US4994767A
Expired / Lapsed
US
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Oscillator phase-noise reduction
Assignee: UK Secretary of State for Defence
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Filing: 1988-07-01
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Granted: 1991-02-19
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Expires: 2008-07-01
Abstract
Abstract An output having reduced additives phase-noise in at least one defined frequency band is obained from a voltage-controlled oscillator (5) by applying a frequency-modulating signal ω m t to the oscillator to produce a sideband within the defined band, the signal having a frequency much higher than the highest multiplicative phase-noise frequency (referred to the unmodulated oscillator frequency) in that band and producing a modulaton index ΔP much greater than the modulation index ΔP n of the total phase-noise (i.e. additive plus multiplicative)in that band. The oscillator output is then phase-modulated with a signal at ω m t selected from the output of a phase-shift frequency-discriminator (9) having an appropriate delay (d) which receives the oscillator (5) output either after the phase-modulation thereof by modulator (8), or before the phase-modulation thereof by modulator (20), or both, in a sense and at an amplitude which tends to cancel the additive phase-noise modulation in the oscillator output. In a preferred form the discriminator (9) receives the oscillator (5) output before its phase-modulation by modulator (20), and a frequency-modulatiing pilot-tone (ω m +ω q )t of modulation index ΔP q is also applied to the oscillator, where ΔP>ΔP q >P n . A feedback loop (29-34) detects variations in the phase and amplitude of the pilot-tone content of the final output and, via multiplier (27), controls the modulating input to modulator (20) in a sense to minimize the pilot-tone content and hence also the additive phase-noise.
Inventors
- 👤 Henry W. Hawkes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-06 19:40
CPC Classifications
H; H03; H03C; H03C3/00; H03C3/02; H03C3/09
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
170 words
A method of reducing the additive phase-noise in the output from an oscillator of given frequency, in at least one defined frequency band, comprising: applying a frequency-modulating signal to the oscillator to produce a frequency-modulation sideband of said given frequency within said band, said signal having a frequency much higher than the highest multiplicative phase-noise frequency in that band and producing a modulation index much greater than the modulation index of the total phase-noise in that band, total phase noise comprising additive phase-noise plus multiplicative phase noise; and phase-modulating the output from said oscillator with a signal at the modulating frequency selected by a filter means from the output of a frequency-discriminator having an appropriate delay which receives an amplitude-limited version of the oscillator output either before or after said phase-modulating thereof, in a sense and at an amplitude which tends to cancel the additive phase-noise modulation in the oscillator output; whereby the thus phase-modulated output from the oscillator is a frequency-modulated output having reduced additive phase-noise in said band.
Claim 2
Independent Claim
170 words
A method of reducing the additive phase-noise in the output from an oscillator of given frequency, in at least one defined frequency band, comprising: applying a frequency-modulating signal to the oscillator to produce a frequency-modulation sideband of said given frequency within said band, said signal having a frequency much higher than the highest multiplicative phase-noise frequency in that band and producing a modulation index much greater than the modulation index of the total phase-noise in that band, total phase noise comprising additive phase-noise plus multiplicative phase noise; and phase-modulating the output from said oscillator with a signal at the modulating frequency selected by a filter means from the output of a frequency-discriminator having an appropriate delay which receives an amplitude-limited version of the oscillator output either before or after said phase-modulating thereof, in a sense and at an amplitude which tends to cancel the additive phase-noise modulation in the oscillator output; whereby the thus phase-modulated output from the oscillator is a frequency-modulated output having reduced additive phase-noise in said band.
Claim 3
Dependent Claim
26 words
A method as claimed in claim 1 wherein said amplitude-limited version of the oscillator output is produced solely by amplitude-limiting the immediate output of the oscillator.
Claim 4
Dependent Claim
46 words
A method as claimed in claim 1 wherein said amplitude-limited version of the oscillator output is produced by amplitude-limiting the immediate output of the oscillator other than sidebands close-in to the instantaneous frequency of the oscillator and, in addition, amplitude-limiting the immediate input to said frequency-discriminator.
Claim 5
Dependent Claim
34 words
A method as claimed in claim 1 wherein the discriminator receives the oscillator output after said phase-modulating thereof and said selected signal is fed back to effect said phase-modulating after relatively high amplification thereof.
Claim 6
Dependent Claim
34 words
A method as claimed in claim 1 wherein the discriminator receives the oscillator output before said phase-modulating thereof and said selected signal is fed forward to effect said phase-modulating after relatively low amplification thereof.
Claim 7
Dependent Claim
55 words
A method as claimed in claim 4 wherein the selected signal is multiplied by an appropriately phase-shifted version of the frequency-modulating signal, and the components of the product at the additive phase-noise frequencies only are selected and multiplied by the non-phase-shifted frequency-modulating signal, the product of said second-mentioned multiplication being applied to effect said phase-modulating.
Claim 8
Dependent Claim
32 words
A method as claimed in claim 4 wherein the selected signal is appropriately phase-shifted and only the resulting components modulated at the additive phase-noise frequencies are applied directly to effect said phase-modulating.
Claim 9
Dependent Claim
82 words
A method as claimed in claim 5, wherein a frequency-modulating pilot-signal is additionally applied to the oscillator to produce a modulation index greater than that of the total phase-noise but less than that of the first-mentioned frequency-modulating signal, and wherein the pilot-signal content of the additive phase-noise-reduced frequency-modulated oscillator output is detected and fed back to control the signal which effects said phase-modulating in a sense to reduce said pilot-signal content and hence the additive phase-noise content in said defined frequency band.
Claim 10
Dependent Claim
17 words
A method as claimed in claim 8 wherein the pilot-signal frequency is outside said defined frequency band.
Claim 11
Dependent Claim
42 words
A method as claimed in claim 1 wherein said additive phase-noise-reduced frequency-modulated output is subsequently phase-modulated with said first-mentioned frequency-modulating signal applied in anti-phase whereby to obtain an output consisting substantially of said given frequency with reduced additive noise in said band.
Claim 12
Dependent Claim
42 words
A method as claimed in claim 1 wherein said additive phase-noise-reduced frequency-modulated output is subsequently filtered to remove said given frequency and all but one of said frequency-modulation sidebands to leave substantially only said one frequency-modulation sideband with reduced additive phase-noise therein.
Claim 13
Dependent Claim
14 words
A method as claimed in claim 1 wherein the oscillator is a voltage-controlled oscillator.
Claim 14
Dependent Claim
181 words
Apparatus for reducing the additive phase-noise in the output from an oscillator of given frequency, in at least one defined frequency band, comprising: an oscillator and means for applying a frequency-modulating signal to the oscillator to produce a frequency-modulation sideband of said given frequency within said band, said signal having a frequency much higher than the highest multiplicative phase-noise frequency in that band and producing a modulation index much greater than the modulation index of the total phase-noise in that band where total phase-noise is defined as additive phase-noise plus multiplicative phase-noise; and a phase-modulator for phase-modulating the output from said oscillator with a signal at the modulating frequency selected by a filter means connected to the output of a frequency-discriminator having an appropriate delay and connected via an amplitude-limiting means to receive the oscillator output either before or after said phase-modulating thereof, in a sense and at an amplitude which tends to cancel the additive phase-noise modulation in the oscillator output; whereby the thus phase-modulated output from the oscillator is a frequency-modulated output having reduced additive phase-noise in said band.
Claim 15
Dependent Claim
181 words
Apparatus for reducing the additive phase-noise in the output from an oscillator of given frequency, in at least one defined frequency band, comprising: an oscillator and means for applying a frequency-modulating signal to the oscillator to produce a frequency-modulation sideband of said given frequency within said band, said signal having a frequency much higher than the highest multiplicative phase-noise frequency in that band and producing a modulation index much greater than the modulation index of the total phase-noise in that band where total phase-noise is defined as additive phase-noise plus multiplicative phase-noise; and a phase-modulator for phase-modulating the output from said oscillator with a signal at the modulating frequency selected by a filter means connected to the output of a frequency-discriminator having an appropriate delay and connected via an amplitude-limiting means to receive the oscillator output either before or after said phase-modulating thereof, in a sense and at an amplitude which tends to cancel the additive phase-noise modulation in the oscillator output; whereby the thus phase-modulated output from the oscillator is a frequency-modulated output having reduced additive phase-noise in said band.
Claim 16
Dependent Claim
21 words
Apparatus as claimed in claim 13 wherein said amplitude-limiting means is connected to amplitude-limit only the immediate output of the oscillator.
Claim 17
Dependent Claim
49 words
Apparatus as claimed in claim 13 wherein said amplitude-limiting means comprises first amplitude-limiting means connected and arranged to amplitude-limit the immediate output of the oscillator other than sidebands close-in to the instantaneous frequency of the oscillator, and second amplitude-limiting means connected to amplitude-limit the immediate input to said frequency-discriminator.
Claim 18
Dependent Claim
41 words
Apparatus as claimed in claim 13 wherein the discriminator is connected to receive the oscillator output after said phase-modulating thereof and said selected signal is fed back to said phase-modulator to effect said phase-modulating via an amplifier of relatively high gain.
Claim 19
Dependent Claim
41 words
Apparatus as claimed in claim 13 wherein the discriminator is connected to receive the oscillator output before said phase-modulating thereof and said selected signal is fed forward to said phase-modulator to effect said phase-modulating via an amplifier of relatively low gain.
Claim 20
Dependent Claim
79 words
Apparatus as claimed in claim 16 wherein the selected signal is fed to a first multiplier which also receives, via a phase-shifter, an appropriately phase-shifted version of the frequency-modulating signal, and the components of the product at the additive phase-noise frequencies only are selected via filter means connected to the first multiplier and fed to a second multiplier which also received the non-phase-shifted frequency-modulating signal, the output of said second-multiplier being fed to said phase-modulator to effect said phase-modulating.
Claim 21
Dependent Claim
41 words
Apparatus as claimed in claim 16 wherein the selected signal from said filter means is fed via an appropriate phase-shifter to said amplifier whereby only the resulting components modulated at the additive phase-noise frequencies are applied directly to effect said phase-modulating.
Claim 22
Dependent Claim
85 words
A method as claimed in claim 17, comprising means for additionally applying a frequency-modulating pilot-signal to the oscillator to produce a modulation index greater than that of the total phase-noise but less than that of the first-mentioned frequency-modulating signal, means for detecting the pilot-signal content of the additive phase-noise-reduced frequency-modulated oscillator output and means for feeding it back to control the signal which effects said phase-modulating in a sense to reduce said pilot-signal content and hence the additive phase-noise content in said defined frequency band.
Claim 23
Dependent Claim
16 words
Apparatus as claimed in claim 20 wherein the pilot-signal frequency is outside said defined frequency band.
Claim 24
Dependent Claim
50 words
Apparatus as claimed in claim 13 wherein said additive phase-noise-reduced frequency-modulated output is fed to a further phase-modulator to which said first-mentioned frequency-modulating signal is fed in anti-phase as a phase-modulating signal whereby to obtain an output consisting substantially of said given frequency with reduced additive noise in said band.
Claim 25
Dependent Claim
47 words
Apparatus as claimed in claim 1 wherein said additive phase-noise-reduced frequency-modulated output is fed to filter means arranged to remove said given frequency and all but one of said frequency-modulation sidebands whereby the filtered output is substantially only said one frequency-modulation sideband with reduced additive phase-noise therein.
Claim 26
Dependent Claim
59 words
Apparatus as claimed in 13 wherein the means for applying the frequency-modulating signal to said oscillator comprises filter means arranged to remove said given frequency and all but one of said frequency-modulation sidebands whereby the filtered output is substantially only said one frequency-modulation sideband with reduced additive phase-noise therein, said frequency-modulating signal being constituted by said frequency-modulation sideband output.
Claim 27
Dependent Claim
13 words
Apparatus as claimed in claim 13 wherein the oscillator is a voltage-controlled oscillator.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-02-18 | 1994-08-20 | 1995-02-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-02-18 | 1998-08-20 | 1999-02-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-02-18 | 2002-08-20 | 2003-02-19 | $7700.00 | Window Closed / Lapsed |