Frequency synthesizer having dual phase locked loops
First Claim
1. A frequency synthesizer capable of selectively switching between an initial frequency and a subsequent frequency separated by an incremental difference, comprising:
- a first phase-locked loop wherein said first phase-locked loop receives a first reference frequency and produces a first output frequency that is a function of said first reference frequency;
a second phase-locked loop wherein said second phase-locked loop receives a second reference frequency and provides a second output frequency that is a function of said second reference frequency; and
a mixer for mixing said first output frequency and said second output frequency to produce said subsequent frequency, wherein said subsequent frequency is a function of both said first reference frequency and said second reference frequency, and said incremental difference between said initial frequency and said subsequent frequency is equal to a difference between said first reference frequency and said second reference frequency.
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Abstract
A frequency synthesizer circuit for the front end of an RF system. The frequency synthesizer uses two pulse-swallow phase-locked loops in a synthesizer architecture that produces an output frequency that is a function of the two reference frequencies used as inputs into the two phase-locked loops. As a result, the frequency synthesizer can be incremented in steps equal to the differential of the reference frequencies of the two phase-locked loops, while the frequency outputs of each of the phase-locked loops can be incremented in much larger steps. This enables the two phase-locked loops to employ relatively large bandwidths, thereby achieving a faster signal lock as well as a better suppression of the voltage controlled oscillator (VCO) phase noise in each loop. The use of a dual loop synthesizer architecture allows for feedback correction of the VCO phase noise outside the loop bandwidth.
35 Citations
24 Claims
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1. A frequency synthesizer capable of selectively switching between an initial frequency and a subsequent frequency separated by an incremental difference, comprising:
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a first phase-locked loop wherein said first phase-locked loop receives a first reference frequency and produces a first output frequency that is a function of said first reference frequency; a second phase-locked loop wherein said second phase-locked loop receives a second reference frequency and provides a second output frequency that is a function of said second reference frequency; and a mixer for mixing said first output frequency and said second output frequency to produce said subsequent frequency, wherein said subsequent frequency is a function of both said first reference frequency and said second reference frequency, and said incremental difference between said initial frequency and said subsequent frequency is equal to a difference between said first reference frequency and said second reference frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. A frequency synthesizer capable of selectively switching between an initial frequency and a subsequent frequency separated by a multiple of a base incremental difference, comprising;
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a first phase-lock loop that receives a first reference frequency; at least one second phase-lock loop that receives a second reference frequency; and a mixer for mixing the output associated with said first phase-locked loop and said second phase-locked loop to produce said subsequent frequency, wherein said base incremental difference is equal to a difference between said first reference frequency and said second reference frequency. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification