A Sub-6GHz 5G New Radio Multi-Band Transmitter with a Switchable Transformer in 14nm FinFET CMOS

This paper presents 2G/3G/4G/5G transmitter that has a compact die area and supports multi bands in 5G new radio (NR). The transmitter with inter-digitated switchable transformer is designed to support n77/n78/n79 of 5G FR1 bands (3.2GHz to 5GHz) and B46/B47 of V2X bands (5.125GHz to 5.925GHz). The transformer provides optimum transformed load impedance at the drive amplifier output with 3-stacked switches. The on-chip transformer with inter-digitated structure results in a high coupling factor to minimize the insertion loss. An interstage matching network between a mixer and a drive amplifier induces a channel flatness characteristic. The designed transmitter is fabricated using a 14nm FinFET CMOS process. It achieves a peak average output power of 7dBm and 2% under measured root mean square (rms) EVM in the case of DFT-s-OFDM 256QAM Full-RB signal, while satisfying the 3GPP specification. It also satisfies 1dB under channel flatness and the adjacent channel leakage ratio (ACLR) −43.2dBc in case of n77/n78, and −42.7dBc in case of n79, while consuming 295mW and 300mW dc power at 7.5dBm and 6.7dBm output power, respectively. The transmitter with inter-digitated switchable transformer has a size of 0.18mm2.