A UHF CMOS Gm-C bandpass filter and automatic tuning design

A CMOS Gm-C bandpass filter using improved Nauta´s transconductor and its matched oscillator are presented. The filter can be operated at ultra high frequency (UHF) band with a high quality factor. Quality factor and frequency tuning is also considered. The simulated results show that the center frequency of the filter using TSMC 0.18μm CMOS process can be operated at about 800MHz under 3.3V supply. To match the filter, the oscillator designed is based on the archetype of the filter and the simulation presents that they are in a good match. An application of the above filter and oscillator in a phase lock loop (PLL) technique for continuous time auto-tuning filter is simply introduced.