CN111509344B

CN111509344B - OMT duplexer based on high-isolation cross-junction coupler

Info

Publication number: CN111509344B
Application number: CN202010399044.1A
Authority: CN
Inventors: 吴秋逸; 杨飞; 杨毅民; 史小卫
Original assignee: Xidian University
Current assignee: Xidian University
Priority date: 2020-05-12
Filing date: 2020-05-12
Publication date: 2021-08-20
Anticipated expiration: 2040-05-12
Also published as: CN111509344A

Abstract

The invention provides an OMT (open multi-port) duplexer based on a high-isolation cross-shaped coupler, which comprises a cover plate, a duplexer main body, a fixing screw, a tuning screw and a common circular waveguide port, wherein the duplexer main body comprises a cross-shaped structure, two identical high-frequency filters and two identical low-frequency filters; the cross structure consists of a common circular waveguide port, four identical waveguide straight arms, four identical waveguide turns and a matching circular table positioned in the center of the bottom of the cross structure; the four same waveguide straight arms are connected with the four same waveguide turning points, one ends of the two same high-frequency filters are respectively connected with one side of a cross structure, and the other side of the cross structure is respectively connected with one ends of the two same low-frequency filters. The OMT duplexer provided by the invention has the advantages of simple structure, short design period, easiness in processing and assembling, smaller insertion loss and higher isolation, and can be applied to mobile terminals and satellite communication systems with higher frequency bands.

Description

OMT duplexer based on high-isolation cross-junction coupler

Technical Field

The invention belongs to the technical field of communication, and particularly relates to an OMT duplexer based on a high-isolation cross-junction coupler in a dual-polarized antenna transceiving system, which can separate orthogonal polarized electromagnetic waves in the dual-polarized antenna transceiving system.

Background

In an overall wireless communication system, filters have proven necessary because they have the ability to select their desired signals and isolate other unwanted signals, and neither communication system can use filters. Waveguide filters are also a particularly important role and are typically designed for use when lower losses and higher power capability are required. When a duplexer is developed to separate a transmitting signal from a receiving signal and use only one antenna, the duplexer is developed from filters, and in addition to the design of the common header, the design of the receiving and transmitting filters becomes more important, and the use of the duplexer doubles the communication rate. Parameters that affect duplexer performance include inter-channel isolation, insertion loss, return loss, etc.

Spectrum resources are non-renewable scarce resources, and the rapid development of wireless communication and ultra-wideband technology requires wider frequency bands, which makes the spectrum increasingly crowded. Therefore, how to improve the frequency utilization efficiency is one of the important research points in the wireless communication technology research nowadays. In order to fully utilize limited spectrum resources, orthogonal mode coupler (OMT-Ortho-mode transducer) technology is adopted to realize frequency multiplexing of orthogonally polarized co-frequency electromagnetic waves, and the orthogonal mode coupler is usually arranged between a feed source (or a radiation unit) and a duplexer in a satellite communication antenna feed system to separate or synthesize two mutually orthogonal polarized waves.

The OMT can be divided into a broadband OMT and a narrowband OMT according to different working frequency band ranges, and the OMT can be divided into a symmetrical OMT and an asymmetrical OMT according to structural requirements, so that the emphasis points of different OMT designs are different. The narrowband OMT has low requirements on the operating bandwidth, and the design goal is to pursue high performance in the operating frequency band of generally about 10%: such as return loss, isolation, cross polarization, insertion loss, etc., and low production cost. Narrow band OMT generally does not require complete symmetry in structure, and is relatively simple in design; however, since the structure is asymmetric, it is difficult to cancel the higher order mode, and the bandwidth is limited. While broadband OMTs generally require symmetric designs in construction.

For example, an article named as a turning Junction Waveguide orthogonal or Waveguide Transducer in IEEE TRANSACTIONS ON MICROWAVE resonance AND techiniques adopts a structure based ON a cross-Junction coupler, the former applies a double-H-plane Waveguide turn AND a Y-Junction power combiner ON the basis of the two designs, so that standing waves of the OMT are improved, AND the latter applies a combination of an E-plane Waveguide turn AND an H-plane Waveguide turn AND then the combination with the upper Y-Junction power combiner, so that the performance is also improved, AND the cross-Junction coupler has better OMT performance. The two designs improve the performance of the OMT to different degrees, but they have curved channels and steps that greatly increase the size of the original cross-junction coupler, making the fabrication also somewhat difficult and less amenable to mass production.

For example, the IEEE paper entitled Computer Aided Design of wireless and orthogonal Transducers designed a Biofot junction-based OMT, which has a stepped Design in the middle diaphragm part, two branch ports horizontally polarized and left and right connected by a Y-junction, and a vertically polarized port connected with an impedance transformer and a waveguide bend, so that the structure of the whole Design appears to be very complex, although it has better OMT performance. Other designs have added multiple screws and steps and various turns to enable better OMT performance.

A patent document entitled "OMT duplexer (having an Ortho-Mode Transducer and Diplexer, search number US20180309180a 1)" published in 25/10/2018 relates to an OMT duplexer. The duplexer consists of a three-port OMT positioned in the middle and two groups of duplexers positioned on two sides, and realizes better isolation effect on cross polarization signals in the frequency ranges of 71 GHz-76 GHz and 81 GHz-86 GHz. However, the structure of the waveguide connecting device is provided with a plurality of relatively complex waveguide connecting fittings, and the fittings are not in the same plane, so that the processing difficulty is increased.

With the rise of frequency, the realization of cross polarization of a radio and an orthogonal mode coupler on a higher frequency band becomes challenging, and no matter a satellite communication system or an antenna system, a duplex scheme integrating an OMT (orthogonal mode transmitter) with simple structure, small insertion loss, good isolation, small return loss and short design period and having good performance is urgently needed, so that the performance can be ensured, the structure is simpler, and the problem of increasingly serious spectrum shortage is solved.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides an OMT duplexer based on a high-isolation cross-junction coupler, which can be used for overcoming the defects of complex structure scale and long design period after the OMT and the duplexer are assembled in the prior art so as to meet the requirements of a mobile terminal and a satellite communication system in a higher frequency band.

In order to achieve the purpose, the invention adopts the technical scheme that:

an OMT duplexer based on a high-isolation cross-junction coupler comprises a cover plate, a duplexer main body, a fixing screw, a tuning screw and a public circular waveguide port, wherein the cover plate is positioned above the duplexer main body; the cross structure is composed of a common circular waveguide port, four identical waveguide straight arms, four identical waveguide turns and a matching circular table located in the center of the bottom of the cross structure, wherein the four identical waveguide straight arms are connected with the four identical waveguide turns, one ends of two identical high-frequency filters are respectively connected with one side of the cross structure, the other side of the cross structure is respectively connected with one ends of two identical low-frequency filters, and an angle formed by each end face of the cross structure and the end face of the corresponding waveguide straight arm is 45 degrees.

In the above claims, the diplexer body (2) is axisymmetrically distributed with respect to the y-axis.

In the above claim, the four waveguide straight arms (212) are of equal length.

In the above claims, the four identical waveguide turns (213) are interleaved with corresponding waveguide straight arms (212) in positive and negative 45 degree directions, respectively.

The above claims, wherein said mating boss (214) has a height of 1.80mm to 2.00 mm.

Compared with the prior art, the invention has the following advantages:

1. the duplexer main body adopted in the invention comprises a cross structure, two identical high-frequency filters and two identical low-frequency filters, wherein the introduction of four identical waveguide turns enables the directions of ports on one side of the cross structure to be consistent, and the OMT duplexer has high symmetry, thereby overcoming the technical problem of complex structure in the prior art, reducing the size in the y direction and having simpler and more compact structure.

2. The OMT duplexer designed by the invention has good performance in the frequency ranges of 36.02 GHz-36.27 GHz and 36.48 GHz-36.74 GHz. The insertion loss is below 0.35dB, and the return loss is above 20 dB. The isolation between different polarization channels can reach 40dB, so that the cross polarization signal isolation device has better cross polarization signal isolation performance.

3. The cross-junction coupler and the filter are directly integrated and designed to obtain the OMT duplexer with better performance, so that the design period is greatly shortened, and the time efficiency is improved.

Drawings

FIG. 1 is a schematic view of the overall structure of the present invention;

figure 2 is a top view of the diplexer body of the present invention;

FIG. 3 is a schematic structural view of a cross-tie structure of the present invention;

FIG. 4 is an OMT and duplexer operation flow diagram;

FIG. 5 shows an insertion loss S of an embodiment of the present invention₂₁And return loss S₁₁A simulation diagram of (1);

FIG. 6 is a simulation of cross polarization isolation for an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and examples

Example 1

With reference to fig. 1, 2 and 3

An OMT duplexer based on a high-isolation cross-junction coupler comprises a cover plate 1, a duplexer main body 2, fixing screws 3, tuning screws 4 and a public circular waveguide port 5, wherein the cover plate 1 is located above the duplexer main body 2, the fixing screws 3 are used for connecting the cover plate 1 and the duplexer main body 2, and the tuning screws 4 are used for adjusting resonance frequency; the cross structure 21 is composed of a common circular waveguide port 211, four identical waveguide straight arms 212, four identical waveguide turns 213 and a matching circular truncated cone 214 located in the center of the bottom of the cross structure 21, wherein the four identical waveguide straight arms 212 are connected with the four identical waveguide turns 213, one ends of two identical high-frequency filters 22 are respectively connected with one side of the cross structure 21, the other side of the cross structure 21 is respectively connected with one ends of two identical low-frequency filters, and an angle formed by each end face of the cross structure 21 and the end face of the corresponding waveguide straight arm 212 is 45 degrees.

When the cross-junction coupler is used for designing an OMT with low insertion loss and good return loss, a waveguide connecting device or a power synthesis device with a complex structure is required to be added behind four waveguide straight arms of the cross-junction coupler, so that the size of the whole device is increased, and the structure is complex; the invention firstly integrates and designs the cross-junction coupler and the waveguide duplexer together, and can prove that the OMT duplexer does not need a separate OMT and duplexer, and the OMT duplexer with good performance can be obtained by directly connecting the channel filter behind the cross-junction coupler.

The fixing screws 3, the tuning screws 4 and the common circular waveguide port 5 are located on the cover plate 1. Wherein, there are 24 set screws, 20 set screws distributed on both sides of the cover plate, and 4 set screws located on the central axis of the cover plate, so that the cover plate 1 and the filter body 2 can be connected more tightly, and the influence caused by the discontinuity generated by the loose cover plate is avoided. The tuning screw 4 is used for adjusting the resonant frequency of the resonant cavity in the duplexer and the coupling amount in the coupling structure, and has great effect on improving the performance of the duplexer.

The duplexer main body 2 is axisymmetrically distributed with the y-axis. The high frequency filter 21 and the low frequency filter 22 are connected behind the cross structure 21 in an axisymmetric manner, so that the present invention is easiest to process and has the most compact structure.

The four waveguide straight arms 212 are equal in length. The waveguide straight arms 212 with the same length enable the electromagnetic waves to have the same phase after being transmitted to the four arms from the common port, and therefore accuracy of signal transmission is guaranteed.

The four identical waveguide turns 213 are respectively cross-connected with the corresponding waveguide straight arms 212 in the positive and negative 45-degree directions. The end of the vertically adjacent waveguide straight arm 212 is connected with the waveguide turn 213, so that the port direction of one side of the cross-shaped structure 21 can be consistent, and the high-frequency filter 22 and the low-frequency filter 23 can be linearly connected to the two sides of the cross-shaped structure, so as to reduce the y-direction size of the OMT duplexer.

The height of the matching circular truncated cone 214 is 1.80 mm-2.00 mm. In the present invention, the height of the matching truncated cone 214 is optimally 1.99 mm. When the cross-junction coupler is used as a device for distinguishing polarization signals, good isolation is required between adjacent rectangular waveguide ports in electromagnetic simulation, wherein the height change of the circular truncated cone directly corresponds to the isolation between the adjacent ports.

Example 2

The height of the matching circular truncated cone 214 is 1.80 mm-2.00 mm. In the present invention, the height of the matching circular truncated cone 214 is 1.80 mm.

Example 3

The height of the matching circular truncated cone 214 is 1.80 mm-2.00 mm. In the present invention, the height of the matching circular truncated cone 214 is 2.00 mm.

The technical effects of the invention are further explained by simulation experiments as follows:

1. simulation conditions and contents:

refer to fig. 4, 5, and 6

The work flow of the duplexer and the OMT is as shown in fig. 4, a path of horizontally polarized signal is provided at the antenna end, which is assumed to be a high frequency signal, and a horizontally polarized transmitting signal with the same frequency is provided at the same time from the path of H-V (vertical polarized signal at the high frequency end), and when passing through the OMT, the horizontally polarized signal and the vertically polarized signal enter respective horizontally polarized channel and vertical polarized channel respectively because of good isolation degree and do not affect each other, thereby realizing antenna duplex and increasing channel capacity.

1.1 the S parameters of the return loss and the insertion loss of the above example 1 were subjected to simulation calculation using commercial simulation software HFSS — 19.0, and the results are shown in fig. 5.

1.2 simulation calculation was carried out on the isolation S parameter curve between the dual polarized signals of the same frequency of the above embodiment 1 by using commercial simulation software HFSS _19.0, and the result is shown in fig. 6.

2. And (3) simulation result analysis:

referring to FIG. 5, the horizontal axis is the frequency range (GHz) and the vertical axis is the S parameter magnitude (dB), in S₁₁The standard of ≦ 20dB, the working frequency band of the OMT duplexer in embodiment 1 is: a first channel: 36.02 GHz-36.27 GHz channel two: 36.48 GHz-36.74 GHz. Typically, the return loss RL is-S₁₁Therefore, the OMT duplexer provided by the invention can be considered to realize the operating characteristic that the return loss is greater than 20 dB. And insertion loss less than 0.35 dB.

Referring to fig. 6, the horizontal axis represents frequency range (GHz) and the vertical axis represents isolation level (dB), and it can be seen that the cross polarization isolation of the OMT duplexer reaches 40 dB.

The simulation results show that the OMT duplexer based on the high-isolation cross-junction coupler disclosed by the invention realizes the working characteristics that the return loss is more than 20dB and the insertion loss is less than 0.35dB in the frequency ranges of 36.02 GHz-36.27 GHz and 36.48 GHz-36.74 GHz. An isolation of more than 40dB makes the present invention have a significant effect on the separation of dual polarized signals.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. An OMT duplexer based on a high-isolation cross-junction coupler comprises a cover plate (1), a duplexer main body (2), a fixing screw (3), a tuning screw (4) and a public circular waveguide port (5), wherein the cover plate (1) is located above the duplexer main body (2), the fixing screw (3) is used for connecting the cover plate (1) and the duplexer main body (2), and the tuning screw (4) is used for adjusting resonance frequency, and the OMT duplexer is characterized in that the duplexer main body (2) comprises a cross-junction structure (21), two identical high-frequency filters (22) and two identical low-frequency filters (23); the cross structure (21) is composed of a common circular waveguide port (211), four identical waveguide straight arms (212), four identical waveguide turns (213) and a matching circular truncated cone (214) located in the center of the bottom of the cross structure (21), wherein the four identical waveguide straight arms (212) are connected with the four identical waveguide turns (213), one ends of two identical high-frequency filters (22) are respectively connected with two ports on one side of the cross structure (21), two ports on the other side of the cross structure (21) are respectively connected with one ends of two identical low-frequency filters, and an angle formed by each end face of the cross structure (21) and the end face of the corresponding waveguide straight arm (212) is 45 degrees.

2. A high isolation cross-junction coupler based OMT duplexer according to claim 1, characterised in that the duplexer body (2) is axisymmetrically distributed with the y-axis.

3. The OMT duplexer based on a high-isolation cross-junction coupler according to claim 1, wherein the four identical waveguide turns (213) are interleaved with the corresponding waveguide straight arms (212) in positive and negative 45-degree directions.

4. The OMT duplexer based on a high-isolation cross-junction coupler as claimed in claim 1, wherein the height of the matching truncated cone (214) is 1.80-2.00 mm.