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A task of blind estimation of multiplicative noise (speckle) variance in multi-look images acquired by radars with synthesized aperture array is considered. It is shown that there are several factors affecting accuracy of such estimation. The main of them are spatial correlation of the speckle, complexity of an analyzed image and peculiarities of a method used. Spatial and spectral domain approaches are analyzed. It is shown that for both approaches spatial correlation of the speckle is to be estimated and taken into account. Results for real life TerraSAR-X data are presented as illustrations and for analyzing methods' accuracy.

This paper is devoted to a novel multi-frequency and bispectrum-based encoding technique designed for radio communication systems. An experimental study of an interference resistance in digital communication is performed using a novel bispectrum-based strategy. Test statistics evaluated in the form of peak values of magnitude bispectrum estimates are proposed for triplet-signals discrimination. Bit error rates assessed experimentally in a radio communication link contaminated by additive Gaussian noise and fading are studied within a wide range of input signal-to-noise ratio (SNR). Advantages of the proposed bispectral-based signal processing as compared with common phase and frequency shift keying are demonstrated and discussed.

The optimal algorithm of multiband spatio-temporal radiometric signal processing is synthesized. Analytical expressions both for the potential fluctuation sensitivity of the system designed according to the algorithm and for the ambiguity function of multiband radiometric systems are deduced. An example of the theory application is demonstrated.

The optimal algorithm for 3D imaging of a spatially extended object is synthesized using a multi-antenna space-distributed radiometric system. The block diagram of the system implementing the obtained algorithm is given. Expressions for limiting errors of coordinate estimation of each area of the object are obtained.

In the work, using ideas and methods presented in [1-6], for the first time optimal and quasioptimal algorithms for estimation of radio brightness in chopper scanning radiometers are synthesized and investigated. The corresponding block diagrams of radiometric devices are developed. Expressions for a limiting error of estimation of radio brightness and potential fluctuation sensitivity are obtained.

A new concept for solving statistical synthesis problems of radiometric devices and systems (RDS) is developed. The reasonability of using ultra-wideband (UWB) RDSs is substantiated. The basic data of mathematical apparatus of V-transforms employed when processing space-time UWB fields and their statistical characteristics is given. A wide class of UWB RDS statistical synthesis problems (compensation, zero-type, modified modulation type, modulation compensation type, multi-antenna systems including cross-correlation-compensation systems and aperture synthesis systems) of the stationary and scanning types are solved. The appropriateness of using the Kravchenko weighting functions for refinement of primary radiometric images in radiometric scanning devices is substantiated.

The report consists of two parts. In the first part, the sampling analysis of weight windows is conducted on the basis of atomic functions (AF) and their application in problems of the classical method of synthetic aperture radar (SAR) is considered. The second part contains fundamentals of a modified method of synthetizing the aperture. The modified ambiguity function for different signals is probed. The lacks of the Ambiguity function are detected at a modified method. The paths of elimination of the indicated lacks are offered by introduction of weight processing in a technique of the modified method. The expediency of application of weight windows based on AF in reduced problems is empirically justified.

Synthetic aperture radar interferometer provides three-dimensional information by using the phase as an information source. An interferogram contains the amplitude as well as the phase information of a SAR image pair. The resultant phase of the interferogram is only measured modulo 2π. To calculate the elevation of each point it is necessary to add the correct integer number of phase cycles to each phase measurement. The problem of solving this 2π-ambiguity is called phase unwrapping. On the one hand decrease of the interferometer's carrier frequency causes larger altitude variation which can be resolved without ambiguity. However, on the other hand decrease of carrier frequency causes decrease of accuracy of the relief altitude estimation. This contradiction may be resolved for example in the multi-frequency interferometric system, but it is expensive. This paper presents a method for the phase-ambiguity resolution in the two-frequency interferometer. By multiplying signals with different carrier frequency, it is possible to resolve phase-ambiguity as well as provide high-precision of relief altitude estimation. This work presents an analytic equation for the errors in the InSAR, for the carrier frequency calculation. The modeled results show accurate relief estimation as well as phase ambiguity resolution.

A class of sum-type Kaiser-Bessel windows is introduced. These windows are optimized for improving the performance of apodized array patterns. Compared with the basic Kaiser-Bessel windows, the proposed windows are shown provide several benefits.

For spaceborne and airborne Synthetic Aperture Radar (SAR) antennas, the problem of sensed Earth strip variation and simultaneous terrain backscatter or irradiated clutter signal suppression, in a given angular sector, is actual. This problem can be solved by using various approaches and techniques. Often it is desirable to provide a sufficient simplicity of the control system based on the variation of a limited set of antenna aperture amplitude and phase distribution parameters. Besides, such antennas frequently contain a number of sub-apertures.Our paper presents the structure of such a sectionalized array, for which the sensed strip and clutter suppression in the local zone position variation is obtained due to a variation of the relative amplitude and phase relationships for sub-apertures. Besides, amplitude factors within each sub-aperture remain constant, and phase shifts are identical but depend on the angular position of the sensed strip center.It is shown that depending on the width of the sector of desired sidelobe suppression, as well as on its displacement with respect to the sensed strip, the obtained clutter suppression varies from -22 to -50 dB. As the problem has several possible solutions, the recommendations are given for taking into account the other factors. In particular, these are the pattern main lobe width, the limits of reasonable variation of amplitude and phase relationships, construction and technological peculiarities of antenna manufacturing, etc. Other approaches to providing the desirable SAR characteristics are discussed relating to the use of antenna arrays with the digital signal processing.

A review of modern optimal and quasi-optimal algorithms for radiometric signal processing, which provide images with a high spatial resolution is given. It is shown that the high resolution is achieved with ultra-wideband or multi-band time or space-time signal processing. Analytical expressions for the limiting error of image estimation, ambiguity functions and potential fluctuation sensitivity of systems designed according to the algorithms are derived.

In the work, for the first time the problem of synthesis algorithms of optimal and quasioptimal radiometric signal processing for restoration of radiometric images in ultrawideband radiometers with a multi-antenna array is solved. The potential accuracy of estimation is calculated. It is shown that the quasioptimal algorithm is close to the algorithm realized in the aperture synthesis systems and used in radio astronomy.

While realizing digital signal processing for equidistant antenna arrays, the problem of providing a high computational efficiency arises. In particular, it relates to the procedure of data weighting, which has the goal of ensuring the best available pattern characteristics (low level of side lobes and narrow enough main lobe). Using quantized representation of samples of well known apodization functions, one gets the degrading of the mentioned above pattern parameters resulting from round-off errors, that does not permit to obtain all potential results. In connection with these effects, in our report we resent a new approach based on the use of convolution of two step-like windows having integer values of weighting factors. As a result, for synthesized apodization functions, the sample values occur to be integer as well. Step parameters (their length and amplitude ratios) are optimized, besides, the approach to the synthesis of apodization functions having flat top is proposed for the case when identical step-like windows are convolved. It is shown that even the use of two-step windows as convolution components results in reduction of pattern maximum side lobe level to -45…-50 dB. The obtained main lobe width is comparable with corresponding parameters of the best apodization functions characterized by approximately the same side lobe level. Recommendations concerning the providing of appropriate tradeoff between the side lobe level and the main lobe width, as well as the corresponding methods of optimization and solution search under restrictions are given. It is shown that even better results (a lower side lobe level) can be achieved using the convolution of three-step windows, but it leads to increasing of maximum of the integer-valued weighting factor.