An 12th-order Active-RC Bandpass Filter with Programmable Bandwidth and Center Frequency for Synthetic Aperture Radar Application

A 12
^th
-order active-RC bandpass filter (BPF) for a synthetic aperture radar (SAR) receiver is presented in this paper. The proposed BPF is composed of six cascaded Biquads and each Biquad is configured as a second-order bandpass stage and the switched resistor and capacitor arrays are used in the Biquad to enable the digital control of the passband center frequency and bandwidth. To achieve desired passband and behave with Chebyshev response, the capacitors in the six Biquads are designed with the same values and resistor values are tunable. The filter has been implemented in a 65 nm CMOS technology and achieved low ripple, low noise and low power consumption. Under 8-bit digital programmable, the center frequency is tunable from 0.98 MHz to 4.83 MHz and the bandwidth is tunable from 0.66 MHz to 5 MHz, and it measures a maximum in-band frequency response deviation of <0.6dB while consuming $\leq$12mW at a 1.2 V supply.