scholarly journals Development of a direct penetrating signal compensator in a distributed reception channel of a surveillance radar

2021 ◽  
Vol 2 (9 (110)) ◽  
pp. 16-26
Author(s):  
Hennadii Khudov ◽  
Serhii Yarosh ◽  
Oleksandr Droban ◽  
Oleksandr Lavrut ◽  
Yurii Hulak ◽  
...  
Keyword(s):  
Transmission Coefficient ◽  
Matched Filter ◽  
Direct Method ◽  
General Structure ◽  
Main Channel ◽  
Signal Amplifier ◽  
Direct Penetration ◽  
Reception Channel ◽  
Weighting Coefficients ◽  
Complex Transmission

General structure of a compensator of a direct penetrating signal in the diversed reception channel was developed. It is advisable to use the antenna and the receiver of the auxiliary diverted reception channel as an auxiliary antenna and an auxiliary channel. To be able to suppress the penetrating signal in the band of the receiving device of the surveillance radar, distance between the antennas should be up to 6 m. In general, the compensator of the penetrating signals should contain an adder in which the signals received by the main channel are added with the signals received by the auxiliary channel and sent through the amplifier with a corresponding complex transmission coefficient. The direct penetration signal compensator features the obligatory condition of adjusting the value of the complex transmission coefficient of the auxiliary channel signal amplifier. The direct penetration signal compensator is digital and uses the direct method of forming weighting coefficients without the use of feedback. To reduce the time of formation of weighting coefficients when using direct methods of calculation of the correlation matrix, the technology of parallel computational processes was used. The quality of operation of the direct penetrating signal suppression system in the diverted reception channel was evaluated. It was established that without the use of suppression of direct penetrating signals, their powerful response at the output of the matched filter mask weak echo signals. When using a direct penetrating signal in the main channel of the compensator, its response at the output of the matched filter is significantly reduced. This makes it possible to observe weak echoes against the background of a strong penetrating signal. The use of the developed direct penetrating signal compensator provides suppression of the direct penetrating signal from 57 dB to 70 dB

Complex transmission coefficient of a multimode waveguide excited by a semiconductor laser

1991 ◽  
Vol 34 (10) ◽  
pp. 1012-1015
Author(s):  
S. M. Zhminchenko ◽  
V. L. Nazarov ◽  
N. N. Sebekina
Keyword(s):  
Semiconductor Laser ◽  
Transmission Coefficient ◽  
Multimode Waveguide ◽  
Complex Transmission

ON SOFTWARE IMPROVEMENT OF IMAGE CHANNEL SUPPRESSION IN SDR RECEIVERS WITH ANALOG CONVERSION TO A LOW INTERMEDIATE FREQUENCY

2020 ◽  
pp. 45-52
Author(s):  
A. S. Yurkov
Keyword(s):  
Signal Processing ◽  
Direct Method ◽  
Digital Signal ◽  
Intermediate Frequency ◽  
Algebraic Equations ◽  
Recursive Filter ◽  
Linear Algebraic Equations ◽  
Reception Channel ◽  
Image Channel ◽  
Parasitic Phase

A method for digital signal processing in SDR receivers with analog conversion to a low intermediate frequency is proposed. In contrast to known systems, the proposed approach does not consider parasitic phase and amplitude distortions, but uses the direct method minimizing of the signal of the mirror reception channel. Generally speaking, this can be done simultaneously at several frequencies. It is shown that in computational terms, this is reduced to signal processing by an algorithm similar to a digital non-recursive filter, and to determine its coefficients, it is sufficient to solve a system of linear algebraic equations.

scholarly journals Synthesis of matched filters.

2021 ◽  
Author(s):  
A.N. Degtyaryov ◽  
◽  
I.L. Afonin ◽  
A.L. Polyakov ◽  
A.S. Kozhemyakin ◽  
...  
Keyword(s):  
Fourier Series ◽  
Impulse Response ◽  
Correlation Functions ◽  
Matched Filter ◽  
Matched Filters ◽  
Low Pass ◽  
Pulse Characteristics ◽  
Low Pass Filters ◽  
Direct Use ◽  
Complex Transmission

Methods for approximating the impulse response of a matched, physically realizable filter with the minimum required number of functional nodes are in thei focus of the paper. Methods for approximating the pulse characteristics of a matched filter are proposed, namely: approximation by causal physically realizable functions, which are the correlation functions of the pulse characteristics of low-pass filters (LPF) Butterworth; using the Fourier series to describe the complex transmission coefficient of the filter; direct use of the Fourier series to approximate the impulse response of a matched filter. As a result, the number of elements of the matched filter is significantly reduced.

Numerical reconstruction of an object image using an X-ray dynamical diffraction Fraunhofer hologram

2013 ◽  
Vol 21 (1) ◽  
pp. 127-130 ◽  
Author(s):  
Minas K. Balyan
Keyword(s):  
Transmission Coefficient ◽  
Analytical Approximation ◽  
Object Image ◽  
Resolution Limit ◽  
Dynamical Diffraction ◽  
X Ray ◽  
Numerical Reconstruction ◽  
Complex Transmission ◽  
Amplitude Transmission

A numerical method of reconstruction of an object image using an X-ray dynamical diffraction Fraunhofer hologram is presented. Analytical approximation methods and numerical methods of iteration are discussed. An example of a reconstruction of an image of a cylindrical beryllium wire is considered. The results of analytical approximation and zero-order iteration coincide with exact values of the amplitude complex transmission coefficient of the object as predicted by the resolution limit of the scheme, except near the edges of the object. Calculations of the first- and second-order iterations improve the result at the edges of the object. This method can be applied for determination of the complex amplitude transmission coefficient of amplitude as well as phase objects. It can be used in X-ray microscopy.

scholarly journals A modified reciprocal equation to predict the complex transmission coefficient of a flow duct

AIP Advances ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 095001
Author(s):  
Lianyun Liu ◽  
Xu Zheng ◽  
Zhiyong Hao ◽  
Yi Qiu
Keyword(s):  
Transmission Coefficient ◽  
Reciprocal Equation ◽  
Complex Transmission ◽  
Flow Duct

Characterization of frozen hydrated biological specimens by low-loss EELS

1992 ◽  
Vol 50 (2) ◽  
pp. 1572-1573
Author(s):  
Songquan Sun ◽  
Richard D. Leapman
Keyword(s):  
Water Content ◽  
Direct Method ◽  
Internal Standard ◽  
Dry Weight ◽  
Dark Field ◽  
Protein Solutions ◽  
Subcellular Compartment ◽  
Differential Shrinkage ◽  
Electron Energy Loss

Analyses of ultrathin cryosections are generally performed after freeze-drying because the presence of water renders the specimens highly susceptible to radiation damage. The water content of a subcellular compartment is an important quantity that must be known, for example, to convert the dry weight concentrations of ions to the physiologically more relevant molar concentrations. Water content can be determined indirectly from dark-field mass measurements provided that there is no differential shrinkage between compartments and that there exists a suitable internal standard. The potential advantage of a more direct method for measuring water has led us to explore the use of electron energy loss spectroscopy (EELS) for characterizing biological specimens in their frozen hydrated state.We have obtained preliminary EELS measurements from pure amorphous ice and from cryosectioned frozen protein solutions. The specimens were cryotransfered into a VG-HB501 field-emission STEM equipped with a 666 Gatan parallel-detection spectrometer and analyzed at approximately −160 C.

A Simple Real-Space Channelling Theory for Electron Diffraction and HREM

1990 ◽  
Vol 48 (1) ◽  
pp. 64-65
Author(s):  
D. Van Dyck
Keyword(s):  
High Resolution ◽  
Electron Diffraction ◽  
Direct Method ◽  
Real Space ◽  
Zone Axis ◽  
Phase Object ◽  
High Resolution Images ◽  
The Many ◽  
Analytical Expressions ◽  
Electron Wavefunction

The computation of the many beam dynamical electron diffraction amplitudes or high resolution images can only be done numerically by using rather sophisticated computer programs so that the physical insight in the diffraction progress is often lost. Furthermore, it is not likely that in this way the inverse problem can be solved exactly, i.e. to reconstruct the structure of the object from the knowledge of the wavefunction at its exit face, as is needed for a direct method [1]. For this purpose, analytical expressions for the electron wavefunction in real or reciprocal space are much more useful. However, the analytical expressions available at present are relatively poor approximations of the dynamical scattering which are only valid either for thin objects ((weak) phase object approximation, thick phase object approximation, kinematical theory) or when the number of beams is very limited (2 or 3). Both requirements are usually invalid for HREM of crystals. There is a need for an analytical expression of the dynamical electron wavefunction which applies for many beam diffraction in thicker crystals. It is well known that, when a crystal is viewed along a zone axis, i.e. parallel to the atom columns, the high resolution images often show a one-to-one correspondence with the configuration of columns provided the distance between the columns is large enough and the resolution of the instrument is sufficient. This is for instance the case in ordered alloys with a column structure [2,3]. From this, it can be suggested that, for a crystal viewed along a zone axis with sufficient separation between the columns, the wave function at the exit face does mainly depend on the projected structure, i.e. on the type of atom columns. Hence, the classical picture of electrons traversing the crystal as plane-like waves in the directions of the Bragg beams which historically stems from the X-ray diffraction picture, is in fact misleading.

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