Distortion of the radiation patterns of phased antenna arrays under the influence of periodic and fluctuating noise.

Issues related to determination of distortions of directional patterns of phased antenna arrays under the influence of periodic and fluctuating multiplicative (modulating) noise are in the focus of the paper. Expressions are obtained for instantaneous directional patterns in terms of voltage and power, as well as the average value of the directional pattern in terms of voltage under the influence of periodic multiplicative noise. So far, since the phase ratios in these instantaneous diagrams change over time, the pattern of the grating fluctuates. The condition is defined under which the structure of the grating pattern «crumbles». At the same time, lower frequencies of acting multiplicative noise lead to distortion of the diagram: its main maximum expands, the level of side lobes increases and lateral reception directions are «smoothed». It is noted that in synthesized arrays, «scattering» of the directional pattern can occur at relatively small values​ of the frequency of multiplicative noise. In lattices with delay lines, periodic multiplicative noise does not cause significant distortion of the directional patterns. Expressions are obtained for determining average directional patterns by voltage and power under the influence of fluctuating multipath noise, including those obtained using correlation function of noise modulation. It has been shown that under the influence of stationary multiplicative noise, the beam pattern on the power of the grating with phase shifters is a convolution of the undistorted diagram on an undistorted scale and the energy spectrum of the noise modulation function. The upper limit of increasing the width of the main lobe of the beam pattern caused by multiplicative noise is determined. It is also shown that as the noise correlation time decreases and the phase distortion depth increases, the diagram expands and its side lobes smooth. It is noted that for distortions of the directional pattern of synthesized arrays, all the basic provisions for phased antenna arrays with phase shifters are true. For lattices with delay lines in the presence of multiplicative noise, the maximum of the average power of the beam pattern does not shift regardless of the shape of the energy spectrum of the noise modulation function. Multiplicative noise can cause only some expansion of the main lobe of the diagram and smoothing of the zero reception directions. Distortions of the grating pattern when exposed to slow fluctuation multiplicative noise are shown. These distortions are determined by changes in the phase and amplitude of the signal over time corresponding to the time shift between the signals in the individual elements of the array, and with slow multiplicative noise, the distortions are small. It is also shown that slow multiplicative noise leads to some reduction in the maximum beam pattern and to smoothing the pattern in the area of the side lobes. In the presence of such noise, the zero reception directions disappear.