Identification system
AssigneeIdentification Devices, Inc.
InventorThomas A. Milheiser
Life of this patent
Estimating the term…
Abstract
A passive integrated transponder (PIT) is attached to or embedded in an item to be identified. It is excited via an inductive coupling from an interrogator. The PIT responds to the interrogator via the inductive coupling with a signal constituting a stream of data unique to the identified item. The signal is in the form of two different frequencies, a shift from one frequency to the second during a bit cell representing a data "one", and a shift from the second frequency to the first frequency representing a data "zero". The responsive signal is then detected and processed for utilization in a data storage or display device.
Claims39
An object identification system, comprising:
- an interrogator comprising means for sending a continuous interrogation signal and means for detecting a responsive identification signal, and
- a transponder comprising means for detecting said interrogation signal and for transmitting an identification signal in response to said detection,
- wherein said identification signal extends over a plurality of bit cells of equal length in time, and comprises a preamble portion having a specified number of bit cells and an identification portion having a specified number of bit cells, and a further encoded portion having a specified number of bit cells having a predetermined signal content interposed between said preamble portion and said identification portion;
- and
- wherein said preamble and identification portions of said identification signal are transmitted according to a first format in which a signal transmission parameter is varied between first and second values during each of said bit cells, and wherein said further encoded portion is transmitted according to a second format in which said identification signal is transmitted without variation in said transmission parameter for a period at least equal to one bit cell.
A transponder for use in an object identification system of the type comprising an interrogator comprising means for sending a continuous interrogation signal and means for detecting a responsive identification signal,
- said transponder comprising means for detecting said interrogation signal and for transmitting an identification signal in response to said detection,
- wherein said identification signal extends over a plurality of bit cells of equal length in time, and comprises a preamble portion having a specified number of bit cells, a data portion hving a specified number of bit cells, and a further portion having a specified number of bit cells each having a predetermined signal content interposed between said preamble portion and said data portion, and
- wherein said preamble and data portions are transmitted according to a first format in which a signal transmission parameter is varied between first and second values during each of said bit cells, and said further portion is transmitted according to a second format in which the identification signal is transmitted without variation in said transmission parameter for a period at least equal to one bit cell.
Method for identifying objects, comprising the steps of:
- emitting a continuous interrogation signal from an interrogator;
- detecting said interrogation signal at a transponder in the vicinity of said interrogator;
- transmitting an encoded identification signal from said transponder to said interrogator;
- and
- receiving and decoding said encoded identification signal at said interrogator;
- wherein said identification signal includes a first preamble portion, a last identification portion, and a further portion interposed between said first and last portions,
- wherein said preamble and identification portions each have a number of equally-spaced bit cells, and said further portion comprises a number of bit cells each of predetermined signal content and
- wherein said preamble and identification portions are transmitted according to a first format in which a signal transmission parameter is varied between first and second values during each of said bit cells, and said further portion is transmitted according to a second format in which said transmission parameter is not varied for a period at least equal to one bit cell.
Dependencies are inferred from the claim text.