Frequency synthesizer applied to a digital television tuner

摘要

A frequency synthesizer applied to a digital television tuner includes: a voltage controlled oscillator (VCO), a phase locked loop (PLL), a frequency divider unit, and a multiplexer. The maximum oscillated frequency of the VCO is twice its minimum frequency. The PLL controls and locks the VCO output frequency by a frequency control signal. The frequency divider unit includes a plurality of first dividers which form a cascade connection. The frequency divider unit receives the VCO output frequency, and subsequently divides the output frequency one by one. The multiplexer receives the dividing signals, and then chooses one of the dividing signals by a frequency selection signal, and generates a local oscillation signal. Hence, the present invention can implement the frequency synthesizer by simple architecture and cover the frequency ranges of Digital Video Broadcasting standard.