A Four-Element 7.5–9-GHz Phased-Array Receiver With 1–8 Simultaneously Reconfigurable Beams in 65-nm CMOS

This article presents a four-element 7.5-9-GHz phased-array receiver with 1-8 concurrent beams in a 65-nm CMOS technology. Each output beam utilizes all the input elements to maximize the beamforming gain. To realize a low-power and compact design, the multielement multibeam phased-array architecture features the gm-based variable-gain phase shifter (VG-PS) and the current-sharing active combiner. The VG-PS with 6-bit phase resolution achieves <; 2° root mean square (rms) phase error and <; 0.3 dB rms gain error at the maximum gain setting. The receiver demonstrates a 20-dB power gain, a 3.6-dB noise figure (NF), and a -19-dBm input 1-dB gain compression point (IP1dB) at 7.5-9 GHz for each element. The chip occupies $5.42\times3.62$ mm² area excluding pads and consumes 860 mW, equivalent to the record low 27 mW per element per beam. To our knowledge, the receiver achieves the maximum number of simultaneously reconfigurable beams with the lowest power consumption per element per beam in RF phase shifting and combining receiver chips.

I. Introduction

Phased arrays have been widely used in 5G and satellite communications due to its large capacity and system reconfigurability. The increasing demand for heavier connectivity and larger data rates inspires the application of spatial multiplexing, which is preferred in systems, such as base stations, to enable concurrent communication with multiple users in different locations. Phased-array architectures with multibeam forming capability have attracted extensive investigation to achieve better spectrum and energy efficiency. Digital beamforming (DBF) can create multiple independent beams with high flexibility and is widely used at sub-6-GHz frequencies. However, the advantage declines as frequency rises because of the drastically growing power consumption. Besides, it mandates large power consumption and high complexity due to multiple power-hungry analog-to-digital converters (ADCs). In contrast, RF beamforming has been widely adopted from X- to W-band [1]–[4] and offers better efficiency for a wide signal bandwidth (e.g., >300 MHz) with a limited number of reconfigurable beams (e.g., ≤16).