Implementation of CMOS tunable on-chip Gm-C IF filter in RF front-end IC for SDR transceiver

This paper presents the implementation of the variance compensation solution for the center frequency of the intermediate frequency (IF) 10.7 MHz Gm-C filter under the effect of operating temperature. The designed filter is implemented in CMOS 0.35μm. A digital processing algorithm is used to estimate the center frequency, then the tunable Gm-C filter will be adjusted by an appropriate bias voltage, resulting the reduction of the frequency variance to under 0.1% when the change of the operating temperature in range of - 40°C to 85
^°
C. This solution has been applied efficiently in a HF/VHF software-defined radio system.