Reactively decoupled dual channel keying circuit for wide-band frequency modulated keyable control circuit

• US 4,047,156 A
• Filed: 04/12/1976
• Issued: 09/06/1977
• Est. Priority Date: 04/12/1976
• Status: Expired due to Term

• Current Assignee: Cooper Industries, Inc. (Eaton Corporation PLC.)
• Original Assignee: Wagner Electric Corp. (Studebaker Electric Co.)
• Inventors: Atkins, Carl E.
• Primary Examiner(s): Yusko, Donald J.
• Application Number:
  US05/675,950
• Time in Patent Office: 512 Days
• Field of Search: 340/171 A, 340/171 R, 340/152 T, 340/258 C, 317/101 R
• US Class Current: 340/13.24
• CPC Class Codes: G06K 7/086 sensing passive circuit, e.g. resonant circuit transponders
• CPC Class Codes: G07C 11/00 Arrangements, systems or apparatus for checking, e.g. the occurrence of a condition, not provided for elsewhere
• CPC Class Codes: G07C 9/00714 with passive electrical components, e.g. resistor, capacitor, inductor
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

A keyable control circuit, has sensing coils located in the vicinity of a plurality of locations where lock control is desired. At least one swept high-frequency oscillator, which is connected to each sensing coil, generates an rf signal, rapidly swept over a wide frequency band. When an external keying circuit, containing more than one resonant circuit, each correctly tuned to a predetermined keying frequency, is inductively coupled to a sensing coil, each resonant circuit absorbs rf energy as the oscillator frequency is swept past its resonant frequency. Electrical interaction between the resonant circuits is accomplished by reactive cancellation. Energy absorption in the external keying circuit induces corresponding reductions in rf energy in the sensing coil as the oscillator frequency is swept past the keying frequencies. Tuned detectors within the keyable control circuit produce a control signal when energy reduction is sensed at each of the predetermined keying frequencies. If correct absorption fails to occur at any one or more of the predetermined frequencies, the control signal is withheld.

A time-gating system enables selective direction of the control signal to one or more using locations while excluding others. This function finds convenient application in automotive use where it is frequently desired to enable simultaneous unlocking of one or more doors while excluding unlocking of the deck lid.

A dead-oscillator detector averts attempted actuation of the unlocking function by the coupling of untuned energy-absorbing material, such as iron, to a sensing coil.

Claims

1. In a dual channel keyable control circuit of the type having swept rf energy coupled to at least one sensing coil, the invention of a keying circuit to trigger said keyable control circuit into producing a control output signal comprising:

a. a first resonant circuit containing at least a first inductor in parallel with a first capacitor said first resonant circuit being resonant at a first rf frequency;

b. a second resonant circuit containing at least a second inductor in parallel with a second capacitor said second resonant circuit being resonant at a second rf frequency different from said first rf frequency;

c. a common connection between said first and second resonant circuits;

d. a reactance in the common connection between said first and second resonant circuits;

e. when said swept rf energy is at the resonant frequency of said first resonant circuit, said reactance feeding into said first resonant circuit a signal of substantially correct amplitude and phase to cancel the rf energy coupled into said first resonant circuit by the proximity of said second resonant circuit; and

f. when said swept rf energy is at the rf frequency of said second resonant circuit, said reactance feeding into said second resonant circuit a signal of substantially correct amplitude and phase to cancel the rf energy coupled into said second resonant circuit by the proximity of said first resonant circuit.

2. A keying circuit as recited in claim 1 wherein said reactance is a capacitance.

3. A keying circuit as recited in claim 2 wherein said first and second inductors are wound in opposite directions.

4. A keying circuit as recited in claim 1 wherein said reactance is an inductance.

5. A keying circuit as recited in claim 4 wherein said first and second inductors are wound in the same direction.