A Reconfigurable RF Filter With 1%–40% Fractional Bandwidth for 5G FR1 Receivers

This letter presents a radio frequency front-end (RFFE) for 5G new radio (NR) receivers operating in frequency range 1 (FR1). The core of this RFFE is a synthetic fourth-order Q -enhanced RF filter employing gm -boosting, noise-canceling, capacitive cross-coupling, and forward body-biasing techniques to achieve 1.7 to 6.4 GHz operating range and 1% to 40% adjustable fractional bandwidth (FBW). The function of the filter is based on subtracting out-of-phase signals in the passband and in-phase signals in the stopband. Two Q -enhanced LC resonators are utilized for outphasing. The filter is preceded by a low-noise transconductance amplifier, and it is followed by a programmable gain amplifier and a differential buffer stage for the measurement purposes and gain equalization. The experimental results demonstrate that the voltage gain is tunable between 18 and 47 dB with 0.2 dB steps, which leads to an equalized output power in all the filter configurations. Fabricated in 22 nm fully depleted silicon on insulator (FD-SOI) technology, the RFFE achieves 4.6-dB NF, −14 dBm IB-IIP3, and 26-dBm IB-IIP2 at 4 GHz. Notably, the fourth-order steep roll-off provides 22-dBm OOB-IIP3 at 2×BW frequency offset. The entire RFFE draws 22–45 mA from a 1-V supply and the filter core occupies 0.11 mm2 chip area.