Sparsity Enhanced Beamforming in The Presence of Coherent Signals

In order to find the directions of coherent signals, a sparsity enhanced beam-forming method is proposed. Unlike the conventional minimum variance distortless response (MVDR) method, the minimum variance in the proposed method corresponds to the orthogonal relationship between the noise subspace and the sparse representation of the received signal vector, whereas the distortless response corresponds to the nonorthogonal relationship between the signal subspace and the sparse representation of the received signal vector. The proposed sparsity enhanced MVDR (SEMVDR) method is carried out by the iterative reweighted Lp-norm constraint minimization. for direction finding of coherent signals. Simulation results are shown that SEMVDR has better performance than the existing algorithms, such as MVDR and MUSIC, when coherent signals are present.

Development of technology of high-speed digital-to-analogue converters to improve the efficiency of direct digital synthesis of radio-frequency signals

The importance of high-speed digital-to-analogue converters for the synthesis of high-frequency coherent signals is shown. A review of the main specialized modes of operation of high-speed digital-to-analogue converters is carried out, which make it possible to effectively use the side components of the spectrum that arose during the restoration of a signal from digital to analogue form. An RF2 reconstruction mode with a modified bipolar pulse sequence is proposed, which makes it possible to increase the amplitude of the images in the eighth and ninth Nyquist zones.

Information technologies for creating spatiotemporal modems multiposition active-passive radar systems

The methods of synthesis of the directional diagram of active transmitting antenna arrays when receiving signals reflected from radar targets are considered. It is shown that when using multifrequency orthogonal coherent signals in the elements and addressable access at their reception it is possible to provide a small level of the side lobes of the spatial uncertainty function in a given sector of observation by selecting the type of intrapulse modulation of partial signals. Orthogonalization of antenna basis of transmitting and receiving antennas allows digital spectral-correlation processing of samples of aggregate signal from each target to solve the technological problem of multidimensional observation space in multiposition systems of coherent radiolocation when detecting, resolving, estimating coordinates and motion parameters of targets. The results of simulation modeling of spatio-temporal radar modems implemented according to the stated principles are given.

Modeling and Parameter Estimation of Partially Coherent Signals in Radio Engineering Systems

The problem of modeling signals of various spatial coherence in radio engineering systems is considered. First, a mathematical model for spatially coherent signals in the form of stochastic differential equations is constructed, followed by its study in the Simulink environment. The following is a method for constructing a mathematical model for a more general case – partially coherent signals, and its accuracy is also evaluated. Based on the developed models, an algorithm for estimating the parameters of partially coherent signals is synthesized. Based on the obtained dependence of the sensitivity of the model to deviation from a priori data, conclusions are drawn about a sufficiently high accuracy of estimation using synthesized algorithms.

The Analysis of Using Spatial Smoothing for DOA Estimation of Coherent Signals in Sparse Arrays

When there is coexistence of uncorrelated and coherent signals in sparse arrays, the conventional algorithms for direction-of-arrival (DOA) estimation using difference coarray fail. In order to solve the problems, this paper analyzes the feasibility of using spatial smoothing in sparse arrays. Firstly, we summarize the two types of sparse arrays, one consisting of identical sparse subarrays and the other consisting of several uniform linear subarrays. Then, we give the feasibility analysis and the processes of applying spatial smoothing. At last, we discuss the performance of the number of detectable coherent signals in different sparse arrays. Numerical experiments prove the conclusions proposed by the paper.