High-performance active polyphase filter design for digital TV tuner

This paper presents the polyphase filter design for the tuner of DTV front-end system. The polyphase filter is designed with an active circuit to improve the chip performance. Most of passive capacitor and resistor components are replaced with MOS transistors. The proposed method not only can reduce the chip area but also gain the signal level. For the prototyping implementation, the current channel bands in Taiwan are referred, which the frequency range is from 530 to 602 MHz for DTV programs. In experiments, the polyphase filter can achieve 85 dB for the image rejection in the center frequency. The main signal can be gained about 2–5 dB without using extra amplifier. The chip size is about 0.09 mm2, and the average power dissipation is about 15 mW, when the chip technology employed TSMC 0.35 μm CMOS process. The proposed chip outperforms with less area and higher gain.