Phase shifters with multiple independently controllable bands utilising frequency‐selective variable gain networks

A dual‐band vector‐sum phase shifter with independent phase control of the 2.4 and 5 GHz Wi‐Fi bands is presented. The network uses band‐limited variable gain amplification, with a broadband hybrid coupler at the input and an in‐phase recombiner at the output. The circuit is prototyped on RF printed circuit board and exhibits performance characteristics comparable to the state‐of‐the‐art single band vector‐sum phase shifters. The prototype achieved an average gain of 2.16 dB over the 2.4 GHz band, with less than 0.26 dB and 1.32° root‐mean‐square (RMS) gain and phase error across all 2.4 and 5 GHz band tuning states. In the 5 GHz band, an average gain of 0.17 dB is achieved, with less than 0.21 dB and 3.88° RMS gain and phase error. The network's ability to generate bandindependent vector modulation over a 12 dB/90° tuning range is demonstrated as well, achieving less than 0.12 dB and 0.27° RMS gain and phase error in the 2.4 GHz band, and less than 0.27 dB and 2.94° gain and phase error in the 5 GHz band.The South African Radio Astronomy Observatory (SARAO)http://wileyonlinelibrary.com/journal/mia2am2022Electrical, Electronic and Computer Engineerin

X-band reflection-type phase shifters using coupled-line couplers on single-layer RF PCB

In this letter, an X-band reflection-type phase shifter is presented. It is based on a single-layer stub-loaded coupled-line coupler loaded by two-varactor tuning circuits. This choice of coupler significantly improves on the phase shifter bandwidth achievable with a branch-line coupler, as it features a lower phase imbalance across the band of interest. The proof-of-concept prototype achieves better than 10-dB return loss across a 20% fractional bandwidth. The phase shifter further exhibits insertion loss of 2.1 ± 1.3 dB and maximum phase shift of 392° at 10 GHz, leading to a state-of-the-art figure of merit at X-band of 115°/dB. The occupied area is 0.25λ g 2 .http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=7260hj2018Electrical, Electronic and Computer Engineerin

Additive manufacturing of interdigital filters with arbitrary line cross section

This article investigates the novel use of additive manufacturing (AM) in the production of interdigital cavity filters. It is found that AM enables the production of interdigitated pins of complex cross-sectional geometry, leading to the development of a suitable synthesis method using a commonly available 2-D eigenmode port impedance solver. The method is validated by manufacturing an L-band interdigital filter of 70% fractional bandwidth with triangular bars through selective laser melting, as well as a classical design using rectangular bars. It is found that triangular bars obtain similar coupling to rectangular bars over the average of 35% wider spacing gaps, reducing its sensitivity to manufacturing error. In addition, neither filter requires postproduction tuning, although the bars do warp slightly during printing. These results illustrate the advantages of using AM for the synthesis of wideband interdigital filters.NewSpace Systemshttp://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=5503870hj2021Electrical, Electronic and Computer Engineerin

Transmission lines characteristic impedance versus Q-factor in CMOS technology

This paper presents a systematic comparison of the relationship between transmission line characteristic impedance and Q-factor of CPW, slow-wave CPW, microstrip, and slow-wave microstrip in the same CMOS back-end-of-line process. It is found that the characteristic impedance for optimal Q-factor depends on the ground-to-ground spacing of the slow-wave transmission line. Although the media are shown to be similar from a mode of propagation point of view, the 60-GHz optimal Q-factor for slow-wave transmission lines is achieved when the characteristic impedance is ≈23 Ω for slow-wave CPWs and ≈43 Ω for slow-wave microstrip lines, with Q-factor increasing for wider ground plane gaps. Moreover, it is shown that slow-wave CPW is found to have a 12% higher optimal Q-factor than slow-wave microstrip for a similar chip area. The data presented here may be used in selecting Z0 values for S-MS and S-CPW passives in CMOS that maximize transmission line Q-factors.The South African Radio Astronomy Observatory (SARAO) (www.sarao.ac.za) and the National Research Foundation (NRF) of South Africa.http://journals.cambridge.org/action/displayJournal?jid=MRF2021-10-20hj2021Electrical, Electronic and Computer Engineerin