A 150 kHz–80 MHz BW Discrete-Time Analog Baseband for Software-Defined-Radio Receivers using a 5th-Order IIR LPF, Active FIR and a 10 bit 300 MS/s ADC in 28 nm CMOS

A discrete-time (DT) analog baseband for software-defined-radio (SDR) receivers is presented. A zero-IF baseband signal at the input of a programmable g
_m
is converted to current, which is integrated on a 5th-order DT infinite-impulse response (IIR) low-pass filter with a bandwidth ranging from 150 kHz to 80 MHz. The IIR is followed by a DT amplifier which integrates selected samples to implement active finite-impulse-response (FIR) filtering while simultaneously offering variable-gain amplification. This integration happens on the DAC capacitance of a 2x interleaved 10 bit successive approximation (SAR) ADC, which finally quantizes the filtered signal at a maximum rate of 300 MS/s. The 28 nm prototype achieves +10 dBm IIP3, 2 nV/√Hz input-referred noise and 52 dB gain range while consuming a maximum power of 15 mW.