An analog integrated polyphase filter for a high performance low-IF receiver

An analog integrated asymmetric polyphase filter is a key building block for the development of a high performance fully integrated low-IF receiver. The asymmetric polyphase filter makes it possible to suppress the mirror signal not at HF, but after quadrature demodulation at a low IF. The most important parameters for the polyphase filter are a high dynamic range and a good mirror signal suppression. This paper reports on the realisation in a 1.2 /spl mu/m CMOS process of a 5th order Butterworth polyphase filter with a bandwidth of 220 kHz centered around 250 kHz. Its measured mirror signal suppression is 64 dB. The active-RC implementation renders a 94.2 dB dynamic range at the input.