A Compact Ka-Band Eight-Element Four-Beam Receiver for Low-Earth-Orbit Satellite Communications in 65-nm CMOS

This letter presents a Ka-band compact eight-element four-beam phased-array receiver to improve communication capacity for millimeter-wave satellite communications. To address the design challenge of the large area induced by the multibeam forming, the receiver utilizes a digital-assisted variable-gain phase shifting technique and an active combining scheme to enable compact implementation and facilitate array design. The receiver achieves a 360° phase shifting range with a 6-bit resolution and a 25-dB attenuation range with a 0.5-dB step. The measured root mean square (rms) phase and amplitude errors are 1.1° and 0.11 dB at 29.5 GHz, respectively. Each element achieves a gain of 26.7 dB, a minimum noise figure (NF) of 3.7 dB, and an input-referred 1-dB gain compression point (IP1 dB) of −32.5 dBm. The proposed receiver demonstrates the state-of-the-art number of simultaneously reconfigurable beams with a compact size among millimeter-wave silicon-based beamformers.

I. Introduction

The emerging low-Earth-orbit satellite communication (LEO SATCOM) employs low-cost large-scale - and Ka-band transmit and receive phased arrays and enables global high-speed Internet access, especially in low-connectivity-density areas [1], [2]. Multibeam capability is highly desirable for satellite terminals to realize multiuser concurrent communication and seamless beam switching, as shown in Fig. 1(a). However, conventional analog phased arrays only support single-beam operation. High power consumption and large area occupation of the multibeam front ends impede their deployment. To realize a two-element four-beam receiver, Peng et al. [3] utilized a symmetrical beam-distribution network, which, however, would introduce large insertion loss (IL). The active phase-shifting and combining architecture proposed in [4] can support reconfigurable multibeam operation; however, the limited gain tunability could not meet the dynamic-range (DR) requirement in a large phased array. Fig. 1.

(a) Multibeam forming enables concurrent communication and seamless beam switching. (b) Architecture of the proposed eight-element four-beam phased-array receiver front end.