Papers by Keyword: Filter

Abstract: In synthetic aperture radar (SAR) inherent speckle will affect the legibility of image details; give the image target detection adverse effects. In order to reduce the SAR image speckles noise, this article provided an improved algorithm based on median filter and wavelet semi-soft threshold shrinkage. First, reduced the SAR image speckle with median filtering method, then, with the filtered image, filtering the image with wavelet half soft threshold value contraction algorithm to noise, Simulation results show that the algorithm based on median filtering and improved algorithm of wavelet half soft threshold shrinkage of SAR image can better remove the speckle noise of the SAR image, while keep better edge, in Equivalent Number of Looks (ENL) and edge keep ability (FOM) aspects, it would be better than median filtering.

Abstract: In view of the difficulty of designing a high-order linear phase filter with prototype parameters directly, this paper proposes a new approach to rapidly construct a high order linear phase filter through cascading two same low-order linear phase filters. A twelve-order HTSC cascaded linear phase filter is fabricated on YBCO/LaAlO3/YBCO substrate with the dimension of 44.1mm ×31.4mm. The measured result shows that the filter has a 56 MHz passband at a center frequency of 1993 MHz. The minimum insertion loss in the passband is 0.59 dB. The group delay variation in passband is less than 5 ns over 78.5% of the filter bandwidth which is in good agree with the simulation result.

Abstract: This paper analyzes an EMI filter solution to diminish the effect of harmonics generated by PWM converters in active filters. Throughout this paper, we have presented specific problems regarding the design, simulation and the validation of the model by testing EMI filters. It can be mentioned that the tests of the experimental model were performed in a laboratory, using existing conditions for the non linear consumer, by generating distorted waveforms.

Abstract: Sinusoidal pulse width modulation (SPWM) technique has been widely used in inverters and motor driver ciruits. In this paper, SPWM was generated by a low cost HT66F50 single-chip, wherein the reduced sampling points of a sine wave, and the fewer sampling points were then used to produce SPWM singals. The full-bridge inverter was modulated by the high switching frequency SPWM for the high side switches and the 60Hz control signals for the low side switches. Thus, it not only reduces the required memory spacein MCU, but also reduces the switching power losses. When the SPWM frequency is 19.53 kHz or 11.72 kHz, the total harmonic distortion (THD) of the inverter’s output is less than 0.6% under the load resistance 50, which is in compliance with the specification of IEEE STD. 519-1992.

Abstract: In this research, a converter, suitable for the convert station of the HVDC light technology, is proposed and optimized. The converter mainly consists of AC chopper, rectifier transformer, low-pass filters and smoothing reactor. This system can restrain the disturbance of the input power and output the power with high quality. This research is going to analyze the working principle of the converter and then optimize the output wave through filters. Circuit’s simulation is carried out by MATLAB to verify the reliability and feasibility of this converter topology.

Abstract: The Buck circuit has been widely used in DC drive, charging and storage circuit, switching power supply and other power electronic devices. There exists very strong duality in the Buck circuit with input LC filter, especially in the structure of circuit, the equivalent circuits and the waveforms of input and output parts. On the basis of a theoretical model established in our work, an experiment is conducted to validate the equivalent circuits of both input and output parts, as well as the waveforms of associated capacitors and inductors. By choosing appropriate component parameters, the experimental results confirm the predictions of the theoretical model proposed.

Abstract: As air conditioning system long-time running, microorganism like bacterium and fungus propagates easily in high humidity environment such as filter equipment. After the microorganism entering indoor environment through air conditioning system, the air quality would be affected seriously. Air conditioning system which is regarded as potential microbial pollution source is becoming more attention. The study was about isolation and identification of fungal microorganisms on the filter surface of the central air conditioning system in a gymnasium, and then researching on the colonies and mycelium grown and reproduce regular of fungal microorganisms in different thermal environment using thermal methods, aim to lay groundwork of propagation and diffusion mechanism study of fungal microorganisms in air conditioning system and effective air microbial contamination solve by thermal methods. By physiology biochemistry experiment and molecular biological identification, it was shown that the dominant fungi were Penicillium spp. and Cladosporium spp., colonies were 600 cfu/cm² and 140 cfu/cm² respectively.

Abstract: This paper deals with quantification of the noise located in the digital signal by an innovative process. This process is associated with the filter that represents the novel information conveyed by the desired signal, residual interference and residual noise which are used to reduce the noise. A typical uniform quantization operation of a sampled signal is identified and interpreted with the framework of stochastic difference equation. A new theorem is proposed with all possible assumptions to support our result to signal noise ratio. AMS [200] Subject Classification: 39A10, 39A30, 39A60, 39B82, 39B99.

Abstract: The advantage of HVDC is large power of transmission, low cost and good control performance. Generation system has harmonic because of the nonlinear characteristics of the converter. It has very important significance for HVDC transmission system to accurate analysis and rational allocation of harmonic filtering device. This paper mainly studies the characteristics and suppression of harmonics on AC side in HVDC system, and the filtering effect of different filter combinations of simulation.

Abstract: As there are a lot of inverters existed in distributed power coupled with nonlinear loads, the quality of energy power has been greatly affected, especially the harmonic problem. This paper presents an optimal configuration method of the filter based on the combination of genetic algorithm and differential evolution algorithm. The proposed method takes filter investment and energy loss cost as objective function. Then, it combines the advantages of both algorithms for optimizing allocation, numbers and parameters of active filter (APF) and passive filter (PF). Simulations are provided showing the validity of the proposed method.