A 2.7-V CMOS dual-mode baseband filter for PDC and WCDMA

A fifth-order analog CMOS RC-opamp baseband filter for a dual-mode cellular phone receiver was designed II] with maximum component sharing in the two modes. The filter meets the bandwidth specifications of both the PDC and WC DMA standards, which represent the two extremes with respect of the channel bandwith, The total area of 4.8 mm(2) was minimized by reducing the filter order from five to three in the PDC mode. Also, the operational amplifiers with adjustable GBW were used to minimize PDC-mode power consumption. The capacitance matrices were made only partially overlapping to reduce the res istance spread. The largest resistors were implemented with T networks and the smallest capacitors with series connections to extend the range of feas ible passive component values. The measured integrated input referred noise is 17 muV and 47 muV in the PDC and WCDMA modes, respectively. The IIP3 is +35 dBV in the WCDMA mode, and the circuit consumes 6.8 mW and 25.4 mW in the PDC and WCDMA modes, respectively. The supply voltage is 2.7 V.