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; a planar antenna loop connected to said antenna tap for transmitting signals at the signal frequencies of said analog signal; said antenna 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; a differentially driven planar antenna loop connected to said antenna drivers for transmitting signals at the signal frequencies 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; a portal planar loop antenna connected to said antenna tap for transmitting signals at the signal frequencies of said analog signal; said antenna responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency; said portal antenna having a magnetic field coupling to tags 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; a transversal planar loop antenna connected to said antenna tap for transmitting signals at the signal frequencies of said analog signal; said antenna responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency; said transversal antenna having a magnetic field coupling to tags 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 analog signals having frequencies 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 said analog signal; a second planar antenna loop connected to another of said antenna taps for transmitting signals at the signal frequency of said analog signal; said first and second planar antenna loops positioned in planes at an angle with respect to each other.
- 9. The improvement set forth in claim 8 wherein planes intersect each other.
- 10. The improvement set forth in claim 8 wherein said antennas are portal antennas and said angle is 45°.
- 11. The improvement set forth in claim 8 wherein said antennas are portal antennas and said angle is a three dimensional angle of 45°.
- 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 analog signals having frequencies 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 said analog signal; a second portal planar antenna loop connected to another of said antenna taps for transmitting signals at the signal frequencies of said analog signal; said first and second portal planar antenna loops positioned in parallel planes spaced along a path of a tag to be detected; each of said antenna loops being 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 having frequencies corresponding to one of said selected frequencies; a first planar antenna loop connected to said first antenna tap for transmitting signals at the signal frequency of said analog signal; a second planar antenna loop connected to said second antenna tap for transmitting signals at the signal frequency of said analog signal; said first and second antenna taps driving 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 11 wherein said phase shift is 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; 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 a tag; said antenna tap 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; a planar portal transceiver loop antenna connected to said antenna tap for transmitting signals at the signal frequencies of said analog signal and for receiving signals transmitted by a tag; said portal planar transceiver loop antenna responsive to signals from said tap for generating a magnetic field surrounding said loop at said analog signal frequency and responsive to signals received from a tag; said antenna tap 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; 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 a tag; said antenna tap responsive to said mode signals for selecting the reactance of an oscillating circuit including said antenna; said planar transceiver antenna loop having 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; a planar transceiver loop antenna connected to said antenna tap for transmitting signals at the signal frequencies of said analog signal and for receiving signals transmitted by a tag; said antenna tap responsive to said mode signals for selecting the reactance of an oscillating circuit including said antenna and for squelching all transmissions in response to said squelch mode signal; said planar transceiver antenna loop having 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 frequencies of said analog signal and for receiving signals transmitted by a tag; a resonant circuit including said antenna; said resonant circuit having a higher Q when said antenna is transmitting than when said antenna is receiving.
RELATED APPLICATION
[0001] This application is a continuation-in-part of copending application Ser. No. 09/088,924 entitled MONITORING SYSTEM filed Jun. 2, 1998.
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09088924 |
Jun 1998 |
US |
Child |
09233755 |
Jan 1999 |
US |