I.G. Antsev, S.V. Bogoslovsky, A.R. Zhezherin, P.I. Ermakov

Identification is a process of object recognition (or its classification) by its identifier. The object identifier is presented to a reader that reads and transmits object-s individual codeword to the system of identification for the procedure of recognition. The representation form of an identifier-s individual codeword is considered. Data encoding in radio frequency identification (RFID) systems is made through the modulation of radio signals. Currently a large number of modulation variants are used. There are three main groups among them: amplitude, phase and frequency modulation. Applied to RFID systems based on surface acoustic waves (SAW) data encoding has several features. To illustrate these features one of the possible SAW device structure is briefly described. The most popular identifiers types (methods of information encoding) in RFID systems on SAW at the moment are considered: identifier encoded by pulse-amplitude modulation, identifier using time position encoding, and Global SAW Tag. The essence of methods is described, their comparative analysis is given, advantages and disadvantages are specified. Main provisions of an information encoding method based on М-ary random FSK modulation of radio signals are considered in detail. The requirements shown to used signals and frequency manipulation code words are resulted. In making decisions about ownership of the received signal for the classified object the principle of matched filtering is used, therefore it was studied the possibility of М-ary random FSK modulation applying to create a family of radio signals, within which cross-correlation function (CCF) of any pair of signals would not exceed a set level. Searching of the desired FSK signals family was made by the method of mathematical modeling in the package MATLAB. The algorithm of signals family searching is step by step described. The results of modeling are illustrated graphically. The study can be concluded that the use of М-ary FSK modulation is useful when creating a family of signals with a given level of cross-correlation.