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### Aperture Synthesis - ScienceDirect

Published literature on the development of laser systems described above would be an indicator. Indicators of progress in heterodyne detector systems may also be found in literature and/or research about some of the applications of coherent ladar (vibrometry, spectroscopy, synthetic aperture ladar, etc.). Additional indicators may be noticed by work on high bandwidth arrays. For heterodyne approaches that do not have sensitive detectors, alternating current (AC) couple array work would also be an indicator.

### Astrophysik und Astroteilchenphysik

A closely related technology to SAL is inverse synthetic aperture ladar (ISAL), in which the transceiver is stationary and the target moves and/or changes aspect relative to the transceiver. This technology is of significant interest for ground-based imaging of space objects, including GEO satellites. ISAL has been the subject of research programs in the United States, such as the DARPA LongView program^{} and research at AFRL.^{} It has also been the subject of research in China.^{}^{} It is natural to expect that organizations researching SAL would also be researching ISAL. From the information available in the open literature, the technological developments in China along these lines are not as advanced as those in the United States, but there is ample evidence of interest in continued development.

As noted above, several contractors have developed and demonstrated synthetic aperture ladar systems using a variety of technological approaches and with a significant range of performance parameters. The other country that has demonstrated significant interest in SAL imaging has been China, with a series of papers since 2004 addressing both hardware demonstrations^{} (based largely on U.S. published results) and theoretical analyses, including an advanced algorithm for atmospheric compensation.^{}

## Aperture synthesis in digital holography, Proceedings …

GeoSTAR will synthesize the multimeter aperture needed to achieve the required spatial resolution, which will overcome the obstacle that has prevented a GEO microwave sounder from being implemented until now.

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The review article contains results of researches of the synthesis problems of radiating systems with incomplete input information arising in particular during optimal design of radio, acoustic or other types of radiating systems (RS) by the given requirements to energy characteristics of radiated field. In mathematical terms, these tasks are reduced to study and numerical solution of one class of two-dimensional nonlinear integral equations of Hammerstein type that depend on two real parameters. It was established that a characteristic feature of this class of equations is nonuniqueness and the branching (or bifurcation) of existing solutions. Methods of solving two-parametric nonlinear spectral problem, which is necessary to finding the set of points of branching are proposed. Algorithms and numerical methods for the finding of branching solutions are built and founded. Numerous examples of specific synthesis problems are presented.

## Aperture Synthesis Methods And Applications To …

The Fourier transform is important inmathematics, engineering, and the physical sciences. Its discretecounterpart, the Discrete Fourier Transform (DFT), which is normallycomputed using the so-called Fast Fourier Transform (FFT), hasrevolutionized modern society, as it is ubiquitous in digitalelectronics and signal processing. Radio astronomers areparticularly avid users of Fourier transforms because Fouriertransforms are keycomponents in data processing (e.g., periodicity searches) andinstruments (e.g., antennas, receivers, spectrometers), and they arethe cornerstores ofinterferometry and aperture synthesis.

## Adaptive aperture synthesis - SPIE Digital Library

One effect of multiple transmit and receive subapertures is increased angular resolution similar to the angular resolution increase from motion based synthetic aperture sensors. Instead of motion, an array of subapertures that both transmit and receive can be used. For nine subapertures in a row, the array will have a diffraction limit consistent with a monolithic aperture that is 1.89 times as large in diameter as the array. This is because eight subapertures are equivalent to the distance moved, , while one subaperture is equivalent to the real aperture, . If transmission occurs from one subaperture in the middle of an array, the receive aperture array is effectively in its normal location. If the transmit beam is moved up one subaperture, it is as though the receive aperture were moved down one subaperture. If this process is continued, the result is something like what is shown in , where the lighter color linear arrays indicate the perceived location of the linear receive array, depending on which transmit subaperture is used. The dark color column shows the actual location of the arrays. The full extent of the linear arrays is