A 4-Channel Poly-Phase Filter for Cognitive Radio Systems

A 4-channel poly-phase filter is proposed for cognitive radio systems. The cognitive radio system can sense the spectrum utilization and achieve higher transmission efficiency. To maximize the dynamic range of the receiver, the multi-channel poly-phase filter is required in the cognitive radio receiver to suppress the interference that is typically generated by legacy users. The filter is able to select different channels according to the demand of the system. A chip is fabricated in 0.18-mum CMOS technology. It dissipates 13.4 mW and achieves 35-dB adjacent channel rejection.