A Multiband FDD SAW-Less Transmitter for 5G-NR Featuring a BW-Extended N-Path Filter-Modulator, a Switched-BB Input, and a Wideband TIA-Based PA Driver

This article reports a multiband frequency-division duplex (FDD) SAW-less transmitter (TX) for 5G new radio (5G-NR). It features a bandwidth-extended N-path filter-modulator (BW-Ext FIL-MOD) to enable high-Q bandpass filtering at a flexible RF and the synthesis of a complex-pole pair via merging positive- and negative-feedback networks (PFN/NFN) enhances its bandpass characteristic, surmounting the tradeoff between the passband flatness and out-of-band (OB) rejection, a switched-baseband (BB) input network to avoid the mutual loading effect between the BW-Ext FIL-MOD and itself, and a transimpedance amplifier (TIA)-based power-amplifier driver (PAD) to absorb both the bias and signal currents of the BW-Ext FIL-MOD for better linearity and power efficiency. Fabricated in 28-nm CMOS, the proposed TX manifests a 20-MHz passband BW and a consistently low OB noise (≤-157.5 dBc/Hz) for different 5G-NR bands between 1.4 and 2.7 GHz. The TX achieves sufficient output power (3 dBm), high TX efficiency (2.8%-3.6%), and high linearity (ACLR1 <; 44 dBc and EVM <; 2%). The active area is 0.31 mm
²
.