Design methodology of an analog 9-beam squint-free wideband IF multi-beamformer for mmW applications

Abstract

An intermediate frequency (IF) squinting-free multi-beamforming method is proposed for multi-antenna systems. The proposed approach uses a low-complexity factorization of a true-time-delay (TTD) multi-beam matrix, which is proposed to be realized using an analog integrated circuits approach. A TTD realization of multi-beams at intermediate frequency is achieved following amplification and synchronous down-conversion via the proposed Delay Vandermonde Matrix (DVM) in which matrix elements correspond to the compound phase compensation required for squint-free steering of each radio-frequency beam. True-time-delays are proposed to be efficiently realized on-chip by applying a sparse factorization to the DVM, which leads to a low circuit complexity implementation requiring a significantly lower number of TTD blocks and phase compensations compared to an equivalent direct implementation for a given N number of beams. The proposed method, for 9- beams, leads to a 60% reduction of analog integrated circuit based TTD blocks and phase compensators. The TTD blocks can be realized on chip using active-RC based integrated analog all-pass filters. The proposed multi-beam algorithm and circuit structure is simulated within the frequency range 55-65 GHz to demonstrate squinting-free wide-band multi-beams at millimeter wave carrier frequencies for emerging 5G applications.