IIP2-Calibration-Free 5G NR Cellular Receiver Front-End With Mixer-Sharing Global N-Path Notch Filter Feedback Achieving +72 dBm IIP2

In this article, a new input-referred second-order intercept point (IIP2)-calibration-free receiver (RX) front-end employing mixer-sharing N-path notch filter feedback is proposed for 5G new radio (NR) cellular applications. An RX front-end architecture with a high-Q N-path RF filtering low-noise amplifier (LNA) enhances the overall IIP2 performance of the RX via the blocker filtering. However, the local oscillator (LO) chain burden increases with the number of switches in the N-path filter. The main down-conversion mixers are reused as part of switches for the N-path notch filter, reducing the LO chain burden and current consumption. The RX front-end comprises a balun-LNA, main down-conversion passive mixers driven by 25% duty-cycle LO signals, isolation resistors, and transimpedance amplifiers. Additional high-pass filters, up-conversion mixers, and reused down-conversion mixers form the global N-path notch filter feedback. Fabricated using a 65 nm CMOS process, the RX front-end was primarily characterized for the mid band of 5G NR sub-6 GHz cellular applications. It achieved a noise figure of 3.67 dB, a conversion gain of 44.7 dB, and an out-of-band input-referred third-order intercept point of 15.35 dBm. Additionally, an IIP2 of >72 dBm was obtained without calibration. The RX front-end drew a 13.83 mA bias current from a 1 V nominal supply voltage, with a 0.45 mm2 active die area.