Resonant circuit tuning system with dynamic impedance matching

• US 7,570,220 B2
• Filed: 06/27/2006
• Issued: 08/04/2009
• Est. Priority Date: 06/27/2006
• Status: Active Grant

• Current Assignee: Sensormatic Electronics LLC (Johnson Controls International plc)
• Original Assignee: Sensormatic Electronics Corporation (Johnson Controls International plc)
• Inventors: Herring, Richard, Padula, Guillermo, Hall, Stewart E.
• Primary Examiner(s): PHAN, THO GIA
• Application Number:
  US11/475,771
• Publication Number:
  US 20070296593A1
• Time in Patent Office: 1,134 Days
• Field of Search: 343/745, 343/866, 343/867, 340/572.5, 340/572.7
• US Class Current: 343/745
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G08B 13/2477 Antenna or antenna activator circuit

Abstract

A resonant circuit tuning system and a method for tuning are provided. The resonant circuit tuning system may include a resonant circuit having a first capacitive element in series between a transmitter and an antenna coil and a second capacitive element in parallel with the transmitter and the antenna coil. At least one of the first capacitive element and second capacitive element may be configured to be varied. The resonant circuit tuning system also may include a controller for controlling a variable value of at least one of the first and second capacitive elements.

Claims

1. A resonant circuit tuning system comprising:

a resonant circuit having a first capacitive element in series between a transmitter and an antenna coil and a second capacitive element in parallel with the transmitter and the antenna coil, at least one of the first capacitive element and second capacitive element configured to be varied;

a controller for controlling a variable value of at least one of the first and second capacitive elements; and

a variable inductive element connected in one of (i) a series arrangement with the antenna and (ii) magnetically coupled to the antenna.

2. A resonant circuit tuning system in accordance with claim 1 wherein the controller is configured to control at least one of the variable capacitive element and variable inductive element to adjust at least one of a resonant frequency and a resonant impedance of the resonant circuit.

3. A resonant circuit tuning system in accordance with claim 1 wherein the resonant circuit is configured in one of a series and a parallel arrangement.

4. A resonant circuit tuning system in accordance with claim 1 wherein the controller is configured to dynamically adjust at least one of the first capacitive element and second capacitive element based on a sensed current.

5. A resonant circuit tuning system in accordance with claim 1 wherein at least one of the first capacitive element and second capacitive element comprises a variable capacitor and the controller is configured to adjust a capacitance ratio.

6. A resonant circuit tuning system in accordance with claim 1 wherein the resonant circuit is configured to operate in connection with at least one of an Electronic Article Surveillance (EAS) system and a Radio Frequency Identification (RFID) system.