Design of a Low-Power Complex Baseband Filter with Tunable Gain and Bandwidth in 65nm CMOS

A low-power fourth-order complex bandpass baseband analog filter (BBA) is designed for low-IF RF receivers supporting MedRadio or Bluetooth applications. The BBA is composed of three variable gain amplifier stages and two complex biquad stages. The gain and bandwidth tuning capabilities are needed to maximize the receiver dynamic range and support the variable data rates. The center frequency and Q-factor tunings are realized for optimum filtering and amplification performances. The gain tuning range is from −15 dB to +52 dB and the bandwidth tuning range is from 250 kHz to 2.9 MHz. The image rejection ratios are found to be 39 and 42 dB at the maximum bandwidth of 2.9 MHz and the minimum bandwidth of 250 kHz conditions, respectively. The layout size is 0.42 mm ² including the I/Q paths, while dissipating 1.5 mA from a 1-V supply.