Electronic identification system
First Claim
1. A short range detecting and identification system of the type including a transmitter, a receiver, and at least one identification tag remotely situated relative to the transmitter and receiver, said transmitter transmitting electromagnetic energy signals of a predetermined frequency, wherein:
- said tag comprises;
a harmonic radiator for deriving from said signals of said predetermined frequency signals harmonically related thereto and selectively radiating said harmonically related signals in a direction to said receiver, encoding means, responsive to a clock signal, for modulating said derived harmonically related signals in accordance with a predeterined digital identification code, and timing means, for deriving said clock signal; and
said receiver comprises;
first detector means for detecting said modulated harmonically related signal radiated from said tag and generating output signals indicative of the identification code modulation of said radiated signal, and second detector means for sensing the presence of reflected signals of said predetermined frequency whereby the presence of an inoperative tag is sensed.
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Abstract
An electronic detection and identification system operating with correlated microwave frequencies wherein a transmitter continuously transmits a beam of electromagnetic energy, in a predetermined direction, so as to impinge on an identification tag suitably attached on a passing object. The identification tag derives a harmonic signal from the impinging beam and radiates a beam of energy, at the harmonic frequency, which is pulse modulated in accordance with a preset identification code. The receiver receives the reflected beam and generates signals representative of the code modulation.
142 Citations
10 Claims
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1. A short range detecting and identification system of the type including a transmitter, a receiver, and at least one identification tag remotely situated relative to the transmitter and receiver, said transmitter transmitting electromagnetic energy signals of a predetermined frequency, wherein:
- said tag comprises;
a harmonic radiator for deriving from said signals of said predetermined frequency signals harmonically related thereto and selectively radiating said harmonically related signals in a direction to said receiver, encoding means, responsive to a clock signal, for modulating said derived harmonically related signals in accordance with a predeterined digital identification code, and timing means, for deriving said clock signal; and
said receiver comprises;
first detector means for detecting said modulated harmonically related signal radiated from said tag and generating output signals indicative of the identification code modulation of said radiated signal, and second detector means for sensing the presence of reflected signals of said predetermined frequency whereby the presence of an inoperative tag is sensed.
- said tag comprises;
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2. The system of claim 1 wherein:
- said transmitter and said receiver antennas are mounted below gound level and maintain radiation pattern main lobes directed in an upward substantially vertical direction.
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3. The system of claim 2 wherein:
- said transmitter and said receiver antennas are situated such that the respective radiation patterns of said antennas overlap thereby generating a substantially constant low level signal in said receiver whereby an inoperative transmitter-receiver station may be detected.
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4. The system of claim 1, wherein said signals harmonically related to said signals of predetermined frequency are the second harmonic of said predetermined frequency.
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5. In a short range detecting and identification system of the type including a transmitter, a receiver, and at least one identification tag remotely situated relative to the transmitter and receiver, the transmitter transmitting electromagnetic energy signals of a predetermined frequency, and the receiver including means for detecting pulse modulated signals from the tag harmonically related to the predetermined frequency signal;
- an improved identification tag comprising;
antenna means for receiving said predetermined frequency signal and selectively radiating said harmonically related signals in a direction to said receiver;
a non-linear device, coupled to said antenna means, for deriving from said signals of said predetermined frequency signals harmonically related thereto;
timing means, for deriving a clock signal;
storage means for storing a binary code word indicative of a predetermined digital identification code;
shift register means, for progressively advancing a stored code to successive member bits in accordance with said clock signals; and
mode selection means for alternatively loading said shift register means with said stored binary code word and applying the output signal of a specified member bit of said shift register means as a biasing voltage to said non-linear device in accordance with said identification code.
- an improved identification tag comprising;
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6. The tag of claim 5, wherein said signals harmonically related to said signals of said predetermined frequency are the first harmonic of said predeterined frequency.
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7. In a short range detecting and identification system of the type including a transmitter, a receiver and at least one identification tag remotely situated relative to the transmitter and receiver, the transmitter transmitting an on-off amplitude modulated wave of a predetermined frequency having a specified duty cycle and the receiver including means for detecting pulse modulated signals from the tag harmonically related to said predetermined frequency signal;
- an improved identification tag comprising;
a harmonic radiator for deriving, from said signals of said predetermined frequency, signals harmonically related thereto and selectively radiating said harmonically related signals in a direction to said receiver;
coding means, responsive to a clock signal, for pulse modulating said derived harmonically related signals in accordance with a predetermined digital identification code; and
timing means including an envelope detector receptive of said predetermined frequency signal, for deriving said clock signal.
- an improved identification tag comprising;
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8. In a short range detecting and identification system of the type including a transmitter, a receiver and at least one identification tag remotely situated from the transmitter and receiver, the transmitter transmitting a signal of predetermined frequency and the receiver including means to detect puLse modulated signals from the tag harmonically related to said predetermined frequency signal;
- an improved tag comprising;
a harmonic radiator for deriving, from said signals of said predetermined frequency, signals harmonically related thereto and selectively radiating said harmonically related signals in a direction to said receiver, encoding means, responsive to a clock signal, for pulse modulating said derived harmonically related signals in accordance with a predetermined digital identification code;
timing means, for deriving said clock signal;
a power source; and
switching means, responsive to said predetermined frequency signals, for applying said power source to said encoding means and said timing means only during such time as said tag is illuminated by said predetermined frequency signal.
- an improved tag comprising;
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9. In a short range detecting and identification system of the type including a transmitter, a receiver and at least one identification tag remotely situated from the transmitter and receiver, the transmitter transmitting a continuous wave signal of predetermined frequency and the receiver including means to detect pulse modulated signals from said tag harmonically related to said predetermined frequency signal;
- an improved tag comprising;
a harmonic radiator including an antenna and a non-linear device, said antenna being coupled across said non-linear device, for deriving from said signals of said predetermined frequency signals harmonically related thereto and selectively radiating said harmonically related signals in a direction to said receiver;
encoding means, responsive to a clock signal, for pulse modulating said derived harmonically related signals in accordance with a predetermined digital identification code;
timing means, for deriving said clock signal; and
means for extracting power for said encoding means and timing means from said predetermined frequency signal including impedance transforming means, receptive of said predetermined frequency signal as received at said antenna, for stepping-up the impedance of said antenna; and
rectifier means, receptive of the output signals of said impedance matching means; and
filter means for establishing direct current signal.
- an improved tag comprising;
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10. A short range detecting and identification system of the type including a transmitter, a receiver and at least two identification tag remotely situated from the transmitter and receiver;
- said transmitter illuminating the approach to an entrance to an enclosure with a signal of predetermined frequency;
said receiver being arranged to receive signals harmonically related to said predetermined frequency signal radiated from said tag from positions in the approach;
said tag comprising;
a harmonic radiator for deriving, from said signals of said predetermined frequency, said signals harmonically related thereto and selectively radiating said harmonically related signals in a direction to said receiver;
encoding means, responsive to a clock signal, for pulse modulating said derived harmonically related signals in accordance with a predetermined digital identification code and timing means, for deriving said clock signal;
wherein;
said entrance is closable and includes latching means; and
said receiver is operably connected to said latching means and activates said latching means in accordance with said predetermined identification code number.
- said transmitter illuminating the approach to an entrance to an enclosure with a signal of predetermined frequency;
Specification