Calibration-Free Blocker Rejection Broadband CMOS Low Noise Amplifier for Advanced Cellular Applications

Abstract

This study presents a broadband complementary metal-oxide semiconductor (CMOS) low noise amplifier (LNA), containing out-of-band (OB) blocker rejection capability without an additional calibration process. In the proposed design, separate all-pass and band-stop filter stages are provided in parallel as main and auxiliary paths, respectively, whose amplitude and phase variations are identically tracked by each other over a process, voltage, and temperature dependency. By appropriately combining an in-band signal and OB blockers passed through those filter blocks, robust OB blocker rejection can be realized in the wide frequency range. The designed LNA incorporates a pre-amplifier stage for broad input matching and low-noise characteristics, an N-path filter-based frequency selective stage, and a combiner stage to suppress undesired OB blockers. The designed calibration-free OB blocker rejection broadband LNA is fabricated in a 65 nm CMOS technology and mainly characterized in long-term evolution frequency division duplexing bands, ranging from 0.7 to 2.7 GHz. The demonstrated design consistently attains transmitter leakage and other OB blocker rejection of more than 22.8 dB and 16 dB in low-band (LB) (0.7−1 GHz) and mid-and high-band (MB and HB) (1.7−2.7 GHz) frequency range from several samples without extra gain or phase adjustment, respectively. The implemented LNA also achieves gains of 10.5−11.0 dB and 8.0−10.0 dB, noise figures of 3.7−4.1 dB and 3.8−4.9 dB, OB third-order intercept points greater than 8.2 dBm and 9.8 dBm, and OB 1-dB compression points greater than −5.2 dBm and −5.5 dBm, for LB and MB/HB, respectively. The implemented design consumes a total bias current of 23.9 mA with a nominal supply of 1.2 V and occupies an active area of 0.53 mm 2 , excluding bonding pads.INDEX TERMS Broadband, calibration-free, cellular, CMOS, feedforward cancellation, long-term evolution (LTE), low-noise amplifier (LNA), N-path filter, out-of-band blocker rejection, wideband.

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

“…According to (8), a larger RN and smaller RSW or RL surely entail higher ZN distinction between the IB and OB frequencies. For example, with RN (N = 4), RSW, and RL of 256.7 Ω, 10 Ω, and 0 Ω, the evaluated relative input impedance is approximately 13.8 (22.8 dB).…”

“…The low-noise pre-amplifier, preferentially placed in the first stage of the LNA, mainly provides broadband input matching and low-noise characteristics through the preceding signal amplification. The single-ended pre-amplifier design forms a complementary common-source (CS) configuration that utilizes input devices (M1N and M1P) with a feedback resistor (RF) [8], [38], [39]. This current-reuse topology indeed facilitates the gain boosting and NF reduction in an amplifier for a particular current consumption.…”