed on the opposing side (29) of the block (2). The recess (20) includes two resonance regions (21), (22) aligned in the Y direction, and a coupling window (23) interposed between them. The resonance region (22) has adjustment sections (221), (222) for adjusting harmonics.

A coupling window (25) is formed at the bottom of the resonance region (21) of the block (2) to communicate the resonance region (21) with the outside. To the coupling window (25), an input waveguide line (82) (see Figure 2) is connected, and radio waves are input from the waveguide line (82) to the resonance region (21) through the coupling window (25).

As shown in Figure 4, a recess (30) for radio wave propagation is formed on the opposing side (39) of the block (3). The recess (30) includes two resonance regions (31), (32) aligned in the Y direction and a coupling window (33) interposed between them. The resonance region (31) has adjustment sections (311), (312) for adjusting harmonics.

A coupling window (35) is formed at the bottom of the resonance region (32) of the block (3) to communicate the resonance region (32) with the outside. An output waveguide line (83) (see Figure 2) is connected to the coupling window (35), and radio waves are output from the resonance region (32) to the waveguide line (83) through the coupling window (35).

As shown in Figure 5, the partition plate (4) is formed with multiple coupling windows (41-45). The partition plate (4) is sandwiched between the blocks (2) and (3) and interposed between the recesses (20) and (30). That is, the partition plate (4) covers both the recesses (20) and (30). In this embodiment, the recesses (20) and (30) have a mirror-symmetric relationship.

The coupling windows (41-44) communicate the resonance region (22) of the block (2) with the resonance region (31) of the block (3). The coupling window (45) communicates the resonance region (21) of the block (2) with the resonance region (32) of the block (3).

When the blocks (2), (3), and the partition plate (4) are assembled and fastened, each resonance region (21), (22), (31), (32) functions as a waveguide resonator. In this embodiment, the waveguide filter (1) includes a total of four waveguide resonators. Each resonance region (21), (22), (31), and (32) has a predetermined dimension that is determined based on the frequency of the radio wave (electromagnetic wave) used.

Each resonance region (21), (22), (31), and (32) has a flat shape whose dimension in a Z direction is shorter than the dimensions in an X direction and the dimensions in a Y direction and resonates with the radio waves in the TE mode. The electric field vector of the resonating radio waves points in the Z direction. The dimensions of each resonance region (21), (22), (31), and (32) in the X direction (propagation direction of the radio waves) are, for example, about 1/2 of the wavelength of the fundamental wave.

Figure 7 is a diagram schematically showing a configuration example of the waveguide filter (1). As shown in the figure, in the waveguide filter (1), a first propagation path P1 is formed via resonance regions (22) and (31) provided with the adjustment sections (221), (222), (311), (312), and a second propagation path P2 is formed without going through the resonance regions (22) and (31).

The resonance regions (22) and (31) are examples of resonators with adjustment. Resonance region (21) arranged upstream of resonance regions (22), (31) is an example of an upstream resonator. Resonance region (32) arranged downstream of resonance regions (22), (31) is an example of a downstream resonator.

Resonance regions (22) and (31) are separated by the partition plate (4), and resonance regions (21) and (32) are also separated by the partition plate (4) (see Figure 2). The partition plate (4) is an example of a partition wall that forms an E-plane of the resonance regions (21), (22), (31), and (32). The E-plane is a plane perpendicular to the electric field vector (Z direction) of the resonant fundamental wave.

The first propagation path P1 is a path that passes through the resonance regions (21), (22), (31), and (32) in order. Specifically, in the first propagation path P1, radio waves propagate through the coupling window (25), the resonance region (21), the coupling window (23), the resonance region (22), the coupling windows (41-44), the resonance region (31), the coupling window (33), the resonance region (32), and the coupling window (35) in order.

The second propagation path P2 is a path that passes through the resonance regions (21) and (32) in order, not through the resonance regions (22) and (31). Specifically, in the second propagation path P2, radio waves propagate through the coupling window (25), the resonance region (21), the coupling window (45), the resonance region (32), and the coupling window (35) in order. The coupling window (45) is an example of a coupling path.

In the first propagation path P1 and the second propagation path P2, the fundamental wave and its harmonics (multiplication) propagate. However, in the first propagation path P1, a phase of the harmonics is adjusted to an opposite phase by adjustment sections (221), (222), (311), (312) provided in the resonance regions (22) and (31).

Therefore, the harmonics adjusted to the opposite phase propagating in the first propagation path P1 and the harmonics propagating in the second propagation path (P2) are synthesized in the resonance region (32), thereby suppressing the passage of the harmonics. In other words, the waveguide filter (1) becomes a bandpass filter that allows the passage of the fundamental wave and also suppresses the passage of the harmonics.

The adjustment sections (221), (222), (311), and (312) are provided within the resonance regions (22) and (31) of the first propagation path P1. The adjustment sections (221), (222), (311), and (312) create spaces where the fundamental wave is unable to penetrate while allowing the harmonics to pass through (see Figures 3 and 4). The phase of the harmonics can be adjusted while the phase of the fundamental wave remains constant.

The width (length in the X direction) of the adjustment sections (221), (222), (311), (312) is preferable, for example, 1/2 or less of the wavelength of the fundamental wave and 1/2 or more of the wavelength of the harmonic (second harmonic).

In addition, since the depth (length in the Y direction) of the adjustment sections (221), (222), (311), and (312) is a factor that determines the amount of phase shift of the harmonic, it is adjusted so that the phase of the harmonic is in the opposite phase. The depth of the adjustment sections (221), (222), (311), and (312) is preferably set within a range of, for example, 1/5 or more and 1/3 or less of the wavelength of the harmonic (second harmonic).

The coupling windows (41-44) formed between the resonance regions, (22) and (31), propagate a portion of the harmonics adjusted in the opposite phase. That is, the coupling windows (41-44) adjust the coupling amount of the harmonic mode of the resonance region (22) and the harmonic mode of the resonance region (31).

The coupling windows (41) and (42) are formed at positions where the harmonic modes are mainly electrically coupled with each other, and the coupling windows (43) and (44) are formed at positions where the harmonic modes are mainly magnetically coupled with each other. By adjusting the position of the coupling windows (41-44) to provide a difference between the amount of electric field coupling and the amount of magnetic field coupling, the amount of harmonic propagation is adjusted.

In the second propagation path P2, the resonance regions (21) and (32) are directly coupled by the coupling window (45), thereby improving the filter characteristics. In the present embodiment, an elliptic function filter using jump coupling between resonators is constructed. The elliptic function filter exhibits steep passing characteristics called poles by coupling between inputs and outputs.

Coupling window (45) formed between resonance regions (21) and (32) propagates part of the harmonics. The coupling window (45) is formed in a central part of the E-plane of resonance regions (21), (32). That is, the center of the E-plane is inside the coupling window (45).

Since the central part of the E-plane is a position where the electric field of the fundamental wave is concentrated but the electric field of the harmonic is not so concentrated. Consequently, by forming the coupling window (45) in the central part of the E-plane, almost all of the fundamental wave propagates while only a part of the harmonic propagates.

The coupling window (41-44) formed between the resonance regions (22) and (31) and the coupling window (45) formed between the resonance regions (21) and (32) are adjusted in position and size so that the propagation amount of the harmonic adjusted to the opposite phase of the first propagation path P1 and the propagation amount of the harmonic of the second propagation path P2 are almost equal.

According to the above described embodiment, by forming the first propagation path P1 through the resonance regions (22) and (31) provided with the adjustment sections (221), (222), (311), (312) for adjusting the phase of the harmonic to the opposite phase and the second propagation path P2 not through the resonance regions (22) and (31) in the waveguide filter (1), it becomes possible to suppress the harmonic while allowing the fundamental wave to pass.

Furthermore, in the second propagation path P2, the resonance regions (21) and (32) are directly coupled by the coupling window (45), so that the elliptic function filter using the jump coupling between the resonators can be constructed and the steep passing characteristic can be obtained for the fundamental wave.

As shown in the reference example in Figure 9, there is also a technique to suppress all the harmonics by not coupling the harmonic mode of the resonance region (22) with the harmonic mode of the resonance region (31) by the coupling window (41-44), but in this case, the resonance regions (21) and (32) cannot be coupled because the harmonics pass through when the resonance regions (21) and (32) are coupled.

On the other hand, in the present embodiment shown in Figure 7, not suppressing all harmonics in the first propagation path P1, the phase of the harmonics is adjusted to the opposite phase, so that the resonance regions (21) and (32) can be coupled to form the second propagation path P2, which makes it possible to obtain steep passage characteristics for the fundamental wave while suppressing the passage of harmonics.

Next, the modified example shown in Figure 8 will be described. Configurations that overlap with the above embodiment may be given the same reference numerals, and overlapping explanations are omitted. The filter apparatus (10) according to the modified example is equipped with a waveguide filter (1F) (example of a filter section) including resonance regions (21), (22), (31), (32), and is also equipped with a waveguide (7) independent of the waveguide filter (1F).

The waveguide filter (1F) has the same configuration as the waveguide filter (1) of the above embodiment except that it does not have a coupling window (45) that directly couples the resonance regions (21) and (32). A first propagation path P1 is formed in the waveguide filter (1F).

The waveguide (7) directly couples the waveguide line (82) for input and the waveguide line (83) for output and is provided as the second propagation path P2. The waveguide (7) propagates only harmonics of the fundamental wave and harmonics supplied from the waveguide line (82) for input.

According to this, the harmonics adjusted to the opposite phase propagating through the first propagation path P1 and the harmonics propagating through the second propagation path P2 are synthesized in the waveguide line (83) for output, thereby suppressing the harmonics.

The waveguide (7) is suitable as the second propagation path P2 because it is easy to make the line propagating only the harmonics by adjusting the width. Not limited to this, the second propagation path P2 may be composed of, for example, a microstrip line and so on.

Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the embodiment described above, and it is of course possible for those skilled in the art to make various modifications.

In the above embodiment, the waveguide filter (1) is mentioned as an example of the filter apparatus, but the filter apparatus may be a filter composed of, for example, a microstrip line and so on.

The following is a list of representative examples of the disclosure.

Clause 1. A filter apparatus, comprising:
a resonator with adjustment that propagates a fundamental wave and harmonics of the fundamental wave,
an adjustment section, which is provided in the resonator with adjustment for adjusting a phase of the harmonics of the fundamental wave to an opposite phase,
a first propagation path, which is formed via the resonator with adjustment, and
a second propagation path, which is formed not via the resonator with adjustment,
wherein the harmonics of the fundamental wave adjusted to the opposite phase propagating through the first propagation path, and the harmonics of the fundamental wave propagating through the second propagation path are synthesized.

Clause 2. The filter apparatus according to clause 1, further comprising:
an upstream resonator arranged upstream of the resonator with adjustment;
a downstream resonator arranged downstream of the resonator with adjustment,
wherein the second propagation path includes a coupling path that couples the upstream resonator and the downstream resonator.

Clause 3. The filter apparatus according to clause 2, wherein
the resonator with adjustment, the upstream resonator, and the downstream resonator are waveguide resonators that cause the fundamental wave to resonate in TE mode.

Clause 4. The filter apparatus according to clause 3, wherein
the filter apparatus is equipped with two resonators with adjustment that are separated by a partition wall that forms an E-plane, and
a coupling window formed in the partition wall propagates a part of the harmonics of the fundamental wave adjusted to the opposite phase.

Clause 5. The filter apparatus according to clause 3 or clause 4, wherein
the upstream resonator and the downstream resonator are separated by a partition wall that forms an E-plane, and
a coupling window as the coupling path formed in the partition wall propagates a part of the harmonics.

Clause 6. The filter apparatus according to clause 1, further comprising:
other resonators arranged upstream or downstream of the resonator with adjustment, wherein
the second propagation path is formed independently of a filter section including the resonator with adjustment and the other resonators.

Clause 7. The filter apparatus according to clause 6, wherein
the second propagation path propagates only the harmonics of the fundamental wave and harmonics supplied from a waveguide line for an input.

Clause 8. A transmitter comprising the filter apparatus according to any of clauses 1 to 7.

Clause 9. A radar comprising the filter apparatus according to any of clauses 1 to 7.

It is to be understood that not necessarily all objects or advantages may be achieved in accordance with any particular embodiment described herein. Thus, for example, those skilled in the art will recognize that certain embodiments may be configured to operate in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

All of the processes described herein may be embodied in, and fully automated via, software code modules executed by a computing system that includes one or more computers or processors. The code modules may be stored in any type of non-transitory computer-readable medium or other computer storage device. Some or all the methods may be embodied in specialized computer hardware.

Many other variations than those described herein will be apparent from this disclosure. For example, depending on the embodiment, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (e.g., not all described acts or events are necessary for the practice of the algorithms). Moreover, in certain embodiments, acts or events can be performed concurrently, e.g., through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. In addition, different tasks or processes can be performed by different machines and/or computing systems that can function together.

The various illustrative logical blocks and modules described in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a processor. A processor can be a microprocessor, but in the alternative, the processor can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor can include electrical circuitry configured to process computer-executable instructions. In another embodiment, a processor includes an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable device that performs logic operations without processing computer-executable instructions. A processor can also be implemented as a combination of computing devices, e.g., a combination of a digital signal processor (DSP) and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor may also include primarily analog components. For example, some or all of the signal processing algorithms described herein may be implemented in analog circuitry or mixed analog and digital circuitry. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few.

Conditional language such as, among others, "can," "could," "might" or "may," unless specifically stated otherwise, are otherwise understood within the context as used in general to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment.

Disjunctive language such as the phrase "at least one of X, Y, or Z," unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (e.g., X, Y, and/or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, or at least one of Z to each be present.

Any process descriptions, elements or blocks in the flow diagrams described herein and/or depicted in the attached figures should be understood as potentially representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or elements in the process. Alternate implementations are included within the scope of the embodiments described herein in which elements or functions may be deleted, executed out of order from that shown, or discussed, including substantially concurrently or in reverse order, depending on the functionality involved as would be understood by those skilled in the art.

Unless otherwise explicitly stated, articles such as "a" or "an" should generally be interpreted to include one or more described items. Accordingly, phrases such as "a device configured to" are intended to include one or more recited devices. Such one or more recited devices can also be collectively configured to carry out the stated recitations. For example, "a processor configured to carry out recitations A, B and C" can include a first processor configured to carry out recitation A working in conjunction with a second processor configured to carry out recitations B and C. The same holds true for the use of definite articles used to introduce embodiment recitations. In addition, even if a specific number of an introduced embodiment recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, typically means at least two recitations, or two or more recitations).

It will be understood by those within the art that, in general, terms used herein, are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including but not limited to," the term "having" should be interpreted as "having at least," the term "includes" should be interpreted as "includes but is not limited to," etc.).

For expository purposes, the term "horizontal" as used herein is defined as a plane parallel to the plane or surface of the floor of the area in which the system being described is used or the method being described is performed, regardless of its orientation. The term "floor" can be interchanged with the term "ground" or "water surface." The term "vertical" refers to a direction perpendicular to the horizontal as just defined. Terms such as "above," "below," "bottom," "top," "side," "higher," "lower," "upper," "over," and "under," are defined with respect to the horizontal plane.

As used herein, the terms "attached," "connected," "mated" and other such relational terms should be construed, unless otherwise noted, to include removable, moveable, fixed, adjustable, and/or releasable connections or attachments. The connections/attachments can include direct connections and/or connections having intermediate structure between the two components discussed.

Numbers preceded by a term such as "approximately," "about," and "substantially" as used herein include the recited numbers, and also represent an amount close to the stated amount that still performs a desired function or achieves a desired result. For example, the terms "approximately," "about," and "substantially" may refer to an amount that is within less than 10% of the stated amount. Features of embodiments disclosed herein preceded by a term such as "approximately," "about," and "substantially" as used herein represent the feature with some variability that still performs a desired function or achieves a desired result for that feature.

It should be emphasized that many variations and modifications may be made to the above-described embodiments, the elements of which are to be understood as being among other acceptable examples. All such modifications and variations are intended to be included herein within the scope of this disclosure and protected by the following claims.

DESCRIPTION OF DRAWING REFERENCE NUMERALS

1 waveguide filter (example of a filter apparatus)
2 block
20 recess
21 resonance region (example of an upstream resonator)
22 resonance region (example of a resonator with adjustment)
221, 222 adjustment section
23, 25 coupling window
29 opposing side
3 block
30 recess
31 resonance region (example of a resonator with adjustment)
32 resonance region (example of a downstream resonator)
311, 312 adjustment section
33, 35 coupling window
39 opposing side
4 partition plate
41-45 coupling window
82, 83 waveguide line
91 magnetron
92 pulse drive circuit
93 circulator
94 terminator
95 circulator
96 rotary joint
97 antenna
98 limiter circuit
99 receiving circuit
100 radar

Claims

A filter apparatus, comprising:
a resonator with adjustment that propagates a fundamental wave and harmonics of the fundamental wave,
an adjustment section, which is provided in the resonator with adjustment for adjusting a phase of the harmonics of the fundamental wave to an opposite phase,
a first propagation path, which is formed via the resonator with adjustment, and
a second propagation path, which is formed not via the resonator with adjustment,
wherein the harmonics of the fundamental wave adjusted to the opposite phase propagating through the first propagation path, and the harmonics of the fundamental wave propagating through the second propagation path are synthesized.
The filter apparatus according to claim 1, further comprising:
an upstream resonator arranged upstream of the resonator with adjustment;
a downstream resonator arranged downstream of the resonator with adjustment,
wherein the second propagation path includes a coupling path that couples the upstream resonator and the downstream resonator.
The filter apparatus according to claim 2, wherein
the resonator with adjustment, the upstream resonator, and the downstream resonator are waveguide resonators that cause the fundamental wave to resonate in a TE mode.
The filter apparatus according to claim 3, wherein
the filter apparatus is equipped with two resonators with adjustment that are separated by a partition wall that forms an E-plane, and
a coupling window formed in the partition wall propagates a part of the harmonics of the fundamental wave adjusted to the opposite phase.
The filter apparatus according to claim 3, wherein
the upstream resonator and the downstream resonator are separated by a partition wall that forms an E-plane, and
a coupling window as the coupling path formed in the partition wall propagates a part of the harmonics.
The filter apparatus according to claim 1, further comprising:
other resonators arranged upstream or downstream of the resonator with adjustment, wherein the second propagation path is formed independently of a filter section including the resonator with adjustment and the other resonators.
The filter apparatus according to claim 6, wherein
the second propagation path propagates only the harmonics of the fundamental wave and harmonics supplied from a waveguide line for an input.
A transmitter comprising the filter apparatus according to claim 1.
A radar comprising the filter apparatus according to claim 1.