Frequency synthesizer with fractional division ratio and jitter compensation
Phase locked loop variable frequency generator
Multiple-multiple modulus prescaler for a phase-locked loop
Fractional N synthesizer
Frequency synthesizer of the fractional type
Frequency modulation in phase-locked loops
Spurless fractional divider direct digital frequency synthesizer and method
Frequency synthesizer with spur compensation
Frequency or phase modulation
ApplicationNo. 516993 filed on 04/30/1990
US Classes:331/16, Tuning compensation331/25, Signal or phase comparator332/127, Phase or frequency locked loop455/76, Synthesizer455/119Carrier frequency stabilization
ExaminersPrimary: Grimm, Siegfried H.
Attorney, Agent or Firm
Foreign Patent References
International ClassH03L 007/18
AbstractA fractional-N synthesizer employing at least a second order sigma-delta modulator is disclosed. The most significant bits from the output accumulator of the sigma-delta modulator are used as the carry out control for the variable divisor of the loop divider. Modulation to the synthesizer is introduced as part of the digital number input to the sigma-delta modulator and spurious signal output is reduced by selection of a large number as the denominator of the fractional portion of the loop divider divisor.