CN113540717A

CN113540717A - Adjustable band-pass filter

Info

Publication number: CN113540717A
Application number: CN202111077494.XA
Authority: CN
Inventors: 杜姗姗; 刘畅; 王明; 樊鑫安
Original assignee: Chengdu Weibin Technology Co Ltd
Current assignee: Chengdu Weibin Technology Co Ltd
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2021-10-22
Anticipated expiration: 2041-09-15
Also published as: CN113540717B

Abstract

A tunable bandpass filter includes a filter body in an external magnetic field. The filter main body comprises a resonant cavity, an upper substrate and a lower substrate which are arranged in the resonant cavity, a radio frequency input end arranged at one end of the resonant cavity and a radio frequency output end arranged at the other end of the resonant cavity; the upper substrate and the lower substrate are arranged up and down oppositely and at intervals, microstrip lines are arranged on the opposite surfaces, the radio frequency input end is connected with the microstrip line of the lower substrate, and the radio frequency output end is connected with the microstrip line of the upper substrate; the upper substrate and the lower substrate are both provided with YIG substrates, the YIG substrates are connected with microstrip lines, the YIG substrates comprise GGG substrates connected with the microstrip lines and YIG films arranged on the top surfaces of the GGG substrates, and a preset distance is reserved between the YIG film surfaces of the upper YIG substrate and the lower YIG substrate. Through the structural design of the resonant cavity and the YIG substrate formed by the YIG film and the GGG substrate, the adjustable center frequency within a certain frequency range is realized, and the adjustable center frequency has the characteristics of simple structure and easiness in assembly.

Description

Adjustable band-pass filter

Technical Field

The invention belongs to the technical field of radio frequency microwaves, and particularly relates to a band-pass filter with adjustable center frequency.

Background

An Yttrium Iron Garnet (YIG) magnetic tuning filter, YTF for short, is a filter with tunable center frequency. In recent years, due to the demand for miniaturization of electronic countermeasure and test equipment, the YIG magnetic modulation filter can be used as a preselector to replace a switch filter bank in a receiver, and the center frequency of the filter is changed by adjusting the size of a magnetic field, interference signals are suppressed, and useful signals are passed, so that the small-volume characteristic of the whole electronic system is realized. The YIG magnetic tuning filter has the advantages of high tuning linearity, high out-of-band rejection and the like besides the advantage of realizing rapid tuning in a wide frequency band with several octaves. Has wide application prospect in both civil and military fields.

The YIG magnetic tuning filter is mainly made by utilizing the ferromagnetic resonance characteristic of the yttrium iron garnet material. The traditional YTF adopts YIG pellets as harmonic oscillators, and is realized by cascading a plurality of YIG pellets by utilizing a ring coupling structure. However, in order to realize a filter with good performance, the YIG small ball needs to be subjected to a complex polishing process to obtain a small ball with accurate size, extremely low eccentricity and optical precision; meanwhile, a plurality of YIG small balls are required to be adjusted and oriented, all the YIG small balls reach easy axis parallelism, synchronous tuning is realized, and therefore a complex tuning device is required to finely adjust the small balls. Therefore, the mass production of products is not easy to realize by using YIG pellets as harmonic oscillators for filtering.

Disclosure of Invention

Aiming at the defects of the related prior art, the invention provides the adjustable band-pass filter, which realizes the adjustability of the center frequency within a certain frequency range by the structural design of a resonant cavity and the YIG substrate formed by the YIG film and the GGG substrate, and has the characteristics of simple structure and easy assembly.

In order to realize the purpose of the invention, the following scheme is adopted:

a tunable bandpass filter comprising a filter body:

the filter main body comprises a resonant cavity, an upper substrate and a lower substrate which are arranged in the resonant cavity, a radio frequency input end arranged at one end of the resonant cavity and a radio frequency output end arranged at the other end of the resonant cavity;

the upper substrate and the lower substrate are arranged up and down oppositely and at intervals, microstrip lines are arranged on the opposite surfaces, the radio frequency input end is connected with the microstrip line of the lower substrate, and the radio frequency output end is connected with the microstrip line of the upper substrate;

the upper substrate and the lower substrate are both provided with YIG substrates, the YIG substrates are connected with microstrip lines, the YIG substrates comprise GGG substrates connected with the microstrip lines and YIG films arranged on the top surfaces of the GGG substrates, and a preset distance is reserved between the YIG film surfaces of the upper YIG substrate and the lower YIG substrate.

Further, the filter body is in an external magnetic field. Two magnetic poles of the external magnetic field are respectively positioned at two sides of the filter main body, and the direction of the magnetic field is vertical to the microstrip line and is parallel to the YIG film.

Furthermore, a pair of metal parting strips which are horizontally arranged at intervals are arranged in the resonant cavity, the height position of each metal parting strip in the resonant cavity is arranged between the upper YIG substrate and the lower YIG substrate, and the YIG substrates are positioned in the area between the metal parting strips in the horizontal direction.

The invention has the beneficial effects that:

1. an Yttrium Iron Garnet (YIG) film substrate is used for replacing an Yttrium Iron Garnet (YIG) pellet as a harmonic oscillator of the filter, and the Yttrium Iron Garnet (YIG) film only has a single crystal orientation, so that the crystal orientation does not need to be readjusted during assembly, a complex cavity structure is saved, and the assembly efficiency is improved;

2. the Yttrium Iron Garnet (YIG) pellet needs to be precisely polished and the size of the pellet is controlled in the preparation process, and the preparation process of the Yttrium Iron Garnet (YIG) film is relatively simple, so that the production rate is improved;

3. the Yttrium Iron Garnet (YIG) pellet generally needs to realize a filter by using a ring coupling mode, and the coupling ring structure has complex requirements and small size but accurate requirements, so the mechanical assembly difficulty is very high, but the structure provided by the invention is that a microstrip line on a substrate is used for exciting an Yttrium Iron Garnet (YIG) film substrate, the assembly is simple, and the realization is easier;

4. with the change of the magnitude of the external magnetic field, the ferromagnetic resonance frequency of the YIG film material changes, thereby realizing the tunable characteristic of the filter. Meanwhile, the working bandwidth of the filter can be adjusted by adjusting the distance between the two YIG substrates, and the closer the distance is, the wider the working bandwidth is, and the farther the distance is, the narrower the working bandwidth is. In addition, the metal parting strips in the resonant cavity can isolate the problem of signal crosstalk between the input and output ports, and the integral isolation degree of the filter is improved.

Drawings

Fig. 1 shows a schematic diagram of the internal structure of the filter body and the external magnetic field according to the embodiment of the present application.

Fig. 2 is a perspective view showing the internal structure of the filter body according to the embodiment of the present application.

Fig. 3 is a perspective view showing a structure of the lower substrate and the YIG substrate according to the embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings, but the described embodiments of the present invention are a part of the embodiments of the present invention, not all of the embodiments of the present invention.

The embodiment of the application provides an adjustable band-pass filter, as shown in fig. 1 to 3, comprising a filter body 1, wherein the filter body 1 is located in an external magnetic field 2.

The filter body 1 comprises a resonant cavity 11, an upper substrate 142 and a lower substrate 141 arranged in the resonant cavity 11, a radio frequency input end 12 arranged at one end of the resonant cavity 11 and a radio frequency output end 13 arranged at the other end; the upper substrate 142 and the lower substrate 141 are disposed opposite to each other at an interval, and microstrip lines 15 are etched on the opposite surfaces. Specifically, the upper substrate 142 and the lower substrate 141 have the same size, the length and the width of the two microstrip lines 15 on the upper substrate 142 and the lower substrate 141 are also the same, and the upper substrate 142 and the lower substrate 141 are parallel to each other and are centrosymmetric with the center of the resonant cavity 11 as the origin. The rf input terminal 12 is connected to the microstrip line 15 of the lower substrate 141, and the rf output terminal 13 is connected to the microstrip line 15 of the upper substrate 142. Specifically, the radio frequency input end 12 and the radio frequency output end 13 are radio frequency insulators and connected with the corresponding microstrip lines 15 through welding. The microstrip line 15 of the lower substrate 141 located below the cavity 11 is used to input the rf signal, and the microstrip line 15 of the upper substrate 142 located above the cavity 11 is used to output the rf signal.

The upper substrate 142 and the lower substrate 141 are both provided with a YIG (yttrium iron garnet) substrate 16, and the YIG substrate 16 is connected with the microstrip line 15. The YIG substrates 16 are disposed symmetrically with respect to the upper and lower YIG substrates 16 at a predetermined distance from the edges of the upper and lower substrates 142 and 141, respectively, for example, at a distance of 0.5mm from the edges. The length direction of the microstrip line 15 is the same as the length direction of the upper substrate 142 and the lower substrate 141, and the microstrip line 15 is located in the middle of the surface of the upper substrate 142 opposite to the lower substrate 141. Specifically, the YIG substrate 16 is disposed on the surfaces of the upper substrate 142 and the lower substrate 141 through a conductive adhesive and connected to the microstrip line 15. The YIG substrate 16 includes a GGG (i.e., gadolinium gallium garnet) substrate 160 connected to the microstrip line 15 and a YIG film 161 provided on the top surface of the GGG substrate 160, and the surfaces of the YIG films 161 of the upper and lower YIG substrates 16 have a predetermined spacing therebetween.

Two magnetic poles of the external magnetic field 2 are respectively positioned at two sides of the filter main body 1, and the magnetic field direction is vertical to the microstrip line 15 and parallel to the YIG film 161.

A pair of metal parting strips 17 arranged horizontally at intervals are arranged in the resonant cavity 11, the height position of the metal parting strips 17 in the resonant cavity 11 is arranged between the upper YIG substrate and the lower YIG substrate 16, and in the horizontal direction, the YIG substrates 16 are positioned in the area between the metal parting strips 17. The projections of the metal spacers 17 are located at both projected ends of the YIG substrate 16 in a top or bottom projection view.

The resonant cavity 11 is formed by milling a metal material, such as a metallic aluminum material. The cavity of the resonant cavity 11 includes a middle cavity, a lower cavity communicated with the lower part of the middle cavity and extending a predetermined distance to one end of the rf input end 12, and an upper cavity communicated with the upper part of the middle cavity and extending a predetermined distance to one end of the rf output end 13, the upper substrate 142 is located on the upper cavity and the upper part of the middle cavity, the lower substrate 141 is located on the lower cavity and the lower part of the middle cavity, the YIG substrate 16 and the metal spacer 17 are both located in the middle cavity, and the metal spacer 17 is located on two end walls of the middle cavity.

Under the action of the external magnetic field 2, when the frequency of an input radio frequency signal is equal to the ferromagnetic resonance frequency of an Yttrium Iron Garnet (YIG) thin film material, the microstrip line 15 of the radio frequency input end 12 couples the radio frequency signal to a YIG substrate 16 connected with the lower substrate 141, and then the radio frequency signal is coupled to the microstrip line 15 of the radio frequency output end 13 through the coupling between the two YIG substrates 16, so that the output of the signal is finally realized. With the change of the magnitude of the external magnetic field, the ferromagnetic resonance frequency of the YIG film material changes, thereby realizing the tunable characteristic of the filter. Meanwhile, the working bandwidth of the filter can be adjusted by adjusting the distance between the two YIG substrates 16, and the closer the distance is, the wider the working bandwidth is, and the farther the distance is, the narrower the working bandwidth is. In addition, the metal division bars 17 in the resonant cavity 11 can isolate the signal crosstalk between the input and output ports, and the overall isolation of the filter is improved.

Two magnetic poles of the external magnetic field 2 are arranged on two sides of the filter main body 1, and the magnetic field direction is perpendicular to the microstrip line 15 and parallel to the YIG film 161. The size range of the magnetic field is set to be 2800Oe to 4500Oe, the filter can be tunable from a frequency band of 9.5GHz to 14.5GHz, and the 3dB working bandwidth is about 20 MHz.

By implementing the embodiment of the invention, the microstrip line coupling structure is used for replacing the traditional complex coupling ring structure, so that the band-pass filter can be adjusted in a certain broadband range, the efficiency of the filter in the assembling, adjusting and testing process is higher, the processing technology is simplified, the processing cost is reduced, and the mass production of the Yttrium Iron Garnet (YIG) tuned filter is more favorably realized.

The foregoing is merely a preferred embodiment of this invention and is not intended to be exhaustive or to limit the invention to the precise form disclosed. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention.

Claims

1. A tuneable bandpass filter comprising a filter body (1), characterized in that:

the filter main body (1) comprises a resonant cavity (11), an upper substrate (142) and a lower substrate (141) which are arranged in the resonant cavity (11), a radio frequency input end (12) arranged at one end of the resonant cavity (11) and a radio frequency output end (13) arranged at the other end of the resonant cavity;

the upper substrate (142) and the lower substrate (141) are opposite up and down and are arranged at intervals, microstrip lines (15) are arranged on the opposite surfaces, the radio frequency input end (12) is connected with the microstrip lines (15) of the lower substrate (141), and the radio frequency output end (13) is connected with the microstrip lines (15) of the upper substrate (142);

the upper substrate (142) and the lower substrate (141) are both provided with a YIG substrate (16), the YIG substrate (16) is connected with the microstrip line (15), the YIG substrate (16) comprises a GGG substrate (160) connected with the microstrip line (15) and a YIG film (161) arranged on the top surface of the GGG substrate (160), and the surfaces of the YIG films (161) of the upper YIG substrate (16) and the lower YIG substrate (16) have a preset distance.

2. A tuneable bandpass filter as claimed in claim 1, characterized in that the filter body (1) is in an external magnetic field (2).

3. A tunable bandpass filter according to claim 2, characterized in that the two poles of the external magnetic field (2) are located on the two sides of the filter body (1), respectively, and the magnetic field direction is perpendicular to the microstrip line (15) and parallel to the YIG film (161).

4. A tunable bandpass filter according to claim 1, characterized in that a pair of metal spacers (17) is provided in the resonator (11) at a horizontal distance from each other, and the metal spacers (17) are provided between the upper and lower YIG substrates (16) at a height position in the resonator (11), and the YIG substrates (16) are located in a region between the metal spacers (17) in the horizontal direction.

5. Tunable bandpass filter according to claim 4, characterized in that the projections of the metal spacers (17) are located at both projected ends of the YIG substrate (16) at the top or bottom projection viewing angle.

6. The tunable bandpass filter according to claim 1, wherein the YIG substrate (16) is disposed on the surfaces of the upper substrate (142) and the lower substrate (141) via conductive paste and connected to the microstrip line (15).

7. A tunable bandpass filter according to claim 1, characterized in that the upper substrate (142) and the lower substrate (141) are parallel to each other and are centrosymmetric with the center of the resonant cavity (11) as the origin.

8. Tunable bandpass filter according to claim 1, characterized in that the rf input (12) and the rf output (13) are rf insulators and connected to the corresponding microstrip lines (15) by soldering.

9. The tunable bandpass filter according to claim 1, characterized in that the microstrip line (15) has a length direction that coincides with the length direction of the upper substrate (142) and the lower substrate (141), and the microstrip line (15) is located in the middle of the side of the upper substrate (142) opposite to the lower substrate (141).

10. The tunable bandpass filter according to claim 4, wherein the resonant cavity (11) is formed by milling a metal material, the cavity of the resonant cavity (11) comprises a middle cavity, a lower cavity which is communicated with the lower part of the middle cavity and extends a predetermined distance to one end where the radio frequency input end (12) is located, and an upper cavity which is communicated with the upper part of the middle cavity and extends a predetermined distance to one end where the radio frequency output end (13) is located, the upper substrate (142) is located at the upper cavity and the upper part of the middle cavity, the lower substrate (141) is located at the lower part of the lower cavity and the lower part of the middle cavity, the YIG substrate (16) and the metal spacer (17) are both located in the middle cavity, and the metal spacer (17) is located on both end walls of the middle cavity.