On the Impact of Phase Impairments on Angle Estimation in True-Time-Delay Systems

An important challenge in joint communication and sensing (JC&S) is accurate parameter estimation. However in JC&S systems the parameter estimation/sensing performance is degraded by various hardware impairments. In this work the impact of phase impairments on angle estimates is analyzed. More specifically, a true-time-delay (TTD) system affected by phase noise and constant phase error (CPE) is characterized in regards of angle of departure (AoD) estimation performance. In TTD systems the signal radiated from each antenna elements is delayed by integer multiples of the reciprocal signal bandwidth. The spatial-frequency response induced by true-time delays, allows for spectrum based angle estimation. Phase noise is generated using measurements of the phase noise from commonly used software-defined radio (SDR) devices. The investigation shows that angle estimation is sensitive to phase impairments. In the analyzed configuration, to achieve angle estimates with mean absolute error less than 1°, the CPE variance has to be below 0.1 for positive SNR values.