Marker tag for a detection system

• US 4,302,846 A
• Filed: 04/24/1978
• Issued: 11/24/1981
• Est. Priority Date: 08/19/1977
• Status: Expired due to Term

• Current Assignee: James H. Stephen, John D. Mccann
• Original Assignee: James H. Stephen, John D. Mccann
• Inventors: McCann, John D., Stephen, James H.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/899,422
• Time in Patent Office: 1,310 Days
• Field of Search: 325/8, 325/9, 325/113, 325/117, 325/140, 325/185, 340/539, 340/568, 340/571, 340/572, 331/76, 343/18 D, 343/6.5 R, 343/6.5 SS, 343/6.8 R, 455/19, 455/41
• US Class Current: 455/19
• CPC Class Codes: G08B 13/2422 using acoustic or microwave tags
• CPC Class Codes: G08B 13/2431 Tag circuit details
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2477 Antenna or antenna activator circuit

Abstract

This invention is directed to a receptor reradiator for use in a system for detecting the position of the receptor reradiator in a surveillance zone. It comprises a first aerial means for receiving the first signal, second aerial means for radiating said reply signal and a non-linear element coupling the first and second aerial means.

Claims

1. A receptor reradiator for use in a system for detecting the position of said receptor reradiator in a surveillance zone, the system transmitting a first frequency signal f₁ and a second frequency signal f₂, so that said first and second signals define a center frequency f_c =(f₁ +f₂)/2, comprising:

a dipole antenna having two metal conductive arms of a total length slightly less than half the wave length of the center frequency signal f_c, said two arms coming together at a point defining the electrical center of the dipole;

a non-linear semiconductor element disposed in one of said arms and offset from the electrical center of said dipole; and

a parallel combination of a capacitance and inductance inserted in the arm containing the semiconductor element and tuned to receive said first and second frequency signals, so that said non-linear semiconductor element causes said dipole to reradiate an intermodulation signal generated by the first and second RF signals.

2. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a cuprous oxide semi-conductor connected between a pair of copper electrodes.

3. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a cuprous sulphide on cadmium sulphide semi-conductor connected between a pair of copper electrodes.

4. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a selenium semi-conductor connected between a pair of copper electrodes.

5. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a titanium dioxide semi-conductor between a titanium electrode and a silver electrode.

6. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a lead sulphide semi-conductor connected between a pair of copper or aluminium electrodes.

7. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a magnesium oxide semi-conductor connected between a magnesium electrode and an aluminium electrode.

8. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a aluminium (AL₂ O₃) semi-conductor connected between a pair of aluminium electrodes.

9. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a zirconia (ZrO₂) on zirconium connected between aluminium electrodes.

10. A receptor reradiator as claimed in claim 1 wherein said semiconductor element and dipole arms comprise a gallium arsenide semi-conductor connected between a pair of gold or aluminium electrodes.