CN114865254B

CN114865254B - Waveguide type adjustable band-pass filter

Info

Publication number: CN114865254B
Application number: CN202210733553.2A
Authority: CN
Inventors: 杜姗姗; 刘畅; 王明
Original assignee: Chengdu Weibin Technology Co ltd
Current assignee: Chengdu Weibin Technology Co ltd
Priority date: 2022-06-27
Filing date: 2022-06-27
Publication date: 2023-06-02
Anticipated expiration: 2042-06-27
Also published as: CN114865254A

Abstract

A waveguide-type tunable bandpass filter comprising: the resonant cavity comprises two ladder-shaped waveguide structures which are symmetrical in center, the ladder heights of the ladder-shaped waveguide structures are gradually reduced from the outer end to the middle, and the lowest ladder of the two ladder-shaped waveguide structures is correspondingly arranged and communicated; the coupling structure is accommodated in the resonant cavity and comprises a metal partition plate arranged in the center of the resonant cavity and a pair of YIG substrates respectively positioned above the top surface and below the bottom surface of the metal partition plate by a preset distance, a through hole is formed in the middle of the metal partition plate, the YIG substrates are arranged corresponding to the through hole, each YIG substrate comprises a GGG substrate and a YIG film arranged on one surface of the GGG substrate, and the YIG films are arranged towards the metal partition plate; and the two magnetic poles of the external magnetic field are arranged on two sides of the resonant cavity and are parallel to the YIG film. A YIG film is formed on a GGG substrate and matched with a metal partition plate to form a coupling structure, and the coupling structure is arranged in a stepped waveguide structure with central symmetry, so that the central frequency is adjustable, and meanwhile, the coupling structure has the characteristics of simple structure and easiness in assembly.

Description

Waveguide type adjustable band-pass filter

Technical Field

The application relates to the technical field of radio frequency microwaves, in particular to a waveguide type adjustable band-pass filter with tunable center frequency.

Background

YTIG (YIG) tone filter, YTF for short, is a filter that can be center frequency tuned over a range of frequencies. In the field of broadband microwave wireless communication, the requirements for broadband tunable devices are more and more widespread, and YIG magnetic tunable filters are very important as tunable filters at the front end of a system radio frequency circuit, so that the system volume can be reduced by replacing a switch filter bank, and the miniaturization of a wireless communication system is realized. The YIG magnetic tuning filter changes the center frequency of the filter by adjusting the size of the magnetic field, suppresses interference signals, and has the advantages of high tuning linearity, high out-of-band suppression and the like besides the advantage of realizing fast tuning in a wide frequency band of several octaves through useful signals. Has a wide application prospect in both civil and military fields.

YIG magnetic tunable filters are based mainly on the ferromagnetic resonance characteristics of yttrium iron garnet materials. In the conventional YIG magnetic tunable filter, a harmonic oscillator is generally implemented by utilizing YIG pellets, and a coupling ring structure is utilized to realize cascade connection of a plurality of YIG pellets. However, in order to realize a filter with good performance, the YIG pellets need to undergo a complex polishing process to obtain pellets with precise dimensions, extremely low eccentricity and optical precision; meanwhile, a plurality of YIG pellets are required to be accurately positioned, and synchronous tuning can be realized only by enabling all the YIG pellets to be parallel to an easy axis, so that a complex tuning device is required to finely tune the pellets. Therefore, the filtering using YIG pellets as resonators is not easy to realize mass production of products.

Disclosure of Invention

In order to solve the defects in the prior art, the application provides a waveguide type tunable bandpass filter, which is characterized in that a YIG film is formed on a Gadolinium Gallium Garnet (GGG) substrate and matched with a metal partition plate to form a coupling structure, the coupling structure is arranged in a central symmetrical stepped waveguide structure, the central frequency of a certain frequency range is adjustable, and meanwhile, the waveguide type tunable bandpass filter has the characteristics of simple structure and easiness in assembly.

In order to achieve the above object, the present invention adopts the following technique:

a waveguide-type tunable bandpass filter comprising:

the resonant cavity comprises two ladder-shaped waveguide structures which are symmetrical in center, the ladder heights of the ladder-shaped waveguide structures are gradually reduced from the outer end to the middle, and the lowest ladder of the two ladder-shaped waveguide structures is correspondingly arranged and communicated;

the coupling structure is accommodated in the resonant cavity and comprises a metal partition plate arranged in the center of the resonant cavity and a pair of YIG substrates respectively positioned above the top surface and below the bottom surface of the metal partition plate by a preset distance, a through hole is formed in the middle of the metal partition plate, the YIG substrates are arranged corresponding to the through hole, each YIG substrate comprises a GGG substrate and a YIG film arranged on one surface of the GGG substrate, and the YIG films are arranged towards the metal partition plate;

and the two magnetic poles of the external magnetic field are arranged on two sides of the resonant cavity and are parallel to the YIG film.

The outer end of one stepped waveguide structure is a radio frequency input end, and the outer end of the other stepped waveguide structure is a radio frequency output end.

Further, the resonant cavities corresponding to the height steps of the stepped waveguide structure are equal in length and are quarter-wave.

Further, the stepped waveguide structure includes 4 steps of different heights.

Further, a metal spacer is positioned between the lowest steps of the two stepped waveguide structures, and a pair of YIG substrates are respectively accommodated in the lowest steps of the two stepped waveguide structures.

Further, the projection of the YIG substrate is square, the via is square, and the projection of the YIG substrate is located within the via.

Further, the housing of the resonant cavity is made of metal aluminum.

Further, YIG thin film is formed on one side of GGG substrate by liquid phase epitaxy technique.

The invention has the beneficial effects that:

1. forming YIG film on GGG substrate and matching with metal baffle to form coupling structure, placing in central symmetrical ladder waveguide structure, matching with metal baffle with through hole to form coupling structure, realizing adjustable central frequency in certain frequency range, and having simple structure and easy assembly;

2. the resonant cavity is of a ladder-shaped waveguide structure and is symmetrical by taking the whole cavity as a center, so that the waveguide ladder impedance transformer is formed, and the filter can obtain better impedance matching, so that the tunable range of the filter is widened;

3. the coupling coefficient of the filter can be changed by adjusting the distance between YIG films, so that the working bandwidth and the return loss of the filter can be adjusted;

4. the YIG film substrate is used for replacing YIG pellets as a harmonic oscillator of the filter, and as the YIG film only has a single crystal orientation, the crystal orientation does not need to be readjusted during assembly, a complex cavity structure is omitted, and meanwhile, the assembly efficiency is improved; in addition, precise polishing and size control are needed in the YIG ball preparation process, and the YIG film preparation process is relatively simple, so that the production rate is improved; in addition, YIG pellets generally need to realize a filter by using a ring coupling mode, and the mechanical assembly difficulty is high because the coupling ring has a complex structure, small size and accurate requirement; however, the structure provided by the invention is a structural form of forming the YIG film on the GGG substrate to form the YIG substrate, and the assembly is simple and easy to realize.

Drawings

Fig. 1 is a side perspective view of a waveguide-type tunable bandpass filter according to embodiments of the application.

Fig. 2 is a perspective view of a waveguide-type tunable bandpass filter according to embodiments of the application.

Fig. 3 is a perspective view of a resonant cavity of a waveguide-type tunable bandpass filter according to embodiments of the application.

Fig. 4 is a perspective cross-sectional view of a waveguide-type tunable bandpass filter according to embodiments of the application.

Fig. 5 is a three-dimensional electromagnetic simulation result of a waveguide type tunable bandpass filter according to the embodiment of the application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings, but the described embodiments of the present invention are some, but not all embodiments of the present invention.

The embodiment of the application provides a waveguide type tunable bandpass filter, which comprises a filter main body and an external magnetic field 8 as shown in fig. 1-4. The filter body comprises a resonator 3 and a coupling structure accommodated in the resonator 3.

The outer shell of the resonant cavity 3 is made of metal aluminum and is of a stepped waveguide structure, and the whole cavity is used as a central symmetrical structure. Specifically, the resonant cavity 3 includes two central symmetrical stepped waveguide structures 31, the step height of the stepped waveguide structures 31 decreases step by step from the outer end to the middle, that is, the middle portion is the lowest, and the height of the resonant cavity 3 increases step by step from the middle to the two ends. The lowest steps of the two stepped waveguide structures 31 are correspondingly arranged and communicate. The resonant cavities corresponding to the height steps of the stepped waveguide structure 31 are equal in length and are quarter-wave long. The different heights of the resonant cavities 3 form the waveguide ladder impedance transformer, so that the filter can obtain better impedance matching, and the tunable range of the filter is further widened.

In this example, the stepped waveguide structure 31 comprises 4 steps of different heights. The outer end of one stepped waveguide structure 31 is a radio frequency input end 1, and the outer end of the other stepped waveguide structure 31 is a radio frequency output end 2.

The coupling structure includes a metal spacer 4 provided at the center of the cavity 3 and a pair of YIG substrates 5 respectively positioned above the top surface and below the bottom surface of the metal spacer 4 by a predetermined distance. The metal partition 4 is located in the middle of the lowest step of the two stepped waveguide structures 31, i.e. in the central position of the resonator 3. A pair of YIG substrates 5 are also located in the middle of the resonant cavity 3 and are respectively accommodated in the lowest steps of the two stepped waveguide structures 31. A pair of YIG substrates 5 are symmetrically disposed on both sides of the metal separator 4 and are positioned on the same axis.

The distance between YIG substrates 5 can change the coupling coefficient of the filter, the closer the distance between YIG substrates 5 is, the larger the coupling coefficient is, the wider the bandwidth of the filter is, the farther the distance is, the narrower the bandwidth is, and the return loss of the filter is affected, and in practical application, the proper YIG substrate 5 interval needs to be selected in combination with the requirements of the filter on the working bandwidth and the return loss.

The metal separator 4 is provided with a through hole 41 in the middle, the YIG substrate 5 is disposed corresponding to the through hole 41, the YIG substrate 5 includes a GGG substrate 7 and a YIG film 6 disposed on one side of the GGG substrate 7, and specifically, the YIG film 6 is formed on one side of the GGG substrate 7 by liquid phase epitaxy. YIG film 6 is disposed toward metal separator 4. Specifically, YIG substrate 5 is square, via 41 is square, and the projection of YIG substrate 5 is located within via 41.

The two magnetic poles of the external magnetic field 8 are arranged on two sides of the resonant cavity 3 and are parallel to the YIG film 6.

Under the action of the external magnetic field 8, when the frequency of an input radio frequency signal is equal to the ferromagnetic resonance frequency of the YIG film 6, the radio frequency signal is coupled to the YIG film 6 connected with the upper GGG substrate 7 by the radio frequency input end 1, and then the radio frequency signal is coupled to the microstrip line of the radio frequency output end 2 by the coupling between the two YIG films 6, so that the signal output is finally realized. Along with the change of the magnitude of the external magnetic field 8, the ferromagnetic resonance frequency of the YIG film 6 is changed, so that the tunable characteristic of the filter is realized; in addition, the metal baffle plate 4 in the resonant cavity 3 can prevent the input microwave energy from leaking to the output end, so that the isolation of the filter is improved.

As shown in fig. 5, the three-dimensional electromagnetic simulation result of the waveguide-type tunable bandpass filter of this embodiment is:

when the external magnetic field 8 is 4100Oe, the center frequency of the corresponding filter is 12GHz, the 3dB bandwidth is about 60MHz, and the insertion loss is about 1 dB; when the size range of the external magnetic field 8 is set to 2000Oe to 6000Oe, the filter can be tunable in the frequency range from 6GHz to 16GHz, and the 3dB working bandwidth is about 50 MHz.

The waveguide type adjustable band-pass filter of the embodiment adopts the YIG film to replace YIG pellets as a harmonic oscillator of the filter, and utilizes the waveguide ladder impedance converter to replace a complex coupling circuit structure, so that the filter is adjustable within a certain broadband range, the efficiency of the filter in the assembling and adjusting process is higher, the processing technology is simplified, the processing cost is reduced, and the mass production of YIG tuned filters is more facilitated.

The foregoing is merely a preferred embodiment of the present application and is not intended to limit the present application, and it will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit and scope of the present application. Thus, if such modifications and variations of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to cover such modifications and variations.

Claims

1. A waveguide tunable bandpass filter, comprising:

the resonant cavity (3) comprises two central symmetrical ladder-shaped waveguide structures (31), the ladder heights of the ladder-shaped waveguide structures (31) are gradually reduced from the outer end to the middle, and the lowest ladder of the two ladder-shaped waveguide structures (31) is correspondingly arranged and communicated;

the coupling structure is contained in the resonant cavity (3) and comprises a metal partition plate (4) arranged in the center of the resonant cavity (3) and a pair of YIG substrates (5) respectively positioned above the top surface and below the bottom surface of the metal partition plate (4) by a preset distance, through holes (41) are formed in the middle of the metal partition plate (4), the YIG substrates (5) are arranged corresponding to the through holes (41), the YIG substrates (5) comprise GGG substrates (7) and YIG films (6) arranged on one surface of the GGG substrates (7), and the YIG films (6) are arranged towards the metal partition plate (4);

and the two magnetic poles of the external magnetic field (8) are arranged at two sides of the resonant cavity (3) and are parallel to the YIG film (6).

2. The waveguide-type tunable bandpass filter according to claim 1 wherein the outer end of one stepped waveguide structure (31) is a radio frequency input (1) and the outer end of the other stepped waveguide structure (31) is a radio frequency output (2).

3. A waveguide-type tunable bandpass filter according to claim 1 wherein the respective height steps of the stepped waveguide structure (31) are equal in length of the corresponding resonant cavities, being quarter wavelength.

4. A waveguide-type tunable bandpass filter according to claim 1 wherein the stepped waveguide structure (31) comprises 4 steps of different height.

5. A waveguide tunable bandpass filter according to claim 1 wherein the metal spacer (4) is located in the middle of the lowest steps of the two stepped waveguide structures (31) and a pair of YIG substrates (5) are respectively accommodated in the lowest steps of the two stepped waveguide structures (31).

6. Waveguide-type tunable bandpass filter according to claim 1 characterized in that the projection of YIG substrate (5) is square, the through-hole (41) is square and the projection of YIG substrate (5) is located in the through-hole (41).

7. Waveguide-type tunable bandpass filter according to claim 1 characterized in that the housing of the resonator (3) is made of metallic aluminium.

8. Waveguide-type tunable bandpass filter according to claim 1 characterized in that YIG film (6) is formed on one side of GGG substrate (7) by liquid phase epitaxy technique.