The design of A CMOS Gm-C lowpass filter with variable cutoff frequency for direct conversion receiver

A CMOS Gm-C filter with variable cutoff frequency applicable for using in the direct conversion receiver is designed. The designed filter comprises the CMOS differential transconductors, and the gm of the transconductor is controlled by the bias voltage. This configuration can compensate variant of the cutoff frequency which could be generated by external noises, and also be used in multiband receiver. As a results of HSPICE simulation, the control range of the cutoff frequency is 1.5MHz-3.5MHz and the gain control range is -2.8dB-2.6dB. The layout of the designed 5th-order Elliptic low-pass filter is performed to fabricate a chip using 2.5V-0.25//m CMOS processing parameter.