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.