A W-band ultra-wideband waveguide filter

Abstract

The application belongs to the field of microwave technology, and particularly relates to a W-waveband ultra-wideband waveguide filter, the filter structure comprising a resonant cavity and metal-loaded capacitance, wherein a downlink filter port and an uplink filter port are arranged at the front end of the cavity; the resonant unit is composed of nine resonant cavities, and two adjacent resonant cavities are connected through direct coupling; a metal column is inserted into the H plane of each resonant cavity through the capacitive loading technology, so as to realize ultra-wideband, high out-of-band suppression and miniaturization; the structure of the application is composed of nine rectangular resonant cavities offset coupling, a circular metal is inserted into the resonant cavity, and the overall structure is symmetrical about the fifth resonant cavity; the structure has fewer parameters in simulation optimization, reduces the design time, and improves the design efficiency.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology, specifically relating to a W-band ultra-wideband waveguide filter. Background Technology

[0002] With the rapid development of microwave technology, the spectrum is becoming increasingly congested, leading to a shift in research towards higher frequency bands, up to the terahertz band. Today, various communication systems must coexist within the limited electromagnetic (EM) spectrum, which is allocated to many commercial applications in the microwave band. In this congested environment, especially with increasing capacity demands, interference between systems and adjacent frequency bands has become a critical issue. To rationally utilize frequency band resources, relevant departments have issued detailed spectrum allocation standards. The W band refers to electromagnetic signals in the frequency range of 75 GHz to 110 GHz. Because this band possesses ultra-wideband, untapped frequency resources, it has become a highly valued research direction for scientists.

[0003] The function of a filter is to selectively transmit signals of a specific frequency while suppressing other frequency signals. In the design of key components of a W-band signal source spread spectrum system, a frequency multiplier used for frequency spreading can multiply the fundamental frequency signal from 37.5 GHz to 55 GHz to 75 GHz to 110 GHz. To further improve the system's spectral characteristics, a broadband bandpass filter with good passband and out-of-band suppression characteristics also needs to be designed. Cascading the filter after the frequency multiplier allows the target signal to pass through while preventing leakage of the fundamental frequency and out-of-band harmonic frequencies.

[0004] Existing filters include a 10th-order Chebyshev response filter, which achieves low insertion loss using electroforming. This filter employs direct magnetic coupling and increases the filter order to achieve a 21% bandwidth with a low insertion loss of 0.4dB. However, due to the waveguide's structural characteristics, the overall filter structure is relatively large. A capacitor-loaded broadband waveguide filter has a passband of 17.4GHz–21.6GHz, an in-band S11 less than -20dB, a suppression greater than 56dB at 16.5GHz, a suppression greater than 46dB at 22.5GHz, and a suppression greater than 91dB between 24.3 and 35GHz. This filter adds a capacitor to a diaphragm waveguide filter, significantly shortening the length of the resonant cavity and effectively reducing the filter's size while improving out-of-band suppression. However, this filter has a narrow bandwidth and many parameters, resulting in a large workload for modeling and simulation. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a W-band ultra-wideband waveguide filter. The filter structure includes a cavity, with a downlink filter port and an uplink filter port at the front end of the cavity. A resonant unit is disposed inside the cavity, consisting of nine resonant cavities, with adjacent resonant cavities connected by direct coupling. A metal pillar is inserted into the H-plane of each resonant cavity to achieve capacitive loading.

[0006] Preferably, the connection between two adjacent resonant cavities via direct coupling includes: each resonant cavity achieving magnetic coupling by offsetting its coupling window with that of the adjacent resonant cavity.

[0007] Preferably, the resonant unit has a left-right symmetrical structure about the fifth resonant cavity in the middle.

[0008] Preferably, the height of the ultra-wideband filter is the same as that of a standard WR-10 rectangular waveguide port, and the input and output ports are set to standard WR-10 rectangular waveguide ports.

[0009] The beneficial effects of this invention are:

[0010] This invention employs an offset magnetic coupling structure to load metal pillars to design a filter, enabling the filter's passband to cover the entire W-band and possessing a good rectangular coefficient. The structure consists of nine rectangular resonant cavities with offset coupling, each containing a circular metal insert, and the overall structure is symmetrical about the fifth resonant cavity. This structure requires fewer parameters during simulation optimization, reducing design time and improving design efficiency. Attached Figure Description

[0011] Figure 1 This is a three-dimensional structural diagram of the W-band ultra-wideband waveguide filter of the present invention;

[0012] Figure 2 This is a planar structural diagram of the W-band ultra-wideband waveguide filter of the present invention.

[0013] Figure 3 The simulation waveform diagram of the W-band ultra-wideband waveguide filter of the present invention is shown. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The W-band ultrawideband waveguide filter proposed in this invention is based on the traditional coupled waveguide filter structure, but changes its coupling method and adds a capacitor on this basis, so that the filter can achieve a relative bandwidth of 44% with low loss, and has a small size and good rectangular coefficient.

[0016] A W-band ultrawideband waveguide filter is disclosed. The structure includes coupled resonant cavities and metal-loaded capacitor pillars. The filter's input and output ports are standard rectangular waveguides WR-10. Calculated using the Chebyshev response formula, this filter is a ninth-order filter. To simplify the design, an H-plane offset magnetic coupling structure is employed, thus the structure consists of nine resonant cavities connected in a direct coupling manner. To achieve ultrawideband performance, high out-of-band rejection, and miniaturization, capacitor loading technology is used to insert metal pillars of different diameters into the H-plane of each resonant cavity.

[0017] Specifically, the W-band ultra-wideband waveguide filter in this invention achieves its goal by inserting metal pillars into each resonant cavity to realize the loading capacitor based on an offset magnetic coupling structure. For example... Figures 1-2 As shown, this broadband waveguide filter consists of nine resonant cavities, achieving a Chebyshev response through direct coupling. Each resonant cavity operates in the TE101 mode, and magnetic coupling is achieved through a misalignment of the coupling windows of adjacent resonant cavities. Capacitance is applied by inserting metal pillars with radius r and length equal to the width of the corresponding resonant cavity into the H-plane of each cavity.

[0018] To facilitate subsequent simulation design and actual manufacturing, the filter structure is symmetrical about the fifth resonant cavity in the middle, and the overall height of the filter is the standard height of a WR-10 rectangular waveguide port. Its input and output ports are set to the standard WR-10 rectangular waveguide port size (2.54mm × 1.27mm).

[0019] Waveguides are transmission media with advantages such as low loss, high bandwidth, and low interference, and are widely used in radio frequency circuit design in microwave and millimeter-wave fields. In a waveguide, electromagnetic waves are transmitted through reflection within a metal casing, thus providing the advantages of low loss and high bandwidth. A waveguide bandpass filter is a device that selectively transmits signals of a specific frequency while suppressing other frequencies. It is typically composed of multiple cascaded filter units, each capable of achieving a specific frequency response. The input and output ports of this invention utilize the WR-10 standard rectangular waveguide suitable for the W-band, with dimensions of 2.54mm * 1.27mm, effectively transmitting electromagnetic waves from 70GHz to 110GHz. Based on the Chebyshev response function and its parameters, the filter of this invention is a 9th-order filter, therefore consisting of 9 resonant cavities. Adjusting the offset between adjacent resonant cavities based on the calculated coupling coefficient achieves a passband effect in the simulated waveform. Directly coupled waveguide filters exhibit poor out-of-band suppression at high frequencies. To improve out-of-band suppression and reduce the overall size of the filter, this invention uses a directly coupled filter as a prototype and implements a capacitor by inserting a metal pillar into the waveguide's E-plane. This capacitor short-circuits the high-frequency signal at a specific frequency, thus achieving out-of-band suppression. In the waveguide, the metal pillar acts like a capacitor; by adjusting the size and position of the metal pillar, the capacitance between the pillar and the waveguide's E-plane can be controlled, thereby achieving out-of-band suppression. Furthermore, the capacitor reduces the transmission line length, thus the metal pillar also contributes to reducing the overall size of the filter.

[0020] This invention combines offset magnetic coupling structure and loaded capacitor technology to improve the overall filter structure, replacing the traditional rectangular diaphragm loaded capacitor with a cylindrical one. Electromagnetic simulation was performed using the commercial electromagnetic simulation software High Frequency Structure Simulator (HFSS), and the simulation waveforms were obtained, as shown below. Figure 3 As shown, the center frequency of the W-band ultra-wideband waveguide filter is 90 GHz, the bandwidth can reach 44%, the out-of-band rejection is 78 dB at 60 GHz, the out-of-band rejection is 33 dB at 120 GHz, the return loss in the passband is greater than 15 dB, and the transmission coefficient is less than 0.1 dB.

[0021] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A W-band ultra-wideband waveguide filter, comprising a cavity, wherein a downlink filter port and an uplink filter port are disposed at the front end of the cavity; characterized in that, The filter is a ninth-order filter, employing an H-plane offset magnetic coupling structure with standard rectangular waveguide WR-10 input and output ports. The H-plane offset magnetic coupling structure comprises nine resonant cavities, with adjacent cavities directly coupled via window misalignment. Capacitor loading technology is used to insert metal pillars of varying diameters into the H-plane of each cavity, with the diameters increasing sequentially from the sides towards the center. During operation, each resonant cavity operates in TE101 mode. The resonant unit is symmetrical about the fifth resonant cavity. The W-band ultra-wideband waveguide filter has a center frequency of 90 GHz, a bandwidth of 44%, an out-of-band rejection of 78 dB at 60 GHz, an out-of-band rejection of 33 dB at 120 GHz, a passband return loss greater than 15 dB, and a transmission coefficient less than 0.1 dB.

2. The W-band ultra-wideband waveguide filter according to claim 1, characterized in that, The diameters of the metal pillars are as follows: the diameter of the first metal pillar is r1=0.1mm, the diameter of the second metal pillar is r2=0.158mm, the diameter of the third metal pillar is r3=0.17mm, the diameter of the fourth metal pillar is r4=0.2mm, and the diameter of the fifth metal pillar is r5=0.238mm.

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