Frequency synthesizer

A frequency synthesizer comprising first, second, and third phase-locked loops and a switch:

• said first phase-locked loop including a first voltage-controlled oscillator, a first frequency divider which divides an output frequency of said first voltage-controlled oscillator, a second frequency divider which divides an output frequency of a basic oscillator, a first phase detector which detects a phase difference between an output of said first frequency divider and an output of said second frequency divider, a first charge pump which transforms an output of said first phase detector into a drive signal for a first integrator, and a first loop filter serving as said first integrator, which feeds an output of said first charge pump back to said first voltage-controlled oscillator;
• said second phase-locked loop including a second voltage-controlled oscillator, a third frequency divider which divides an output frequency of said second voltage-controlled oscillator, a fourth frequency divider which divides the output frequency of a basic oscillator, a second phase detector which detects a phase difference between an output of said third frequency divider and an output of said fourth frequency divider, a second charge pump which transforms an output of said second phase detector into a drive signal for a second integrator, and a second loop filter serving as said second integrator, which feeds an output of said second charge pump back to said second voltage-controlled oscillator;
• said third phase-locked loop including a mixer which combines the output of said first voltage-controlled oscillator with that of said second voltage-controlled oscillator to produce an intermediate-frequency output, a filer which removes unnecessary components from the intermediate-frequency output of said mixer, a fifth frequency divider which divides an output frequency of said filter, a third phase detector which detects a phase difference between the output of the fourth frequency divider and an output of the fifth frequency divider, a third charge pump which transforms an output of said third phase detector into a drive signal for said first loop filter which feeds an output of said third charge pump back to the first voltage-controlled oscillator;
• and
• said switch being disposed before said first loop filter so as to select said first phase-locked loop or said third phase-locked loop.

A frequency synthesizer comprising first and second phase-locked loops and a switch:

• said first phase-locked loop including a voltage-controlled oscillator, a first frequency divider which divides an output frequency of said voltage-controlled oscillator, a second frequency divider which divides an output frequency of a basic oscillator, a first phase detector which detects a phase difference between an output of said first frequency divider and an output of said second frequency divider, a first charge pump which transforms an output of said first phase detector into a drive signal for an integrator, and a loop filter serving as said integrator, which feeds an output of the first charge pump back to said voltage-controlled oscillator;
• said second phase-locked loop including said voltage-controlled oscillator, a third frequency divider which divides an output frequency of said voltage-controlled oscillator, a fourth frequency divider consisting of a plurality of fractional frequency dividers which divides an output frequency of said basic oscillator, a fifth frequency divider which divides an output frequency of said fourth frequency divider, a second phase detector which detects a phase difference between an output of said third frequency divider and an output of said fifth frequency divider, a second charge pump which transforms an output of said second phase detector into the drive signal for said loop filter;
• and
• said switch disposed before said loop filter and selecting either of said first phase-locked loop or said second phase-locked loop.