A Highly linear Lowpass Filter for GSM /WCDMA Receivers

Based on SMIC 0.35mum process, a fourth-order active-opamp RC lowpass filter used in GSM/WCDMA communication system is presented. The filter meets the bandwidth specifications of the PDC and WCDMA standards especially the high IIP3, and shares the maximum number of components between the two modes. The total area is 1578mum*515mum. The operational amplifiers with adjustable GBW were used to optimize GSM-mode power consumption. The capacitance matrix was used to tune the cutoff frequency with the consideration of the varieties of the temperature and technology. Also, the capacitances were made partially overlapping to reduce the resistance spread. The measured noise figure is 42dBm and 38 dBm in the GSM and WCDMA modes, respectively. In the WCDMA mode, the IIP3 is 40dBm, and the power dissipation is 17.9mW. While in the GSM mode, the IIP3 is 38dBm and the circuit consumes 11.3mW. The supply voltage is 3.3V