Registers – Coded record sensors – Particular sensor structure
Reexamination Certificate
1998-09-24
2001-01-09
Lee, Michael G. (Department: 2876)
Registers
Coded record sensors
Particular sensor structure
C235S385000, C235S492000, C340S572800
Reexamination Certificate
active
06170748
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to object identification systems, and is particularly directed to a pulsed magnetic field-based, tagged object information storage and retrieval system, that operates independently of the orientation of the information storage medium or ‘tag’ placed on the object. When interrogated by a repetitively pulsed exciting magnetic field generated by a tag reader, a tag transponder embedded in the tag pauses to allow its circuitry to settle, and then emits a pulse position modulation (PPM) response magnetic field waveform at the same frequency as and prior to the next exciting pulse.
BACKGROUND OF THE INVENTION
The identification of objects, such as packages, retail sales items, shipping containers, and the like, is often accomplished by affixing an information storage medium such as a ‘bar code’ label to an object. The bar code is encoded with previously assembled and stored information that fully describes the object. In order to read the label, the object must be oriented so that the bar code may be ‘viewed’ by an optical (e.g. laser) scanner, either as a stationary device or a hand held unit.
A familiar example of the use of such a scanner is a check-out line of a retail sales establishment, where a clerk orients each item with the bar code label face down, and then passes the item across a generally horizontal viewing window. As the object is passed over the window, the bar code is read by the scanner located beneath the window, which outputs data to an adjacent point-of-sales terminal, where the sales transaction is processed. If the object is not properly oriented to allow the scanner to read the label, the sales clerk will not hear an audible tone confirming success of the scan, and will repeat the process.
A similar technique is employed in the transportation industry, where items (e.g., baggage) being unloaded from a vehicle (e.g, aircraft) are placed upon a conveyor belt in a prescribed orientation, so that they may be viewed by the scanner. If the object has not been properly placed on the conveyor, the object will require further handling by other personnel to properly orient the bar code label so that it can be read by a downstream (stationary or hand held) scanner. This need to physically orient encoded label-containing items relative to an optical scanner is both labor-intensive and time-consuming, and constitutes an unwanted expense.
Non-limiting examples of proposals to address this problem include a variety of transponder tag-based systems, such as those described in the Bickley et al, U.S. Pat. No. 5,430,441; Watanabe et al, U.S. Pat. No. 5,478,991; and Brooks et al, U.S. Pat. No. 5,485,154. In each of these schemes, the tag is powered by an exciting source that continuously generates an exciting magnetic field to power the tag. In the Bickley et al and Watanabe et al approaches the tag responds by modulating the continuously transmitted field. In the Brooks et al scheme, the tag responds by generating a signal at a frequency different from the exciting frequency to avoid interference. An obvious drawback of each patented approach is the fact that they continuously consume power. Indeed, in the Brooks et al scheme, the amount of excitation energy required is so large, that it requires the use of a shielded tunnel to prevent electromagnetic contamination of the surrounding environment.
SUMMARY OF THE INVENTION
In accordance with the present invention, both the physical handling and orientation problems associated with conventional bar code label scan systems, and the power consumption shortcomings and circuitry complexity of continuously operated sources, such as those of the above-described patented schemes, are successfully obviated by a pulsed magnetic field-based information storage and retrieval system, which tags an object with a normally unpowered transponder containing memory for storing object identification information.
The tag transponder of the invention operates independently of its orientation and is powered by a low duty cycle, pulsed (rather than continuous) magnetic field, through which a tag access unit, such as a tag reader or a writer repetitively ‘pings’ the tag. This pulsed magnetic field is sensed by a coil in the tag and provides a power burst that stimulates the transponder's circuitry to either capture and store information embedded in the pulse during write mode, or to respond to a read or interrogate ‘ping’ by emitting a PPM magnetic field waveform containing object identification information stored in non-volatile transponder memory.
Once powered up during read mode, in response to each magnetic field pulse, the tag's transponder pauses or waits for a prescribed stabilization and data bit defining interval before emitting a PPM reply waveform. The PPM reply magnetic signal is transmitted at the same frequency as the exciting pulse, prior to the next exciting pulse from the reader. AT the reader, the transponder's magnetic reply signal may be detected by a coil that is separate from that used to generate the tag-excitation magnetic field.
In a preferred, but non-limiting, embodiment of the invention, the tag transponder may be affixed to flexible strip of rugged, protective material, such as Mylar. To provide magnetic field powering of and emission of a PPM response signal from the flexible strip-mounted transponder, a thin conductive coil is embedded in the Mylar and coupled to respective power terminals of the tag's transponder circuitry. In response to a pulsed interrogation magnetic field generated by the tag reader, a voltage sufficient to power the transponder's microcircuit is induced across the power terminals in proportion to the time derivative of the magnetic field passing through the coil.
The transponder circuitry includes a power burst storage capacitor that stores energy during successive positive half cycles of an alternating interrogation magnetic field burst. This power burst storage capacitor is used to power the components of the transponder circuitry. The transponder coil is further coupled to a reply energy storage capacitor, which is coupled through a diode oriented such that the reply energy storage capacitor stores energy during successive negative half cycles of a received burst.
During read/response mode, the energy stored in the reply energy storage capacitor is used in conjunction with the tag's coil and a controllably gated FET switch coupled across the diode to generate a PPM modulated alternating magnetic field at the same frequency of the magnetic field read burst to be emitted from the coil, and containing (tag identification) information stored in memory.
During write mode, information to be programmed or written into the tag may be encoded in the repetitively transmitted tag-powering magnetic field bursts. For on-the-fly applications, the tag transponder's memory may be programmed electronically by means of a programmable voltage pulse generator, or magnetically by means of a write coil and a shielded programmable magnetic field generator, into which the transponder-embedded strip is inserted at the time of use.
To control the mode and timing of the operation of the transponder's circuitry, the tag coil is further coupled through a rectifier to a counter, which is operative to count positive half cycles contained in each magnetic field burst from the reader. The number of cycles within a read burst is different from that for a write mode of operation. The count output is used to initiate and control the mode of operation of a state machine. During read mode the state machine accesses object information data that has been previously written to or stored in non-volatile memory in preparation for transmission of successive bits of the stored object identification data during successive PPM reply waveforms.
The state machine has an output coupled to an FET switch, the source-drain path of which is coupled across the diode in circuit with the reply energy storage capacitor. During a reply window between s
Belcher Donald K.
Boyd Robert W.
Hash Ronald J.
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Lee Michael G.
Widata Corporation
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