Field-Programmable LNAs With Interferer-Reflecting Loop for Input Linearity Enhancement

A field-programmable (FP) low-noise amplifier (LNA) with interferer-reflecting (IR) loop is introduced. The user can program its gain, noise figure, linearity and power consumption during operation. The IR loop uses a frequency-selective shunt-shunt feedback around the noise-canceling LNA to reduce the input impedance out of band and to suppress the input voltage swing created by blockers. A notch filter at the desired operation frequency in the feedback path results in selectivity at the RF input so that all out-of-band blockers are suppressed without the need to know blocker locations and the LNA input linearity is improved. 65 nm CMOS chip prototypes have been implemented with on-chip LC, bondwire LC or N-path notch filters. The FP N-path IR-LNA operates from 0.2 to 1.6 GHz; with the IR disabled, the NF is 2.4 dB, B1 dB is -15 dBm, and the OOB-IIP₃ is +2.5 dBm with a 13 mW power consumption; with the IR on, the NF is 3.6 dB, the RF channel input bandwidth is 20 MHz, the B1 dB is -4 dBm and the OOB-IIP₃ is +14.5 dBm. The LNA has an analog V_DD of 1.6 V and an LO V_DD of 1 V and dissipates 15.8 to 20.2 mW across operating frequencies.