A Wideband Receiver Front-End Employing New Fine RF Gain Control Driven by Frequency-Translated Impedance Property

A new gain control methodology employing frequency-translated (FT) impedance property is proposed for RF amplifiers. By adaptively controlling the baseband impedance through the FT property, fine RF gain control can be achieved without degradation in the RF characteristics such as noise figure (NF), gain, input matching, and bandwidth. To verify the proposed method, a wideband receiver (RX) front-end (FE) with the fine RF gain control has been designed for 2G/3G/4G cellular applications. The implemented RX FE consists of a wideband capacitor cross-coupled common-gate low-noise amplifier, a 25% duty cycle passive mixer with baseband impedance array, a baseband transconductor with variable input capacitance, and a trans-impedance amplifier. The RX FE was fabricated in a 65 nm CMOS process. It has a conversion gain from 26 dB to 42 dB with 1 dB gain resolution, and achieves a minimum NF lower than 3.3 dB, out-of-band IIP3 of -2 dBm, and IIP2 of more than 56 dBm. It draws an average current of 14.8 mA from a 1.2 V supply voltage.