Patent ID: 6175281
Filing Date: 2001-01-16
Classification: H03L

Abstract:
A PLL frequency synthesizer comprising:a reference frequency generator which issues a first frequency signal;a PLL section which is connected to said reference frequency generator, which receives said first frequency signal and a second frequency signal, and outputs a phase error signal based on said first frequency signal and said second frequency signal;a first filter which is connected to said PLL section, which smoothes said phase error signal output from said PLL section according to a first reference characteristic, and which outputs a first smoothed phase error signal;a second filter which is connected to said PLL section, which smoothes said phase error signal output from said PLL section according to a second reference characteristic, and outputs a second smoothed phase error signal;a switch which is connected to said first filter and to said second filter and which issues either said first smoothed phase error signal output from said first filter or said second smoothed phase error signal output from said second filter in accordance with a changeover signal applied to said switch;an output frequency generator which is connected to said switch and to said PLL section and which issues to said PLL section said second frequency signal based on said first smoothed phase error signal or said second smoothed phase error signal; anda switch controller which is connected to said switch to control the changeover of said switch by issuing said changeover signal;said switch controller controlling the changeover of said switch such that said first smoothed phase error signal is applied to said output frequency generator when the output of the frequency synthesizer is applied to a first communication system, and said second smoothed phase error signal is applied to said output frequency generator when the output of the frequency synthesizer is applied to a second communication system, said output frequency generator outputting a frequency within a predetermined frequency range encompassing both said first and second communication systems; whereinsaid output frequency generator has a first power supply and a second power supply, so that said first power supply is selected when said switch is changed over to the connection with said first filter by said switch controller, while said second power supply is selected when said switch is changed over to the connection with said second filter by said switch controller.