A Low Power CMOS gm-C Polyphase Filter for Low-IF GPS Receiver

In this paper a 0.35 micro meter CMOS gm-C polyphase filter for low-IF GPS receiver is presented. This gm-C filter is a combination of two 3
^rd
order channel-select Chebyshev low pass and one 5
^th
order polyphase Elliptic filters. The overall filter has a pass band of 2.9 to 5.3 MHz, 30 dB pass band gain with less than 1 dB in-band ripple, more than 60 dB attenuation at 2.5 MHz offset from the center frequency, more than 18 dB image rejection and drains 1.95 mA from a 2.2V supply. An inverter-based low noise and high frequency transconductor is designed for the filter. Also, a new technique to reduce the number of coupling transconductance cells in a polyphase filter, while using the same gm unit across the filter, is introduced. A quadrature offset removal circuit is employed to remove the offset of this 30 dB gain filter.