Injection locking using direct digital tuning
First Claim
1. A method of digitally pre-tuning and injection locking a voltage controlled oscillator (VCO) having an output of a specified frequency, said method comprising the steps of:
- (a) digitally pre-tuning said VCO to within a specified locking bandwidth (LBW);
(b) injecting an input reference signal into said VCO; and
(c) locking said VCO to said input reference signal, wherein the step of digitally pre-tuning comprises the steps of;
(i) digitizing said VCO output;
(ii) determining said VCO output frequency;
(iii) adjusting said VCO output frequency; and
(iv) repeating steps (a) to (c) until a desired oscillation frequency is reached.
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Abstract
The invention relates to the field of electronics and more particularly to the tuning and injection locking of voltage controlled oscillators (VCOs). An improved injection locking circuit is provided which allows the VCO to injection lock with a smaller reference signal and therefore a smaller locking bandwidth (LBW). In order to allow the VCO to injection lock with a lower power reference signal, this invention includes a pre-tuning algorithm to place the VCO frequency such that the desired frequency is in the LBW. Tuning of the VCO is achieved using direct digital tuning that does not require an input reference. Injection locking is performed using a low frequency clock harmonic as the reference signal. More specifically, tuning is accomplished by sub-sampling and digitizing the output signal of the VCO, determining the center frequency, and adjusting the VCO control voltage.
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Citations
27 Claims
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1. A method of digitally pre-tuning and injection locking a voltage controlled oscillator (VCO) having an output of a specified frequency, said method comprising the steps of:
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(a) digitally pre-tuning said VCO to within a specified locking bandwidth (LBW);
(b) injecting an input reference signal into said VCO; and
(c) locking said VCO to said input reference signal, wherein the step of digitally pre-tuning comprises the steps of;
(i) digitizing said VCO output;
(ii) determining said VCO output frequency;
(iii) adjusting said VCO output frequency; and
(iv) repeating steps (a) to (c) until a desired oscillation frequency is reached. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A circuit for digitally pre-tuning and injection locking a voltage controlled oscillator (VCO) comprising:
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(a) a reference oscillator for producing a low frequency clock harmonic;
(b) a VCO electrically connected to said reference oscillator; and
(c) a feedback circuit electrically connected to said VCO for digitally pre-tuning said VCO prior to receipt of said low frequency clock harmonic by said VCO. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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Specification