Mathematical description of imaging processes in ultra-wideband active aperture synthesis systems using stochastic sounding signals

Mathematical models of the fields of stochastic ultra-wideband signals that are necessary for solving problems of aperture synthesis of images using active radar methods are presented. The expediency of using V-transformations in these problems has been substantiated, the effectiveness of which has already been proven for the mathematical description of ultra-wideband spatio-temporal fields in the methods of passive and active radar, as well as remote sensing, that are used to solve problems of radio astronomy, medicine, navigation. Using modern methods of mathematical analysis and the theory of ultra-wideband systems, the physical essence of radio images obtained with the help of algorithms for coherent and incoherent signal processing is investigated. According to these algorithms, it is proposed to divide images into coherent and incoherent. Coherent images include those in which its amplitude and phase are recorded separately. In the case of an incoherent image, only its amplitude (power or related characteristic) is recorded. To describe of the obtained radio image structure, new concepts of the spectral density of the complex spatial coherence function (SDCSCF) and the spectral density of the spatial autocorrelation function of the amplitude-phase distribution (SDFSAF APD) are introduced. Application-use of functions is expedient and fundamentally necessary for solving problems of aperture synthesis using stochastic ultra-wideband signals. A mathematical description of the structures obtained by aperture synthesis of radio images is given. Here, studies are conducted for the general case of using a continuous (idealized) aperture, and for using an antenna system with spatially separated receiving elements. Simulation of the heuristic synthesized algorithm for constructing incoherent radio images is conducted. The possibility of using antenna arrays and synthesized aperture synthesis algorithms for solving problems of image formation in a survey located directly under the aircraft (at sounding angles close to vertical) are substantiated.

Radar imaging complex with SAR and ASR for aerospace vechicle

The subject of this study in the article is the algorithms for radio monitoring of the Earth in various views from aerospace transport. The goal is to design a structural diagram of a radio complex that can operate simultaneously in two modes: modified antenna aperture synthesis (SAR) and aperture synthesis (RAS), in accordance with algorithms synthesized using the maximum likelihood method. The modified SAR mode allows obtaining high-resolution radio images in the observation angle range ±(20°...50°) from the direction to the nadir. A method for combining a modified PCA algorithm is used, which differs from the classical imaging algorithm by the possibility of obtaining a higher spatial resolution, the payment for this is the complication of the signal processing algorithm associated with the implementation of decorrelating filters that expand the spectrum of received signals in each receiving path, and the RAS mode, which allows imaging using passive or active radar principles. The passive RAS mode provides for the imaging in the observation angle range of ±20° from the nadir based on the results of processing signals of its own broadband radio-thermal radiation, and active mode – in the same observation angle range, but using the broadband noise signal of the backlight. An important result in the formation of a radio image in the specified viewing area when using the active mode of the RAS is that the images are close in physical content, namely, proportional to the specific effective reflection surface of the underlying surface. Additionally, a distinctive feature of the synthesized algorithms is the use of wideband probing signals and, accordingly, the same input paths of receivers, which makes it possible to increase the signal-to-noise ratio of the output effect. Conclusions. The scientific novelty of the results obtained is as follows: a structural diagram of the radio complex was developed on the basis of algorithms synthesized using the maximum likelihood method. For the formation of a radio image in the radio complex, a combination of SAR and RAS (with two modes of operation) is implemented. This implementation is important, since it allows obtaining high-resolution images in the observation angle range of ±50° from the direction to the nadir. It is advisable to place the complex on airplanes, helicopters and spacecraft (preferably those that move in low orbits)

Evaluation of the performance of algorithms for synthesizing radar images using Cuda technology

The features of the implementation of the algorithm for the synthesis of detail radar images for an aperture synthesis radar using the built-in functions of the Cuda library are presented. The estimation of computational complexity from the standpoint of the organization of parallel computing on Nvidia GPUs is given. The estimation of the real performance of radar synthesis is given, taking into account the volume and features of the placement of primary radar information.