U.S. Philips Corporation

Josef Preishuberpflugl

Bernhard Spiess

Siegfried H Arnold

Hubert Watzinger

A transmission and receiving device for contact data transmission between the device and a transponder. The transmission and receiving device has an antenna resonant circuit, a synchronous demodulator, a measuring unit, a control unit, and a reference signal generator. In operation, the device and the transponder are inductively coupled to each other through the antenna resonance circuit of the device and an antenna resonance circuit in the transponder. In response to an interrogation by the device, the transponder sends a load modulated digital signal to the device. The synchronous demodulator detects digital response data contained in the load modulated digital signal. The measuring unit measures a phase shift between a reference signal generated by the reference signal generator and a resonance signal generated in the antenna resonance circuit in the device by the sent load modulated digital signal. The control unit controls the synchronous demodulator such that the synchronous demodulator changes its demodulation mode between amplitude demodulation and phase demodulation, in dependence of the measured phase shift.

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Graz, Austria

Josef Preishuberpflugl