Oscillator having low phase noise
AssigneeNemeth-Bates Corp
InventorRobert Nemeth
Life of this patent
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Abstract
Phase noise in a carrier signal is reduced by use of a phase locked loop which is responsive to the carrier signal and another signal of comparable noise level but having non-correlated phase noise.
Claims32
A method for reducing phase noise in a signal coherently derived from a supplied carrier signal, comprising the steps of providing a second carrier signal, said second carrier signal having non-correlated phase noise with a noise level comparable to or below the noise level of said supplied carrier signal, supplying signals derived from said supplied carrier signal and said second carrier signal to a first phase locked loop, said first phase locked loop including an oscillator for generating said coherently derived signal and operating said first phase locked loop to lower the phase noise of said coherently derived signal to a value which is less than 20 log K above the phase noise of said supplied carrier signal, where K is the ratio of the frequency of said coherently derived signal to the frequency of said supplied carrier signal.
A phase noise improvement circuit comprising a first phase locked loop responsive to a first supplied signal derived from a first reference oscillator having a selected reference frequency and a second supplied signal derived from a second reference oscillator, said second reference oscillator having phase noise which is noncorrelated with the phase noise of said first supplied signal outside a relatively narrow bandwidth and a noise level comparable to or below the noise level of said first supplied signal, and a second phase locked loop having a narrow bandwidth for phase locking said second reference oscillator to said first supplied signal within said narrow bandwidth.
Apparatus responsive to a supplied reference signal for providing an output signal having a selected frequency and low phase noise over a selected noise bandwidth, comprising:
- a first phase locked loop for generating said output signal and responsive to said reference signal and another signal and having a loop bandwidth corresponding to said selected noise bandwidth;
- and a second phase locked loop responsive to said supplied reference signal for generating said other signal, said second phase locked loop have a relatively narrow bandwidth for generating said other signal to be coherent with said reference signal but having uncorrelated phase noise at frequencies outside the narrow bandwidth.
Dependencies are inferred from the claim text.