Cost-efficient CMOS RF tunable bandpass filter with active inductor-less biquads

This paper presents a CMOS RF tunable 4^th-order active bandpass filter with the proposed inductor-less biquads. The NMOS cross-coupled pair is utilized in the biquad for the positive-feedback to form the complex pole, which enables the filter working at high frequency of 5GHz with low power of only 4.8mW from 1.2V power supply. Due to the inductor-less topology, the proposed filter only occupies 0.011mm² silicon area, which is cost-efficient and suitable for integration on chip. The center frequency can be tuned from 2GHz to 5GHz, and the Q factor is tuned from 2 to 8 to cover different bandwidth from 250MHz to 2.5GHz, which makes it suitable for the multi-band/multi-mode and SDR applications. The filer is demonstrated in a standard 65nm CMOS process. As for the center frequency of 5GHz and Q of 2, the simulated P1dB is -6.7dBm, and the simulated input referred noise (IRN) density is 14.2nV/sqrt(Hz).