The study analysed possible resolution of two ground-based MIMO microwave camera designs by means of two-dimensional spatial cross-sections of a generalized ambiguity function. We used stepped-frequency modulated broadband signals as time-orthogonal probing signals for the microwave camera transmitters. We employed a mathematical simulation of the space-time signal processing system pertaining to MIMO microwave camera receivers to illustrate 2D and 3D microwave imaging of stationary extended multipoint objects situated at various altitudes above the earth surface.

In advanced portable radars using the principles of MIMO, obtaining a high resolution and a sufficient S/N ratio is important due to the use of a reduced number of widely directed transmitting and receiving antenna elements, for example, sub lattices with low directional coefficients. In such radars, probing signals in the form of burst of broadband LFM pulses are applicable. When processing these signals reflected from moving targets, two methods are fundamentally possible: classical one in the time domain with matched filtering of the burst of LFM-pulses and subsequent inter-period accumulation, and the spectral one based on preliminary calculation of the full spectrum of the pulses burst with subsequent accumulation over the frequency intervals of Doppler ambiguity. In this case, there are two options for the accumulation of spectra: 1) incoherent and 2) coherent, and their efficiency for a burst of LFM-pulses has not been studied before. In this work on the simulation model of the processing system in the spectral domain the output S/N ratios for these variants of the spectral processing method for a burst of LFM-pulses are determined and compared. In addition, the issues of presenting the results of spectral accumulation in the coordinates «Doppler frequency – delay» plane were worked out. The following results are obtained for a specific variant of the burst signal: the efficiency of coherent spectrum accumulation under the influence of noise exceeds the efficiency of incoherent by a value of about 12 dB; in the case of incoherent accumulation of spectrum modules in the case of a group targets, the accumulated amplitude spectrum, with a sufficient duration of the pulses burst, contains all the Doppler-resoluted target marks; in the case of coherent accumulation of complex spectra of group targets with different Doppler frequencies and ranges, the targets can be resolved based on the analysis of the module of the accumulated complex spectrum in the «Doppler frequency – range» plane; 4) with incoherent and coherent of spectral accumulation over ambiguous Doppler intervals, a single FFT of a LFM-pulses burst is required. The remaining operations are the algebraic summation of the spectral samples over the ambiguity intervals and taking the modulus from the accumulated complex spectrum.

A bench for special aspects of backscattering amplitude characteristics measurement of small and ultrasmall RCS objects in Ka-band is presented. The RCS of quadrocopter Syma X12 are defined for ±2GHz band from different radiation directions for both vertical and horizontal polarization.

Introduction. One of the classes of modern radio engineering systems are systems with spatial diversity of transmitting, receiving or transceiving elements. In such systems, an increase of the information content is achieved by signal coprocessing ensuring synchronization in time and phase of the carrier oscillation. Currently, the researchers do not pay enough attention to the requirements for the accuracy of synchronization of distributed systems of different applications, as well as simple and affordable ways to synchronize them.Objective. The paper main objective is the search for technical solutions for clock and phase synchronization without atomic frequency standards and external sources of coordinate-time information.Methods and materials. The paper considers a distributed radio engineering system with non-rigid structure. Each element of the system has reference signal from its own crystal oscillator. The oscillators are not physically aligned. The phases of their oscillations are periodically compared by the method of two-way transmission of synchronizing signals (from one element to another and vice versa). The synchronization technique (software algorithmic approach) is reduced to the coprocessing signal correction according to estimated frequency (phase) drifts. The testing of the proposed technical solution is presented on a hardware model consisting of ten receiving and transmitting modules.Results. The experiment showed that RMS of synchronization errors does not exceeded 12 degrees by phase (for VHF), or 0.2 ns by time. These results are acquired for spatial diversity up to several hundred meters, mutual speed of the modules up to several meters per second and may be extended for higher frequencies (in particular, UHF).Conclusion. The paper proposes a method of multilateral propagation to synchronize distributed radioengineering systems. Combined with software algorithmic technique this method enables to obtain synchronization accuracy in real-time sufficient for coherent diversity technique.

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