Frequency snythesizer for implementing generator of highly pure signals and circuit devices, such as VCQ, BLL and SG, used therein

A frequency synthesizer comprising:

• a control section;
• a first signal generator responsive to said control section for generating a frequency signal of a predetermined frequency Fp;
• a second signal generator responsive to said control section for generating a frequency signal of a predetermined frequency Fq;
• a mixer for mixing said frequency signal Fp from said first signal generator and said frequency signal Fq from said second signal generator;
• a PLL having a voltage controlled oscillator and a phase detector responsive to the information from said control section for causing an output frequency signal from said voltage controlled oscillator to lock to a frequency of either .vertline.Fp-Fq.vertline. or Fp+Fq output from said mixer;
• and
• a frequency detector for detecting the output frequency of said voltage controlled oscillator on the basis of information from said control section and for causing said voltage controlled oscillator to pull-in one of the output frequencies (.vertline.Fp-Fq.vertline. and Fp+Fq) of said mixer.

A frequency synthesizer comprising:

• a control section;
• a first signal generator responsive to said control section for selectively outputting one of frequency signals whose frequencies are represented by Fp=a.times.P.times..DELTA.F (where coefficient a=3, 5, . . . , 2n+1, and coefficient P=0, 1, 2, . . . h);
• a second signal generator responsive to said control section for selectively outputting one of frequency signals whose frequencies are represented by Fq=2.times.Q .times..DELTA.F (where a coefficient Q=0, 1, 2, . . . Qmax, and Qmax=(a-1)/2);
• a mixer for mixing a frequency signal Fp from said first signal generator and a frequency signal Fq from said second signal generator;
• and
• a signal selecting circuit for selecting either of two frequency signals .vertline.Fp-Fq.vertline. or Fp+Fq output from said mixer,
• said control section determining the value of P and Q satisfying the following expressions (1) and (2) on the basis of a desired frequency setting signal Fi=m.times..DELTA.F (where coefficient m=0, 1, 2, . . . k) and quotient T and remainder s of m/a to control said first and second signal generators and said signal selecting circuit,
• when s is an odd number
• P=T+1, Q=(a-s)/2 (1)
• when s is an even number
• P=T, Q=s/2 (2)
• and said frequency synthesizer outputting .vertline.Fp-Fq.vertline. when s is an odd number and Fp +Fq when s is an even number.