CN113131111A

CN113131111A - W-band-pass filter

Info

Publication number: CN113131111A
Application number: CN202110415151.3A
Authority: CN
Inventors: 黄昭宇; 王青平; 江云; 刘博源; 叶源; 袁文韬; 吴微微; 张晓发; 胡卫东; 袁乃昌
Original assignee: National University of Defense Technology
Current assignee: National University of Defense Technology
Priority date: 2021-04-17
Filing date: 2021-04-17
Publication date: 2021-07-16
Anticipated expiration: 2041-04-17
Also published as: CN113131111B

Abstract

The invention belongs to the field of filters and discloses a W-band-pass filter. The filter comprises a metal outer wall, a metal inner core, an external coupling structure, an internal coupling structure and a medium supporting bar; the metal inner core, the external coupling structure, the internal coupling structure and the medium supporting bar are all arranged in the metal outer wall; the metal inner core realizes impedance transformation through width change of the cross section; the variation of the diameter of the external coupling structure can change the external coupling strength of the filter; the change of the diameter of the internal coupling structure can change the internal coupling strength of the filter. The filter can realize that the size of a device is far smaller than that of a device based on a traditional waveguide structure, simultaneously keeps good performances of small insertion loss and high power capacity, solves the problem of overlarge size of the waveguide filter, and is beneficial to the miniaturization and integration design of a W-band communication system.

Description

W-band-pass filter

Technical Field

The invention relates to the technical field of filters, in particular to a W-band-pass filter based on a 3D (3-dimensional) rectangular coaxial structure.

Background

With the continuous development of communication systems, the coverage area of the microwave frequency band has been used up, the spectrum resources are increasingly strained, and people look at higher frequency ranges. The W-band (i.e. covering the electromagnetic spectrum of 75-110 GHz) has a smaller wavelength than the microwave band, which gives the W-band communication system the following advantages: the system integration degree is high; the penetrability is strong, and the standard of quasi-all-weather can be achieved; the usable frequency bandwidth improves the channel capacity of the communication system; the imaging resolution is greatly improved. The filter is an important passive device in a communication system, can play a role in effectively inhibiting clutter signals, further ensures the efficient and stable work of the whole communication system, and is very necessary for designing a high-performance filter. Because the wavelength of the electromagnetic wave of the W wave Band is short, the radiation loss of the electromagnetic wave is enhanced, the microstrip line structure is not suitable for the design of the W wave Band Filter any more, the current design mainly focuses on the Waveguide structure, and for example, an H-Plane Coupling W wave Band Filter Based on the Waveguide structure is proposed in the paper of W-Band Waveguide Filter base on H-Plane Offset Coupling in the prior art. Filters designed with waveguide structures are usually manufactured by machining processes and have the defect of large volume, which hinders the design of miniaturization and integration of W-band systems.

The filter in the invention is based on a 3D rectangular coaxial structure and is prepared by adopting an advanced MEMS (micro electro mechanical system) manufacturing process. The rectangular coaxial structure has the advantages of small radiation loss and high power capacity; the MEMS technology is adopted for preparation, so that the volume of the MEMS is reduced to a great extent, and the MEMS structure meets the design requirement of miniaturization.

Disclosure of Invention

The invention provides a W-band bandpass filter which is miniaturized and maintains the characteristics of small insertion loss and high power capacity.

The technical scheme of the invention is as follows:

a W-band-pass filter comprises a metal outer wall 10, a metal inner core 11, an external coupling structure 12, an internal coupling structure 13 and periodically distributed medium supporting bars 14; the metal inner core 11 is suspended in an air cavity formed by the metal outer wall 10 through a medium supporting strip 14; the two ends of a rectangular cavity formed by the metal outer wall 10 are narrow, windows 101 which are periodically distributed are arranged on the rectangular cavity, and the two ends of the rectangular cavity are carved into U-shaped grooves; the metal inner core 11 is a long strip which is narrowed from the middle to two ends through 4 levels, and the cross section of the long strip is rectangular; the external coupling structure 12 and the internal coupling structure 13 are both cylinders penetrating through the metal inner core 11, and the upper surface and the lower surface of each cylinder are respectively attached to the inner cavity of the metal outer wall 10; the medium supporting bar 14 penetrates through the metal inner core 11, and two ends of the medium supporting bar are inserted into the cavity wall of the metal outer wall 10.

In particular, the characteristic of impedance transformation is achieved by varying the cross-sectional width of the metal core 11.

In particular, the metal core 11 has a central symmetrical structure and a cross-sectional width gradually decreases from the middle to both ends.

In particular, by varying the size of the diameter of the out-coupling structure 12, the strength of the out-coupling is varied; the strength of the internal coupling is changed by changing the size of the diameter of the internal coupling structure 13.

Specifically, the metal outer wall 10 and the metal inner core 11 together form a rectangular coaxial structure, and the lengths of the metal outer wall 10 and the metal inner core 11 are the same.

In particular, the narrowest stage of the metal inner core 11 and the U-shaped grooves at the two ends of the metal outer wall 10 together form the input/output port of the filter.

In particular, the filter is fabricated using a copper-based MEMS process.

The invention has the beneficial effects that:

the filter provided by the invention is designed on the basis of a 3D rectangular coaxial structure, and an advanced copper-based MEMS (micro-electromechanical systems) process is adopted in preparation, so that the size of the filter is effectively reduced while excellent performance is kept, and the design requirements of integration and miniaturization of a W-band communication system are met.

Drawings

FIG. 1 is a filter metal outer wall structure;

FIG. 2 is a filter internal structure;

FIG. 3 is a schematic view of a process layer;

FIG. 4 is a coplanar waveguide structure;

fig. 5 is a simulation result of the S parameter of the filter.

The reference numbers illustrate:

10-a metal outer wall; 101-a window; 11-a metal core; 12-an out-coupling structure; 13-an internal coupling structure; 14-media support strip.

Detailed Description

The invention is further described with reference to the following figures and specific examples.

The invention relates to a W-band-pass filter, which comprises a metal outer wall 10, a metal inner core 11, an external coupling structure 12, an internal coupling structure 13 and periodically distributed medium supporting bars 14.

As shown in fig. 1, fig. 1 is a structure of a metal outer wall 10 of a filter. The drawing (a) is a three-dimensional schematic drawing, (b) a front view, and (c) a top view, as can be seen from the above drawings, two ends of a cavity formed by the metal outer wall 10 are narrow, windows 101 are periodically distributed on the cavity, and particularly, upper half portions of two ends of the metal outer wall 10 are removed to form a U-groove shape.

Fig. 2 is a schematic structural diagram of the metal core 11, the external coupling structure 12, the internal coupling structure 13 and the dielectric support strip 14. The metal inner core 11 is a central symmetrical structure, the width of the cross section of the metal inner core gradually decreases from the middle to the two ends, and the total number of the cross section is 4. The external coupling structure 12 and the internal coupling structure 13 are both cylindrical. Changing the strength of external coupling by changing the diameter of the external coupling structure; the strength of the internal coupling is changed by changing the size of the diameter of the internal coupling structure. In particular the diameter of the inner coupling structure 13 is larger than the diameter of the outer coupling structure 12. The number of the dielectric support bars 14 is determined according to the width and the length of the metal inner core 11, and the number of the dielectric support bars 14 is as small as possible under the condition that the metal inner core 11 can be supported, so that the electromagnetic energy loss caused by adding the dielectric support bars 14 can be reduced.

The metal outer wall 10 and the metal inner core 11 jointly form a rectangular coaxial structure, and the length of the metal outer wall 10 is the same as that of the metal inner core 11. Air is filled between the metal inner core and the metal outer wall, so that the dielectric loss of the structure is reduced. Because the metal outer wall forms a relatively closed space, the radiation loss of the metal outer wall is reduced; and the 3D structure made of metal increases the power capacity of the device.

The preparation of the filter adopts a copper-based MEMS process, and the process flow can comprise the following steps of firstly coating a layer of photoresist on a substrate to form a sacrificial layer; then photoetching the sacrificial layer by using a photoetching machine, and manufacturing a required structure on the sacrificial layer; and then depositing copper on the surface by adopting an electrochemical plating method and carrying out planarization treatment, thereby completing the preparation of a layer structure. The filter designed in the invention needs 5 layers of structures, namely, a final filter structure is formed by overlapping five layers of structures, as shown in fig. 3, the five layers are sequentially from the first layer to the fifth layer from bottom to top, and after the five layers of structures are overlapped, a stripping liquid is needed to remove the sacrificial layer. In particular, in order to remove the sacrificial layer better by the stripping solution, periodic windowing needs to be performed on the metal outer wall 10, the number of the windows 101 is not too large, the radiation loss is increased, and the sacrificial layer cannot be removed cleanly due to too small number of the windows.

The narrowest stage of the metal inner core 11 and the U-shaped grooves at the two ends of the metal outer wall 10 together form the input and output ports of the filter, as shown in fig. 4. In the test, a ground-signal-ground probe test method can be used; when in use, the solid active chip can be interconnected with the solid active chip in a gold wire bonding mode, namely, the ground of the chip is connected with the ground of the filter through the gold wire, and the radio-frequency signal output of the chip is connected with the metal inner core 11 of the filter through the gold wire.

FIG. 5 is a diagram of simulation results of a filter according to the present invention, which is a third order Chebyshev-type filter. As can be seen from the curve of S11, this filter has three transmission poles; as can be seen from the curve of S21, the center frequency of the filter is 97.4GHz, the 3-dB bandwidth is 7GHz, and the minimum insertion loss of the filter in the 3-dB bandwidth is 0.91dB, so that the loss is small.

Particularly, the length of the filter is 8.1mm-8.4mm, the width of the filter is 0.85mm-0.89mm, the height of the filter is 0.48mm-0.51mm, and the occupied volume is small.

The embodiments described above are presented to enable a person having ordinary skill in the art to make and use the invention. It will be readily apparent to those skilled in the art that various modifications to the above-described embodiments may be made, and the generic principles defined herein may be applied to other embodiments without the use of inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications to the present invention based on the disclosure of the present invention within the protection scope of the present invention.

Claims

1. A W-band-pass filter is characterized by comprising a metal outer wall (10), a metal inner core (11), an external coupling structure (12), an internal coupling structure (13) and periodically distributed dielectric support bars (14); the metal inner core (11) is suspended in an air cavity formed by the metal outer wall (10) through a medium supporting strip (14); two ends of a rectangular cavity formed by the metal outer wall (10) are narrow, windows (101) distributed periodically are arranged on the rectangular cavity, and two ends of the rectangular cavity are carved into U-shaped grooves; the metal inner core (11) is a strip which is narrowed from the middle to two ends through 4 levels, and the section of the strip is rectangular; the external coupling structure (12) and the internal coupling structure (13) are cylinders penetrating through the metal inner core (11), and the upper surface and the lower surface of each cylinder are respectively attached to the inner cavity of the metal outer wall (10); the medium supporting strip (14) penetrates through the metal inner core (11), and two ends of the medium supporting strip are inserted into the cavity wall of the metal outer wall (10).

2. A W-band bandpass filter according to claim 1, characterized in that the characteristic of impedance transformation is achieved by varying the cross-sectional width of the metallic core (11).

3. A W-band bandpass filter according to claim 1, characterized in that the metal core (11) is of a centrosymmetric structure and its cross-sectional width decreases stepwise from the middle to the ends.

4. A W-band bandpass filter according to claim 1, characterized in that the strength of the external coupling is varied by varying the size of the diameter of the external coupling structure (12); the strength of the internal coupling is changed by changing the size of the diameter of the internal coupling structure (13).

5. A W-band bandpass filter according to claim 1, characterized in that the outer metal wall (10) and the inner metal core (11) together form a rectangular coaxial structure, the length of the outer metal wall (10) and the length of the inner metal core (11) being the same.

6. A W-band bandpass filter according to claim 1, characterized in that the narrowest section of the metal inner core (11) and the U-shaped slots at the ends of the metal outer wall (10) together form the input/output port of the filter.

7. The W-band bandpass filter of claim 1 wherein the filter is fabricated using a copper-based MEMS process.