Dual frequency identification system
First Claim
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1. An identification system comprising, in combination:
- an interrogator for transmitting a radio frequency signal; and
a tag including means receptive of said radio frequency signal for phase modulating said signal alternately at a first non-zero frequency and a second non-zero frequency in accordance with a preselected code and including means for re-radiating the thus modulated signal to said interrogator,said tag further including means producing a digital code signal for identifying said tag, which code signal is said preselected code, and further including a clock source coupled to said means producing said digital code signal for causing said code signal to be produced at a rate determined by the frequency of said clock,said interrogator further including means for demodulating the radio frequency component of the returned signal to thus produce a signal alternating between said first frequency and said second frequency and further including first and second amplitude modulated (AM) radios, each radio having a tuner adjustable over a band of frequencies, said tuners being tuned to pass said first and second frequencies respectively for passing signals indicative of said first and second frequencies, respectively, when present.
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Abstract
An identification system comprising one or more tags and an interrogator. A tag is responsive to a radio frequency signal transmitted from the interrogator for phase modulating the signal alternately with a first frequency and a second frequency depending on a preselected code and for re-radiating the phase modulated signal back to the interrogator.
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Citations
2 Claims
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1. An identification system comprising, in combination:
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an interrogator for transmitting a radio frequency signal; and a tag including means receptive of said radio frequency signal for phase modulating said signal alternately at a first non-zero frequency and a second non-zero frequency in accordance with a preselected code and including means for re-radiating the thus modulated signal to said interrogator, said tag further including means producing a digital code signal for identifying said tag, which code signal is said preselected code, and further including a clock source coupled to said means producing said digital code signal for causing said code signal to be produced at a rate determined by the frequency of said clock, said interrogator further including means for demodulating the radio frequency component of the returned signal to thus produce a signal alternating between said first frequency and said second frequency and further including first and second amplitude modulated (AM) radios, each radio having a tuner adjustable over a band of frequencies, said tuners being tuned to pass said first and second frequencies respectively for passing signals indicative of said first and second frequencies, respectively, when present.
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2. An identification system comprising in combination:
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an interrogator for transmitting a radio frequency signal; and a tag including means receptive of said radio frequency signal for phase modulating said signal alternately at a first non-zero frequency and a second non-zero frequency in accordance with a preselected code and including means for re-radiating the thus modulated signal to said interrogator, said interrogator further including means for demodulating the radio frequency component of the returned signal to thus produce a signal alternating between said first frequency and said second frequency and further including first and second amplitude modulated radios, each radio having a tuner adjustable over a band of frequencies, said tuner being tuned to said first and second frequencies respectively for passing signals indicative of said first and second frequencies, respectively, when present.
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Specification