초록 ▼

An electronic identification system includes common transceiver and signal processing apparatus, and relative small electronic circuitry, referred to as a “tag”, secured to each item of a population to be identified. Each tag is assigned a multi-bit digital code which may or may not be unique. The c

An electronic identification system includes common transceiver and signal processing apparatus, and relative small electronic circuitry, referred to as a “tag”, secured to each item of a population to be identified. Each tag is assigned a multi-bit digital code which may or may not be unique. The common equipment determines whether any desired tag-bearing item is nearby by emitting a phase modulated radio frequency wave embodying the requisite tag code, and examining the output of a homodyne mixer, operating on a radar-like recovered reflection signal, for a predetermined signatory response. Such a response will be generated only by a tag circuit responding to a match between its stored encoding and that of the interrogation signal by changing the effective cross sectional reflecting area of the tag antenna.

대표청구항 ▼

In combination in electronic identification apparatus, transceiver means including means for emitting a carrier modulated with a digital word, means for recovering a reflected signal of like frequency, and means for processing said recovered like frequency signal to determine the incidence of a tag-

In combination in electronic identification apparatus, transceiver means including means for emitting a carrier modulated with a digital word, means for recovering a reflected signal of like frequency, and means for processing said recovered like frequency signal to determine the incidence of a tag-signalling amplitude variation therein, and at least one tag circuit means, said tag circuit means including an antenna, register means for storing a tag encoding, demodulator means connected to said antenna for recovering said modulated digital word, controlled means for selectively varying the electrical length of said antenna comprising selectively conductive means connected in parallel with a section of said antenna, and means connected to said demodulator means and said register means responsive to a match between the incoming demodulated digital word and the encoding contents of said register means for signalling said control means to vary said antenna electrical length comprising means for turning on said selectively conductive means responsive to the output of said match responsive means.