A 0.35‐2 GHz GaAs Multifunctional Chip With Bidirectional True Time Delay

ABSTRACT This paper presents a 0.35–2 GHz bidirectional true time delay (TTD) transmit/receive (T/R) multifunctional chip utilizing a 0.25‐μm GaAs enhancement/depletion (E/ d ‐mode) pseudomorphic high electron mobility transistor (pHEMT) process. The chip integrates several key components: a 6‐bit TTD with coverage of 945 ps and a step of 15 ps, a bidirectional amplifier (BA) featuring an improved common source‐common gate structure, a 1.6‐dB amplitude equalizer (AE), and seven parallel drivers (PDs) for TTD and BA control. The 6‐bit TTD employs all‐pass networks for the delay path and utilizes three types of reference paths to compensate for the amplitude imbalance between the delay path and the reference path. Meanwhile, the BA employs a dual‐C structure combined with dual R‐L feedback to mitigate process variation sensitivity significantly. Besides, the 1.6‐dB AE is utilized to achieve an overall 1‐dB positive gain slope in both transmit and receive modes. In transmit mode, the chip achieves a gain of 4.9–5.9 dB with output power at 1 dB compression point (OP1dB) exceeding 19.3 dBm. In receive mode, the chip achieves a gain of 5.1–6.1 dB, accompanied by a noise figure (NF) lower than 2.56 dB, and an OP1dB larger than 5.4 dBm. Both transmit and receive modes achieve 1‐dB positive gain slope. Meanwhile, the transmit and receive root‐mean‐square (RMS) TTD errors are less than 12.7 and 12.4 ps with associated RMS amplitude errors lower than 0.52 and 0.43 dB, respectively. To the authors' knowledge, this study represents the first demonstration of a GaAs‐based bidirectional TTD multifunction chip operating in the UHF band.