Wideband Single-Sideband Time Modulator Based on Practical 2-bit Switched-Type Phase Shifter
Ruihua Chen, Chong He, Gang Ni, Jingfeng Chen, Junping Geng, Ronghong Jin
Abstract
A single-sideband time modulator (SSBTM) with a wide bandwidth of one decade ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R$ </tex-math></inline-formula> = 10) is presented in this article. The proposed SSBTM is based on a periodically controlled wideband 2-bit switched-type phase shifter (STPS). With periodic phase modulation and ON–OFF amplitude control, it can realize an equivalent 6-bit amplitude–phase control at the generated first harmonic component. Compared to the conventional STPS, the proposed SSBTM has a concise structure, which requires only two phase shift stages. The bandwidth of the 2-bit STPS in the SSBTM is broadened by cascading multiple all-pass networks (APNs). Additionally, the tradeoff between bandwidth and efficiency for the amplitude–phase control using the SSBTM is derived theoretically. Wideband 90° and 180° phase shifters (PSs) in the SSBTM are designed by cascading four-stage APNs, which work from 300 MHz to 3 GHz. An equivalent 6-bit amplitude–phase control is measured with the root-mean-square (rms) amplitude and phase errors of 0.3 dB and 1.1°, respectively. The corresponding 8-element time-modulated antenna arrays (TMAAs) working at 750 MHz, 1.2 GHz, 2 GHz, and 2.6 GHz are fabricated, and the receiving power patterns are tested from −40° to 40° with a 10° step, demonstrating the effectiveness of the proposed wideband SSBTM for harmonic beam scanning.