A New TDU-Based Hierarchical Beamforming Framework to Suppress Grating Lobes and Save Space

paper introduces a new hierarchical beamforming network (HBFN) design methodology that introduces a new degree of freedom in the time delay unit (TDU) allocation across beamforming layers. By varying the TDU delay range within a single layer instead of using a uniform delay profile, this method reduces quantization error magnitudes, significantly suppresses grating lobes and optimizes physical space utilization. This approach alters the statistical structure of quantization errors, leading to an 11.2 dB reduction in grating lobes for a 16W16 planar array in full-wave EM simulation. Additionally, a large-scale 256W256 array model demonstrates an 18.0 dB grating lobe suppression and a space saving of up to 29.9%, confirming the scalability of the approach. The reduced space requirement of TDUs enables improved mobility, supporting the transition to flat panel arrays and making it well-suited for radar, satellite and mmWave communication systems. This paper presents a rigorous analytical framework, full-wave electromagnetic validation and a discussion of the practical impact of these findings in phased array design.