D-Band Filtering Six-Port Junction

Chen, Xun (2022). D-Band Filtering Six-Port Junction. University of Birmingham. Ph.D.

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Abstract

Featured with low cost, simple structure, high phase accuracy, calibration convenience and algorithm transparentness (Four outputs provide flexibility for algorithm), six port junctions (SPJs) have found their application in microwave measurments, receivers, and angle-of-arrival (AoA) measurements. This thesis aims to demonstrate a novel filtering SPJ working in the D-band (150 GHz, a radar band) with minimum magnitude imbalance. One circuit synthesis technique and five designs will be presented.
The technique is a general and systematic way to incorporate non-resonant circuits (NRCs) into a single coupling matrix (CM). With the matrix, a compound circuit with resonant and non-resonant circuits can be designed as a whole. The CM technique also allows combining ideal circuits with practical circuits. In this way, the influence of the impairment from the practical circuits can be investigated without computationally intensive simulations.
The five case designs include three filtering couplers (named Coupler-A, -B and -C) and two filtering SPJs (named SPJ-A and -B). Coupler-A is an amplitude-balance enhanced 180° filtering coupler. The influence of physical configuration on the amplitude balance has been investigated. This amplitude balancing approach ran through the coupler and SPJ designs in this thesis.
SPJ-A is an E-plane X-band filtering SPJ. The bandwidth is from 9.8 GHz to 10.2 GHz. The measured minimum return loss is 15 dB and the phase error is 10°. Thanks to the E-plane configuration, the measured insertion-loss is only 0.4 dB. As a prototype prior to the D-band filtering SPJ, this work verified the theory and the proposed topology.
Coupler-B is an E-plane D-band 180° filtering coupler while Coupler-C is an E-plane D-band 90° filtering coupler. Fan-shaped resonators were proposed in the Coupler-B design. E-plane configuration is feasible using the proposed resonator. The measurement showed less than 0.46 dB insertion loss in the working band of 148 to 152 GHz. SPJ-B is an E-plane D-band filtering SPJ. It combined the design in Coupler-B and Coupler-C. Silicon chips based absorbers were used in SPJ-B for compactness. The measurement showed a minimum 11-dB return loss and a maximum 2-dB insertion loss at D-band. The phase error is 15°.
There are two appendixes. Appendix I gives the settings in simulation and optimization when using the commercial simulation software. Appendix II gives the design of an H-plane filtering SPJ working at 10 GHz. Coupler A was used in the implementation. This SPJ was not fabricated due to the potential large insertion loss H-plane configuration brings. Only simulated response will be presented in Appendix II.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):