scholarly journals Search for binary code sequences with low autocorrelation sidelobes by the evolutionary method

2020 ◽  
pp. 44-53
Author(s):  
Sergey Sharov ◽  
Sergey Tolmachev
Keyword(s):  
Autocorrelation Function ◽  
Binary Code ◽  
Hamming Distance ◽  
Additional Restriction ◽  
Main Peak ◽  
Minimum Level ◽  
Range Resolution ◽  
Radar Systems ◽  
The Difference ◽  
Aperiodic Autocorrelation

Introduction: The parameters chosen for complex coded signals used in active radar systems of aircraft for detecting objects largelydetermines their qualitative characteristics and the possibility of covert operation. An important task in the design of such on-boardsystems is the formation of ensembles of pseudorandom-noise binary code sequences of a fixed length with predefined characteristics.Purpose: Search for PRN binary code sequences of a given length, optimal by the criterion of the minimum level of the sidelobes of theaperiodic autocorrelation function. Results: A procedure of search for binary code sequences with specified parameters based on theevolutionary approach is proposed. The minimum level of positive sidelobes of the autocorrelation function is used as a criterion forthe selection of code sequences. An additional restriction is imposed on the length of a substring of codes of the same character. Thepossibility of forming a representative array of sequences with the best ratio of the main peak of the aperiodic autocorrelation functionto its maximum positive sidelobe is shown on the example of 31-bit code sequences. An algorithm is proposed for generating a PRNseries of signals using the code sequences found. The Hamming distance is used as a measure of the difference between two binary codesequences in the series. The proposed approach is advantageous as compared to the well-known method of generating PRN signals basedon pseudorandom m-sequences. Practical relevance: The results obtained can be used in algorithms of airborne radar systems with ahigh range resolution to detect physical objects on the background of an underlying surface, for example, objects on the water surface.

scholarly journals A Comparative Study between Frequency-Modulated Continous Wave LADAR and Linear LiDAR

2014 ◽  
Vol XL-1 ◽  
pp. 233-239 ◽  
Author(s):  
R. D. Massaro ◽  
J. E. Anderson ◽  
J. D. Nelson ◽  
J. D. Edwards
Keyword(s):  
Continuous Wave ◽  
Single Frequency ◽  
Range Resolution ◽  
Linear Mode ◽  
Radar Systems ◽  
Flash Lidar ◽  
Geiger Mode ◽  
The Difference ◽  
Set Up ◽  
The Given

Topographic Light Detection and Ranging (LiDAR) technology has advanced greatly in the past decade. Pulse repetition rates of terrestrial and airborne systems havemultiplied thus vastly increasing data acquisition rates. Geiger-mode and FLASH LiDAR have also become far more mature technologies. However, a new and relatively unknown technology is maturing rapidly: Frequency-Modulated Continuous Wave Laser Detection and Ranging (FMCW-LADAR). Possessing attributes more akin to modern radar systems, FMCWLADAR has the ability to more finely resolve objects separated by very small ranges. For tactical military applications (as described here), this can be a real advantage over single frequency, direct-detect systems. In fact, FMCW-LADAR can range resolve objects at 10<sup>−7</sup> to 10<sup>−6</sup> meter scales. FMCW-LADAR can also detect objects at greater range with less power. In this study, a FMCWLADAR instrument and traditional LiDAR instrument are compared. The co-located terrestrial scanning instruments were set up to perform simultaneous 3-D measurements of the given scene. Several targets were placed in the scene to expose the difference in the range resolution capabilities of the two instruments. The scans were performed at or nearly the same horizontal and vertical angular resolutions. It is demonstrated that the FMCW-LADAR surpasses the perfomance of the linear mode LiDAR scanner in terms of range resolution. Some results showing the maximum range acquisition are discussed but this was not studied in detail as the scanners’ laser powers differed by a small amount. Applications and implications of this technology are also discussed.

scholarly journals New Bounds on the Minimum Average Distance of Binary Codes

2010 ◽  
Vol 2 (3) ◽  
pp. 489
Author(s):  
M. Basu ◽  
S. Bagchi
Keyword(s):  
Lower Bounds ◽  
Binary Code ◽  
Hamming Distance ◽  
Average Distance ◽  
Upper And Lower Bounds ◽  
Binary Codes ◽  
Large N

The minimum average Hamming distance of binary codes of length n and cardinality M is denoted by b(n,M). All the known lower bounds b(n,M) are useful when M is at least of size about 2n-1/n . In this paper, for large n, we improve upper and lower bounds for b(n,M). Keywords: Binary code; Hamming distance; Minimum average Hamming distance. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i3.2708                  J. Sci. Res. 2 (3), 489-493 (2010) 

A Procedure for the Automatic Determination of Filter Cutoff Frequency for the Processing of Biomechanical Data

1999 ◽  
Vol 15 (3) ◽  
pp. 303-317 ◽  
Author(s):  
John H. Challis
Keyword(s):  
White Noise ◽  
Autocorrelation Function ◽  
Cutoff Frequency ◽  
Human Movement ◽  
Data Sets ◽  
Mathematical Functions ◽  
The Best Approximation ◽  
Second Derivatives ◽  
Low Pass ◽  
The Difference

This article presents and evaluates a new procedure that automatically determines the cutoff frequency for the low-pass filtering of biomechanical data. The cutoff frequency was estimated by exploiting the properties of the autocorrelation function of white noise. The new procedure systematically varies the cutoff frequency of a Butterworth filter until the signal representing the difference between the filtered and unfiltered data is the best approximation to white noise as assessed using the autocorrelation function. The procedure was evaluated using signals generated from mathematical functions. Noise was added to these signals so mat they approximated signals arising from me analysis of human movement. The optimal cutoff frequency was computed by finding the cutoff frequency that gave me smallest difference between the estimated and true signal values. The new procedure produced similar cutoff frequencies and root mean square differences to me optimal values, for me zeroth, first and second derivatives of the signals. On the data sets investigated, this new procedure performed very similarly to the generalized cross-validated quintic spline.

scholarly journals Metaretinochrome in membranes as an effective donor of 11-cis retinal for the synthesis of squid rhodopsin.

1984 ◽  
Vol 84 (1) ◽  
pp. 49-62 ◽  
Author(s):  
T Seki
Keyword(s):  
Absorption Band ◽  
Schiff Bases ◽  
Sodium Dodecyl ◽  
Electrophoretic Pattern ◽  
Difference Spectrum ◽  
Main Peak ◽  
Visible Absorption ◽  
The Difference ◽  
Protein Moiety

Aporetinochrome, which is a protein moiety of retinochrome without chromophore retinal, is found in the membrane containing retinochrome. All of the prosthetic retinal of retinochrome in membranes, which is all-trans retinal, is bound to the chromophoric site on the protein moiety, with protonated Schiff bases showing an absorption band with the maximum at 495 nm. On exposure to light, retinochrome is converted to metaretinochrome at room temperature. The prosthetic retinals of metaretinochrome in membranes, which are 11-cis retinals, are in two states: retinals bound to the chromophoric site with protonated Schiff bases, and the free retinals, which are separated from the protein moiety. These states are suggested from the following observations. (a) The ratio of the absorbance at 470 nm of metaretinochrome to that at 495 nm of the parental retinochrome differs because of differences in samples and is higher in the purer preparations. (b) The difference spectrum of absorption of metaretinochrome caused by alkalinization shows two minimum peaks at approximately 420 and 470 nm. (c) The rate of bleaching of metaretinochrome in membranes with dilute NH2OH is much faster than that of retinochrome, and the absorption band in the near-UV region is more susceptible to NH2OH than the visible absorption band. The state of the prosthetic retinals in metaretinochrome was confirmed directly by the reaction of metaretinochrome in membranes with NaBH4. After treatment with NaBH4, the sodium dodecyl sulfate-polyacrylamide gel electrophoretic pattern shows two fluorescent bands: one at the position that corresponds to the retinochrome protein (mol wt 27,000 +/- 2,000), and another at the front of migration, where no band of protein is observed. Retinoids extracted from the NaBH4-treated metaretinochrome in membranes and analyzed with high-pressure liquid chromatography show a main peak of 11-cis retinol. The results of this and earlier (Seki et al., 1982) papers are summarized, and it is strongly suggested that metaretinochrome in the squid retina may play the role of 11-cis retinal donor for opsin and contribute to the synthesis of the squid rhodopsin.

scholarly journals Attenuation-Based Estimates of Rainfall Rates Aloft with Vertically Pointing Ka-Band Radars

2005 ◽  
Vol 22 (1) ◽  
pp. 43-54 ◽  
Author(s):  
Sergey Y. Matrosov
Keyword(s):  
Mie Scattering ◽  
Rainfall Rate ◽  
Suggested Approach ◽  
Ka Band ◽  
Retrieval Error ◽  
Range Resolution ◽  
Retrieval Errors ◽  
The Difference ◽  
Radar Calibration ◽  
In The Beginning

Abstract An approach is suggested to retrieve low-resolution rainfall rate profiles and layer-averaged rainfall rates, Ra, from radar reflectivity measurements made by vertically pointing Ka-band radars. This approach is based on the effects of attenuation of radar signals in rain and takes advantage of the nearly linear relation between specific attenuation and rainfall rate at Ka-band frequencies. The variability of this relation due to temperature, details of raindrop size distributions, and the nature of rain (convective versus stratiform) is rather small (∼10%) and contributes little to errors in rainfall rate retrievals. The main contribution to the retrieval errors comes from the uncertainty of the difference in the nonattenuated radar reflectivities in the beginning and the end of the range resolution interval. For 2- and 1-dB uncertainties in this difference, the retrieval errors due to this main contribution are less than 34% and 17%, correspondingly, for rains with Ra ≈ 10 mm h−1 at a 1-km resolution interval. The heavier rain rates are retrieved with a better accuracy since this retrieval error contribution is proportional to 1/Ra. The retrieval accuracy can also be improved but at the expense of more coarse vertical resolutions of retrievals since the main retrieval error contribution is also proportional to the reciprocal of the resolution interval. The Mie scattering effects at Ka band results in less variability in nonattenuated reflectivities (cf. lower radar frequencies), which aids the suggested approach. Given that radar receivers are not saturated, the rainfall rates can be retrieved using cloud radars that were originally designed for measuring only nonprecipitating and weakly precipitating clouds. An important advantage of the attenuation-based retrievals of rainfall is that absolute radar calibration is not required. The inclusion of rainfall information will improve the characterization of the atmospheric column obtained with such radars used for climate research. The applications of the suggested approach are illustrated using the vertically pointing Ka-band radar measurements made during a field experiment in southern Florida. The retrieval results are in good agreement with surface estimates of rainfall rates.

scholarly journals Velocity autocorrelation function and self-diffusion coefficient in large molecular dynamics models of liquid argon and water

2021 ◽  
Vol 13 (2) ◽  
pp. 149-156
Author(s):  
Yuri I. Naberukhin ◽  
◽  
Alexey V. Anikeenko ◽  
Vladimir P. Voloshin ◽  
◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Diffusion Coefficient ◽  
Autocorrelation Function ◽  
Liquid Argon ◽  
Time Interval ◽  
Velocity Autocorrelation Function ◽  
Self Diffusion ◽  
Velocity Autocorrelation ◽  
The Difference ◽  
Self Diffusion Coefficient

Autocorrelation function of the particle velocity Z(t) is calculated using the molecular dynamics method in the models of liquid argon and water. The large size of the models (more than a hundred thousand particles) allowed us to trace these functions up to 50 picoseconds in argon and up to 10 picoseconds in water, and to achieve a calculation accuracy sufficient for analytical analysis of their shape. The difference in the determination of the self-diffusion coefficient using Einstein's law and the integral of Z(t) (Green-Kubo integral) is analyzed and it is shown to be 3% at best when t is of the order of several picoseconds. The asymptote of the function Z(t) in argon is close to the power law αt–3/2 predicted by hydrodynamics, but with an amplitude that depends on the time interval under consideration. In water, the asymptote of Z(t) has nothing in common with that in argon: it has α < 0 and the exponent is close to -5/2, and not to -3/2.

scholarly journals A Novel Method of Radar Emitter Identification Based on the Coherent Feature

2020 ◽  
Vol 10 (15) ◽  
pp. 5256
Author(s):  
Jian Xue ◽  
Lan Tang ◽  
Xinggan Zhang ◽  
Lin Jin
Keyword(s):  
Autocorrelation Function ◽  
Simulation Analysis ◽  
Signal To Noise Ratio ◽  
Main Idea ◽  
Main Peak ◽  
Support Vector ◽  
Coherent Signals ◽  
Feature Extraction Method ◽  
New Feature ◽  
Peak Value

To deal with the problem of reliability degradation of radar emitter identification (REID) based on the traditional five parameters in a complex electromagnetic environment, a new feature extraction method based on the autocorrelation function of coherent signals, which makes full use of the coherent characteristic of modern radar emitters, is proposed in this paper. The main idea of this paper is utilizing the instantaneous autocorrelation function to obtain the correlation results of coherent and noncoherent signals. To this end, a new feature parameter, named the ratio of the secondary peak value to the main peak value (SMR), is defined to describe the difference of correlation results between coherent and noncoherent signals. Through simulation analysis, the feasibility of using SMR as the coherent feature for REID is verified. In order to evaluate the effectiveness of the coherent feature, an analytical hierarchy process (AHP) was introduced to compare the comprehensive performance of the coherent feature and the existing parameters, and then convolution neural network (CNN) and support vector machine (SVM) were selected as the classifier to check the recognition capability of the proposed feature. Simulation results show that the proposed feature can not only be used as a new feature for REID but can also be used as a supplement to existing feature parameters to improve the accuracy of REID as it is more insensitive to the signal-to-noise ratio (SNR) and signal modulation type changes.

Fast algorithm for calculating autocorrelation function in code synthesis tasks by enumerative technique

2021 ◽  
Vol 1 (1) ◽  
pp. 13-18
Author(s):  
A. V. Korobeinikov
Keyword(s):  
Computational Complexity ◽  
Autocorrelation Function ◽  
Linear Dependence ◽  
Fast Algorithm ◽  
Binary Code ◽  
Code Combination ◽  
Current Code

The fast algorithm for calculating the autocorrelation function (ACF) of a binary code is developed in relation to the problem of synthesizing codes with a given ACF by enumerative technique. The algorithm is applicable for any duration of the N code. The computational complexity of calculating the ACF is 2N multiplication operations and 2N addition operations. The linear dependence of computational complexity on the duration of the N code is noted. To calculate the ACF of the newly created code combination, the previous code, its ACF, and the index of the changed code element are used. The condition of applicability of the algorithm is that the search of code combinations must be performed by changing only one element in the current code combination. An enumerative technique is proposed that allows a complete enumertion of all 2N existing combinations by sequentially changing the code combination of just one element.

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