A resource-reuse microwave photonic true-time-delay network for broadband multibeam beamforming

Conventional phase-shifter-based beamforming in broadband phased-array systems is prone to beam squint, whereas existing microwave photonic true-time-delay networks often require substantial delay resources. To address these limitations, we propose a cascaded-tap multiplexing network (CTMN) for broadband microwave photonic multibeam beamforming. The architecture combines stepwise accumulation along a dispersion-compensating fibre (DCF) trunk with progressively shortened single-mode fibre (SMF) compensation sections, enabling equally spaced adjacent-channel true-time-delay differences at a given wavelength and continuous beam-steering. Simulations show that a 1 × 16 array with 16-channel CTMN and an 87.5 % reduction in dispersive fibre resources can scan continuously from −60° to 60° for a 67-GHz RF signal. In a four-channel CTMN experiment, the maximum deviation between the average adjacent-channel delay difference and the theoretical value is 0.2023 ps, and continuous beam steering from −43.95° to 44.61° is achieved with a steering angle error below 2°. These results indicate that the proposed CTMN significantly reduces consumption of dispersive fibre resources while maintaining broadband continuous beam-steering and multi-beamforming capability, offering a feasible route towards scalable microwave photonic phased-array systems.