Signal direction determining system and directional loop antenna array therefor

• US 4,489,313 A
• Filed: 09/01/1982
• Issued: 12/18/1984
• Est. Priority Date: 09/01/1982
• Status: Expired due to Term

• Current Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Pfister, Henry F.
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US06/413,612
• Time in Patent Office: 839 Days
• Field of Search: 343/742, 343/867, 343/894, 343/442, 343/443, 343/448, 340/572, 340/552, 340/540, 340/657, 340/658, 340/674, 340/673
• US Class Current: 340/540
• CPC Class Codes: G01S 3/32 derived from different combinations of signals from separate antennas, e.g. comparing sum with difference
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22
• CPC Class Codes: G08B 13/2477 Antenna or antenna activator circuit
• CPC Class Codes: G08B 21/185 Electrical failure alarms

Abstract

A directional loop antenna array is provided by two flat parallel spaced apart open loops with a shorted turn disposed between the open loops equidistant therefrom. The signals from the open loops are vectorially added and subtracted in a sum and difference circuit and the phase angle between the sum and difference signals is ascertained in a phase detector circuit that feeds an indicator. The so determined phase angle is either greater or less than 90° depending upon the relative magnitudes of the loop signals.

Claims

1. A signal direction determining system for providing an output indicative of the direction to a source of AC signals from a directional loop antenna array where said array includes at least a pair of open loops of electrically conductive material, said system comprising means coupled to said open loops for providing a first output corresponding to the sum of any AC signals induced in said loops by said source and a second output corresponding to the difference between said induced signals;

and phase detecting and indicating means coupled to said first and second outputs for providing a further output dependent upon which open loop has the greater induced signal, said further output being indicative of the direction to said source.

2. A signal direction determining system according to claim 1, wherein at least one closed loop of electrically conductive material is located between said pair of open loops.

3. A signal direction determining system according to claim 2, wherein said open loops are substantially congruent, each of flat construction, and in parallel coaxial relationship one to the other.

4. A signal direction determining system according to claim 3, wherein said closed loop consists of a metal door frame, and said open loops are disposed on opposite sides of said frame.

5. A signal direction determining system according to claim 3, wherein said closed loop consists of at least one shorted turn.

6. A directional loop antenna array comprising at least one closed loop of electrically conductive material located between a pair of open loops of electrically conductive material, said open loops each having means for effecting coupling thereto of a utilization device.

7. A directional loop antenna array according to claim 6, wherein said open loops are substantially congruent, each of flat construction, and in parallel coaxial relationship one to the other.

8. A directional loop antenna array according to claim 7, wherein said closed loop consists of a metal door frame, and said open loops are disposed in opposite sides of said frame.

9. A directional loop antenna array according to claim 7, wherein said closed loop consists of at least one shorted turn.

10. A directional loop antenna array according to claim 9, wherein said closed loop is spaced between parallel to and equidistant from said open loops.