Browsing by Author "Chen, Shin-Chang"

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A Decoupling Technique for Increasing the Port Isolation Between Two Strongly Coupled Antennas
(2008-12-01)
Chen, Shin-Chang
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Wang, Yu-Shin
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Chun, Shyh-Jong
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電信工程研究所
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Institute of Communications Engineering
A compact decoupling network for enhancing the port isolation between two closely spaced antennas is proposed in this paper. In the network, we first connect two transmission lines (TLs) individually to the input ports of two strongly coupled antennas. The length of the TLs is designed so that the trans-admittance between ports changes from a complex one at the antenna inputs to a pure imaginary one. A shunt reactive component is then attached in between the TL ends to cancel the resultant imaginary trans-admittance. Finally, a simple lumped-element circuit is added to each port for input impedance matching. The even-odd mode analysis is adopted to investigate the currents excited on the antennas for predicting the radiation pattern of the two-element antenna array. Two examples of printed antennas at 2.45 GHz are tackled by using the proposed decoupling structure. The measurement results agree quite well with the simulation ones. High antenna isolation and good input return loss are simultaneously achieved in both cases, which demonstrates the feasibility of the structure. The decoupled antenna array in each example radiates, as prediction, toward different but complementary directions when the input power is fed in turn to the two input ports. The array efficiency is estimated better than 75% in each example. This pattern diversity effect is helpful for reducing the channel correlation in a multiple-input multiple-output (MIMO) communication system.
A new high isolation dual-antennas with miniature decoupling network design
(2007)
Chen, Shin-Chang
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Wang, Yu-Shin
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Ling, Ching-Wei
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Chung, Shyh-Jong
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電信工程研究所
Copyright protection for images with EXIF metadata
(2008)
Huang, Hsiang-Cheh
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Chen, Yueh-Hong
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Chen, Shin-Chang
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交大名義發表
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National Chiao Tung University
In this paper, we propose an application of robust watermarking with the aid of EXIF metadata in digital images. Application for robust watermarking is one of the major branches in digital rights management (DRM) systems. Furthermore, implementation schemes for robust watermarking generally alter selected pixels in the spatial domain, or corresponding coefficients in the transform domain, to accomplish the embedding process. We consider not only the pixels or coefficients in the images, but we also employ the EXIF metadata, which serves as the role of watermark, to further protect the copyrights. Taking the manufacturer, camera model, date and time stamp, and some other information in the EXIF metadata as the watermark information, conventional watermarking techniques can be applied to ordinary pictures taken by ourselves, and watermarked images with good quality can be produced. Even when the marked image has been intentionally modified, the original EXIF with selected information can be recovered from the watermark extraction process. Simulation results present the effectiveness of such an implementation.
Copyright Protection with EXIF Metadata and Error Control Codes
(2008)
Huang, Hsiang-Cheh
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Fang, Wai-Chi
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Chen, Shin-Chang
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交大名義發表
;
National Chiao Tung University
In this paper, we propose a practical scheme for copyright protection of images with the aid of EXIF metadata and error control codes. Application for robust watermarking is one of the major branches in digital rights management (DRM) systems and digital forensics. By use of robust watermarking, it generally alters selected coefficients in the transform domain to accomplish the embedding process. We consider not only the image contents itself, but we also employ the EXIF metadata, which serves as the role of watermark, to be integrated into our scheme. Moreover; for enhancing the copyright protection capability, channel coding is employed Taking the manufacturer, camera model, date and time stamp, and some other information in the EXIF metadata into account, conventional watermarking techniques can be applied to ordinary pictures taken by ourselves, and watermarked images with good quality can be produced. Even when the marked image has been intentionally modified, the original EXIF with selected information can mostly be recovered from the channel decoding process. Simulation results present the effectiveness of such an implementation.
Privacy Protection and Authentication for Medical Images with Record-Based Watermarking
(2009)
Huang, Hsiang-Cheh
;
Fang, Wai-Chi
;
Chen, Shin-Chang
;
交大名義發表
;
National Chiao Tung University
In this paper, we propose a practical scheme for privacy protection and authentication of medical images with the aid of EXIF metadata and associated records of the patients. By using watermarking, the goals mentioned above can be reached. Application for robust watermarking is one of the major branches in digital rights management (DRM) systems. With robust watermarking, it generally alters selected coefficients in the transform domain to accomplish the embedding process. We consider not only the image contents itself, but we also employ the EXIF metadata, which contains the patients\' records and serves as the role of watermark, to be integrated into our scheme. By doing so, the false negative probability for obtaining the record can be reduced. Moreover, taking the information that the medical doctor recorded in the EXIF metadata into account, conventional watermarking techniques can be applied to medical images, and watermarked images with good quality can be produced. Even when the marked image has been intentionally modified, the original EXIF with selected information can mostly be recovered from the decoding process. Simulation results present the effectiveness of such an implementation.