Radiation detector

• US 3,931,573 A
• Filed: 05/05/1972
• Issued: 01/06/1976
• Est. Priority Date: 05/05/1972
• Status: Expired due to Term

• Current Assignee: General Microwave Patent Corporation
• Original Assignee: General Motors Corporation (General Motors Company)
• Inventors: Hopfer, Samuel
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Karlsen, Ernest F.
• Application Number:
  US05/250,582
• Time in Patent Office: 1,341 Days
• Field of Search: 324/106, 324/46, 324/95, 136/212, 136/211, 136/213, 250/83.3 R, 250/83.3 H, 310/4, 325/67, 325/363, 343/703
• US Class Current: 324/106
• CPC Class Codes: G01R 29/0878 Sensors; antennas; probes; detectors wave guide measuring sections G01R1/24
• CPC Class Codes: G01R 5/26 operated by deformation of a bimetallic element

Abstract

A detection device for electromagnetic radiation uses strips of thin resistive films connected in electrically conductive paths with the area of spacing between adjacent ones of the strips being greater than the area of the strips to achieve an impedance which is largely resistive over a broad band of radio frequencies. The strips are mounted in dielectric material and exposed to free space radiation. A radiation hazard meter is produced with thermally sinked thermocouple elements forming the resistive strips.

Claims

1. An electrical circuit device for detecting free space radio frequency radiation fields, said device including:

a plurality of spaced conductive strips in the form of thin resistive films whose thickness is small compared to the skin depth at the radio frequency, said strips being connected in an electrically conductive path,

and a non-metallic housing for said strips including means for surrounding said strips with dielectric material for passing said radiation fields to said strips,

the area of spacing between adjacent ones of said strips being greater than the area of said strips so that the impedance of said strips is largely resistive over a broad band of radio frequencies.

2. A radiation detecting device as recited in claim 1 wherein said strips have thermal characteristics so that changes in temperature with absorption of radiation can be detected.

3. A radiation detecting device as recited in claim 2 wherein said strips include thermoelectric materials forming thermocouples.

4. A radiation detecting device as recited in claim 2 wherein each of said strips includes a plurality of thermocouples connected in series-aiding relation, and said strips are connected in series-aiding relation.

5. A radiation detecting device as recited in claim 4 wherein a first plurality of said strips are parallel and are arranged to be transverse to a second plurality of said strips to be respectively responsive to two transverse components of an electric field.

6. A radiation detecting device as recited in claim 5 wherein a third plurality of said strips are parallel and are arranged to be transverse to the strips of said first and second pluralities to be responsive to a third transverse component of an electric field.

7. A radiation detecting device as recited in claim 5 wherein the strips of said first and second pluralities cross each other at the cold junctions thereof;

and further comprising dielectric means having a high thermal conductivity and connected in thermally conductive relation to said cold junctions to provide a substantially uniform reference temperature for said cold junctions.

8. An electrical circuit device for detecting radio frequency radiation, said device including:

a plurality of spaced conductive strips in the form of thin resistive films whose thickness is small compared to the skin depth at the radio frequency, said strips having substantial resistance and being connected in an electrically conductive path, a first group of said strips being parallel and a second group of said strips being parallel and transverse to said first strips to form a grid,

the spacing between adjacent ones of said parallel strips being greater than the width of said strips, so that the impedance of said grid of strips to free space radio frequency radiation is largely resistive over a broad band of radio frequencies,

and dielectric means for mounting said strips for exposure to free space radiation fields.

9. A radiation detecting device as recited in claim 8 wherein the resistance of each of said strips is less than 100 ohms per square, and the equivalent resistance of said grid of strips to free space radio frequency radiation is greater than 300 ohms per square.

10. A thermoelectric device for radiation detection comprising:

a plurality of conductive means forming thermocouples formed of different thin resistive films connected in a sequence of alternatingly different films connected to form a plurality of cold junctions and hot junctions therebetween;

and dielectric means spaced from said hot junctions and having a high thermal conductivity and connecting said cold junctions in thermally conductive relation to provide a substantially uniform reference temperature for said cold junctions.

11. A radiation detecting device as recited in claim 10 wherein said conductive means includes a thin dielectric planar substrate with said films deposited thereon;

said dielectric means includes a block of dielectric material having a plurality of projecting pads for engaging said substrate at said cold junctions.

12. A radiation detecting device as recited in claim 11 wherein said dielectric material is boron nitride.

13. A radiation detecting device as recited in claim 10, wherein said dielectric means has a substantial bulk and forms a thermal sink for said cold junctions.

32. A radiation detecting device as recited in claim 10, wherein said dielectric means includes a substantially solid member for thermally isolating said thermocouples from external infra-red radiation.

33. A free space radiation detecting device as recited in claim 32, wherein said dielectric means further includes a second substantially solid member similar to the first-mentioned solid member for enclosing said thermocouples.

14. An electrical circuit device for detecting free space radio frequency radiation fields, said device including:

a plurality of spaced conductive strips in the form of thin resistive films whose thickness is small compared to the skin depth at the radio frequency, said strips being connected in an electrically conductive path,

and a non-metallic housing for said strips including means for surrounding said strips with dielectric material for passing said radiation fields to said strips,

said strips being arranged to present a generally resistive impedance substantially greater than that of free space to said radio frequency radiation fields and having a negligible reflective characteristic,

said detecting device having the property that, for a value of ohms per square equal to free space, power absorption from free space by said strips is not a maximum.

15. A radiation detecting device as recited in claim 14 wherein said transverse strips have a transmission characteristic to transmit at least about half of said radiation field to which said strips are exposed.

16. A radiation transformer for radiation fields at radio frequencies comprising:

a non-metallic housing containing a plurality of spaced resistive strips with the spacing between said strips being large compared to the width of the strips,

and means for deriving electrical signals from said strips;

said transformer having the property that, for a value of ohms per square equal to free space, power absorption from free space by the transformer is not a maximum.

17. A radiation transformer as recited in claim 16, and further comprising a second plurality of spaced resistive strips having a construction similar to that of the first mentioned plurality of resistive strips and oriented transversely thereto and connected electrically to said first plurality of strips.

18. A radiation transformer as recited in claim 16, wherein said strips each include a plurality of thermocouples.

19. A device for detecting free space radio frequency radiation, said device comprising:

an electrically continuous resistive strip with, separate portions extending in transverse directions over an area and having a largely resistive impedance effective over said area to free space radio frequency radiation and substantially greater than that of free space and having a negligible reflective characteristic,

said detecting device having the property that, for a value of ohms per square equal to free space, power absorption from free space by the detecting device is less than a maximum.

20. A free space radiation detecting device as recited in claim 19, wherein said separate portions extend at substantially right angles corresponding respectively to orthogonal components of the free space radiation.

21. A device for detecting free space radio frequency radiation as recited in claim 19, wherein said strip includes an additional portion extending transversely to said separate portions.

22. A device for detecting free space radio frequency radiation, as recited in claim 21, wherein said separate and additional portions respectively extend along three orthogonal axes corresponding respectively to orthogonal components of free space radiation.

23. A device for detecting free space radio frequency radiation as recited in claim 19, wherein said resistive impedance is a plurality of times that of free space.

24. A device for detecting free space radio frequency radiation as recited in claim 19, wherein said resistive impedance is about 1,000 ohms.

25. A device for detecting free space radio frequency radiation as recited in claim 19, and further comprising a dielectric and thermally insulating enclosure for said strip to permit the passage of free space radio frequency radiation and to isolate said strip from external infra-red radiation.

26. A device for detecting free space radio frequency radiation as recited in claim 19, and further comprising means for connecting said resistive strip in a measuring circuit.

27. A device for detecting free space radio frequency radiation as recited in claim 19, wherein said resistive strip has electrical characteristics that vary with the amount of radiation absorbed thereby.

28. A device for detecting free space radio frequency radiation as recited in claim 27, wherein each of said separate strip portions includes a thermocouple.

29. A device for detecting free space radio frequency radiation as recited in claim 28, wherein each of said separate strip portions includes a plurality of series connected thermocouples extending in the direction of the strip portion.

30. A device for detecting free space radio frequency radiation as recited in claim 19, wherein said separate strip portions extend along orthogonal sides of a unit square, and the width of said strip is substantially less than the length of a side of said unit square.

31. A device for detecting free space radio frequency radiation as recited in claim 30, wherein the length of said unit square side is many times the width of said strip.