US5832772A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Micropower RF material proximity sensor
Assignee: University of California
•
Filing: 1995-01-27
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Granted: 1998-11-10
•
Expires: 2015-01-27
Abstract
Abstract A level detector or proximity detector for materials capable of sensing through plastic container walls or encapsulating materials is of the sensor. Thus, it can be used in corrosive environments, as well as in a wide variety of applications. An antenna has a characteristic impedance which depends on the materials in proximity to the antenna. An RF oscillator, which includes the antenna and is based on a single transistor in a Colpitt's configuration, produces an oscillating signal. A detector is coupled to the oscillator which signals changes in the oscillating signal caused by changes in the materials in proximity to the antenna. The oscillator is turned on and off at a pulse repetition frequency with a low duty cycle to conserve power. The antenna consists of a straight monopole about one-quarter wavelength long at the nominal frequency of the oscillator. The antenna may be horizontally disposed on a container and very accurately detects the fill level within the container as the material inside the container reaches the level of the antenna.
Inventors
- 👤 Thomas E. McEwan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 08:38
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/28; G01F23/284; G01F23/2845
Claims Analysis
Total Claims: 45
Claim 1
Independent Claim
90 words
An apparatus for detecting a proximity of a material, comprising: an oscillator which oscillates at a nominal frequency and produces an oscillator signal; an antenna coupled to the oscillator which is resonant at the nominal frequency of the oscillator and which has a characteristic impedance which depends on materials in proximity to the antenna; and a detector coupled to the oscillator which detects changes in the oscillator signal as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna.
Claim 2
Independent Claim
90 words
An apparatus for detecting a proximity of a material, comprising: an oscillator which oscillates at a nominal frequency and produces an oscillator signal; an antenna coupled to the oscillator which is resonant at the nominal frequency of the oscillator and which has a characteristic impedance which depends on materials in proximity to the antenna; and a detector coupled to the oscillator which detects changes in the oscillator signal as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna.
Claim 3
Dependent Claim
29 words
The apparatus of claim 1, including circuitry for turning the oscillator on and off at a pulse repetition frequency so that the oscillator produces the oscillator signal in bursts.
Claim 4
Dependent Claim
17 words
The apparatus of claim 2, wherein the oscillator signal has a duty cycle of less than 1%.
Claim 5
Dependent Claim
16 words
The apparatus of claim 1, wherein the detector is responsive to amplitude of the oscillator signal.
Claim 6
Dependent Claim
16 words
The apparatus of claim 1, wherein the oscillator has a frequency of greater than 100 MHz.
Claim 7
Dependent Claim
16 words
The apparatus of claim 1, wherein the oscillator has a frequency of greater than 1 GHz.
Claim 8
Dependent Claim
28 words
The apparatus of claim 1, wherein the oscillator has a nominal frequency, and the antenna comprises a straight monopole about one quarter wavelength long at the nominal frequency.
Claim 9
Dependent Claim
37 words
The apparatus of claim 1, wherein the oscillator comprises a bipolar device, having a base, an emitter and a collector, and having a base-emitter junction which rectifies resonant signals at its collector to produce the oscillator signal.
Claim 10
Dependent Claim
16 words
The apparatus of claim 8, wherein the detector is responsive to amplitude of the oscillator signal.
Claim 11
Dependent Claim
46 words
The apparatus of claim 8, including circuitry, coupled to the emitter of the bipolar device, for turning the oscillator on and off at a pulse repetition frequency so that the oscillator produces the oscillator signal in bursts, and with a duty cycle of less than 1%.
Claim 12
Dependent Claim
11 words
The apparatus of claim 1, including a battery driven power supply.
Claim 13
Independent Claim
98 words
An apparatus for detecting a level of material in a container, comprising: an oscillator which oscillates at a nominal frequency and produces an oscillator signal; an antenna coupled to the oscillator which is resonant at the nominal frequency of the oscillator and which has a characteristic impedance which depends on proximity of the material in the container to the antenna; and a detector coupled to the oscillator which detects changes in the oscillator signal as a result of changes in the characteristic impedance of the antenna caused by proximity to the antenna of the material in the container.
Claim 14
Independent Claim
98 words
An apparatus for detecting a level of material in a container, comprising: an oscillator which oscillates at a nominal frequency and produces an oscillator signal; an antenna coupled to the oscillator which is resonant at the nominal frequency of the oscillator and which has a characteristic impedance which depends on proximity of the material in the container to the antenna; and a detector coupled to the oscillator which detects changes in the oscillator signal as a result of changes in the characteristic impedance of the antenna caused by proximity to the antenna of the material in the container.
Claim 15
Dependent Claim
29 words
The apparatus of claim 12, including circuitry for turning the oscillator on and off at a pulse repetition frequency so that the oscillator produces the oscillator signal in bursts.
Claim 16
Dependent Claim
17 words
The apparatus of claim 13, wherein the oscillator signal has a duty cycle of less than 1%.
Claim 17
Dependent Claim
16 words
The apparatus of claim 12, wherein the detector is responsive to amplitude of the oscillator signal.
Claim 18
Dependent Claim
16 words
The apparatus of claim 12, wherein the oscillator has a frequency of greater than 100 MHz.
Claim 19
Dependent Claim
16 words
The apparatus of claim 12, wherein the oscillator has a frequency of greater than 1 GHz.
Claim 20
Dependent Claim
28 words
The apparatus of claim 12, wherein the oscillator has a nominal frequency, and the antenna comprises a straight monopole about one quarter wavelength long at the nominal frequency.
Claim 21
Dependent Claim
37 words
The apparatus of claim 12, wherein the oscillator comprises a bipolar device, having a base, an emitter and a collector, and having a base-emitter junction which rectifies resonant signals at its collector to produce the oscillator signal.
Claim 22
Dependent Claim
16 words
The apparatus of claim 19, wherein the detector is responsive to amplitude of the oscillator signal.
Claim 23
Dependent Claim
46 words
The apparatus of claim 20, including circuitry, coupled to the emitter of the bipolar device, for turning the oscillator on and off at a pulse repetition frequency so that the oscillator produces the oscillator signal in bursts, and with a duty cycle of less than 1%.
Claim 24
Dependent Claim
21 words
The apparatus of claim 12, including an encapsulation on the antenna to isolate the antenna from corrosive effects of the material.
Claim 25
Dependent Claim
19 words
The apparatus of claim 12, wherein the antenna is mounted on the container at a level to be monitored.
Claim 26
Dependent Claim
23 words
The apparatus of claim 12, wherein the antenna is mounted on an outside surface of the container at a level to be monitored.
Claim 27
Dependent Claim
11 words
The apparatus of claim 12, including a battery driven power supply.
Claim 28
Independent Claim
159 words
An apparatus for detecting a proximity of a material, comprising: an antenna which is resonant at a nominal frequency and has a characteristic impedance which depends on proximity to the antenna of the material; a transistor having a first terminal coupled to the antenna to provide theretogether a radio frequency resonant circuit which oscillates at the nominal frequency at which the antenna is resonant with an amplitude dependent on the characteristic impedance of the antenna, a second terminal receiving a bias potential and a third terminal; a detector coupled to the transistor which detects changes in the oscillation of the resonant circuit as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna; and a control circuit coupled to the third terminal of the transistor which turns the transistor on and off with a duty cycle to produce a sequence of bursts of oscillations at the nominal frequency.
Claim 29
Independent Claim
159 words
An apparatus for detecting a proximity of a material, comprising: an antenna which is resonant at a nominal frequency and has a characteristic impedance which depends on proximity to the antenna of the material; a transistor having a first terminal coupled to the antenna to provide theretogether a radio frequency resonant circuit which oscillates at the nominal frequency at which the antenna is resonant with an amplitude dependent on the characteristic impedance of the antenna, a second terminal receiving a bias potential and a third terminal; a detector coupled to the transistor which detects changes in the oscillation of the resonant circuit as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna; and a control circuit coupled to the third terminal of the transistor which turns the transistor on and off with a duty cycle to produce a sequence of bursts of oscillations at the nominal frequency.
Claim 30
Dependent Claim
35 words
The apparatus of claim 26, wherein the detector comprises a threshold detector coupled to the third terminal of the transistor which indicates when the amplitude of the bursts of oscillations decreases by a threshold amount.
Claim 31
Dependent Claim
58 words
The apparatus of claim 26, wherein the duty cycle of the control circuit is less than 1%, and the detector comprises a pulse stretching circuit coupled to the third terminal of the transistor, and a threshold detector coupled to the pulse stretching circuit which indicates when the amplitude of the bursts of oscillations decreases by a threshold amount.
Claim 32
Dependent Claim
36 words
The apparatus of claim 28, wherein the transistor comprises a bipolar transistor, and the first terminal is the collector, the second terminal is the base and the third terminal is the emitter of the bipolar transistor.
Claim 33
Dependent Claim
14 words
The apparatus of claim 26, wherein the nominal frequency is greater than 100 MHz.
Claim 34
Dependent Claim
14 words
The apparatus of claim 26, wherein the nominal frequency is greater than 1 GHz.
Claim 35
Dependent Claim
19 words
The apparatus of claim 26, wherein the nominal frequency is in a range from 300 MHz to 5 GHz.
Claim 36
Dependent Claim
21 words
The apparatus of claim 26, including an encapsulation on the antenna to isolate the antenna from corrosive effects of the material.
Claim 37
Dependent Claim
33 words
The apparatus of claim 26, wherein the antenna is mounted on an exterior wall of a container, and disposed horizontally to detect whether the container is filled to a level near the antenna.
Claim 38
Independent Claim
77 words
A method for detecting proximity of a material to a particular location, comprising: placing an antenna having a characteristic impedance which depends on materials in proximity to the antenna in the particular location; establishing a resonating signal at a nominal frequency in the antenna; and detecting changes in the resonating signal at the nominal frequency as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna.
Claim 39
Independent Claim
77 words
A method for detecting proximity of a material to a particular location, comprising: placing an antenna having a characteristic impedance which depends on materials in proximity to the antenna in the particular location; establishing a resonating signal at a nominal frequency in the antenna; and detecting changes in the resonating signal at the nominal frequency as a result of changes in the characteristic impedance of the antenna caused by changes in materials in proximity to the antenna.
Claim 40
Dependent Claim
18 words
The method of claim 35, including turning the resonating signal on and off at a pulse repetition frequency.
Claim 41
Dependent Claim
17 words
The method of claim 36, wherein the resonating signal has a duty cycle of less than 1%.
Claim 42
Dependent Claim
18 words
The method of claim 35, wherein the step of detecting is responsive to amplitude of the resonating signal.
Claim 43
Dependent Claim
17 words
The method of claim 35, wherein the resonating signal has a frequency of greater than 100 MHz.
Claim 44
Dependent Claim
17 words
The method of claim 35, wherein the resonating signal has a frequency of greater than 1 GHz.
Claim 45
Dependent Claim
29 words
The method of claim 35, wherein the resonating signal has a nominal frequency, and the antenna comprises a straight monopole about one quarter wavelength long at the nominal frequency.
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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) | 2001-11-09 | 2002-05-11 | 2002-11-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2005-11-09 | 2006-05-11 | 2006-11-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2009-11-09 | 2010-05-11 | 2010-11-10 | $7700.00 | Window Closed / Lapsed |