Wideband Chebyshev-Distributed Quasi-TTD 3 × 4 Beamforming Network for Low-Sidelobe and Frequency-Invariant Beam Pointing

A wideband 3×4 beamforming network (BFN) is presented, integrating a 3×4 Blass-like matrix with Chebyshev amplitude distribution for low sidelobe levels (SLLs) and a 4×4 phase-compensation network to ensure frequency-invariant beam pointing. Phase shifters with adjustable phase-slope are introduced to flatten the phase response of the Blass-like matrix, and further to realize quasi–true-time-delay characteristics for the overall BFN. A prototype operating at 5.8 GHz was fabricated and measured, showing an output amplitude ratio of 0.332:1:1:0.332, an amplitude imbalance of 1.5 dB, and a linear phase error of 10° over a 31% bandwidth. The BFN enables a multi-beam antenna array to achieve low SLLs of -15 dB and stable beam pointing from 4.9 GHz to 6.7 GHz, validating its effectiveness for wideband multi-beam applications.