CMOS on-chip active RF tracking filter for digital TV tuner ICs

Abstract

A full frequency band active RF tracking filter design for a digital TV tuner is implemented for the first time. By combined control of the Gm and C values in the biquad of the Gm-C filter, the proposed tracking bandpass filter satisfies full frequency band tuning while maintaining narrow bandwidth. The Gm cell of the tracking filter is based on a dynamic source degenerated differential pair with optimised transistor size ratio, which provides good linearity and high-frequency operation. The fabricated tracking filter based on a 0.13 µm CMOS process shows 48–780 MHz tracking range with 15–60 MHz bandwidth, more than 50 dB of third-order harmonic rejection, 14 dB unwanted signal rejection at N+6 channel offset, and a maximum IIP3 of 3.8 dBm at 4.7 dB gain while drawing 30 mA from a 1.2 V supply.