Phase-Shifter-Less Beam Scanning of a Receive Array Using Spatial LO Distribution

Abstract

A new scheme for phase-shifter-less beam scanning is proposed, which is based on spatial distribution of local oscillator (LO) signal among a number of heterodyne receivers. Each receiver connected to an element of the phased array receives not only the RF signal but also the LO signal. The required inter-element phase shift is acquired by different path lengths from the antenna radiating the LO signal to the array elements. The low-noise amplifier (LNA) following each array element amplifies both the RF and LO signals. Since the LO signal is of a relatively higher power level, the LNA nonlinearity is employed intentionally to mix the RF and LO signals. The generated IF signal at the output corresponds to a directive receive pattern at the RF frequency whose main lobe can be scanned by varying the position of the LO feed antenna. This paper demonstrates the configuration in which the scan range of the main lobe can be as wide as 106 degrees while maintaining a constant maximum gain with less than 10% variation. Over this scan range, the characteristics of the array receive pattern are not affected for RF received power levels exceeding −100 dBm.