This article presents the results of the research of noiseimmunity of wireless communication systems using signals that are formed on the basis of eight-position quadrature-amplitude modulation (8-QAM) and eight-position amplitude modulation of many components (8-AMMC). The research was conducted using simulation of a wireless communication system, built using a detector, implemented on the basis of a phase locked loop. The influence of phase locked loop parameters on the detection quality of these signals in the condition of the interference in the communication channel was researched, and a comparative analysis of the noise immunity of wireless communication systems using these signals was carried out.

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This article considers the experimental research of transient processes that occur in digital phase-locked loops (DPLL) after closing the feedback loop. Firmware implementation of DPLL device was made for this purpose. The paper shows the block diagram of the DPLL and describes its mathematical model. In particular, the location of poles and zeros of DPLL transfer function was determined by the transfer function of the 2nd order analog PLL and the formulas for digital filter coefficients were deducted. The article also represents the block diagram of hardware part of the firmware DPLL. Its key part is the STM microcontroller which is connected to the PC. For convenience reasons, the unique interface between the microcontroller and the PC was created in order to present waveforms of several signals simultaneously. Moreover, the paper depicts the algorithm of software part of the firmware DPLL in general as well as the detailed algorithm of voltage-controlled oscillator (VCO) operation – it works as direct digital synthesizer (DDS). The experimental research of the frequency acquisition process of harmonic oscillation was performed for three different sets of DPLL parameters. For each case the location of DPLL poles and zeros and plots of DPLL key signals (tracking error, current frequency and phase of output signal) were shown. Obtained diagrams demonstrate that a change of the DPLL natural frequency and damping factor influences on the transient process duration. Pictures signal waveforms from oscilloscope confirm these results. Furthermore, the results of the firmware DPLL research correspond to investigation results of existing simulation model of this DPLL with sufficient accuracy.

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The article is devoted to the problem of quickly measurement of the initial velocity of a mortar shell. In the article is carried out the simulation modeling of two optimal modifications of the radar response parameters meter from such a target. The structural diagrams of both modifications and the parameters of their analytical mathematical models are given and described. Numerical tests of both models are carried out for a test trajectory that simulates the uniformly decelerated motion of the shell. According to the simulation results, the values of the meters parameters, which ensure the monitoring of the radar response frequency from the shell during the entire observation time and in a wide range of changes in the energy potential, are determined. The possibility of significantly reducing the capture time of the radar response frequency is shown.