CMOS integrated transformer-feedback Q-enhanced LC bandpass filter for wireless receivers

An active integrated LC filter with tunable gain and quality factor is implemented in a standard 0.18 mum CMOS process. The circuit uses transformer feedback and a novel level-shifted single-transistor Q-enhancement technique to maximize the allowable voltage swing across the integrated LC resonator while providing single to differential signal conversion. To illustrate the concept, the circuit is designed and simulated for a wireless receiver front-end. The filter operates at a center frequency of 2.44 GHz with a 3-dB bandwidth of 84 MHz and is targeted at input filtering for Bluetooth and ZigBee applications. Simulation results show that the design achieves a power gain of 4.2 dB, an input 1-dB compression point (P-1dB) of -4.9 dBm, and a worst-case dynamic range (DR) of 65 dB over the filter bandwidth. Alternate implementations targeting low-voltage and low-power consumption circuits are also presented.