DAMPED SINUSOIDAL CURRENT PULSE GENERATOR AND METHOD

• US 3,673,437 A
• Filed: 06/29/1970
• Issued: 06/27/1972
• Est. Priority Date: 06/29/1970
• Status: Expired due to Term

• Current Assignee: Donald A. Wright
• Original Assignee: Donald A. Wright
• Inventors: Wright, Donald A.
• Primary Examiner(s): Miller, Jr., Stanley D.
• Application Number:
  US05/050,840
• Time in Patent Office: 729 Days
• Field of Search: 328/65,67,213,223 324/34,41 307/252N,252J,108 340/38L,258C,258D 194/100 331/165,166
• US Class Current: 327/129
• CPC Class Codes: G01N 27/72 by investigating magnetic variables
• CPC Class Codes: G08B 13/2437 Tag layered structure, processes for making layered tags
• CPC Class Codes: G08B 13/2442 Tag materials and material properties thereof, e.g. magnetic material details
• 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

Abstract

A damped sinusoidal electromagnetic field is produced by oscillatory current flow in a conductor of an inductive component of an underdamped LC resonant circuit. Energy is stored in the resonant circuit when the resonant circuit is coupled to a steady state D.C. electrical energy source by the triggering into conduction of an SCR connected in series with the resonant circuit and the D.C. source. Energy is transferred to the resonant circuit by an inductor connected in series therewith. The inductance of the inductor is sufficiently less than that of the inductive component of the resonant circuit such that sufficient energy is stored in the resonant circuit at a sufficient rate to cause current flow in the SCR to ultimately cease. Thereupon the SCR shuts off the transfer of energy from the D.C. source to the resonant circuit, and damped sinusoidal oscillation occurs in the resonant circuit to produce a damped sinusoidal electromagnetic field. The SCR is intermittently triggered into conduction to produce an intermittent series of damped sinusoidal electromagnetic fields.

Claims

1. An electrical circuit for producing a damped sinusoidal electromagnetic field in an interrogation zone for activating a responder passing through the zone, comprising a resonant circuit adapted to receive electrical energy and including an inductive component and a capacitive component connected in parallel, the inductive component comprising a conductor for producing an electromagnetic field;

means for intermittently coupling a source of electrical energy to the resonant circuit to transfer a predetermined amount of electrical energy to the resonant circuit, the dissipation of residual transferred energy in the resonant circuit upon decoupling of the energy source and resonant circuit producing in the interrogation zone a damped sinusoidal electromagnetic field of sufficient intensity to activate a responder; and

an inductor connected in series with the resonant circuit and the coupling means, wherein the inductance of the inductive component is at least 4.7 times the inductance of the inductor; and

which coupling means comprises a trigger circuit and an SCR having an anode lead, a cathode lead and a gate lead, the SCR being connected in series between the energy source and the inductor by the anode and cathode leads, and the trigger circuit being coupled to the SCR gate lead to forward bias the SCR in response to a turn-on control signal to transfer electrical energy through the inductor to the resonant circuit until current flow in the inductor essentially stops, whereupon the SCR ceases to conduct to decouple the energy source and resonant circuit.

2. An electrical circuit according to Claim 1, wherein the inductance of the inductive component is from 4.7 to 25.0 times the inductance of the inductor.

3. An electrical circuit according to claim 2 wherein the inductance of the inductive component is about 6.0 times the inductance of the inductor.

4. An electrical circuit for producing a damped sinusoidal electromagnetic field, comprising an underdamped resonant circuit including an inductive component and a capacitive component connected in parallel with one another, which inductive component comprises a conductor for producing an electromagnetic field when current flows in the conductor;

a D.C. source connected in series with the resonant circuit for providing electrical energy to the resonant circuit;

an SCR connected in series with the resonant circuit and the D.C. source for enabling electrical energy transfer from the D.C. source to the resonant circuit when the SCR is in a conducting state;

triggering means connected to the SCR for intermittently triggering the SCR into conduction; and

an inductor connected in series with the SCR, the resonant circuit and the D.C. source for transferring energy, upon conduction of the SCR, from the D.C. source to the resonant circuit, which inductor has an inductance sufficiently less than the inductance of the inductive component in the resonant circuit such that sufficient energy is stored in the resonant circuit at a sufficient rate to cause the current in the SCR to ultimately cease to thereby then enable damped sinusoidal oscillation in the resonant circuit, whereby upon oscillation in the resonant circuit a damped sinusoidal electromagnetic field is produced.

5. An electrical circuit according to claim 4, wherein the inductance of the inductive component is at least 4.7 times the inductance of the inductor.

6. An electrical circuit according to claim 5, wherein the inductance of the inductive component is from 4.7 to 25.0 times the inductance of the inductor.

7. An electrical circuit according to claim 6, wherein the inductance of the inductive component is 6.0 times the inductance of the inductor.