Patent ID: 7240838

Claim:
A reader for identifying passive transponders of the type including an antenna for receiving a first signal from the reader and for transmitting a second signal, comprising: a modulated carrier signal generator constructed and arranged to produce as an output a modulated carrier signal that represents data to be transmitted; an antenna that receives as an input the modulated carrier signal from the modulated carrier signal generator and transmits the modulated carrier signal as the first signal; a demodulator connected to receive as an input a modulated said second signal transmitted to the antenna; and a decoder connected to receive an output of the demodulator; wherein the modulated carrier signal generator is constructed and arranged to generate the modulated carrier signal so as to include pauses in the signal during which the modulated carrier signal does not oscillate, the modulated carrier signal generator maintaining the modulated carrier signal at the maximum voltage during the pauses, wherein, the modulated carrier signal generator comprises: a time base that generates a sinusoidal signal; a modulator that transmits data; and a control circuit arranged to receive the sinusoidal signal from the time base and the data from the modulator, the control circuit producing as an output the modulated carrier signal based on the sinusoidal signal and the data, and wherein the modulated carrier signal generator is constructed and arranged so that the modulated carrier signal represents a succession of bits with said pause inserted between adjacent said bits.