RADIO FREQUENCY ACCESS CONTROL SYSTEM AND METHOD

• US 20120231733A1
• Filed: 03/08/2012
• Published: 09/13/2012
• Est. Priority Date: 03/08/2011
• Status: Active Grant

• Current Assignee: Near Field Magnetics, Inc.
• Original Assignee: Near Field Magnetics, Inc.
• Inventors: McManus, David, Gott, Robert Alan
• Granted Patent: US 8,989,657 B2
• Time in Patent Office: Days
• US Class Current: 455/41.1
• CPC Class Codes: H04B 5/48 Transceivers

Abstract

An access control system includes a transmitter initiator that has a magnetic flux antenna constructed and arranged to direct magnetic energy in an angular direction, a plurality of RF tone detectors, a microcontroller, and a plurality of RF burst generators. The system includes at least one receiver responder that has a magnetic flux antenna, a plurality of RF tone detectors, a microcontroller, and a RF burst generator. The transmitter initiator'"'"'s magnetic flux antenna and the receiver responder'"'"'s magnetic flux antenna define an open-air gap therebetween. The transmitter initiator'"'"'s magnetic flux antenna has a paramagnetic housing, electromagnetic windings within the paramagnetic housing, and at least one ferromagnetic element disposed within the open air gap. The paramagnetic housing and the ferromagnetic element are constructed and arranged to direct a magnetic field across the open air gap. The system is configured for wireless communication via near-field magnetic induction.

Claims

1. An access control system comprising:

at least one receiver responder comprising

a receiver responder magnetic flux antenna,

a plurality of RF tone detectors electrically coupled with the receiver responder magnetic flux antenna,

a microcontroller electrically coupled with the plurality of RF tone detectors,

a responder RF burst generator electrically coupled with the microcontroller and the receiver responder magnetic flux antenna; and

a transmitter initiator comprising

a transmitter initiator magnetic flux antenna constructed and arranged to direct magnetic energy in an angular direction, wherein the transmitter initiator magnetic flux antenna and the receiver responder magnetic flux antenna define an open-air gap therebetween, and wherein the transmitter initiator magnetic flux antenna comprises

a paramagnetic housing,

electromagnetic windings disposed within the paramagnetic housing, and

at least one ferromagnetic element disposed within the open-air gap, wherein the paramagnetic housing and the ferromagnetic element are constructed and arranged to direct a magnetic field across the open air gap, and

a plurality of RF tone detectors electromagnetically coupled with the transmitter initiator magnetic flux antenna,

a transmitter initiator microcontroller electromagnetically coupled with the plurality of RF tone detectors, and

a plurality of RF burst generators electrically coupled with the transmitter initiator microcontroller and with the transmitter initiator magnetic flux antenna;

wherein the system is configured for wireless communication between the transmitter initiator and the at least one receiver responder via near-field magnetic induction.

2. The access control system of claim 1, wherein the receiver responder magnetic flux antenna is configured as a focused-beam directional antenna comprising

a paramagnetic housing,

electromagnetic windings disposed within the paramagnetic housing, and

at least one ferromagnetic element disposed within the open-air gap,

wherein the paramagnetic housing and the ferromagnetic element are constructed and arranged to direct a magnetic field across the open air gap.

3. The access control system of claim 1, wherein the receiver responder magnetic flux antenna is configured as an omni-directional antenna.

4. The access control system of claim 1, wherein the at least one receiver responder further comprises a power amplifier electrically coupled with the receiver responder magnetic flux antenna, wherein the power amplifier is an adjustable gain amplifier comprising at least one gain stage having a voltage-controlled resistor.

5. The access control system of claim 1, wherein the transponder initiator further comprises a power amplifier electrically coupled with the transmitter initiator magnetic flux antenna, wherein the power amplifier is an adjustable gain amplifier comprising at least one gain stage having a voltage-controlled resistor.

6. The access control system of claim 1, wherein the at least one receiver responder is selected from the group consisting of a fob, a smart card, and a portable device communication-operable with near-field magnetic inductance.

7. The access control system of claim 1, wherein the open air gap is from about 2 to about 5 meters.

8. The access control system of claim 1, wherein the transmitter initiator and the receiver responder are configured to wirelessly communicate a signal having a frequency from about 120 KHz to about 135 KHz.

9. A method of access control comprising the steps of:

generating at least one RF burst at a transmitter initiator;

summing the at least one RF burst into a summed RF burst signal;

transforming the summed RF burst signal into a drive current;

conducting the drive current through coil windings of a directional magnetic flux antenna;

transmitting an RF initiator signal via magnetic induction across an open air gap to at least one receiver responder;

receiving the RF initiator signal across the open air gap by the at least one receiver responder, wherein the receiver responder has a receiver responder magnetic flux antenna and a RF tone detector;

detecting, by the at least one receiver responder, a frequency of the RF transmitter signal;

generating, based on the frequency of the RF transmitter initiator signal, a serial data stream having a unique identifier corresponding to the at least one receiver responder;

transmitting, by the receiver responder, at least one responder tone burst containing the serial data stream;

receiving the responder tone burst at the directional magnetic flux antenna;

demodulating, by the transmitter initiator, the responder tone burst to provide a unique identifier value; and

determining, based on the unique identifier value, whether access is permitted.

10. The method of claim 9, wherein the directional flux antenna is configured as a focused-beam antenna.

11. The method of claim 9, wherein the receiver magnetic flux antenna is configured as an omni-directional antenna.

12. The method of claim 9, wherein the step of generating a serial data stream further comprises the steps of:

generating a plurality of RF bursts; and

amplifying the plurality of RF bursts.

13. The method of claim 9, further comprising the steps of:

amplifying the receiver tone burst with an adjustable gain amplifier.

14. The method of claim 9, further comprising the step of modulating, by the transmitter initiator, the RF initiator signal in at least one of intensity, frequency, phase, and direction.

15. The method of claim 14, wherein the modulating step utilizes Frequency Shift Keying modulation.

16. The method of claim 9, wherein the RF initiator signal and the responder tone burst are between about 120 KHz and about 135 KHz.

17. The method of claim 9, wherein the RF initiator signal includes a unique identifier comprising a sequence of numbers selected from the group consisting of real numbers, imaginary numbers, and complex numbers.

18. The method of claim 9, further comprising the steps of:

establishing a first communication link with a first one of the at least one receiver responder;

abolishing the first communication link with the first one of the at least one receiver responder; and

establishing a second communication link with a second one of the at least one receiver responder.