Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1997-08-12
1999-03-16
Mullen, Jr., Thomas J
Communications: electrical
Condition responsive indicating system
Specific condition
310313R, 333187, G08B 1314
Patent
active
058835750
ABSTRACT:
An RF tag having an antenna for receiving a RF signal having a frequency band between first and second frequencies and an acoustical resonator having a resonant frequency related to the first and second frequencies. The acoustical resonator has first and second electrodes that sandwich a layer of piezoelectric material. The antenna is connected to one of these electrodes. The resonator filters the signal received on the antenna. The filter can function either as a notch filter or as a bandpass filter. A resonator that acts as a bandpass filter includes a third electrode and a second layer piezoelectric material sandwiched between the second electrode and the third electrode. A frequency multiplier circuit may be incorporated in the RF tag to provide a response signal that occupies a frequency band at a frequency above the second frequency. In one embodiment of the present invention, multiple resonators having different resonant frequencies are utilized to generate a response code. In one embodiment of the present invention, the resonators are suspended on a support member over a substrate at locations on the support member which differ in thickness.
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Canfield Philip
Ruby Richard C.
Hewlett--Packard Company
Mullen, Jr. Thomas J
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