Novel DC offset cancellation in direct conversion receivers

A new approach for DC offset cancellation in direct conversion receivers is proposed in this paper. The proposed method is based on AC-coupling. A differential voltage current conveyor (DVCC) with non-unity voltage and current gain factors is used to realize a large-value floating capacitor. The proposed approach using the modified DVCC requires small die area and achieves good DC offset cancellation capability. A first-order high-pass filter with 100-Hz cutoff frequency by using only 50-pF capacitor and 100-kOmega resistor is realized as an example. Validity of the proposed circuit is confirmed by SPECTRE simulation using TSMC 0.18-mum CMOS n-well technology. And also the proposed circuit is laid out using ON Semiconductor 1.2-mum CMOS n-well technology to demonstrate the effectiveness from the view point of die area.