Design of Integrated Poly-Phase Filter for GSM Handset

As one of the key modules of low-IF receive, the poly-phase filter plays an important role in image rejection and adjacent channel interference. Its performance directly affects the receiving sensitivity of the whole system. This paper adopts the structure of active RC and the method of frequency shift to design a five order poly-phase filter. The simulation results show that the filter is centered at 100 kHz with bandwidth of 220 kHz. It has maximum voltage gain of about 63dB and image reject ratio 30dB. So it can satisfy the requirement of GSM system.