Transponder

• US 8,830,029 B2
• Filed: 06/29/2012
• Issued: 09/09/2014
• Est. Priority Date: 06/30/2011
• Status: Active Grant

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Inventors: Akbari-Dilmahani, Rahim
• Primary Examiner(s): Bugg, George
• Assistant Examiner(s): Labbees, Edny
• Application Number:
  US13/538,223
• Publication Number:
  US 20130162395A1
• Time in Patent Office: 802 Days
• Field of Search: 3405721-5729, 340/10.1, 340/10.34, 340/5.2, 340/5.61, 340/5.62, 343/867, 235375-385, 336/83
• US Class Current: 340/5.61
• CPC Class Codes: G05B 1/01 electric
• CPC Class Codes: G06K 19/07792 the antenna adapted for extending in three dimensions
• CPC Class Codes: H01Q 1/3241 particular used in keyless entry systems
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop

Abstract

A transponder is disclosed to receive a wireless electromagnetic query signal and transmit a corresponding wireless electromagnetic response signal. The transponder comprises a first coil and at least one further coil that function as antennas to receive the wireless electromagnetic query signal and generate separate wired electrical incoming signals. An axis of the first coil and an axis of the at least one further coil are differently aligned in space, and each coil is associated with at least one means for limiting the voltage of the respective incoming signal. The separate wired electrical incoming signals are rectified and converted to current signals. The peak values of the current signals are detected and compared, such that a control signal is generated to identify one coil between the first coil and the at least one further coil that has a larger peak value of current.

Claims

1. A transponder, comprising:

a first coil, coupled to receive a wireless electromagnetic query signal, the first coil acting as a first antenna and generating a first wired electrical incoming signal from the query signal;

at least one further coil, coupled to receive the wireless electromagnetic query signal, the at least one further coil acting as a second antenna and generating a second wired electrical incoming signal from the query signal, an axis of the first coil and an axis of the at least one further coil having different spatial alignments, each of the first and at least one further coils being associated with at least one limiter means for limiting the voltages of the first and second wired electrical incoming signals;

at least one full-wave rectifier, coupled to the first coil and the at least one further coil, the at least one full-wave rectifier generating a first rectified incoming signal and a second rectified incoming signal from the first and second wired electrical incoming signal, respectively;

at least one current-controlled source of current, coupled to the at least one full-wave rectifier, the at least one current-controlled source of current generating a first current signal and a second current signal that correspond to the first and second rectified incoming signals, respectively;

at least one current detector, coupled to the at least one current-controlled source of current, the at least one current detector detecting a first peak value of current signal and a second peak value of current signal that are associated with the peak values of the first and second current signals, respectively;

a comparison arrangement, coupled to the at least one current detector, the comparison arrangement comparing the first and second peak value of current signals and generating a control signal, the control signal identifying one coil between the first coil and the at least one further coil that has a larger peak value of current.

2. The transponder according to claim 1, wherein the at least one limiter means includes a full-wave rectifier and a voltage limiter, the full-wave rectifier generating a supply voltage for the purpose of limiting the voltages of the first and second wired electrical incoming signals, the full-wave rectifier associated with each coil being parallel-circuited on the output side and further coupled to the voltage limiter for the purpose of limiting the supply voltage.

3. The transponder according to claim 1, wherein a voltage smoothing means is assigned to a voltage limiter included in the at least one limiter means.

4. The transponder according to claim 1, wherein a total of two coils are provided, the comparison arrangement including a comparator for comparing the peak values of the current signals, an output signal of the comparator is the control signal.

5. The transponder according to claim 1, wherein the at least one further coil is associated with at least two coils such that more than two coils are included in the transponder, the comparison arrangement includes comprising a plurality of comparators and a logic circuit, each comparator comparing two of a plurality of peak values of a plurality of current signals, output signals of the plurality of comparators being processed in the logic circuit to generate the control signal.

6. The transponder according to claim 1, wherein the transponder comprises a total of three coils, and an axis of each coil is disposed perpendicularly, in relation to the axes of the other two coils.

7. The transponder according to claim 1, wherein the at least one current-controlled source of current comprises at least one current mirrors that generates, in addition to the first and second current signals, a first mirrored current and a second mirrored current, and wherein a summing element is provided for summing up the first and second mirrored current and generating a pulsating composite signal that has a frequency doubling the frequency of the wireless electromagnetic query signal.

8. The transponder according to claim 7, wherein a comparator is provided for comparing the pulsating composite signal to a reference signal to generate a first clocking signal that has a frequency doubling the frequency of the wireless electromagnetic query signal.

9. The transponder according to claim 8 wherein the first clocking signal is converted to a second clocking signal having a lower frequency by a frequency divider.

10. The transponder according to claim 9, wherein the frequency divider is a frequency-halving means such that the frequency of the second clocking signal is equal to the frequency of the wireless electromagnetic query signal.

11. The transponder according to claim 1, wherein the transponder is at least in part executed as a CMOS-integrated circuit.