Pulse shaping in ISO/IEC14443 measurement systems using inverse system parameters for feed-forward compensation

An arbitrary pulse shaping of the amplitude modulating signal is a standard procedure used to assess the demodulator capabilities of RFID proximity cards working under the ISO/IEC 14443-2A standard requirements. The physical nature of the standard measurement setup can distort the modulating signal in a way that the extracted timing parameters of the desired compared with the gained pulse shaping differ significantly. Therefore, a feed-forward compensation of the modulating signals is proposed to ensure a good agreement of the output signal with the given timing parameters specified by the standard. The feed-forward compensator is derived from the inverse, non-minimum phase, measurement system characteristic by on-line self transfer function identification. A real-time implementation of the feed-forward compensator is accomplished by means of a parallel bi-quad IIR filter structure. The result of a comparative measurement has shown that the absolute timing errors are in the range of 0.2 carrier periods (about 15ns).