A CMOS G_m-C complex filter with a reconfigurable center and cutoff frequencies in low-IF WiMAX receivers

This paper presents a reconfigurable fifth-order complex G_m-C filter for different data rates in low-IF WiMAX applications.The design procedure and linearized measures to realize the complex filter are described.In order to achieve the reconfigurability of bandwidth window,the center frequency and the cutoff frequency filter are adjusted simultaneously by changing capacitor values while keeping transconductors unchanged.Also,the filter integrates an on-chip automatic frequency tuning circuit based on a PLL.Experimental results show that it has an IRR of 32 dB,a THD of -43 dB,and an input-referred noise of 21μVrms.The chip is fabricated in 0.13μm CMOS process,occupies 0.7×1 mm~2,and consumes 4.8 mA current from a 1.2 V power supply.