US3576460A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Impedance match for periodic microwave circuits and tubes using same
Assignee: Varian Medical Systems Inc
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Filing: 1968-08-08
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Granted: 1971-04-27
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Expires: 1988-08-08
Abstract
Abstract A traveling wave tube amplifier is disclosed. The amplifier includes an electron gun for forming and projecting a stream of electrons over an elongated beam path to a beam collector electrode. A coupled cavity slow wave circuit is arranged along the electron beam path for electromagnetic interaction with the beam to produce an amplified output signal at the downstream end of the circuit. The slow wave circuit is made up of a number of severed slow wave circuit portions. Each of the severed circuit portions includes a plurality of substantially identical coupled cavity resonators forming a main periodic slow wave circuit portion having a passband with at least one bandedge frequency of interest which is capable of producing bandedge oscillations by interaction with the electron stream. Matching circuit portions are provided at opposite ends of the slow wave circuit portions for impedance matching the main periodic circuit section to the load and input transmission lines to prevent trapping of wave energy on the main circuit portion which could otherwise lead to bandedge oscillation. The matching circuit portions comprise at least two periods of the periodic slow wave circuit having essentially the same general physical configuration as that of the main circuit portion. The matching section has a cutoff frequency of interest substantially outside of the passband of the main circuit portion and is dimensioned to have an electrical length at the bandedge frequency of interest of the main periodic section to provide essentially a quarter wave transformer section.
Inventors
- 👤 Ward A Harman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 00:14
CPC Classifications
H; H01; H01J; H01J23/00; H01J23/36; H01J23/16; H01J23/24
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
265 words
In a high frequency electron tube apparatus, means forming a periodic slow wave circuit having a main circuit portion and at least one matching circuit portion at one end of said main circuit portion, means for causing a stream of electrons to pass adjacent said main and matching portions of said slow wave circuit for cumulative electronic interaction with high frequency wave energy traveling on said slow wave circuit to produce a wave of increasing intensity with time traveling on said slow wave circuit, said main portion of said slow wave circuit having a passband with at least one bandedge frequency of interest which is capable of producing bandedge oscillations by interaction with the electron stream, means for extracting output high-frequency wave energy from the tube apparatus at a frequency within the passband of said main circuit portion, the improvement wherein, said matching circuit portion comprises at least two periods of said periodic slow wave circuit, said matching circuit portion having the same general physical configuration as that of said main circuit portion, said matching circuit portion having at the bandedge of interest essentially only one cutoff frequency substantially outside of the passband of said main circuit portion, said matching circuit portion having an overall physical length which is defined by the relationship where, n is any integer value excluding zero, and lambda g is the physical length of the matching circuit portion which will produce 2 pi radians of phase shift of the wave energy traveling on said matching circuit at the bandedge frequency of said main circuit portion, whereby bandedge oscillations are inhibited.
Claim 2
Dependent Claim
265 words
In a high frequency electron tube apparatus, means forming a periodic slow wave circuit having a main circuit portion and at least one matching circuit portion at one end of said main circuit portion, means for causing a stream of electrons to pass adjacent said main and matching portions of said slow wave circuit for cumulative electronic interaction with high frequency wave energy traveling on said slow wave circuit to produce a wave of increasing intensity with time traveling on said slow wave circuit, said main portion of said slow wave circuit having a passband with at least one bandedge frequency of interest which is capable of producing bandedge oscillations by interaction with the electron stream, means for extracting output high-frequency wave energy from the tube apparatus at a frequency within the passband of said main circuit portion, the improvement wherein, said matching circuit portion comprises at least two periods of said periodic slow wave circuit, said matching circuit portion having the same general physical configuration as that of said main circuit portion, said matching circuit portion having at the bandedge of interest essentially only one cutoff frequency substantially outside of the passband of said main circuit portion, said matching circuit portion having an overall physical length which is defined by the relationship where, n is any integer value excluding zero, and lambda g is the physical length of the matching circuit portion which will produce 2 pi radians of phase shift of the wave energy traveling on said matching circuit at the bandedge frequency of said main circuit portion, whereby bandedge oscillations are inhibited.
Claim 3
Dependent Claim
42 words
The apparatus of claim 1 wherein said matching circuit portion has a characteristic impedance of a value intermediate the characteristic impedance of said main circuit portion and the characteristic impedance of said means for extracting the high frequency energy from the tube.
Claim 4
Dependent Claim
39 words
The apparatus of claim 1 wherein said slow wave circuit comprises an array of cavity resonators electromagnetically coupled together to form a slow wave circuit, said cavity resonators being centrally apertured for passage of said stream of electrons therethrough.
Claim 5
Dependent Claim
97 words
The apparatus of claim 3 including inductive coupling means forming the predominant electromagnetic coupling between said cavity resonators to form a fundamental backward wave slow wave circuit, said means for causing a stream of electrons to pass adjacent said slow wave circuit including means for projecting the electrons through said apertured coupled cavity array with sufficient velocity to predominately interact with the first space harmonic wave on said slow wave circuit within the passband of said slow wave circuit, whereby forward wave interaction is obtained between wave energy on said slow wave circuit and the electron stReam.
Claim 6
Dependent Claim
135 words
The apparatus of claim 4 wherein said matching portion of said slow wave circuit includes only two coupled cavity resonators, said resonators having a phase shift per cavity at the upper bandedge frequency of the passband of said main circuit portion falling within the range of 3/2 pi to 2 pi radians, and said matching cavities each having a phase shift relative to the phase shift at the same frequency in each of said coupled cavities of said main circuit portion of approximately 45*, whereby the composite relative phase differential between the phase of wave energy in the terminal cavity of the main circuit section and the terminal cavity at the matching circuit portion is approximately 90* to form a quarter wave impedance transformer between said main circuit portion and said wave energy extracting means.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-26 | 1974-10-26 | 1975-04-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-26 | 1978-10-26 | 1979-04-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-26 | 1982-10-26 | 1983-04-27 | $7700.00 | Window Closed / Lapsed |