A 22-to-50 GHz Bi-directional Beamforming CMOS Front-end with Distributed Impedance Reshaping Technique for 5G NR FR2 Applications

This paper presents an ultra-wideband beam-forming front-end in 65nm CMOS for n257/n258/n259/n260/n261/n262 5G FR2 applications. Multiple impedance reshaping techniques are introduced to enable a continuous ultra-wideband design. To address the challenges of broadband matching and the losses introduced by matching elements, an implicit distributed inductor matching method is proposed to compress the impedance trace for low-noise amplifier (LNA) input matching. A bidirectional synergized transformer-based reflection-type phase shifter (STB-RTPS) is demonstrated, achieving broadband phase shifting. Over the frequency band of 22.1–49.8 GHz, the RX front-end achieves a measured RX noise figure (NF) of 5.2–6.3 dB. In TX mode, over the bandwidth of 22.8–49.3 GHz, the design achieves a saturated output power of 18.61 dBm and an output 1dB compression point of 16.76 dBm. Both TX and RX offer 6-bit phase control and 4-bit amplitude control, achieving an in-band EVM of < -26 dB for 400 Msym/s 64QAM wireless communication.