Communications: electrical – Selective – Interrogation response
Reexamination Certificate
1997-05-23
2001-09-11
Cuchlinski, Jr., William A. (Department: 3661)
Communications: electrical
Selective
Interrogation response
C340S505000, C340S572100, C342S041000, C342S042000, C342S050000, C342S051000
Reexamination Certificate
active
06288629
ABSTRACT:
FIELD OF THE INVENTION
The field of the invention is the field of Radio Frequency (RF) Transponders (RF Tags), wherein a Base Station sends power and information to one or more RF Tags which contain logic and memory circuits for storing information about objects, people, items, or animals associated with the RF Tags. The RF Tags can be used for identification and location (RFID Tags) of objects and to send information to the base station by modulating the load on an RF Tag antenna.
BACKGROUND OF THE INVENTION
RF Tags can be used in a multiplicity of ways for locating and identifying accompanying objects, items, annims, and people, whether these objects, items, animals, and people are stationary or mobile, and transmitting information about the state of the of the objects, items, animals, and people. It has been known since the early 60's in U.S. Pat. No. 3,098,971 by R. M. Richardson, that electronic components on a transponder could be powered by radio frequency (RF) power sent by a “base station” at a carrier frequency and received by an antenna on the tag. The signal picked up by the tag antenna induces an alternating current in the antenna which can be rectified by an RF diode and the rectified current can be used for a power supply for the electronic components. The tag antenna loading is changed by something that was to be measured, for example a microphone resistance in the cited patent. The oscillating current induced in the tag antenna from the incoming RF energy would thus be changed, and the change in the oscillating current would lead to a change in the RF power radiated from the tag antenna. This change in the radiated power from the tag antenna can be picked up by the base station antenna and thus the microphone would in effect broadcast power without itself having a self contained power supply. In the cited patent, the antenna current also oscillates at a harmonic of the carrier frequency because the diode current contains a doubled frequency component, and this frequency can be picked up and sorted out from the carrier frequency much more easily than if it were merely reflected. Since this type of tag carries no power supply of its own, it is called a “passive” tag to distinguish it from an active tag containing a battery. The battery supplies energy to run the active tag electronics. An active tag may also change the loading on the tag antenna for the purpose of transmitting information to the base station, or it may act as a transmitter to broadcast the information from the tag antenna directly to the base station.
The “rebroadcast” of the incoming RF energy at the carrier frequency is conventionally called “back scattering”, even though the tag broadcasts the energy in a pattern determined solely by the tag antenna and most of the energy may not be directed “back” to the transmitting antenna.
In the 70's, suggestions to use tags with logic and read/write memories were made. In this way, the tag could not only be used to measure some characteristic, for example the temperature of an animal in U.S. Pat. No. 4,075,632 to Baldwin et. al., but could also identify the animal. The antenna load was changed by use of a transistor.
Prior art tags have used electronic logic and memory circuits and receiver circuits and modulator circuits for receiving information from the base station and for sending information from the tag to the base station.
U.S. Pat. No. 5,214,410, hereby incorporated by reference, teaches a method for a base station to communicate with a plurality of Tags.
Prior art tags typically use a number of discrete components connected together with an antenna. However, to substantially reduce the cost of the tags, a single chip connected to an antenna must be used.
The environment of RF tags is such that the power transferred to the tags may vary because the tag is moving with respect to the base station or because other sources of interference are changing while the base station is trying to write information to the non-volatile tag memory. Typically, the information is written a single byte at a time. The tag voltage is assumed to be high enough to write to the E
2
PROM memory elements during the entire time the byte is being written to memory. However, if the voltage is not high enough, not enough charge will be stored in the E
2
PROM memory elements. Enough charge may be stored that the base station writing the memory can call for a read back of the memory that was just written, and the read back data will be correct. However, if the tag is moved to another location, the same or another base station may read the memory and get a different result if not enough charge is stored in the E
2
PROM memory elements.
RELATED APPLICATIONS
Copending patent applications assigned to the assignee of the present invention and hereby incorporated by reference, are identified as follows:
Ser. No. 08/303,965 filed Sep. 9, 1994 entitled RF Group Select Protocol, by Cesar et al., (now U.S. Pat. No. 5,673,037, issued Sep. 30, 1997);
Ser. No. 08/304,340 filed Sep. 9, 1994 entitled Multiple Item RF ID Protocol, by Chan et al., (now U.S. Pat. No. 5,550,547, issued Aug. 27, 1996);
Ser. No. 08/521,898 filed Aug. 31, 1995 entitled Diode Modulator for RF Transponder by Friedman et al., (now U.S. Pat. No. 5,606,323, issued Feb. 25, 1997).
Application submitted Aug. 9, 1996 entitled RFID System with Broadcast Capability by Cesar et al., Application No. 08/694,606 filed Aug. 9, 1996, (now U.S. Pat. No. 5,942,987 issued Aug. 24, 1999); and
Application submitted Jul. 29, 1996 entitled RFID Transponder with Electronic Circuitry Enabling and Disabling Capability, by Heinrich et al., Application No. 08/681,741 filed Jul. 29, 1996, (now U.S. Pat. No. 5,874,902 issued Feb. 23, 1999).
SUMMARY OF THE INVENTION
A field in the volatile memory of an RF tag is defined as a “write-OK” flag. This field may consist of multiple bits, which can define multiple states, or it may consist of only a single bit, which can be in a first state or a second state. It may consist of a latch. When the tag first powers up in the field of a base station, the “write-OK” flag is cleared or set to the second state. When a base station wants to send data for a tag to write to memory, the base station or the tag first sets the “write-OK” flag to the first state. After the flag has been set, the base station then starts the “write to memory” procedure. During the entire “write to memory” procedure, the tag measures the tag voltage. If a determined percentage of the tag voltage falls below a stable reference voltage, the tag clears the “write-OK” flag, (i.e. sets the flag to the second state). After the data has been written to memory, the tag or the base station can check whether the “write-OK” flag is still set, and if the “write-OK” flag is still set, the data in the memory can be trusted.
REFERENCES:
patent: 5440302 (1995-08-01), Irmer et al.
patent: 5517194 (1996-05-01), Carroll et al.
patent: 5521590 (1996-05-01), Hanaoka et al.
patent: 5712630 (1998-01-01), Nanboku et al.
Cofino Thomas Anthony
Friedman Daniel Joseph
Goldman Kenneth Alan
Heinrich Harley Kent
Beaulieu Yonel
Cuchlinski Jr. William A.
Intermec IP Corp.
O'Melveny & Myers LLP
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