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Vol 61, No 8 (2018)
- Year: 2018
- Articles: 5
- URL: https://journals.rcsi.science/0735-2727/issue/view/10930
Article
Sub-Nyquist Sampling and Parameters Estimation of Wideband LFM Signals Based on FRFT
Abstract
Last years, most sub-Nyquist sampling and parameters estimation methods for linear frequency modulated (LFM) signals are based on compressed sensing (CS) theory. However, nearly all CS reconstruction algorithms are with high computational complexity and difficult to be implemented in hardware. In this paper, a novel framework of sub-Nyquist sampling and low-complexity parameters estimation for LFM signals is proposed. The incoherent sampling in CS theory is introduced into the construction of sub-Nyquist sampling system, but no CS reconstruction algorithm is employed in the estimation of parameters. Based on the energy aggregation of LFM signals in the proper fractional Fourier transform (FRFT) domain, the chirp rate and center frequency can be estimated by linear operations. Accordingly, the proposed estimation method is easily realized compared with existing estimation methods based on CS. Simulation results verify its effectiveness and accuracy.
333-341
Method for Enhancing the Accuracy of Frequency Offset Estimation in OFDM Modulation Based Communication Systems
Abstract
The paper proposes a method for enhancing the accuracy of estimation of frequency offset for OFDM modulation based communication systems. An increase accuracy of the proposed method is achieved at the expense of combined use of pilot and information symbols of OFDM signal. The main factors determining the accuracy of proposed method were identified. Mathematical simulation of the proposed method was performed for a multipath radio wave propagation channel. The proposed method efficiency was shown in comparison with existing methods for the estimation of frequency offset. Advantages and disadvantages of existing and proposed methods were described. The relationships of the root-mean-square error of frequency offset estimation as a function of the signal-to-noise ratio were built for the proposed and existing methods. The attainable high accuracy of frequency offset estimation by employing the proposed method makes its use expedient in control and measuring equipment. Conclusions have been made regarding the simulation results obtained and the expediency of proposed method applications.
342-349
Stochastic Estimation of Ephemerides of Navigation Satellites in Perturbed Orbits
Abstract
The errors of navigation satellite ephemerides are one of the key factors to determine the accuracy of satellite navigation. To improve the accuracy of ephemerides calculation, modern satellites are equipped with inter-satellite measurement equipment. However, random interference is inevitably present in the data transmission path and it is necessary to minimize its effect. To perform this task, it is proposed to use the stochastic estimation of ephemerides of navigation satellites that are moving along disturbed orbits in the form of a procedure of parametric optimization based on the minimization of the additive set of two functionals. The optimization of the first functional provides the minimum of uncertainty in the estimation of ephemerides. The optimization of the second functional provides the minimum of the norm of the vector of orbital parameters variations in the current time interval. To illustrate the effectiveness of the proposed approach, a numerical simulation of the satellite constellation’s ephemerides estimation was carried out for the corresponding trajectory perturbations. The simulation results illustrate the possibility to determine the ephemerides of navigation satellites with the accuracy within units of meters based on the approach considered that uses the noisy inter-satellite measurements.
350-360
Detection Efficiency of Signal with Unknown Non-Power Parameter Using Algorithms Based on the Compressive Sensing Theory
Abstract
The problem of detecting quasi-deterministic signals against the background of noise during the digital processing has been considered. In this case, at the specified detection efficiency, the minimum criterion of required arithmetic operations was used as a synthesis criterion for such algorithms. To this end, such algorithms were synthesized based on concepts of the compressive sensing theory. The computer simulation was used to check the efficiency of developed algorithms making it possible to determine the manner in which the total probability of detection errors depends on the signal-to-noise ratio and the compression ratio (ratio of the number of elements in the sufficient statistic vectors before and after “compression”). The detection efficiency losses of proposed algorithms were determined in comparison with the classical optimal algorithm in accordance with the maximum likelihood method at different values of signal-to-noise ratio and compression ratio. At the same time, the paper indicates the gain in the number of used arithmetic operations of proposed algorithms as compared to the classical one. The presented results allow us to make a sound choice of detection algorithm depending on the available hardware resources and admissible degradation of the detection efficiency.
361-370
Band-Notched Planar UWB Microstrip Antenna with T-Shaped Slot
Abstract
Ever growing demand for higher data rates requires appropriate radiation systems with large bandwidth and stable gain. Microstrip antennas with unidirectional radiation patterns and stable gain are most useful for this purpose. A ground plane defect of microstrip patch antenna is used to breed multiband applications. As a result, the performance of gain, directivity, and bandwidth is enhanced, the geometry and shape of an ultrawideband (UWB) antenna are simplified, and its size is reduced. Thus, it results in the efficient performance with respect to wideband operation. A novel band notching of microstrip truncated UWB antenna is implemented for insusceptibility in the range 5.2–5.8 GHz. The suggested structure contains circular truncated and T-shaped slots for band notching. The optimal results can be obtained by selecting the antenna parameters. Advantages of the proposed antenna include small size, better impedance match and simple design. Details of the suggested and observational solutions are demonstrated in this paper. The S11 parameter of antenna is–45.5 dB at a resonant frequency of 4.6, 5.5, and 9.8 GHz. The gain of antenna is 5.47 dB, and the value of VSWR is smaller than 2, which makes the proposed structure an ideal choice for its application in wireless communication, 5G and IoT.
371-376