2013/2
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Recent Submissions
- ItemA BIC Based Initial Training Set Selection Algorithm for Active Learning and Its Application in Audio Detection(Společnost pro radioelektronické inženýrství, 2013-06) Leng, Yan; Qi, Guang-hui; Xu, Xin-yanTo construct a classification system or a detection system, large amounts of labeled samples are needed. However, manual labeling is dull and time consuming, so researchers have proposed the active learning technology. The initial training set selection is the first step of an active learning process, but currently there have been few studies on it. Most active learning algorithms adopt random sampling or algorithms like sampling by clustering (SBC) to select the initial training samples. But these two kinds of method would lose their effectiveness in detecting events of small probability. Because sometimes they could not select or select too few samples of the small probability events. To solve this problem, this paper proposes a BIC based initial training set selection algorithm. The BIC based algorithm performs clustering on the whole training set first. Then uses BIC to judge the status of clusters. Finally, it adopts different selection strategies for clusters of different status. Experimental results on two real data sets show that, compared to random sampling and SBC, the proposed BIC based initial training set selection algorithm can efficiently solve the detection problem of small probability events. In the mean time, it has obvious advantages in detecting events of non-small probability.
- ItemDiamond Based DDR IMPATTs: Prospects and Potentiality as Millimeter-Wave Source at 94 GHz Atmospheric Window(Společnost pro radioelektronické inženýrství, 2013-06) Acharyya, Aritra; Datta, Koyel; Ghosh, Raya; Sarkar, Monalisa; Sanyal, Roshmy; Banerjee, Suranjana; Banerjee, J. P.Large-signal simulation is carried out in this paper to investigate the prospects and potentiality of Double-Drift Region (DDR) Impact Avalanche Transit Time (IMPATT) device based on semiconducting type-IIb diamond as millimeter-wave source operating at 94 GHz atmospheric window frequency. Large-signal simulation method developed by the authors and presented in this paper is based on non-sinusoidal voltage excitation. The simulation is carried out to obtain the large-signal characteristics such as RF power output, DC to RF conversion efficiency etc. of DDR diamond IMPATT device designed to operate at 94 GHz. The results show that the device is capable of delivering a peak RF power output of 7.01 W with 10.18% DC to RF conversion efficiency for a bias current density of 6.0×10^8 A m-2 and voltage modulation of 60% at 94 GHz; whereas for the same voltage modulation 94 GHz DDR Si IMPATT can deliver only 693.82 mW RF power with 8.74 efficiency for the bias current density of 3.4×10^8 A m-2.
- ItemContrast Enhancement in Poor Visibility Conditions Using Guided Filtering(Společnost pro radioelektronické inženýrství, 2013-06) Chowdhry, Danish Ali; Siddiqui, Adil Masood; Touqir, ImranIn this paper, extraction of atmospheric veil is proposed to enhance the contrast of the images captured under poor visibility conditions. The method based on guided filtering can accurately recover hidden edges, maintain structural similarity (SSIM) to input image and it is effective for both color and gray level images. The proposed algorithm works without prior information about the scene and its complexity is linear function of the input image size. Experimental comparisons with state of the art algorithms demonstrate that our approach can significantly enhance the contrast and restore the visibility in fine details.
- ItemA 300 GHz "Always-in-Focus" Focusing System for Target Detection(Společnost pro radioelektronické inženýrství, 2013-06) Montero-de-Paz, Javier; Enrique Garcia-Munoz, Luis; Segovia-Vargas, DanielA focusing system for a 300 GHz radar with 5 m target distance and 10 mm diameter spot size resolution is proposed. The focusing system is based on a Gaussian telescope scheme and its main parameters have been de¬signed using Gaussian beam quasi-optical propagation theory with an in-house developed MATLAB® based analysis tool. Then, this approach has been applied to a real focusing system based on two elliptical mirrors in order to reduce the distortion and cross-polar level and a plane mirror to provide scanning capabilities. The over¬all system has been simulated with a full-wave electromag¬netic simulator and its behavior is presented. With this approach, the focusing system always works "in-focus" since the only mirror that is rotated when scanning is the output plane mirror, so the beam is almost not distorted. The design process, although based in the well-known Gaussian beam quasi-optical propagation theory, provides a fast and accurate method and minimizes the overall size of the mirrors. As a consequence, the size of the focusing system is also reduced.
- ItemDesign of Dual-band Branch-Line Coupler Based on Shunt Open-Circuit DCRLH Cells(Společnost pro radioelektronické inženýrství, 2013-06) Lu, Ke; Wang, Guang-ming; Tian, BoIn this article, the shunt open-circuit dual composite right/left-handed (DCRLH) cell is initially proposed and one dual-band branch-line coupler based on the proposed cells is designed. It is found that, compared with DCRLH cell, the frequency selectivity, matching condition and adjustment range of the shunt open-circuit DCRLH cell improve greatly. Moreover, the shunt open-circuit DCRLH cell exhibits two adjustable frequency points with -90degrees phase shift within its first two passbands. In order to explore this exotic property effectively, the influence of the primary geometrical parameter is investigated through parametric analysis. Thus, one dual-band branch-line coupler based on the shunt open-circuit DCRLH cells is designed. Both simulated and measured results indicate that comparative performance is achieved. Different from part of previous dual-band branch line couplers, for the proposed coupler, the signs of phase difference of two output ports within the two operating frequency bands are identical with each other. This branch-line coupler is quite suitable for the application which is sensitive to the variation of phase difference and its effective area is compact.