Inventory management system

• US 5,406,297 A
• Filed: 04/13/1993
• Issued: 04/11/1995
• Est. Priority Date: 04/09/1991
• Status: Expired due to Fees

• Current Assignee: Comtec Industries
• Original Assignee: Comtec Industries
• Inventors: Escobosa, Marcus P., Moore, Herbert J., Caswell, Robert L.
• Primary Examiner(s): Hajec, Donald
• Assistant Examiner(s): Ho, Tan
• Application Number:
  US08/045,209
• Time in Patent Office: 728 Days
• Field of Search: 343/741, 343/742, 343/744, 343/748, 343/876, 340/572, 340/359, 455/78, 455/83, 307/256, 307/317.1
• US Class Current: 343/741
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: G06Q 10/087 Inventory or stock management, e.g. order filling, procurement or balancing against orders
• CPC Class Codes: G07C 3/00 Registering or indicating the condition or the working of machines or other apparatus, other than vehicles
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

An inventory management system which includes a transponder, an interrogation transceiver and control devices utilized therewith. The control devices operate to minimize the power consumption of the transponder while permitting selected, coded operation of the inventory management system. The interrogation transceiver provides linkage to the transponder by means of a modulated radio frequency (RF) carrier during system operation. A transmit/receive switch is also included in the invention to prevent harmful coupling between the transponder receiver and the transponder transmitter. This could occur during data exchanges between the transponder and the interrogation receiver.

Claims

1. A diode switch circuit comprising,

diode means (D1) having an anode and a cathode,

first impedance means (R1) for connecting said anode to a constant power source,

coupling means (Y3) connecting said anode to an output,

second impedance means (C1,C2) for connecting said cathode to a variable input source (Y5) whereby said diode means is selectively back biased by said constant power source via said first impedance means in response to signals from said variable input source, and

loop antenna means (LOOP 1) connected to the cathode of said diode means whereby said loop antenna means is operatively connected to said input source and operatively disconnected from said output means when said diode means is back biased and operatively disconnected from said input source and operatively connected to said output means when said diode means is not back biased.

2. The circuit recited in claim 1 wherein,

said second impedance means includes a plurality of capacitors connected together at a common junction with said variable input source.

3. The circuit recited in claim 1 wherein,

said first impedance means includes a resistor means and inductor means.

4. The circuit recited in claim 1 wherein,

said resistor means and said inductor means are connected in series.

5. The circuit recited in claim 4 including,

capacitor means (C3) connected to said anode whereby said inductor means and said capacitor means provide impedance matching between said loop antenna means and said output means.

6. The circuit recited in claim 1 wherein,

said output means comprises a relatively high impedance.

7. The circuit recited in claim 1 wherein,

second impedance means is connected to said loop antenna means in order to resonate said loop antenna means and thereby produce a match with said variable input source.

8. The circuit recited in claim 7 wherein,

said second impedance means comprises capacitance means.

9. The circuit recited in claim 1 wherein,

the variable input source comprises a transmitter and the output means comprises a receiver.

10. The circuit recited in claim 1 wherein,

said coupling means provides DC isolation between said anode and the output.