US4829233A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Microwave probe
Assignee: United Kingdom Atomic Energy Authority
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Filing: 1988-03-04
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Granted: 1989-05-09
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Expires: 2008-03-04
Abstract
Abstract A microwave probe for determining properties of a fluid medium, and particularly for separating measuring dielectric constant and dielectric loss, comprises an insulating substrate metallized on one face, an electrically isolated, ring-shaped, resonant element defined on the opposite face, and shielded means to couple microwaves into and from the element such that the element can undergo a resonance. The resonant frequency depends on the dielectric constant of an adjacent medium, while the Q-factor of the resonance depends on the dielectric loss of the medium. In one method of operation microwaves are coupled into the element to force an oscillation, and the driving frquency is varied to obtain a resonance.
Inventors
- 👤 Michael A. Flemming
- 👤 Graham N. Plested
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 20:59
CPC Classifications
G; G01; G01N; G01N22/00
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
121 words
A fluid-characterising apparatus comprising a probe immersible in a fluid to be characterised, the probe comprising an electrically insulating substrate, with a substantially continuous conducting layer, and an electrically isolated, ring-shaped resonant element separated by the substrate from the conducting layer, shielded means for causing microwaves to propagate in the element, and shielded means for sensing microwaves so propagating, the causing and sensing means being coupled to the element sufficiently weakly to have negligible effect on the natural resonance of the element, and such that if the probe is immersed in the fluid then part of the electromagnetic fields due to microwaves propagating in the element extends into the fluid so that the fluid affects the resonant response of the element.
Claim 2
Dependent Claim
121 words
A fluid-characterising apparatus comprising a probe immersible in a fluid to be characterised, the probe comprising an electrically insulating substrate, with a substantially continuous conducting layer, and an electrically isolated, ring-shaped resonant element separated by the substrate from the conducting layer, shielded means for causing microwaves to propagate in the element, and shielded means for sensing microwaves so propagating, the causing and sensing means being coupled to the element sufficiently weakly to have negligible effect on the natural resonance of the element, and such that if the probe is immersed in the fluid then part of the electromagnetic fields due to microwaves propagating in the element extends into the fluid so that the fluid affects the resonant response of the element.
Claim 3
Dependent Claim
50 words
An apparatus as claimed in claim 1 wherein the causing means and the sensing means each comprises a shielded conductor extending normal to the conducting layer and terminating at an aperture in the conducting layer adjacent to a portion of the resonant element but separated from it by the substrate.
Claim 4
Dependent Claim
42 words
An apparatus as claimed in claim 2 wherein the apparatus also comprises a variable frequency microwave generator, and means for determining from the sensed microwaves a resonant frequency and a Q-factor of a resonance of the probe, and hence characterising the fluid.
Claim 5
Dependent Claim
40 words
An apparatus as claimed in claim 2 wherein the apparatus also comprises a frequency-modulated microwave generator, and means for determining from the sensed microwaves the mean amplitude, and the amplitude of the modulation in amplitude, and hence characterising the fluid.
Claim 6
Dependent Claim
71 words
An apparatus as claimed in claim 2 wherein the probe also comprises a varactor connected to the resonant element, the apparatus comprises a constant frequency microwave source, means for applying an alternating electrical signal to the varactor so as to modulate the resonant frequency of the element, and means for determining from the sensed microwaves the mean amplitude, and the amplitude of the modulation in amplitude, and hence characterising the fluid.
Claim 7
Dependent Claim
42 words
An apparatus as claimed in claim 5 wherein the probe comprises two varactors each connected to the conducting layer, and connected to respective positions on the resonant element at which, at a desired frequency of operation, there are antinodes of electric field.
Claim 8
Independent Claim
122 words
A method of characterising a fluid comprising the operations of immersing a probe in fluid, the probe comprising an electrically insulating substrate, with a substantially continuous conducting layer, and an electrically isolated, ring-shaped resonant element separated by the substrate from the conducting layer, shielded means for causing microwaves to propagate in the element, and shielded means for sensing microwaves so propagating, thecausing and sensing means being coupled to the element sufficiently weakly to have negligible effect on the natural resonance of the element, such that part of the electromagnetic fields due to any microwaves propagating in the element extends into the fluid, causing microwaves to propagate in the element, sensing the microwaves so propagating, and from the sensed microwaves characterising the fluid.
Claim 9
Independent Claim
122 words
A method of characterising a fluid comprising the operations of immersing a probe in fluid, the probe comprising an electrically insulating substrate, with a substantially continuous conducting layer, and an electrically isolated, ring-shaped resonant element separated by the substrate from the conducting layer, shielded means for causing microwaves to propagate in the element, and shielded means for sensing microwaves so propagating, thecausing and sensing means being coupled to the element sufficiently weakly to have negligible effect on the natural resonance of the element, such that part of the electromagnetic fields due to any microwaves propagating in the element extends into the fluid, causing microwaves to propagate in the element, sensing the microwaves so propagating, and from the sensed microwaves characterising the fluid.
Claim 10
Dependent Claim
48 words
A method as claimed in claim 7 comprising the operations of causing microwaves of a plurality of different frequencies near to a resonant frequency to propagate in the element, determining from the sensed microwaves the resonant frequency and the Q-factor of the resonance, and hence characterising the fluid.
Claim 11
Dependent Claim
53 words
A method as claimed in claim 7 comprising the operations of causing microwaves of a frequency near to a resonant frequency to propagate in the element, modulating the frequency of the microwaves, determining from the sensed microwaves the mean amplitude, and the amplitude of the modulation in amplitude, and hence characterising the fluid.
Claim 12
Dependent Claim
60 words
A method as claimed in claim 7 wherein the probe also comprises a varactor connected to the resonant element, the method comprising the operations of causing microwaves of a constant frequency near to a resonant frequency to propagate in the element, and applying an alternating electrical signal to the varactor so as to modulate the resonant frequency of the element.
References Cited (Backward Citations)
US3509456A
Cited
US3581197A
Cited
GB1354474A
Cited
US3750013A
Cited
GB1480629A
Cited
US3942107A
Cited
GB2048492A
Cited
SU842514A1
Cited
EP0082560A2
Cited
SU1322131A1
Cited
GB2129944A
Cited
WO1986006495A1
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-05-08 | 1992-11-07 | 1993-05-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-08 | 1996-11-07 | 1997-05-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-08 | 2000-11-07 | 2001-05-09 | $7700.00 | Window Closed / Lapsed |