US3820035A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Microwave automatic frequency control circuit
Assignee: Varian Medical Systems Inc
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Filing: 1973-02-26
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Granted: 1974-06-25
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Expires: 1993-02-26
Abstract
Abstract The frequency of a microwave source, such as a magnetron of klystron, is locked to the variable frequency of a resonant load. A sample of the microwave power incident on the load is derived from the magnetron and compared in a phase comparator with a sample of the microwave energy reflected from the resonant load to derive an error signal representative of the frequency departure of the frequency of the microwave source from the resonant frequency of the load. The error signal is utilized for driving a tuner for tuning the frequency of the microwave source to the frequency of the load. In a preferred embodiment the phase comparator comprises a three db four port microwave hybrid coupler having a pair of outputs, the outputs of which are rectified by microwave diodes and subtracted to produce the error signal. The length of the transmission path from the microwave source to the phase comparator circuit is made longer than the length of the transmission path from the microwave source to the load and back to the phase comparator circuit in order to skew the frequency discriminator output characteristic of the phase comparator in order to eliminate ambiguities in the sense of the error signal at frequencies far removed from the resonant frequency of the load.
Inventors
- 👤 G Meddaugh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 22:23
CPC Classifications
H; H03; H03L; H03L7/00; H03L7/02; H03L7/04
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
231 words
In a microwave circuit of the type for locking the frequency of a microwave source to the resonant frequency of a resonant load; load means resonant at a microwave frequency for producing electromagnetic interaction between the resonant fields of said resonant load and a load medium to be disposed in energy exchanging relation with said load means; microwave source means for producing microwave energy of a microwave source frequency; tuner means for tuning the source frequency of said microwave source means; means for interconnecting said load means and said source means for coupling microwave energy from said source means to said load means for exciting microwave resonance of said resonant load means; means for comparing the phase of the microwave energy supplied from said source means to said load means with the phase of microwave energy reflected from said resonant load back toward said source means to derive an error output the sense of which is determinative of the sense of departure, if any, of the microwave frequency of said source means from the microwave resonant frequency of said load means; and means for applying said error output to said tuner means for causing said tuner means to tune the frequency of said source means to produce a coincidence between the resonant frequency of said load and the frequency of the microwave energy supplied to said load from said source means.
Claim 2
Dependent Claim
231 words
In a microwave circuit of the type for locking the frequency of a microwave source to the resonant frequency of a resonant load; load means resonant at a microwave frequency for producing electromagnetic interaction between the resonant fields of said resonant load and a load medium to be disposed in energy exchanging relation with said load means; microwave source means for producing microwave energy of a microwave source frequency; tuner means for tuning the source frequency of said microwave source means; means for interconnecting said load means and said source means for coupling microwave energy from said source means to said load means for exciting microwave resonance of said resonant load means; means for comparing the phase of the microwave energy supplied from said source means to said load means with the phase of microwave energy reflected from said resonant load back toward said source means to derive an error output the sense of which is determinative of the sense of departure, if any, of the microwave frequency of said source means from the microwave resonant frequency of said load means; and means for applying said error output to said tuner means for causing said tuner means to tune the frequency of said source means to produce a coincidence between the resonant frequency of said load and the frequency of the microwave energy supplied to said load from said source means.
Claim 3
Dependent Claim
208 words
The apparatus of claim 1 wherein said phase comparing means includes a microwave hybrid coupler means having; first and second input ports and first and second output ports, means for connecting said hybrid coupler means to receive a sample of the microwave energy applied to said load means at said first input port and to receive The load-reflected microwave energy at said second input port, means within said hybrid coupler for splitting the load-applied energy derived from said first input port into first and second incident signal components, means for shifting the phase of said second incident signal component by 90* relative to the phase of said first incident signal component, means for supplying said first incident signal component to said first output port and said second 90* phase shifted incident signal component to said second output port, means for splitting the reflected wave energy derived from said second input port into first and second reflected signal components, means for shifting the phase of said second reflected signal component by 90* relative to the phase of said first reflected signal component, means for supplying said 90* phase shifted second reflected signal component to said first output port and said first reflected signal component to said second output port.
Claim 4
Dependent Claim
47 words
The apparatus of claim 2 including first and second diode means connected to receive the output microwave energy derived from said first and second output ports, respectively, of said hybrid coupler means for rectifying said respective output signals to derive first and second rectified output signals, respectively.
Claim 5
Dependent Claim
26 words
The apparatus of claim 3 including means for comparing the sense and magnitude of said first and second rectified output signals to derive said error output.
Claim 6
Dependent Claim
42 words
The apparatus of claim 1 wherein said resonant load means comprises a resonant wave supportive structure, said structure being apertured for passage of a load medium therethrough in microwave energy exchanging relation with the microwave energy within said resonant wave supportive structure.
Claim 7
Dependent Claim
67 words
The apparatus of claim 5 wherein said resonant wave supportive structure comprises a coupled cavity microwave circuit, and including means for forming and projecting a stream of electrons as said load medium through said coupled cavity circuit for cumulative electromagnetic interaction with the electromagnetic microwave field of said microwave structure for accelerating electrons of said electron stream to an energy in excess of 0.5 million electron volts.
Claim 8
Dependent Claim
95 words
The apparatus of claim 1 wherein the electrical length of transmission path traversed by said phase compared incident microwave energy supplied directly from said microwave source means to said phase comparator means is greater than the electrical length of transmission path traversed by said phase compared reflected microwave energy in traveling from said microwave source means to said resonant load and thence to said phase comparator means, whereby the frequency discriminating characteristic of said error output is skewed to provide an unambiguous error output over a relative wide tunable range of said microwave source means.
Claim 9
Dependent Claim
58 words
The apparatus of claim 7 wherein the length of the transmission path for said phase compared incident wave energy exceeds the length of transmission path for the phase compared reflected wave energy by less than the length which will produce the first 180* of relative phase shift over the expected tuning range of said tunable microwave source means.
Claim 10
Dependent Claim
67 words
The apparatus of claim 7 wherein the length L by which the direct incident energy transmission path to said comparator means exceeds the reflected energy transmission path to said comparator means satisfies the relation: L Delta f/v < 1/2 where Delta f is the usable tuning range of said microwave source, and v is the velocity of wave energy propagation along said excess transmission path length L.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-24 | 1977-12-24 | 1978-06-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-24 | 1981-12-24 | 1982-06-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-24 | 1985-12-24 | 1986-06-25 | $7700.00 | Window Closed / Lapsed |