Low Power and Low Cost Millimeter-Wave Digital Beamformer Using An Orthogonal Coding Scheme

Abstract

A novel four-channel receiver architecture is proposed using an orthogonal coding scheme for low-cost and low complexity millimeter-wave (mm- Wave) digital beamforming. In this proposed architecture, multiple signals are encoded with othogonal Walsh-Hadamard (WH) codes and multiplexed into a single channel. The combined signal is fed into a single Analog-to-Digital converter (ADC) at the digital baseband, leading to significant reduction in size, weight, power and cost (SWaP-C). As a result, the hardware complexity of the receiver is reduced by more than 95 %. A key challenge addressed in this paper is the signal-to-noise ratio (SNR) degradation due to inter-channel interference. Interference is greatly dependent on the choice of the employed orthogonal WH codes. In this paper, we introduce methods to achieve greater than 30 dB inter-channel interference rejection across a bandwidth of 400 MHz. As such, the proposed reduced SWaP-C and interference mitigation can have a major impact in realizing innovations for the 28-GHz and beyond mmWave links.