ANALYSIS OF SPECTRA OF MULTI-FREQUENCY AMPLITUDE MODULATED RADIO SIGNALS

The article presents the results of modeling the spectra of multi-frequency radio signals formed by phase modulation of a high-frequency pulsed amplitude-modulated radio signal by harmonic oscillation of an intermediate frequency in a phase modulator. Based on the obtained expression for the spectrum of the complex contour of the multi-frequency amplitude-modulated signal at the output of the phase modulator, the components of its spectrum were analyzed depending on the modulation parameters. It was established that the amplitude of these components of the spectrum and their number in the spectrum is uniquely determined by the values of the Bessel function of the first kind from the real argument - the phase modulation index. The value of the phase modulation index is directly proportional to the amplitude of the harmonic oscillation of the intermediate frequency and the steepness of the phase modulation characteristic. Frequency differences between adjacent components of the multi-frequency spectrum are uniquely determined by the frequency of the harmonic oscillation of the intermediate frequency. Each spectral component is a function of the form sinc (x), and the width of the spectrum is inversely proportional to the duration of the initial pulse amplitude-modulated radio signal. The initial phase of the central component of the spectrum corresponds to the initial phase of the high-frequency pulse amplitude-modulated radio signal. The initial phases of the side components of the spectrum depend on the nature of the change in the Bessel functions by the given phase modulation index. According to the nature of the change of the spectrum parameters according to the modulation parameters, the multi-frequency amplitude-modulated signal can be classified as a family of noise-like signals. The formation of multi-frequency amplitude-modulated signals is carried out by single-channel devices, and no strict linearity restrictions are imposed on power amplification stages. The practical application of the studied signals provides an opportunity to potentially increase the energy and structural stealth of radio communication and radar systems.