Importance

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Abstract

An identification device is provided which includes an inactive code carrier, such as a standing acoustic wave component, a frequency mixing section, and a double antenna input. Each of the antennas are tuned to a separate predetermined transmitted signal wherein the frequencies are different. The two separately received RF frequencies are mixed to produce an intermediate frequency having the sum or difference of the two received frequencies. The intermediate frequency is coupled to the standing acoustic wave device which applies a coded signal to the intermediate frequency. The intermediate frequency is then recombined with one of the original incoming RF frequencies to be retransmitted from the identification device. The mixer section can include a diode and a coil for matching the impedance of the incoming signal with the inactive code carrier. The code carrier or standing acoustic wave component is usually tuned to the lower intermediate frequency and thus, is a selective filter for the frequencies emanating from the mixing section.

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First Claim