A Band-Shifting Millimeter-Wave T/R Front-End Using Inductance-Mutation Transformer Technique for Multi-Band Phased-Array Transceivers

This article introduces a band-shifting transmit/receive (T/R) front-end (FE) using the inductance-mutation technique for multiband phased-array transceivers. The proposed inductance-mutation transformer technique enables variable inductances and features insignificant performance deterioration during the wideband frequency shift, compared to the typical capacitance-based frequency shift method. In order to demonstrate the effectiveness of the proposed technique, a band-shifting T/R FE prototype is designed and fabricated in a standard 28 nm bulk CMOS process. The T/R FE circuit contains a differential power amplifier (PA) with a cascade output stage, a two-stage cascade low noise amplifier (LNA), and a dual-resonance T/R switch. Both the PA and LNA employ the proposed inductance-mutation technique in the interstage matching network. The compact dual-resonance T/R switch at the antenna interface is embedded to support the wideband time-division uplink/downlink. It is demonstrated in the measurement results that the 3-dB operation band of the FE can be shifted between a low-frequency (LF) band of 24.1–38.8 GHz and a high-frequency (HF) band of 35.4–43.5 GHz for the transmitter (TX) mode, and shifted between 23.9–35.3 and 29.2–43.7 GHz for the receiver (RX) mode. Meanwhile, the PA achieves the measured peak gain of 19.1/17.2 dB and the measured OP1dB of 17.8/15.0 dBm for the LF/HF bands, and the LNA in the LF/HF bands has the peak gain of 21.3/18.3 dB and the minimum noise figure of 5.1/5.8 dB. In the system-level modulation measurement, the TX mode realizes $<$ $-$ 25 dB EVM for 400 Msym/s 64-QAM wireless communication with $>$ 9 dBm average output power across the frequency of interest. Combining the LF and HF bands, the proposed T/R FE can cover multiple operating bands of 5G NR, such as n257–n261. Thanks to the band shift feature, an extra 24-dB image rejection for the HF signals converted from a potential intermediate frequency signal of 10 GHz is provided by the T/R FE.