Passive identification system

• US 3,878,528 A
• Filed: 10/12/1973
• Issued: 04/15/1975
• Est. Priority Date: 10/12/1973
• Status: Expired due to Term

• Current Assignee: Henrie Lionel Majeau
• Original Assignee: Henrie Lionel Majeau
• Inventors: Majeau, Henrie Lionel
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/405,744
• Time in Patent Office: 550 Days
• Field of Search: 343/6.5SS,6.5R
• US Class Current: 342/44
• CPC Class Codes: B61L 25/045 using reradiating tags
• CPC Class Codes: G01S 13/753 using frequency selective elements, e.g. resonator

Abstract

A transceiver-responder identification system which utilizes a swept frequency spectrum signal in the microwave frequency range. The energy generated by the transceiver portion is transmitted in a predetermined number of discrete frequency steps within a frequency octave. This swept spectrum signal is received by the responder portion, which doubles the stepped frequencies comprising the swept spectrum signal, and then routes the signal through a selective filter arrangement comprising a transmission line bounded by a series of directional ring filters, each filter being tuned to one of the frequencies in the swept spectrum signal. If the ring filter corresponding to a specific frequency is physically complete, the signal energy present at that frequency will be coupled into the ring and subsequently dissipated in a load. If the ring filter corresponding to a specific frequency is not physically complete, the signal energy at that frequency continues along the transmission line. This remaining signal energy is then retransmitted to the transceiver portion. By arranging complete and incomplete rings in a unique pattern for each responder in the system, each responder will then transmit a signal unique to the animal or article bearing the responder, which signal is decoded by the transceiver and coverted to a corresponding digital word comprising ones and zeros. This digital word provides a common format for article identification purposes. The ones and zeros correspond to the presence or absence of return signal energy at the various frequencies originally generated and transmitted to the responder.

Claims

1. A passive identification system using a given range of frequencies for communication between a transceiver and at least one passive responder, comprising:

signal generating means in said transceiver for generatinG a frequency spectrum signal within said given frequency range, which frequency spectrum signal comprises a series of successive discrete frequencies;

means for transmitting said frequency spectrum to a passive responder, which responder retransmits to said transceiver selected frequencies from said series of successive discrete frequencies;

means in said transceiver and said responder for changing the frequency of each of said successive discrete frequencies by a given factor;

means in said transceiver for comparing said frequency spectrum with said retransmitted selected frequencies so as to determine coincidence between each of said frequency changed successive discrete frequencies transmitted to said responder, and the selected frequencies retransmitted from said responder to said transceiver; and

, means responsive to said comparing means for generating an identification code indicative of said coincidence with respect to each successive discrete frequency in said frequency spectrum signal.

2. An apparatus in accordance with claim 1, wherein said system includes a plurality of responders.

3. An apparatus in accordance with claim 2, wherein said given frequency range is one frequency octave.

4. An apparatus according to claim 1, including means for offsetting the frequency of each of said series of successive discrete frequencies by a specified small amount compared to said discrete frequencies, and offsetting means operable only on the series of successive discrete frequencies otherwise applied to said comparing means.

5. An apparatus according to claim 1, wherein said frequency changing means is a multiplier with a factor of 2.

6. An apparatus according to claim 1, wherein said comparing means includes a mixer having two inputs, one input coupled to said frequency offsetting means, and the other input responsive to said retransmitted selected frequencies from said responder, said mixer generating sum and difference frequencies of said two inputs.

7. An apparatus according to claim 6, wherein said comparing means further includes a detector, coupled to said mixer, for determining the presence or absence of retransmitted frequencies identical to any one of said series of successive discrete frequencies.

8. An apparatus according to claim 7, including a clock generator, and wherein said code generating means is a comparator, which comparator is responsive to said detector and said clock generator a binary code which is dependent on the presence or absence of a selected frequency identical to each of said series of successive discrete frequencies, the presence of a coincidence between one of said series of successive discrete frequencies and one of said selected frequencies being represented by one binary character, and the absence of a coincidence between one of said series of successive discrete frequencies and said selected frequencies being represented by the other binary character.

9. An apparatus according to claim 8, including display means, coupled to said comparator for presenting said code in recognizable form.