| 摘要 |
The apparatus embodies an inquiry unit with a radio frequency emitter and an answering unit (transponder) with a frequency divider for the frequency of the emitter of the inquiry unit. The divided frequency is modulated with the data inside the transponder as a carrier frequency in a phase modulator for the transmission of the answer and the so modulated signal is delivered to a demodulator of the inquiry unit. In the demodulator, the original data sequence is recovered from the received phase modulated signal with the help of an unmodulated reference signal derived from the frequency transmitted by the inquiry unit itself, using an algorithm implemented by means of a digital signal processor, independently of the phase relationship between the phase modulated signal and the internal reference and with negligible delay.
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