Rectifying antenna circuit

• US 6,140,924 A
• Filed: 01/05/1999
• Issued: 10/31/2000
• Est. Priority Date: 02/07/1998
• Status: Expired due to Term

• Current Assignee: National University of Singapore
• Original Assignee: Nat'L University of Singapore
• Inventors: Joe, Jurianto, Chia, Michael Yan Wah, Marath, Ashok Kumar
• Primary Examiner(s): MULLEN, THOMAS J
• Application Number:
  US09/225,188
• Time in Patent Office: 665 Days
• Field of Search: 340/572.5, 340/572.7, 342/42, 342/44, 342/51, 323/220, 323/229, 323/232, 323/233
• US Class Current: 340/572.5
• CPC Class Codes: G08B 13/2431 Tag circuit details
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them

Abstract

A rectifying antenna circuit for a passive RF transponder comprising a series resonant circuit of an antenna, a voltage rectifier circuit including a diode and a capacitance shunting the diode, the capacitance providing a primary voltage amplification role and the diode providing a rectification and a voltage amplification role.

Claims

1. A rectifying antenna circuit for a passive RF transponder comprising a series resonant circuit consisting of:

an antenna;

a voltage rectifier circuit including a diode; and

a reactance shunting the diode, the reactance providing primarily a voltage amplification role and the diode providing primarily a rectification role.

2. A circuit according to claim 1, wherein the reactance comprises primarily an inductance.

3. A circuit according to claim 1, wherein the reactance comprises primarily a capacitance.

4. A circuit according to claim 3, wherein the capacitance comprises a discrete capacitive component.

5. A circuit according to claim 4, wherein the capacitive component is a variable capacitor, adjustment of the capacitance retuning the resonant frequency of the rectifying antenna circuit.

6. A circuit according to claim 1, wherein the reactance comprises a micro-strip transmission line.

7. A circuit according to claim 6, wherein the reactance of the micro-strip transmission line is adjustable by varying the dimensions of the micro-strip, such adjustment of the reactance retuning the resonant frequency of the rectifying antenna circuit.

8. A circuit according to claim 1, wherein the voltage rectifier circuit includes two diodes.

9. A circuit according to claim 1, wherein the diode comprises a Schottky diode.

10. A circuit according to claim 1, wherein a matching circuit is provided in series between the antenna and the reactance and voltage rectifier circuit.

11. A circuit according to claim 10, wherein the matching circuit is a short stub matching circuit in the form of low-loss micro-strip transmission lines.

12. A passive RF transponder including a rectifying antenna circuit according to claim 1.