Blocker-Tolerant Broadband CMOS Low-Noise Amplifier Employing N-Path Filter-Based Load

This study proposes a broadband complementary metal-oxide semiconductor (CMOS) low-noise amplifier (LNA) with intrinsic band-selective out-of-band (OB) blocker rejection capabilities. The proposed LNA design utilizes a differential four-phase N-path filter as the amplifier load to offer a substantial total load impedance difference between the in-band (IB) and OB frequency bands. This ensures that the LNA design securely accomplishes a high-quality-factor frequency selectivity response with lower radio frequency signal losses and its OB rejection performance is maintained against process, voltage, and temperature variations, compared with the case of using the N-path filter as a signal path. To validate its blocker-tolerable performance, the designed LNA was fabricated using a 65-nm CMOS technology and was primarily characterized in the frequency division duplexing bands of the long-term evolution and fifth-generation new radio standards, spanning from 1.7 to 2.7 GHz. The implemented design consistently achieved a transmitter leakage rejection greater than 17 dB across all target frequency bands from several samples. Furthermore, the design attained IB voltage gains greater than 36.4 dB and 40.4 dB, noise figures (NFs) of 1.78 dB and 1.5 dB, OB input 1-dB compression point greater than –27.0 dBm and –26.7 dBm, and full-/half-duplexing OB input-referred third-order intercept points greater than 4.1/3.8 dBm and 4.8/5.0 dBm at the mid- and high-bands, respectively. The OB-induced NF degradation was maintained at less than 0.7 dB. A total bias current of 37.7 mA was required with a nominal supply voltage of 1.2 V. The occupied active area of the implemented design was approximately 0.77 mm2, excluding the bonding pads and input/output cells.