A Retrodirective Array Enabled by CMOS Chips for Two-Way Wireless Communication with Automatic Beam Tracking

This article proposes and demonstrates a retrodirective array (RDA) for two-way wireless communication with automatic beam tracking. The proposed RDA is enabled by specifically designed chips made using a domestic complementary metal-oxide semiconductor (CMOS) process. The highly integrated CMOS chip includes a receiving (Rx) chain, a transmitting (Tx) chain, and a unique tracking phase-locked loop (PLL) for the crucial conjugated phase recovery in the RDA. This article also proposes a method to reduce the beam pointing error (BPE) in a conventional RDA. To validate the above ideas simply yet without loss of generality, a 2.4 GHz RDA is demonstrated through two-way communication links between the Rx and Tx chains, and an on-chip quadrature coupler is designed to achieve a non-retrodirective signal suppression of 23 dBc. The experimental results demonstrate that the proposed RDA, which incorporates domestically manufactured low-cost 0.18 μm CMOS chips, is capable of automatically tracking beams covering ±40° with a reduced BPE. Each CMOS chip in the RDA has a compact size of 4.62 mm2 and a low power consumption of 0.15 W. To the best of the authors’ knowledge, this is the first research to demonstrate an RDA with a fully customized CMOS chip for wireless communication with automatic beam tracking.