A 0.22 mm² 0.5~4 GHz Active Single-Sideband Time Modulator With a Single Digital-Sequence Control

This letter proposes a novel single-sideband time modulator (STM) that uses a periodically controlled 4-bit active vector modulator with regularly controlled gate widths. Timing sequences for control bits are generated from a single digital sequence using a $\div 16$ frequency divider. By precisely delaying the single digital sequence, the proposed active STM achieves high-precision and frequency-independent phase-shifting performance while enhancing the sideband suppression ratio (SSR) without raising insertion loss. Fabricated in 0.13- $\mu $ m CMOS technology, it occupies a compact area of $1.1\times 0.2$ mm2. Measured results show an equivalent 10-bit phase resolution, root mean square (rms) phase error of 0.13°~0.36°, and rms gain error of 0.05~0.31 dB in a frequency range of 0.5~4.0 GHz. The measured SSR is less than −23.5 dBc, and the instantaneous bandwidth is expanded to $16~f_{\text {P}}$ .

I. Introduction

Time-modulated array (TMA), first proposed in the 1960s [1], introduces an additional degree of time into antenna array design. It uses a time modulator in each antenna element to adjust the time delay of time modulation sequences for phase shifting, achieving precise beam steering [1]. Recently, the TMA applications have expanded to adaptive beamforming [2], direction finding [3], and meta-surfaces [4].