Fractional N/M synthesis
AssigneeMotorola, Inc.
InventorsGregory Black, Alexander W. Hietala
Life of this patent
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Abstract
A frequency synthesizer having a frequency divider and a frequency multiplier in the feedback loop is disclosed. The minimum frequency separation between two adjacent synthesized channels is equal to the reference frequency divided by the multiplication ratio of the multiplier. The division ratio of the frequency divider, which can be analyzed as the sum of an integer and a fractional portion, is varied with time by a digital sequence, resulting in a minimum frequency increment equal to a fraction of the reference frequency. The multiplier acts to reduce the nonlinearities of the frequency synthesizer when the fractional portion of the division ratio causes a large variation in the instantaneous division ratio by reducing the effective division ratio of the loop.
Claims31
A frequency synthesizer which phase locks an output signal of a variable frequency oscillator to a reference signal, the frequency synthesizer comprising:
- means, coupled to the variable frequency oscillator, for dividing the frequency of the output signal to produce a frequency divided signal;
- means, coupled to said means for dividing, for frequency multiplying said frequency divided signal to produce a frequency divided and multiplied signal;
- and
- means, coupled to said means for frequency multiplying, for comparing the phase of said frequency divided and multiplied signal to the phase of the reference signal to produce a control signal which is coupled to the variable frequency oscillator.
A frequency synthesizer which phase locks an output signal of a variable frequency oscillator to a reference signal, the frequency synthesizer comprising:
- means, coupled to the variable frequency oscillator, for dividing the frequency of the output signal to produce a frequency divided signal;
- means, coupled to said means for dividing, for essentially frequency multiplying said frequency divided signal and for comparing the phase of said frequency divided and multiplied signal to the phase of the reference signal to produce a control signal which is coupled to the variable frequency oscillator.
A radio transceiver having a frequency synthesizer which phase locks an output signal of a variable frequency oscillator to a reference signal, the radio transceiver comprising:
- means for transmitting a radio frequency signal of a frequency related to the output signal of the variable frequency oscillator;
- means, coupled to the variable frequency oscillator, for dividing the frequency of the output signal to produce a frequency divided signal;
- means, coupled to said means for dividing, for frequency multiplying said frequency divided signal to produce a frequency divided and multiplied signal;
- and
- means, coupled to said means for frequency multiplying, for comparing the phase of said frequency divided and multiplied signal to the phase of the reference signal to produce a control signal which is coupled to the variable frequency oscillator.
A radio transceiver having a frequency synthesizer which phase locks an output signal of a variable frequency oscillator to a reference signal, the radio transceiver comprising:
- means for transmitting a radio frequency signal of a frequency related to the output signal of the variable frequency oscillator;
- means, coupled to the variable frequency oscillator, for dividing the frequency of the output signal to produce a frequency divided signal;
- means, coupled to said means for dividing, for essentially frequency multiplying said frequency divided signal and for comparing the phase of said frequency divided and multiplied signal to the phase of the reference signal to produce a control signal which is coupled to the variable frequency oscillator.
A method of synthesizing a signal having a predetermined frequency by phase locking an output signal of a variable frequency oscillator to a reference signal, the method comprising the steps of:
- dividing the frequency of the output signal of the variable frequency oscillator to produce a frequency divided signal;
- frequency multiplying said frequency divided signal to produce a frequency divided and multiplied signal;
- and
- comparing the phase of said frequency divided and multiplied signal to the phase of the reference signal to produce a control signal which is coupled to the variable frequency oscillator.
A method of synthesizing a signal having a predetermined frequency by phase locking an output signal of a variable frequency oscillator to a reference signal, the method comprising the steps of:
- dividing the frequency of the output signal of the variable frequency oscillator to produce a frequency divided signal;
- selecting a frequency multiple of said frequency divided signal and comparing the phase of said frequency divided and multiplied signal to the phase of the reference signal to produce a control signal which is coupled to the variable frequency oscillator.
Dependencies are inferred from the claim text.