US3879653A
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Microwave spectrometer employing a bimodal cavity resonator
Assignee: Varian Medical Systems Inc
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Filing: 1974-02-06
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Granted: 1975-04-22
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Expires: 1994-02-06
Abstract
Abstract A pulsed electron paramagnetic resonance spectrometer employs a bimodal sample cavity. Coherent microwave power from a common source is applied to the cavity for exciting and observing resonance of the sample via separate pumping and observing microwave channels. An automatic frequency control circuit locks the frequency of the common source to the resonant frequency of the observing mode of the bimodal cavity. All modulating frequencies, delays, pulse repetition rates, etc. are derived from a master clock. Free induction decay resonance signals are separated from saturation-recovery resonance signals in the observing channel by proper adjustment of the relative phases at a detector crystal in the observing channel of a reference microwave signal, a cross-coupled pump signal, and a signal reflected from the observing cavity mode, and by furthermore adjusting the polarizing magnetic field to the center of a resonance line. The proper phase adjustment yields a dispersion free induction decay signal and an absorption saturation recovery signal. Alternatively or in combination with the first method, saturation recovery signals are separated from the free induction decay signals detected in the observing channel by modulating the observing power level from a nonsaturating microwave power level to a still lower power level at a low modulation frequency. The detected resonance signal is then phase sensitive detected at the modulation frequency to detect the saturation recovery signal to the exclusion of the free induction decay signal.
Inventors
- 👤 James S Hyde
- 👤 Martin A Huisjen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 07:29
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/60
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
217 words
In a microwave spectrometer: cavity resonator means for supporting electromagnetic fields of first and second orthogonal resonant modes of oscillation of said cavity resonator at the same frequency, said cavity resonator means having a common region shared by said first and second orthogonal modes of oscillation, and means for disposing a sample to be analyzed within said shared region of said cavity resonator means; a source of microwave energy at the resonant frequency of said first and second orthogonal modes of oscillation; first means for coupling microwave energy derived from said source of microwave energy to said cavity resonator means for exciting said first resonant mode of oscillation to the substantial exclusion of exciting said second mode of oscillation except for cross coupling of said first and second resonant modes due to resonance of the sample; second means for coupling microwave energy derived from said source of microwave energy, and at the same frequency as coupled to said cavity resonator via said first coupling means, to said cavity resonator means for exciting said second resonant mode of oscillation to the substantial exclusion of exciting said first resonant of oscillation except for cross coupling of said first and second modes due to resonance of the sample; and means for detecting microwave resonance of the sample to be analyzed.
Claim 2
Dependent Claim
217 words
In a microwave spectrometer: cavity resonator means for supporting electromagnetic fields of first and second orthogonal resonant modes of oscillation of said cavity resonator at the same frequency, said cavity resonator means having a common region shared by said first and second orthogonal modes of oscillation, and means for disposing a sample to be analyzed within said shared region of said cavity resonator means; a source of microwave energy at the resonant frequency of said first and second orthogonal modes of oscillation; first means for coupling microwave energy derived from said source of microwave energy to said cavity resonator means for exciting said first resonant mode of oscillation to the substantial exclusion of exciting said second mode of oscillation except for cross coupling of said first and second resonant modes due to resonance of the sample; second means for coupling microwave energy derived from said source of microwave energy, and at the same frequency as coupled to said cavity resonator via said first coupling means, to said cavity resonator means for exciting said second resonant mode of oscillation to the substantial exclusion of exciting said first resonant of oscillation except for cross coupling of said first and second modes due to resonance of the sample; and means for detecting microwave resonance of the sample to be analyzed.
Claim 3
Dependent Claim
217 words
In a microwave spectrometer: cavity resonator means for supporting electromagnetic fields of first and second orthogonal resonant modes of oscillation of said cavity resonator at the same frequency, said cavity resonator means having a common region shared by said first and second orthogonal modes of oscillation, and means for disposing a sample to be analyzed within said shared region of said cavity resonator means; a source of microwave energy at the resonant frequency of said first and second orthogonal modes of oscillation; first means for coupling microwave energy derived from said source of microwave energy to said cavity resonator means for exciting said first resonant mode of oscillation to the substantial exclusion of exciting said second mode of oscillation except for cross coupling of said first and second resonant modes due to resonance of the sample; second means for coupling microwave energy derived from said source of microwave energy, and at the same frequency as coupled to said cavity resonator via said first coupling means, to said cavity resonator means for exciting said second resonant mode of oscillation to the substantial exclusion of exciting said first resonant of oscillation except for cross coupling of said first and second modes due to resonance of the sample; and means for detecting microwave resonance of the sample to be analyzed.
Claim 4
Dependent Claim
217 words
In a microwave spectrometer: cavity resonator means for supporting electromagnetic fields of first and second orthogonal resonant modes of oscillation of said cavity resonator at the same frequency, said cavity resonator means having a common region shared by said first and second orthogonal modes of oscillation, and means for disposing a sample to be analyzed within said shared region of said cavity resonator means; a source of microwave energy at the resonant frequency of said first and second orthogonal modes of oscillation; first means for coupling microwave energy derived from said source of microwave energy to said cavity resonator means for exciting said first resonant mode of oscillation to the substantial exclusion of exciting said second mode of oscillation except for cross coupling of said first and second resonant modes due to resonance of the sample; second means for coupling microwave energy derived from said source of microwave energy, and at the same frequency as coupled to said cavity resonator via said first coupling means, to said cavity resonator means for exciting said second resonant mode of oscillation to the substantial exclusion of exciting said first resonant of oscillation except for cross coupling of said first and second modes due to resonance of the sample; and means for detecting microwave resonance of the sample to be analyzed.
Claim 5
Dependent Claim
43 words
The apparatus of claim 1 including, means for variably adjusting the relative amplitudes of the microwave energy at the same frequency coupled into said first and second orthogonal resonant modes of said cavity resonator means via said first and second microwave coupling means.
Claim 6
Dependent Claim
43 words
The apparatus of claim 1 including, means for variably adjusting the relative phases of the microwave energy at the same frequency Coupled into said first and second orthogonal resonant modes of said cavity resonator means via said first and second microwave coupling means.
Claim 7
Dependent Claim
130 words
The apparatus of claim 1 wherein said first coupling means includes a circulator means having first, second and third ports, said first port of said circulator being connected to receive microwave energy from said microwave source means and to direct said received microwave power out of said second port to said cavity resonator means while directing microwave power in the opposite direction from said resonator means to said circulator and thence to said third port of said circulator means, microwave detector means coupled to receive microwave power coupled out of said third port of said circulator means for detecting same, reference arm means for bypassing microwave power from said microwave source mans around said circulator means to said detector means for providing reference phase microwave energy to said detector means.
Claim 8
Dependent Claim
98 words
The apparatus of claim 1 including means for periodically pulsing the microwave excitation of said second mode of oscillation at a certain pulse repetition frequency to excite a corresponding train of free-induction-decay transient resonances of the sample with successive transient resonances alternating in time displaced relation with successive pulses of the microwave excitation, and means for changing the power level of excitation of said first mode of oscillation of said cavity from a nonsaturating power level to a lower power level, and means for obtaining the difference in the detected resonance signals corresponding to the two power levels.
Claim 9
Dependent Claim
84 words
The apparatus of claim 5 wherein said means for changing the power levels includes, modulator means for modulating the power level of excitation of said first mode of oscillation of said cavity at a certain modulation frequency which is lower in frequency than the certain pulse repetition frequency, and wherein said means for obtaining the difference in the detected resonance signals includes means for synchronously detecting the modulation component at the certain modulation frequency in the resonant signal as detected by said microwave detector.
Claim 10
Dependent Claim
23 words
The apparatus of claim 1 including means for deriving the certain pulse repetition frequency and the certain modulation frequency from a common clock.
Claim 11
Dependent Claim
32 words
The apparatus of claim 1 including means for locking the frequency of said source of microwave energy to the resonant frequency of the first mode of oscillation of said bimodal cavity resonator.
Claim 12
Dependent Claim
69 words
The apparatus of claim 1 including, means for periodically pulsing the microwave excitation of said second mode of oscillation at a certain pulse repetition frequency to excite a corresponding train of free-induction-decay transient resonances of the sample with successive transient resonances alternating in time displaced relation with successive pulses of the microwave excitation, and wherein said microwave detecting means comprises a transient detector for detecting the transient resonance signals.
Claim 13
Dependent Claim
16 words
The apparatus of claim 8 including means for sweeping the intensity of the polarizing magnetic field.
Claim 14
Dependent Claim
144 words
In a method for exciting and detecting electron paramagnetic resonance of a sample under analysis the steps of: disposing a sample under analysis in the shared field region of a bimodal cavity resonator disposed in a polarizing DC magnetic field such bimodal cavity resonator being dimensioned and arranged for supporting first and second orthogonal electromagnetic modes of oscillation at the same frequency such that the sample is permeated by alternating magnetic fields of both modes and the polarizing field in the same shared field region of said resonator, exciting both modes of oscillation of said cavity resonator with microwave energy at the same frequency and derived from a common source for exposing the sample to alternating magnetic fields of both resonant modes of oscillation at the same frequency to excite electron paramagnetic rEsonance of the sample; and detecting electron paramagnetic resonance of the sample.
Claim 15
Dependent Claim
144 words
In a method for exciting and detecting electron paramagnetic resonance of a sample under analysis the steps of: disposing a sample under analysis in the shared field region of a bimodal cavity resonator disposed in a polarizing DC magnetic field such bimodal cavity resonator being dimensioned and arranged for supporting first and second orthogonal electromagnetic modes of oscillation at the same frequency such that the sample is permeated by alternating magnetic fields of both modes and the polarizing field in the same shared field region of said resonator, exciting both modes of oscillation of said cavity resonator with microwave energy at the same frequency and derived from a common source for exposing the sample to alternating magnetic fields of both resonant modes of oscillation at the same frequency to excite electron paramagnetic rEsonance of the sample; and detecting electron paramagnetic resonance of the sample.
Claim 16
Dependent Claim
172 words
The method of claim 11 including the step of, setting the ratio of the frequency of the exciting microwave energy to the intensity of the polarizing magnetic field to the center of an excited electron paramagnetic resonance line of the sample under analysis, and wherein the step of detecting electron paramagnetic resonance of the sample includes the step of, combining in a microwave detector a reference microwave signal derived from the microwave source with a second microwave signal component as coupled from the second mode to the first mode of the bimodal cavity, due to the resonance of the sample, adjusting the relative phase of the reference and said microwave signals to detect the dispersion mode of resonance of the sample as excited by alternating electromagnetic fields of the second mode of oscillation of said cavity resonator; and combining in the microwave detector a third microwave signal derived from the first mode of oscillation of the bimodal cavity resonator as influenced by resonance of the sample for detecting resonance of the sample.
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) | 1978-04-21 | 1978-10-21 | 1979-04-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-21 | 1982-10-21 | 1983-04-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-21 | 1986-10-21 | 1987-04-22 | $7700.00 | Window Closed / Lapsed |