EVALUATION NOISE IMMUNITY OF THE BINARY DIGITAL MODEM WITH SIGNALS TYPE NOISE USING THE CHARACTERISTIC FUNCTION METHOD

The issue of improving modems with noise signals implies increasing the accuracy of theoretical estimation of noise immunity of the proposed methods of demodulation of information components of signals. Important is the task of assessing the immunity of digital modems, enabling engineers to ascertain the prospect of system development at the design stage. The article investigates the noise immunity of a binary digital modem with phase manipulation of the noise signal and the autocorrelation algorithm of its reception, which uses as noise carrier Gaussian signals. The paper presents a technique for calculating the bit error rate (BER) in a demodulator, which is characterized by the fact that the functional for estimating the received information bit contains components with different laws of probability distribution. The presented methodology is based on a mathematical apparatus of characte­ristic functions, which allows determining the potential noise immunity of a digital modem, providing a reduction of the discrepancies between theoretical and experimental data for determining the BER. Summing up the whole research it is worth noting the following research results: 1 noise immunity analysis of digital binary modem of noise signals was performed using mathematical apparatus of characteristic functions at autocorrelation method of operation of Gaussian type noise signal demodulator in the presence of Gaussian additive interference; 2 an analytical expression was found to calculate the characteristic density function of the random variable distribution at the output of a binary digital correlator; 3 the ratio was obtained to determine the potential noise immunity of the demodulator. The results of the study showed that the application of this technique eli­minates significant differences between the results of the theoretical evaluation of the noise immunity of the demodulator and the results of its simulation.