A 4-Channel Self-Synchronizing Receiver Array Without LO Distribution with Angle-of-Arrival Estimation

We present a 4-channel self-synchronizing binary-phase-shift keying (BPSK) receiver array in which each channel autonomously locks to the incoming carrier, enabling direct-conversion operation without the need for a local oscillator (LO) distribution network or synchronization. Each channel generates its own demodulated data stream, enabling either coherent combining for enhanced signal-to-noise ratio (SNR) or independent processing to realize spatial diversity. Since the architecture eliminates LO distribution and each branch performs its own carrier recovery and demodulation, the system is inherently scalable. With each receiver branch employing an independent phase-locked loop (PLL) that locks to the received carrier, the system preserves the inter-element phase relationships imposed by the arriving wavefront. Consequently, the relative phase across channels can be exploited for angle-of-arrival (AoA) estimation and angular localization. Each channel employs a two-stage low-noise amplifier (LNA) followed by a 28~GHz PLL. The $4\times1$ receiver chip is implemented in 130~nm SiGe BiCMOS technology.