A 0.6–4.0 GHz RF-Resampling Beamforming Receiver With Frequency-Scaling True-Time-Delays up to Three Carrier Cycles

Abstract

True-time-delays (TTDs) enable wideband analog and hybrid beamforming by mitigating the beam squint problem. This letter reports a TTD beamforming receiver supporting delays up to three carrier-frequency cycles. The implementation is the first published work in which the delays scale with the carrier frequency. The scaling enables TTDs for large arrays at low-GHz frequencies where long delays are required due to $\lambda _{c}/2$ antenna spacing. The delays are implemented through delayed resampling of a passive mixer’s discrete-time output. Driving the mixers with pulse-skipped local oscillator (LO) signals allows the delay range to exceed one carrier cycle. A polyphase receiver structure prevents aliasing of noise and unwanted tones caused by LO pulse-skipping. Our prototype implementation demonstrates squint-free beamforming for an-800 MHz instantaneous RF bandwidth. The proposed TTD is efficient for large arrays since the power consumption per antenna is only 5–13-mW across the 0.6–4.0-GHz frequency range. The prototype was implemented in 28-nm FD-SOI CMOS, and the die area including bonding pads is only 1.2 mm2.