Process for carrying out a non-contact remote enquiry

Abstract

The invention relates to a system suitable for a remote interrogation of passive transponders using chirp signals for interrogation. The transponder preferably has an encoding unit ( ), a calibrating unit ( ) and a measuring unit ( ) each with a plurality of parallel channels ( to and to ). The encoding unit and the calibrating unit are preferably jointly incorporated with a common delay line ( ) on the same SAW chip. The interrogation signals received in the transponder via an antenna ( ) are delayed characteristically and code-specifically, in particular in the encoding and calibrating unit. Decoding in the interrogation station is preformed by discrete Fourier transformation of the response signal and subsequent evaluation of the spectrum. To correct general disturbing influences on the delay of the response signal, said signal is calibrated using a single calibrating component in the response signal. Calibration occurs by appropriate shift of the spectrum of the stored response signal. For partial correction of individual disturbing influences on the delay of the response signal components, the calibrated response signal undergoes additional correction. If further measuring response signals similar to the identifying and calibrating response signals are produced then they can, for example, be used to measure temperature by appropriate evaluation of the digitally stored response signal. The preferred combination of measuring and encoding unit enables each transponder to be calibrated individually, and consequently, for example, measurement of the absolute temperature.