Spectral method for the spatio-spectral sensitivity domain filling in aperture synthesis system

et al. 2021

reks

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.

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Section: Introductionmentioning

confidence: 99%

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

Volosyuk

et al. 2021

reks

show abstract

“…Algorithm (6) corresponds to the following basic signal processing operations: forming the envelope of the reference signal   S t,  r for different range sections (the number of range sections is determined by a specific signal shape and antenna directivity patterns for transmission and reception); setting of the decorrelation filter, the impulse response of which is determined by…”

Section: Geometry Of the Radar Imaging Problemmentioning

confidence: 99%

“…, r (in the optimal form, this function is adaptive, since it requires a priori knowledge of    r ); formation of observation envelopes   U t,r for different parts of the range; performing double correlation processing operations in accordance with (6).…”

Section: Geometry Of the Radar Imaging Problemmentioning

confidence: 99%

“…It should be noted that the most difficult operation in (6) is the formation of the function     12 W t , t , r . However, in practice, it can be realized as the average value of    r , which is typical for a certain type of underlying surface.…”

Section: Geometry Of the Radar Imaging Problemmentioning

confidence: 99%

“…Note that algorithm(6) allows obtaining high spatial resolution for viewing angles ±(20°...50°) from the direction to the nadir.…”

mentioning

confidence: 99%

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Radar imaging complex with SAR and ASR for aerospace vechicle

Belousov²,

et al. 2021

reks

The subject of study in the article is the algorithms for radio monitoring of the Earth in a wide field of view from aerospace transport. The goal is to design a structural diagram of a radio complex that can operate simultaneously in two modes: modified synthetic aperture (SAR) and aperture synthesis (ASR), in accordance with algorithms synthesized by 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 of combining a modified SAR 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 ASR mode, which allows imaging using passive or active radar principles. The passive ASR 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 the 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 ASR is that the images are close in physical content, namely, proportional to the specific effective reflection surface of the underlying surface. In addition, 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 by the maximum likelihood method. For the formation of a radio image in the radio complex, a combination of SAR and ASR (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).

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A new method of multi-frequency active aperture synthesis for imaging of SAR blind zone under aerospace vehicle

Volosyuk

2017 14th International Conference the Experience of Designing and Application of CAD Systems in Microelectronics (CADSM)

et al. 2017