Dielectric-loaded surface-condition sensor and method
First Claim
1. A sensor for use in identifying any one of air, water and ice and determining a thickness ti of said ice, comprising:
- an antenna having an input port and an output aperture, said antenna configured to have an aperture impedance over a predetermined microwave frequency range; and
a dielectric member having an outer surface and an inner surface that is spaced from said outer surface by a dielectric thickness td ;
wherein;
said dielectric member has a refractive index n in a predetermined microwave frequency range;
said dielectric thickness td is substantially equal to (mc)/(2nfr) in which m is a predetermined integer, c is the speed of light and fr is a frequency in said microwave frequency range; and
said dielectric member is arranged with said inner surface between said antenna and said outer surface and with said inner surface positioned across said aperture;
said sensor returning a composite, microwave reflection signal in response to an input microwave signal that is swept over said frequency range and coupled to said input port, wherein said composite, microwave reflection signal includes reflections from said inner and outer surfaces and contains information for identifying said any one of air, water and ice on said outer surface and for determining said thickness ti.
3 Assignments
0 Petitions
Accused Products
Abstract
A dielectric-loaded, microwave sensor which can detect dielectric coatings, e.g., air, water and ice, on a road surface. The sensor includes an antenna having an aperture and also includes a dielectric member with a lower surface and an upper surface. The dielectric member is arranged with its lower surface across the antenna aperture and the sensor is embedded in a road with the dielectric member'"'"'s upper surface coplanar with the road'"'"'s surface. An antenna beam, which is incident upon the dielectric member, generates a return microwave signal which is the composite of microwave reflections from the dielectric member'"'"'s inner and outer surfaces. Air, water and ice can be uniquely identified by the absence or presence of an amplitude minimum at predetermined frequencies of the return microwave signal. The thickness of an ice coating is determined by observation of the frequency of the amplitude minimum.
54 Citations
28 Claims
-
1. A sensor for use in identifying any one of air, water and ice and determining a thickness ti of said ice, comprising:
-
an antenna having an input port and an output aperture, said antenna configured to have an aperture impedance over a predetermined microwave frequency range; and a dielectric member having an outer surface and an inner surface that is spaced from said outer surface by a dielectric thickness td ; wherein; said dielectric member has a refractive index n in a predetermined microwave frequency range; said dielectric thickness td is substantially equal to (mc)/(2nfr) in which m is a predetermined integer, c is the speed of light and fr is a frequency in said microwave frequency range; and said dielectric member is arranged with said inner surface between said antenna and said outer surface and with said inner surface positioned across said aperture; said sensor returning a composite, microwave reflection signal in response to an input microwave signal that is swept over said frequency range and coupled to said input port, wherein said composite, microwave reflection signal includes reflections from said inner and outer surfaces and contains information for identifying said any one of air, water and ice on said outer surface and for determining said thickness ti.
-
-
2. A sensor for use in identifying any one of air, water and ice and determining a thickness ti of said ice, comprising:
-
an antenna having an input port and an output aperture, said antenna configured to have an aperture impedance over a predetermined microwave frequency range; and a dielectric member having an outer surface and an inner surface that is spaced from said outer surface by a dielectric thickness td ; wherein; said dielectric member has a refractive index n in a predetermined microwave frequency range; said dielectric thickness td is substantially equal to (mc)/(2nfr) in which m is a predetermined integer, c is the speed of light and fr is a frequency in said microwave frequency range; and said dielectric member is arranged with said inner surface between said antenna and said outer surface and with said inner surface positioned across said aperture; said sensor returning a composite, microwave reflection signal in response to an input microwave signal that is swept over said frequency range and coupled to said input port, wherein said composite, microwave reflection signal includes reflections from said inner and outer surfaces and contains information for identifying said any one of air, water and ice on said outer surface and for determining said thickness ti, wherein said refractive index n is substantially equal to the refractive index of ice in said predetermined microwave frequency range. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A sensor for use in identifying an unknown dielectric, comprising:
-
an antenna having an input port and an output aperture, said antenna configured to have an aperture impedance over a predetermined microwave frequency range; and a dielectric member having an outer surface and an inner surface that is spaced from said outer surface by a dielectric thickness td ; wherein; said dielectric member has a refractive index n in a predetermined microwave frequency range; said dielectric thickness td is substantially equal to (mc)/(2nfr) in which m is a predetermined integer, c is the speed of light and fr is a frequency in said microwave frequency range; and said dielectric member is arranged with said inner surface between said antenna and said outer surface and with said inner surface positioned across said aperture; said sensor returning a composite, microwave reflection signal in response to an input microwave signal that is swept over said frequency range and coupled to said input port wherein said composite, microwave reflection signal includes reflections from said outer and inner surfaces and contains information for identifying said unknown dielectric. - View Dependent Claims (12)
-
-
13. A sensor system for identifying any one of air, water and ice and determining a thickness ti of said ice, comprising:
-
an antenna having an input port and an output aperture, said antenna configured to have an aperture impedance over a predetermined microwave frequency range; a dielectric member having an outer surface and an inner surface that is spaced from said outer surface by a dielectric thickness td ; a swept-frequency microwave generator; and a microwave, scalar spectrum analyzer; wherein; said dielectric member has a refractive index n in a predetermined microwave frequency range; said dielectric thickness td is substantially equal to (mc)/(2nfr) in which m is a predetermined integer, c is the speed of light and fr is a frequency in said microwave frequency range; said dielectric member is arranged with said inner surface between said antenna and said outer surface and with said inner surface positioned across said aperture; said microwave generator is coupled to said input port for exciting said antenna and directing a swept-frequency antenna beam at said lower surface; and said scalar spectrum analyzer is coupled to said input port for receiving a composite, microwave reflection signal which includes reflections of said swept-frequency antenna beam from said inner surface and said outer surface, and for observing the absence or presence of amplitude minima at predetermined frequencies of said reflection signal which identifies said any one of air, water and ice on said outer surface and said thickness ti. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21)
-
-
22. A method for sensing the presence of any one of air, water and ice and determining a thickness ti of said ice, said method comprising the steps of:
-
providing a reference dielectric medium which has a refractive index n in a predetermined microwave frequency range, said reference dielectric medium also provided with an outer surface and an inner surface that is spaced from said outer surface by a reference thickness tr ; exposing said outer surface to a coating of any unknown one of air, water and ice; directing a frequency-swept antenna beam upon said inner surface to generate a return microwave signal which includes microwave reflections from said outer and inner surfaces; identifying said unknown one of air, water or ice on said outer surface by observation of the absence or presence of an amplitude minimum at predetermined frequencies of said return microwave signal; and determining, in response to said identifying step, said ice thickness by observation of the frequency of said amplitude minimum.
-
-
23. A method for sensing the presence of any one of air, water and ice and determining a thickness ti of said ice, said method comprising the steps of;
-
providing a reference dielectric medium which has a refractive index n in a predetermined microwave frequency range, said reference dielectric medium also provided with an outer surface and an inner surface that is spaced from said outer surface by a reference thickness tr ; exposing said outer surface to a coating of any unknown one of air, water and ice; directing a frequency-swept antenna beam upon said inner surface to generate a return microwave signal which includes microwave reflections from said outer and inner surfaces; identifying said unknown one of air, water or ice on said outer surface by observation of the absence or presence of an amplitude minimum at predetermined frequencies of said return microwave signal, and determining, in response to said identifying step, said ice thickness by observation of the frequency of said amplitude minimum, wherein said providing step includes the step of selecting said refractive index n to be substantially equal to the refractive index of ice in said microwave frequency range.
-
-
24. A method for sensing the presence of any one of air, water and ice and determining a thickness ti of said ice, said method comprising the steps of:
-
providing a reference dielectric medium which has a refractive index n in a predetermined microwave frequency range, said reference dielectric medium also provided with an outer surface and an inner surface that is spaced from said outer surface by a reference thickness tr ; exposing said outer surface to a coating of any unknown one of air, water and ice; directing a frequency-swept antenna beam upon said inner surface to generate a return microwave signal which includes microwave reflections from said outer and inner surfaces; identifying said unknown one of air, water or ice on said outer surface by observation of the absence or presence of an amplitude minimum at predetermined frequencies of said return microwave signal, and determining, in response to said identifying step, said ice thickness by observation of the frequency of said amplitude minimum, and wherein said identifying step includes the steps of; detecting said return microwave signal to produce a detected amplitude response; and correlating said amplitude minimum in said detected amplitude response with frequencies of said frequency-swept antenna beam.
-
-
25. A method for sensing the presence of any one of air, water and ice and determining a thickness ti of said ice, said method comprising the steps of:
-
providing a reference dielectric medium which has a refractive index n in a predetermined microwave frequency range, said reference dielectric medium also provided with an outer surface and an inner surface that is spaced from said outer surface by a reference thickness tr ; exposing said outer surface to a coating of any unknown one of air, water and ice; directing a frequency-swept antenna beam upon said inner surface to generate a return microwave signal which includes microwave reflections from said outer and inner surfaces; identifying said unknown one of air water or ice on said outer surface by observation of the absence or presence of an amplitude minimum at predetermined frequencies of said return microwave signal, and determining in response to said identifying step, said ice thickness by observation of the frequency of said amplitude minimum, and wherein said identifying step includes the steps of; detecting said return microwave signal to produce a detected amplitude response; comparing said detected amplitude response with a plurality of predetermined amplitude responses which are each representative of a different one of air, water and various thicknesses of ice; and selecting one of said predetermined amplitude responses which best matches said detected amplitude response.
-
-
26. A method for sensing the presence of any one of air, water and ice and determining a thickness ti of said ice, said method comprising the steps of:
-
providing a reference dielectric medium which has a refractive index n in a predetermined microwave frequency range, said reference dielectric medium also provided with an outer surface and an inner surface that is spaced from said outer surface by a reference thickness tr ; exposing said outer surface to a coating of any unknown one of air, water and ice; directing a frequency-swept antenna beam upon said inner surface to generate a return microwave signal which includes microwave reflections from said outer and inner surfaces; identifying said unknown one of air, water or ice on said outer surface by observation of the absence or presence of an amplitude minimum at predetermined frequencies of said return microwave signal, and determining, in response to said identifying step, said ice thickness by observation of the frequency of said amplitude minimum, and wherein said determining step includes the steps of; measuring a frequency delta between an observed amplitude minimum and a calibrated amplitude minimum; and establishing said ice thickness from said frequency delta.
-
-
27. A method for sensing the presence of any one of air, water and ice and determining a thickness ti of said ice, said method comprising the steps of:
-
providing a reference dielectric medium which has a refractive index n in a predetermined microwave frequency range, said reference electric medium also provided with an outer surface and an inner surface that is spaced from said outer surface by a reference thickness tr ; exposing said outer surface to a coating of any unknown one of air, water and ice; directing a frequency-swept antenna beam upon said inner surface to generate a return microwave signal which includes microwave reflections from said outer and inner surfaces; identifying said unknown one of air, water or ice on said outer surface by observation of the absence or presence of an amplitude minimum at predetermined frequencies of said return microwave signal, and determining, in response to said identifying step, said ice thickness by observation of the frequency of said amplitude minimum, and wherein said identifying step includes the steps of; responding to the absence of said amplitude minimum with the identification of water; responding to the presence of an amplitude minimum at a frequency of substantially (mc)/(2ntr), in which m is a predetermined integer and c is the speed of light, with the identification of air; and responding to the presence of an amplitude minimum at a frequency fi which is different from (mc)/(2ntdm) with the identification of ice; and wherein said determining step includes the step of calculating said ice thickness ti as ti ={(mc)/(2nfi)}-tr.
-
-
28. A method for sensing the refractive index and thickness tu of unknown dielectric, said method comprising the steps of:
-
providing a reference dielectric medium which has a reference refractive index nr in a predetermined microwave frequency range, said reference dielectric medium also having an outer surface and an inner surface that is spaced from said outer surface by a reference thickness tr ; exposing said outer surface to a coating of said unknown dielectric; directing a frequency-swept antenna beam upon said inner surface to generate a return microwave signal which includes microwave reflections from said outer and inner surfaces; identifying the refractive index nu of said unknown dielectric by observation of the intensity of said return microwave signal; detecting the frequency separation Δ
f between a pair of amplitude minima in said return microwave signal; anddetermining, in response to said detecting step, said thickness tu in accordance with the equation tu =c/(2nu Δ
f).
-
Specification