Papers by Keyword: Discrete Fourier Transform

Abstract: The possibility of using lattice periodic functions in the processing of narrowband signals with methods of discrete Fourier transform, instantaneous spectral density, and synchronous detection providing reduction of the number of readouts being processed, is shown. Results of the method’s experimental evaluation are considered. Suggested method can be used for increasing efficiency of correlation analysis of narrow band signals and for precise measuring of mains electricity supply frequency.

Abstract: Abstract. Neutral un-effectual grounded system (NUGS) is widely used in Chinese medium voltage power distribution network. However, existing earthed fault location methods in NUGS are not satisfactory in practical application due to weak fault current and unstable arc. Based on analysis of spectrum characteristics of current signals in single-phase earthed fault feeder, this paper proposed an earthed fault location method based on support vector machine (SVM). Firstly, the zero sequence current signal was sampled, and its spectrum was gotten by discrete Fourier transform. Secondly, the three dimensional feature vector that constituted by fundament, harmonic, inter harmonic component, had been extracted as the input of SVM. Furthermore, the SVM was trained with the samples obtained by simulation under different fault distance, different fault resistance and different fault close angle. Finally, the earthed fault feeder is selected using the trained SVM. The simulation results indicate that the fault location by the presented method is more precise.

Abstract: Presented to the π / 4 differential quaternary phase shift keying signal (π/4-DQPSK) using the discrete Fourier transform (DFT) for software demodulation algorithm in consideration of the actual received waveform into transition to π/4-DQPSK District and stable region, and only the waveform sampling point DFT transform the region stable recovery decision. simulation gives the demodulation method to achieve the same differential demodulation relatively simple structure, and the anti-noise in the signal to noise ratio greater than 3dB better performance than the differential demodulation performance, expected the algorithm is applied π/4-DQPSK software radio receiver design.

Abstract: In this paper, an area-efficient low power fast fourier transform (FFT) processor is proposed for multi input multi output-orthogonal frequency division multiplexing (MIMO-OFDM) in wireless communication system. It consists of a modified architecture of radix-2 algorithm which is described as modified radix-2 multipath delay commutation (MOD-R2MDC). The OFDM receiver with modified R2MDC (MOD-R2MDC) FFT was designed by Hardware Description Language (HDL) coding The Xilinx ISE Design Suite 10.1 is used as a synthesis tool for getting the power and area. The Model-Sim 6.3c is used for simulation. Also the existing OFDM system has been tested with these FFT algorithms and their performances were analyzed with respect to occupancy area in FPGA and power consumption. A low-power and area efficient architecture enables the real-time operations of MIMO OFDM system.

Abstract: In asynchronous sampling, discrete Fourier transform (DFT) spectrum involves errors. Scholars have done great investigations on the correction techniques of DFT spectrum, but the errors have not been completely eliminated all along. In this paper, spectrums were examined from the principle of conservation of energy. It is unnoticed before that the energy of the digital signal, which is the analysis object of DFT, isn't equal to that of the finite continuous signal truncated by rectangular window. Thus the energy of their spectrums are different according to the Parseval's theorem. The Energy Loss-Gain (ELG) error was introduced to express the energy difference between these two spectrums. The ELG error is zero if the observed continuous signal is truncated in integral multiple of half cycle and it is related to the cycle number and sampling number in one cycle. Analysis show that the ELG error decreases with the increment of these two parameters, which are helpful to the engineering.

Abstract: Maximum security is essential for a robotic device to achieve its optimum control. In this research, we present robotic motions, controlled by technological speech recognition techniques, using commands of Thai Speech Recognition (TSR). Examples of such speech words used are; Sai, Khwa, Na, Lang Khun, Long and Yood, which are the equivalent English language representations for; turn left, turn right, forwards, backwards, upwards, downwards, and stop, respectively. The speech commands are independent for any particular user and so, as a result, they are highly beneficial for general and practical use. The three main important parts of this paper comprise; Pre-processing, Discrete Fourier Transform (DFT), and Back Propagation Neural Network (BPN). The experimental results, when reviewed, exhibit results showing that the average accuracy percentages are equal to 71.00% for female commands, and 70.00% for male commands, respectively.

Abstract: Building Integrated with Photovotaic (BIPV) will become an effective way of building energy efficiency. A capacity determination method of energy storage system based on spectral analysis for BIPV was presented. To take both the isolated operation and grid-connected operation into account, the energy storage capacity can be determined based on spectrum analysis results of the control power to smooth power fluctuations in microgrid. Results indicate that the power control target of tie-line in microgrid can be achieved and the power fluctuations of BIPV output power and load power can be effectively smoothed by a relatively small capacity of energy storage system determined by the presented method.

Abstract: In order to reduce the Orthogonal Frequency division Multiplexing (OFDM) Inter-Carrier Interference (ICI), Put forward a kind of modulation method that based on the orthogonal frequency division multiplexing of orthogonal wavelet, Using orthogonal wavelet instead of discrete Fourier transform, optimize the design for OFDM systems, on the premise of without protection interval to reduce the system interference, using MATLAB to simulate the OFDM system, results show that the optimization of the OFDM can reduce the power of the ICI and Inter-symbol Interference (ISI) and improve the comprehensive anti-jamming of the OFDM system.

Abstract: The inter-harmonic spectrum of an electrical voltage or current from discrete Fourier transform can not only be caused by genuine inter-harmonic components, but can also be caused by other system disturbances. Therefore, the existence determination of genuine inter-harmonic s from the spectrum becomes the premise for further calculation of inter-harmonic parameters. From the theoretical perspective, this paper firstly analyzes and points out that the waveform difference among each cycle in the analysis window is the cause of the existence of inter-harmonic spectrum, and then presents a method to determine the existence of genuine inter-harmonic components, which is based on inter-harmonic time-frequency contour chart and the component appearance rate. The presented method firstly performs continuous discrete Fourier transform on the captured signal with certain duration and obtains the corresponding absolute time-frequency matrix, and then the genuine inter-harmonics can be distinguished based on the component appearance rate of the matrix and the criterion threshold. The method is easy to implement with clear principle, it can distinguish the genuine inter-harmonic s from the measured signal. The analysis on several data groups from real measurements verifies the effectiveness and the practicability of the method.

Abstract: The purpose of the research is to assess the increase of the muscle strength and power. Movement of the human body when the moving one impacts a stationary or moving body is taken under consideration. The waveform produced by an impact is transformed into frequency domain. The acceleration record is transformed as a complex spectrum, by the use of a Discrete Fourier Transformation. In this paper the applications of the discrete Fourier transform is discussed and it was pointed out that it can be fruitfully applied to analyze movement techniques during competition or training exercises. The acceleration response spectrum contains knowledge about efficiency of certain techniques. It has distinct features which can show that the energy is concentrated around several discrete frequencies. Data from the shape of a frequency response spectra curve can provide the coach and the performer with valuable information on technique and also give information on recommendations with respect to corrections and adjustments that can lead to performance enhancement. In this paper, the technique of a database creation is proposed what allows us to establish a particular set of circumstances under a specified protocol to observe and evaluate the implications of the resulting observations.