| 摘要 |
PURPOSE:To obtain a frequency synthesizer to be operated stably and small in phase noise by using a voltage controlled oscillator outputting plural different frequency ranges according to an external switching signal, and a frequency multiplier outputting plural different multiples according to an external switching signal. CONSTITUTION:An output (output frequency = f0) of a voltage controlled oscilla tor 15 and an output (output frequency = f3) of a frequency multiplier 17 are mixed by a mixer 18, from which its difference signal (f0-f3) is outputted. The difference signal (f0-f3) is subject to 1/N division by the 2nd frequency divider 16, from which a frequency (f0-f3)/N is obtained and supplied to a phase comparator 13 as one input. Further, the output of a reference oscillator 11 is subject to 1/M frequency division by the 1st frequency divider 12, the frequency is a frequency fr, which is supplied to the other input of the phase comparator 13, which feeds the comparison output of the said two inputs to a control terminal 1501 of the voltage controlled oscillator 15 via an LPF 14 to constitute a PLL as a whole. |
