Phase-shifter-less beam scanning in a planar array of antennas with nonlinear front-end and spatial LO power distribution

Abstract

Previous attempts to realize phase-shifter-less beam-scanning are mainly concentrated on using arrays of coupled oscillators [1], [2]. In such schemes, an array of oscillators with identical free-running frequencies is required. In the configuration proposed in [3], several fully synchronized oscillators whose number equals the number of array elements are utilized to realize electronic beam-steering. The present paper proposes a scheme for spatial distribution of the local oscillator (LO) power instead of using a power splitting network such that the required phase difference among array elements is maintained through spatial phase shift without using microwave phase shifters. It will be shown that mixing of the LO and the RF signal can be performed in the low-noise amplifiers (LNAs) of the front-end. In this approach, both phase shifters and mixers are eliminated, and the required variation of inter-element phase difference is achieved by varying the location of the LO mechanically. This will reduce the cost and complexity of the proposed receive array, considerably. Obviously, this is achieved at the cost of replacing a full-electronic beam-scanning by a semi-mechanical one. Mechanical scanning of the main beam is also employed in high-gain dielectric lens antennas [4].