Photonic True-Time-Delay Beamformer for a Phased Array Antenna Receiver based on Self-Heterodyne Detection

Abstract

In this paper, we propose a novel photonic true-time delay beamforming system for a phased array antenna receiver. The beamformer relies on simple tunable optical delay lines and also on self-heterodyne coherent detection. Each tunable delay line is implemented by a MachZehnder delay interferometer with tunable coupling ratio, which allows varying the delay from 0 up to the delay of the interferometer. Self-heterodyne coherent detection allows achieving maximum sensitivity inherent to coherent detection, and also laser phase noise cancellation, photonic RF phase shifting, and photonic RF frequency downconversion. The proposed system is analytically described and numerically validated. Numerical results show that, considering a beamsteering range of $ \pm 30^\circ $ , the system is able to beamform the signals received by ${\boldsymbol{N}}$ antenna elements with negligible distortion, thereby proving to be very promising for high-end phased array antenna receivers operating at high RF frequencies.