A V-Band 16% Efficiency Frequency Doubler-Based RF Beamforming Front-End Module for Vector Modulated Signal Transmission

This paper presents a millimeter-wave frequency multiplier (FM)-based RF beamforming front-end (FE) suitable for high-frequency vector signal transmission. The design considerations (i.e., tuning range, phase resolution, and magnitude variation) of the phase shifter are discussed in the context of FM-based FE. These considerations guided the design of the proposed FE which incorporates an 8-bit phase shifter, a driver amplifier, and a frequency doubler with their matching networks co-designed to minimize the FE area. A proof-of-concept prototype is designed using 45-nm CMOS-SOI technology. The measurements conducted at 62 GHz output frequency showed an average conversion gain (CG) of 5.7 dB, a doubler drain efficiency of 22.7%, and an FE drain efficiency of 16%. When the phase is varied to cover the full 360° in a step of 2.8° with an RMS phase error of 0.57°, the CG deviated by a maximum of ±0.35 dB. Using a low-complexity digital pre-distortion technique, the designed FE maintained an error vector magnitude of -30 dB and an average drain efficiency of 6% when used to generate a 256-QAM 200 MHz orthogonal frequency division multiplexing vector modulated signal and the phase is varied to cover the full 360°.