Monitoring antenna system

• US 6,351,215 B2
• Filed: 01/20/1999
• Issued: 02/26/2002
• Est. Priority Date: 06/02/1998
• Status: Expired due to Term

• Current Assignee: Addison Technologies A Texas Limited Partnership
• Original Assignee: RF Code Incorporated
• Inventors: Rodgers, James L., Fowler, Billy C., Jaecks, Howard K.
• Primary Examiner(s): Wu, Daniel J.
• Application Number:
  US09/233,755
• Publication Number:
  US 20010038332A1
• Time in Patent Office: 1,133 Days
• Field of Search: 340/572.7, 340/572.1, 343/745, 343/748, 343/893, 343/894, 343/867, 343/866
• US Class Current: 340/572.1
• CPC Class Codes: G01S 13/753 using frequency selective elements, e.g. resonator
• CPC Class Codes: G01S 13/756 using a signal generator for modifying the reflectivity of the reflector G01S13/758 takes precedence
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• 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: G06K 19/0724 the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types
• CPC Class Codes: G06K 19/07779 the inductive antenna being a coil
• CPC Class Codes: G06K 19/07783 the coil being planar
• 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 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: H01Q 1/2208 associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems methods or arrangements for sensing record carriers, e.g. for reading patterns G06K7/00; record carrier for use with machines and with at least a part designed to carry digital markings G06K19/00
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 23/00 Antennas with active circuits or circuit elements integrated within them or attached to them
• 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 monitoring system incorporates antennas that transmit signals at predetermined frequencies; the transmitted signals are received by tags located in the active monitoring area of the antenna which then transmit signals back to the antenna. The antennas are tuned to each desired frequency prior to driving the antennas to transmit at the desired frequency. The system transmits a range of frequencies in a sequence that uses overlapping frequency steps. The monitoring system is also constructed having a variable configuration resulting in the ability to be reconfigured under program control to conform to varying system requirements. The integrated monitoring system employs programmable formats for reconfiguration such that upon program input from a host computer the system can assume predetermined configurations to conform to the particular tasks for the specific application. The monitoring system incorporates an antenna system that employs digitally controlled, differentially driven, scanning transceivers, and walk through magnetic induction antennas positionable in various configurations to maximize detection of tags being transported through the antenna system.

Claims

1. In a monitoring system for detecting the presence of a tag the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies;

an antenna tap connected to said signal source for receiving said digital signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

a planar antenna loop connected to said antenna tap for transmitting signals at the signal frequency of said analog signal;

wherein

said antenna is responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency.

2. In a monitoring system for detecting the presence of a tag, the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies;

an antenna tap connected to said signal source for receiving said digital signals and generating an analog signal having a signal frequency of one of said selected frequencies, said tap including differential antenna drivers; and

a differentially drive planar antenna loop connected to said antenna drivers for transmitting signals at the signal frequency of said analog signal.

3. The combination set forth in claim 2 wherein said antenna is responsive to the analog signals from said drivers for generating a magnetic field surrounding said loop at said analog signal frequency.

4. In a monitoring system for detecting the presence of a tag, the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies;

an antenna tap connected to said signal source for receiving said digital signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

a portal planar loop antenna connected to said antenna tap for transmitting signals at the signal frequency of said analog signal;

wherein

said antenna is responsive to the signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency; and

said portal antenna has a magnetic field coupling to the tag in said magnetic field being transported through said loop.

5. The improvement set forth in claim 4 wherein said portal antenna is positioned and sized to permit tag carrying items to be transported perpendicularly through the plane of said antenna loop.

6. In a monitoring system for detecting the presence of a tag, the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies;

an antenna tap connected to said signal source for receiving said digital signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

a transversal planar loop antenna connected to said antenna tap for transmitting signals at the signal frequency of said analog signal;

wherein

said antenna is responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency; and

said transversal antenna has a magnetic field coupling to the tag in said magnetic field being transported adjacent said loop.

7. The improvement set forth in claim 6 wherein said transversal antenna is positioned and sized to permit tag carrying items to be transported through the magnetic field of said antenna parallel to the plane of said antenna loop.

8. In a monitoring system for detecting the presence of a tag the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies;

a plurality of antenna taps connected to said signal source for receiving said digital signals and generating respective first and second analog signals each having a frequency corresponding to one of said selected frequencies;

a first planar antenna loop connected to one of said antenna taps for transmitting signals at the signal frequency of the first analog signal; and

a second planar antenna loop connected to another of said antenna taps for transmitting signals at the signal frequency of the second analog signal;

wherein

said first and second planar antenna loops are positioned in planes at an angle with respect to each other.

9. The improvement set forth in claim 8 wherein said planes intersect each other.

10. The improvement set forth in claim 8 wherein said antennas are portal antennas and said angle is about 45°

.

11. The improvement set forth in claim 10 wherein the first planar antenna loop and the second planar antenna loop are formed around an axis;

the first plane is perpendicular to the axis; and

a line of intersection, between the second plane and a vertical plane that includes the axis, forms an angle of about 45°

with the axis.

12. In a monitoring system for detecting the presence of a tag the improvement comprising;

a digital signal source for generating digital signals representing selected frequencies;

a plurality of antenna taps connected to said signal source for receiving said digital signals and generating respective first and second analog signals each having a frequency corresponding to one of said selected frequencies;

a first portal planar antenna loop connected to one of said antenna taps for transmitting signals at the signal frequency of the first analog signal; and

a second portal planar antenna loop connected to another of said antenna taps for transmitting signals at the signal frequency of the second analog signal;

wherein

said first and second portal planar antenna loops are positioned in parallel planes spaced along a path of the tag to be detected; and

each of said antenna loops is driven differentially with respect to each other to cancel noise existing along said path.

13. In a monitoring system for detecting the presence of a tag, the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies;

a first antenna tap and a second antenna tap each connected to said signal source for receiving said digital signals and generating analog signals each having a frequency correspondence to one of said selected frequencies; and

a first planar antenna loop connected to said first antenna tap for transmitting signals at the signal frequency of the first analog signal;

a second planar antenna loop connected to said second antenna tap for transmitting signals at the signal frequency of the second analog signal;

wherein

said first and second antenna taps drive said first and second planar antenna loops respectively with respective signals that are phase shifted with respect to each other.

14. The combination set forth in claim 13 wherein said phase shift is about 90°

.

15. In a monitoring system for detecting the presence of a tag the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies and for generating transmit mode signals and receive mode signals;

an antenna tap connected to said signal source for receiving said digital signals and said mode signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

a planar transceiver antenna loop connected to said antenna tap for transmitting signals at the signal frequencies of said analog signal and for receiving signals transmitted by the tag;

wherein

said antenna tap is connected to said planar transceiver antenna loop for receiving and amplifying tag signals detected by said antenna.

16. The combination set forth in claim 15 wherein said antenna is responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency.

17. The combination set forth in claim 15 wherein said antenna tap differentially drives said planar transceiver loop antenna.

18. In a monitoring system for detecting the presence of a tag, the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies and for generating transmit mode signals and receive mode signals;

an antenna tap connected to said signal source for receiving said digital signals and mode signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

a planar portal transceiver loop antenna connected to said antenna tap for transmitting signals at the signal frequency of said analog signal and for receiving signals transmitted by the tag;

wherein

said portal planar transceiver loop antenna is responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency and is responsive to signals received from a tag; and

said antenna tap is connected to said antenna for receiving and amplifying tag signals detected by said antenna.

19. In a monitoring system for detecting the presence of a tag, the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies and for generating transmit mode signals and receive mode signals;

an antenna tap connected to said signal source for receiving said digital signals and said mode signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

a planar transceiver antenna loop connected to said antenna tap for transmitting signals at the signal frequency of said analog signal and for receiving signals transmitted by the tag;

wherein

said antenna tap responsive to said mode signals for selecting the reactance of a resonant circuit including said antenna; and

said planar transceiver antenna loop has a higher Q during said transmit mode signal than during said receive mode signal.

20. In a monitoring system for detecting the presence of a tag, the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies and for generating transmit mode signals, receive mode, signals, and squelch mode signals;

an antenna tap connected to said signal source for receiving said digital signals and mode signals and generating an analog signal having a signal frequency of one of said selected frequencies; and

a planar transceiver loop antenna connected to said antenna tap for transmitting signals at the signal frequency of said analog signal and for receiving signals transmitted by the tag;

wherein

said antenna tap is responsive to said mode signals for selecting the reactance of a resonant circuit including said antenna and for squelching all transmissions in response to said squelch mode signal; and

said planar transceiver antenna loop has a higher Q during said transmit mode signal than during said receive mode signal and being squelched during said squelch signal.

21. In a monitoring system for detecting the presence of a tag the improvement comprising:

a digital signal source for generating digital signals representing selected frequencies;

an antenna tap connected to said signal source for receiving said digital signals and generating an analog signal having a signal frequency of one of said selected frequencies;

a planar transceiver antenna loop connected to said antenna tap for transmitting signals at the signal frequency of said analog signal and for receiving signals transmitted by the tag; and

a resonant circuit including said antenna;

wherein

said resonant circuit has a higher Q when said antenna is transmitting than when said antenna is receiving.