Communications: electrical – Selective – Interrogation response
Reexamination Certificate
2004-12-03
2008-12-30
Bugg, George A (Department: 2612)
Communications: electrical
Selective
Interrogation response
C340S572100, C340S539100, C340S572400, C340S572700
Reexamination Certificate
active
07471188
ABSTRACT:
There has been a problem in battryless RFID chips that a high voltage AC signal is generated when an antenna is exposed to a high electromagnetic field, and a DC voltage that is obtained through rectification of the AC signal becomes a high voltage accordingly. As a result, heat generation of a logic circuit and a clock generator circuit or element break down occur. The invention takes the following measures: a DC voltage generated through rectification of an AC signal is compared with a reference voltage in a comparator circuit, and a switch element is turned ON when the DC voltage becomes higher so as to add capacitance to an antenna circuit. Accordingly, resonance point of an antenna changes which in turn attenuates an AC signal generated in the antenna circuit, thereby suppressing a DC voltage.
REFERENCES:
patent: 6229443 (2001-05-01), Roesner
patent: 6321067 (2001-11-01), Suga et al.
patent: 6427065 (2002-07-01), Suga et al.
patent: 7158031 (2007-01-01), Tuttle
patent: 2003/0016133 (2003-01-01), Egbert
patent: 2000-299440 (2000-10-01), None
Koyama Jun
Saito Toshihiko
Bugg George A
Cook Alex Ltd.
Hunnings Travis R
Semiconductor Energy Laboratory Co,. Ltd.
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