We demonstrate significantly improved performance of a microwave true time delay line based on an integrated optical frequency comb source. The broadband micro-comb (over 100 nm wide) features a record low free spectral range (FSR) of 49 GHz, resulting in an unprecedented record high channel number (81 over the C band)—the highest number of channels for an integrated comb source used for microwave signal processing. We theoretically analyze the performance of a phased array antenna and show that this large channel count results in a high angular resolution and wide beam-steering tunable range. This demonstrates the feasibility of our approach as a competitive solution toward implementing integrated photonic true time delays in radar and communications systems.

A wideband-generalized pattern multiplication approach to evaluate the performance of an optical beamforming-based wideband antenna array is proposed and experimentally demonstrated, which enables the far-field measurement of a large wideband array with a small anechoic chamber. Because the optimum reception of a wideband microwave signal is highly related to the time-domain distortions of the beamforming system, a correlation-receiver-based radiation pattern is applied to take the fidelity of the wideband signals into account. A four-element optical beamforming system is built to verify the feasibility of the proposed method. The results achieved by the proposed method agree well with the conventional direct measurements.