Full-text resources of PSJD and other databases are now available in the new Library of Science.
Visit https://bibliotekanauki.pl
Preferences help
Polish version English version Language
enabled [disable] Abstract
Number of results

Results found: 16

Number of results on page
first rewind previous Page / 1 next fast forward last

Search results

Search:
in the keywords:  84.40.Ua
help Sort By:

help Limit search:
first rewind previous Page / 1 next fast forward last
1
Content available remote

Performance Enhancement of Telemedicine Network by Free Space Optics Links Provisioning

100%
Siraj M., Shoaib M., Memon I.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 1
43-45
EN
Health care has benefited immensely with the implementation of fast moving information technology. It is a challenging assignment for the researchers to implement the present day technologies such as wireless mesh networks. Wireless mesh networks are deployed to guarantee a reliable and stable network infrastructure backbone to telemedicine systems. They are preferred to other wireless networks, as the solution which they provide is robust for broadband services. They are robust because if routing is not possible due to some mesh nodes failure, routing can be done by the other mesh nodes present. Wireless mesh network cannot only spread coverage but also save both cabling cost and human resource. However, their performance is degraded due to interference and varying load. Interference is a critical issue in wireless mesh networks. The interference occurs because of the congested unlicensed radio frequency spectrum. This problem can be addressed by applying free space optics technology for transmission instead of radio frequency technology in the unlicensed spectrum. Network capacity issue is addressed by provisioning free space optics links to generate the much needed throughput and to minimize interference. Telemedicine network is a network, which requires a high capacity bandwidth to cater for a large number of remote patients. It is observed that free space optics links provisioning results in a significant performance enhancement for the telemedicine network.
2
Content available remote

Comparison of Reduction Methods for Peak-to-Average-Power-Ratio (PAPR) in MIMO-OFDM Systems with a New Approach

100%
Tören M., Çıflıklı C.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 1
417-421
EN
This study is based on the comparison of the results of an analysis recommended for the peak-to-average-power-ratio (PAPR) reduction methods. This is one of the most significant problems in the multiple input-multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. The information in the signals of the wireless communication systems can be given in the frequency domain [S.H. Han, J.H. Lee, IEEE Signal Proc. Lett. 11, 887 (2004)]. Of the methods applied for the PAPR reduction, which is one of the problems occurring in the frequency domain of the signals in MIMO-OFDM systems, the selective mapping (SLM) and the partial transmit sequences (PTS) are compared using a different approach. In the MIMO-OFDM systems, Fourier analysis is performed and the values of the signals on the frequency plane are taken although it is not clear which value of the signal at which time is taken [S.H. Han, J.H. Lee, IEEE Signal Proc. Lett. 11, 887 (2004)]. For the constant state of time, Fourier analysis approach is not appropriate for the detection of accurate frequency values. To solve this problem, a new wavelet transform-based (WT) analysis is recommended for the MIMO-OFDM systems with a new approach. It is shown that this analysis will be preferred instead of the Fourier analysis because of the optimization of the frequency-based temporary solutions of the signal. This approach of analysis is used along with the methods used for solving the PAPR problem in the MIMO-OFDM systems. Thereby, a comparison showing at which rate the methods for the solution of the problem contribute to solving the problem with this approach can be carried out. Numerical results show at which rate the methods with this approach can be carried out to contribute for solving the problem.
3
Content available remote

Matched Filtration of LFM Signals with Non-Zero Initial Frequency

63%
Leszczynski T.
Acta Physica Polonica A
|
2013
|
vol. 124
|
issue 3
494-497
EN
This paper presents the results of the research considering the influence of the initial frequency on linear frequency modulation signal compression. The signal compression has been performed using the digital matched filtration in the time domain. The ratio of peak to side lobe ratio with the width of the main lobe equaling one sampling period is the measure of the quality of compression. In general, a lower value of peak to side lobe ratio is obtained for linear frequency modulation signals with a non-zero initial frequency than with a zero initial frequency. The peak to side lobe ratio is systematically decreasing with the increase of the initial frequency f_1. The existing methods of band signals sampling, where the spectrum of the signals is transferred by means of the carrier signal f_0 of a significantly higher frequency than the band B (f_0 ≫ B) may be effectively used for sampling signals considered in this study, which do not have a carrier. As a result, for the linear frequency modulation signals with a non-zero initial frequency f_1 = nB and a final frequency f_2 = (n + 1) B, n = 1, 2, ..., the same peak to side lobe ratio values will be obtained as for linear frequency modulation signals with a zero initial frequency and the identical band and time duration. The results of this research could be implemented in sonar and radiolocation techniques and medicine.
4
Content available remote

Structure Optimization of Phase-Coded Sounding Signals

63%
Szczegielniak D., Milewski A.
Acta Physica Polonica A
|
2010
|
vol. 118
|
issue 1
164-167
EN
Pulse compression with a small sidelobe level is one of challenges in designing of modern radar, sonar or ultrasound imaging systems. It may be performed by means of matched filter, that is by correlating the received sounding signal with a stored replica of the transmitted signal. The advantage of the pulse compression method is the increase of the average transmission power while retaining the range resolution corresponding to a short pulse. Phase coding is one of the early techniques for pulse compression of radar signals. Polyphase sequences, which have low sidelobe levels, ensure an easily detectable peak in the output of a matched filter, in other words an easy detection of a received sounding signal. In this paper, an evolutionary algorithm combined with a local optimizer is used to search for polyphase codes with a small sidelobe level of an aperiodic autocorrelation function. The evolutionary algorithm is based on a floating-point representation and the Gaussian mutation is used to produce offspring for the next generation. The self-adaptation mechanism is used to control the mutation operator during the evolutionary process. This research demonstrates that optimization methods can effectively find polyphase sequences with low autocorrelation and seems to be very promising for the future research in area of computer optimization for polyphase codes synthesis.
5
Content available remote

Automatic Classification of LFM Signals for Radar Emitter Recognition Using Wavelet Decomposition and LVQ Classifier

63%
Świercz E.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 4
488-494
EN
The paper presents a novel approach, based on the wavelet decomposition and the learning vector quantisation algorithm, to automatic classification of signals with linear frequency modulation, generated by radar emitters. The goal of radar transmitter classification is to determine the particular transmitter, from which a signal originated, using only the just received waveform. To categorise a current linear frequency modulation signal to the particular transmitter, the discrete wavelet decomposition of the received signal is accomplished in order to get a representative set of features with good classification properties. The learning vector quantisation algorithm with a previously defined set of features as an input of the learning vector quantisation neural net is proposed as the intelligent classification algorithm, which combines competitive learning with supervision. After the learning process, the learning vector quantisation algorithm is ready to perform the classification process for different data than data used in the learning stage. Simulation results show the high classification accuracy for experimentally chosen wavelets and suggested architecture of the learning vector quantisation classifier.
6
Content available remote

The Radar Ambiguity Function Application for the Frequency Modulated Signals Designing

63%
Kawalec A., Ziołkowski C., Leśnik C., Pietrasinski J.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 3
335-339
EN
The optimization of the transmitted signal time-frequency structure is the very important part of the radar system design from the point of view of the radar system effectiveness. In this meaning the radar ambiguity function is the basic tool used for the radar system features testing. The synthesis procedure of the signal with simultaneous amplitude and phase manipulation is presented in the paper. The procedure is based on the Zak transform that is connected with the radar ambiguity function. The Legendre polynomials were applied in the procedure mentioned above. The results of the simulation tests are presented as examples of the consideration main effects.
7
Content available remote

Nonlinear Frequency Modulated Signal Design

63%
Leśnik C.
Acta Physica Polonica A
|
2009
|
vol. 116
|
issue 3
351-354
EN
The signal time-frequency structure designing is the important problem of radar system solution optimisation. The radar ambiguity function is the very useful signal characteristic that enables to know the signal potential possibilities. The effective numerical methods of the radar ambiguity function calculation give possibility for synthesis of the radar signal having expected features. The synthesis method concerning the nonlinear frequency modulation radar signal is presented in the paper. For the radar ambiguity function calculation the Zak transform is used in the method. The nonlinear frequency modulation signal model was described in which application limitations were taken into account. Examples of simulation research results are presented as a comment of the considerations.
8
Content available remote

Video on Demand Over Optical Wireless Communication Links

63%
Siraj M., Memon M., Khan M.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 4
826-828
EN
Video on demand technology is a modern wireless communication application which requires a large bandwidth. Optical wireless networks, as a potential alternative to radio frequency, is an emerging technology that is easier to set up and provides a cost effective solution, where a physical network is difficult to deploy. Optical wireless networks can be used as a backbone to provide the much needed bandwidth for video on demand application. In this paper, Wavelength Division Multiplexing modulation scheme is proposed for the optical wireless networks due to its significance of transmitting distinct data channels at different wavelengths. Wavelength Division Multiplexing can be easily integrated with optical wireless networks, consequently resulting in an increased data rate. This paper presents a novel approach of integrating video on demand with the state of art Wavelength Division Multiplexing based optical wireless networks. Furthermore, the paper discusses the challenges and advantages over the convention modulation schemes.
9
Content available remote

Modification of a Weighting Function for NLFM Radar Signal Designing

63%
Leśnik C., Kawalec A.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 6A
A-143-A-149
EN
Modification of the weighting raised cosine with a power n function by time convolution with auxiliary changeable time duration uniform rectangular window is presented in this paper. The analytical form of the modified weighting raised cosine function for fixed power in frequency domain was derived. Proposed method was applied to fine tuning of properties of the nonlinear frequency modulation of radar signals. Synthesis of nonlinear frequency modulation radar signals problem was solved using the well-known principle of stationary phase. The selected testing results are shown and some final conclusions are formulated.
10
Content available remote

Structure Optimization of Coded Polyphase Signals with the Enhanced Tolerance to the Doppler Frequency Shift

63%
Szczegielniak D., Milewski A., Szczegielniak M.
Acta Physica Polonica A
|
2015
|
vol. 128
|
issue 3
452-455
EN
The aim of this research was to verify if It is possible to solve the synthesis problem of polyphase codes efficiently with an acceptable quality in the context of radar applications - with the greatest possible effectiveness of the recognition of such signals in the presence of the noise and occurrence of the Doppler effect. The received results confirmed that the implemented optimization algorithm can search polyphase sequences successfully with a low level of sidelobes and an enhanced tolerance to the Doppler effect. Applying optimization methods allows to form ambiguity function in a measure in the assumed optimization range which seems to be encouraging for future examinations in the field of the computer optimization for the coded radar signals synthesis.
11
Content available remote

Antenna Beam Broadening in Multifunction Phased Array Radar

51%
Fatemi Mofrad R., Sadeghzadeh R.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 4
461-466
EN
A phased array antenna is designed for multifunction phased array radar simulation test bed. Effect of element pattern, mutual coupling between elements, phase quantization, amplitude and phase error and elements failure rates on array pattern are discussed. Target angle measurement and side lobe cancelling, in order to reduce jamming power through side lobes, is illustrated in this antenna. Also antenna beam width is broadened with different methods and compared with narrow beam characteristics. It is shown that, for special broadening factors, beam broadening may lead to a better coverage and power efficiency relative to narrow beam antenna.
12
Content available remote

Design and Thinning of Linear and Planar Antenna Arrays Using a Binary Teaching Learning Optimizer

51%
Recioui A.
Acta Physica Polonica A
|
2016
|
vol. 130
|
issue 1
7-8
EN
In this paper, a binary variant of the teaching learning optimization technique is used to the design and thinning of linear and planar arrays. The purpose of the optimization task is to enhance the ratio directivity/sidelobe level which turns out to be having two conflicting parameters. The binary variant of the teaching learning optimization technique searches the way of exciting some selected elements. The array thinning problem requires some elements to be excited with the others having no current in them. This is a binary (ON-OFF) problem that requires an optimization technique that can handle the binary variables. The teaching learning optimization has been proposed initially to handle real valued variables. The results show good agreement between the desired and calculated radiation patterns with reduction in resource usage in terms of power consumption.
13
Content available remote

Noise Radar with Microwave Correlation Receiver

45%
Susek W., Stec B., Rećko C.
Acta Physica Polonica A
|
2011
|
vol. 119
|
issue 4
483-487
EN
The idea of microwave quadrature correlation as well as the block diagram of the microwave broadband correlation receiver and principle of quadrature correlation detection of noise signals using an analog microwave correlator are presented in the paper. Measurement results for the correlation function of noise signals are shown and application of such solution in the noise radar for precise determination of distance changes and velocity of these changes is also presented. Results for short range noise radar operation are presented both for static and moving. Experimental results using 2.6-3.6 GHz noise like waveform for the signal from a breathing human is presented. Conclusions and future plans for the use of presented detection technique in broad-band noise radars close the paper.
14
Content available remote

Design and Analysis of a Microstrip Antenna Based on Superconducting Material for Millimeter Wave Applications

45%
Djidel S., Bouamar M., Khedrouche D.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 1
109-111
EN
In this paper, we present a design and analysis of microstrip antenna based on superconducting material for millimeter wave applications. The proposed antenna is simulated using electromagnetic microwave studio computer simulator CST. The structure is made by two materials: the yttrium barium copper oxide (YBCO) thin film superconductor material as the patch and silicon Si as substrate with permittivity of 11.9. The superconductor material is characterized by a conductivity of 1.62×10⁷ S/m and critical high temperature of 89 K. The simulated results concerning the return loss show that our structure has ultra wide band over 27 to 70 GHz. Low return loss of the superconductor antenna compared with his perfect conductor counterpart is achieved. In addition, good radiation pattern characteristics are obtained in the frequency band of operation. The proposed antenna has also overall size of 3×3 mm², which facilitate its integration in architecture of communications systems.
15
Content available remote

On the Possibility of Developing Matched Acousto-Optical Light Filtering Method for Incoherent Telecommunications and Earth Remote Investigations

38%
Proklov V., Byshevski-Konopko O., Lugovskoi A.
Acta Physica Polonica A
|
2015
|
vol. 127
|
issue 1
29-35
EN
This is a systematic study of the possibility of creating multi-frequency matched acousto-optic light filters and constructing on new basic principles of the non-coherent optical transmission systems with optical code division multiple accesses and hyperspectral sensors for remote sensing using pre-detector optimal filtering of optical information.
16
Content available remote

Bandwidth Improvement for Compact Microstrip Patch Antenna Using Metamaterials

38%
Bougoutaia T., Khedrouche D., Hocini A.
Acta Physica Polonica A
|
2016
|
vol. 129
|
issue 4
538-540
EN
An improved ultra-wideband (UWB) and high gain rectangular microstrip antenna is specifically designed in this paper using planar metamaterial based on double-ring resonators (DRR). The antenna has three double-ring resonators (DRRs) etched on the metal patch, and a partial ground plane so that the impedance matching characteristics of the antenna are much better. The -10 dB impedance bandwidth of the proposed antenna is 2.33-16.96 GHz. The antenna is promising for many applications such as WiMAX (2500-2690 MHz), Bluetooth (2400-2480 MHz) and UWB (3.1-10.7 GHz) applications. In addition, the proposed antenna has an average gain of 4.24 dB and a peak gain of 6.87 dB at 12.2 GHz.
first rewind previous Page / 1 next fast forward last
JavaScript is turned off in your web browser. Turn it on to take full advantage of this site, then refresh the page.