US3784899A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Metal detection system
Assignee: Aerojet Rocketdyne Inc
•
Filing: 1970-02-26
•
Granted: 1974-01-08
•
Expires: 1990-02-26
Abstract
Abstract In accordance with the present disclosure, the probability of the presence of metal in a predetermined region is determined by deriving representations of first and second antenna temperatures, each representative of the strength of received microwave signals of different polarizations. The probability of the presence of metal is determined by ascertaining the existance of a change in the antenna temperature of one polarization which is not coincident, in time, with a change in the antenna temperature of the other polarization. One method for ascertaining the probability of the presence of metal resides in deriving a representation of the average of the first and second antenna temperatures and a representation of the difference of the first and second antenna temperatures. A ratio is obtained by dividing the representation of the average of the first and second antenna temperatures by the representation of the difference between the first and second antenna temperatures to determine a representation of the probability of the presence of metal. One feature of the present invention resides in the provision of analog computer means for carrying out the process in accordance with the present invention.
Inventors
- 👤 G Chalfin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 04:41
CPC Classifications
G; G01; G01V; G01V8/00; G01V8/005
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
121 words
A method of determining the probability of the presence of metal in a predetermined region, said method comprising the steps of: a. deriving a representation of a first temperature derived by receipt of radiation of a first polarization from said region, b. deriving a representation of a second temperature derived by receipt of radiation of a second polarization from said region, c. deriving a representation of the average of said first and second temperatures, d. deriving a representation of the difference between said first and second temperatures, and e. dividing a predetermined change in the representation of the average of the first and second temperatures by a predetermined change in the representation of the difference between the first and second temperatures.
Claim 2
Independent Claim
121 words
A method of determining the probability of the presence of metal in a predetermined region, said method comprising the steps of: a. deriving a representation of a first temperature derived by receipt of radiation of a first polarization from said region, b. deriving a representation of a second temperature derived by receipt of radiation of a second polarization from said region, c. deriving a representation of the average of said first and second temperatures, d. deriving a representation of the difference between said first and second temperatures, and e. dividing a predetermined change in the representation of the average of the first and second temperatures by a predetermined change in the representation of the difference between the first and second temperatures.
Claim 3
Dependent Claim
82 words
A method according to claim 1 further including deriving a representation of a background temperature, said representation of the average of said first and second temperatures being obtained by subtracting the representation of said background temperature from the average of the representations of said first and second temperatures, and said representation of the difference between said first and second temperatures being obtained by subtracting the representation of said background temperature from the difference between the representations of the first and second temperatures.
Claim 4
Dependent Claim
104 words
A method according to claim 2 further including setting the representation of the average of said first and second temperatures to zero when the result of the subtraction of the representation of the background temperature from the average of the representations of said first and second temperatures fails to exceed a first predetermined level, and setting the representation of the difference between said first and second temperatures to zero when the result of the subtraction of the representation of the representation of the background temperatures from the difference between the representations if the first and second temperatures fails to exceed a second predetermined level.
Claim 5
Dependent Claim
27 words
A method according to claim 1 wherein the radiation of a first polarization and the radiation of a second polarization comprise of respectively differently polarized microwave radiation.
Claim 6
Dependent Claim
133 words
Apparatus for determining the presence of metal in a region comprising: first receiver means for determining the strength of a first radiation of a first polarization received from said region; second receiver means for determining the strength of a second radiation of a second polarization received from said region, said second Polarization being different from said first polarization; difference means connected to said first and second means for deriving a representation of the difference between the strengths of said first and second radiations; and determining means connected to said first, second and third means for detecting a predetermined change in the strength of at least one of said first and second radiations which is not time coincident with a predetermined change in the difference between the strengths of said first and second radiations.
Claim 7
Dependent Claim
133 words
Apparatus for determining the presence of metal in a region comprising: first receiver means for determining the strength of a first radiation of a first polarization received from said region; second receiver means for determining the strength of a second radiation of a second polarization received from said region, said second Polarization being different from said first polarization; difference means connected to said first and second means for deriving a representation of the difference between the strengths of said first and second radiations; and determining means connected to said first, second and third means for detecting a predetermined change in the strength of at least one of said first and second radiations which is not time coincident with a predetermined change in the difference between the strengths of said first and second radiations.
Claim 8
Dependent Claim
80 words
Apparatus according to claim 5 wherein said determining means comprises averaging means connected to said first and second receiver means for deriving a representation of the average of the strengths of said first and second radiations, and divider means connected to said averaging means and to said difference means for dividing the representation of the average of the strengths of the first and second radiations by the representation of the difference between the strengths of said first and second radiations.
Claim 9
Dependent Claim
192 words
Apparatus according to claim 6 wherein said averaging means comprises an average circuit connected to said first and second receiver means for producing a first signal representative of the average of the radiation strengths received by said first and second receiver means, first integrator means connected to said average circuit for integrating said first signal to produce a first integral signal, and first subtraction means connected to said average circuit and to said first integrator means for subtracting said first integrated signal from said first signal to produce a resultant average signal; and wherein said difference means comprises a difference circuit connected to said first and second receiver means for producing a second signal representative of the difference between the radiation strengths received by said first and second receiver means, integrator means connected to said difference circuit for integrating said second signal to produce a second integrated signal, and second subtraction means connected to said difference circuit and to said second integrator means for subtracting said second integrated signal from said second signal to produce a resultant difference signal, said divider means dividing said resultant average signal by said resultant difference signal.
Claim 10
Dependent Claim
79 words
Apparatus according to claim 7 further including threshold means for establishing first and second threshold signals, first squelch means connected to said threshold means and to said first subtraction means for setting said resultant average signal to zero when it does not exceed said first threshold signal, and second squelch means connected to said threshold means and to said second subtraction means for setting said resultant difference signal to zero when it does not exceed said second threshold signal.
Claim 11
Dependent Claim
106 words
Apparatus according to claim 7 wherein said first integrator means comprises first integrate circuit connected to said average circuit, first sensing means connected to said average circuit for detecting changes in said first signal, first timer means connected to said first sensing means for initiating said first integrator means in response to said first sensing means, and second integrator means comprises second integrate circuit connected to said difference circuit, second sensing means connected to said difference circuit for detecting changes in said second signal, second timer means connected to said second sensing means for initiating, said second integrator means in response to said second sensing means.
Claim 12
Dependent Claim
144 words
Apparatus for determining the presence of metal in a region comprising: first receiving means for receiving microwave radiation of a first polarization from said region and for providing a first signal having a value dependant upon the strength of said first radiation; second signal receiving means for receiving microwave radiation of a second polarization from said region and for providing a second signal having a value depeNdant upon the strength of said second radiation; and electronic digital computer means for receiving said first and second signals, said computer means being programmed to respond to said first and second signals to determine the existence of a predetermined change of the value of at least one of said first and second signals which is not time coincident with the existence of a predetermined change of the difference between the values of said first and second signals.
Claim 13
Dependent Claim
144 words
Apparatus for determining the presence of metal in a region comprising: first receiving means for receiving microwave radiation of a first polarization from said region and for providing a first signal having a value dependant upon the strength of said first radiation; second signal receiving means for receiving microwave radiation of a second polarization from said region and for providing a second signal having a value depeNdant upon the strength of said second radiation; and electronic digital computer means for receiving said first and second signals, said computer means being programmed to respond to said first and second signals to determine the existence of a predetermined change of the value of at least one of said first and second signals which is not time coincident with the existence of a predetermined change of the difference between the values of said first and second signals.
Claim 14
Dependent Claim
70 words
Apparatus according to claim 10 wherein said computer is programmed to respond to said first and second signals to determine the average of the values of said first and second signals and to determine the difference between the values of said first and second signals and to divide the average so determined by the difference so determined to obtain a representation of the probability of metal present in said region.
Claim 15
Dependent Claim
110 words
Apparatus according to claim 11 wherein said computer means is further programmed to respond to the representation of the average of the values of said first and second signals to integrate the average value and to subtract the integrated average value from the average value to obtain a corrected average value, and said computer means is further programmed to respond to the representation of the difference between the values of said first and second signals to integrate the difference value and to subtract the integrated difference value from the difference value to obtain a corrected difference value, the computer means dividing the corrected average value by the corrected difference value.
Claim 16
Dependent Claim
30 words
Apparatus according to claim 12 wherein said computer means is further programmed to perform the division only when either the difference value or the average value exceeds respective predetermined values.
Claim 17
Dependent Claim
30 words
Apparatus according to claim 11 wherein said computer means is further programmed to perform the division only when either the difference value or the average value exceeds respective predetermined values.
References Cited (Backward Citations)
US3395338A
Cited
US3344881A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-01-07 | 1977-07-09 | 1978-01-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-01-07 | 1981-07-09 | 1982-01-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-01-07 | 1985-07-09 | 1986-01-08 | $7700.00 | Window Closed / Lapsed |