A UHF-band RF tunable filter is developed for TV white space CMOS transmitter applications. It is based on the combined Sallen-Key and LC notch structure. The inherent transmission zero of the Sallen-Key core is carefully chosen to suppress the 7 th -harmonic component of the transmitter output, and the LC notch filter is set to suppress the 9 th -harmonic component. The filter is built in 0.18-μm CMOS process and consumes 6.2-mA from a 1.8-V supply. The filter's cutoff frequency is tuned from 100-MHz to 500-MHz in five steps. It is successfully adopted in a TV white space CMOS transmitter integrated circuit. Keywords: RF tunable filter, Sallen-Key filter, harmonic rejection filter Classification: Integrated circuits
References[1] "Second report and order and memorandum opinion and order: Unlicensed operation in the TV broadcast bands," FCC, Washington, DC, FCC ET Docket 04-186, Nov. 2008.