• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.1
• /
• pp.15-20
• /
• 2012

In this paper, we designed and analysed K-band front-end module for digital microwave communication system receiver which improvement of dynamic range. We also suggested method of minimum amplified input signal level used to minimize noise figure of low-noise amplifier for High dynamic range. The designed modules consist of active mixer with conversions gain and PL-DRO with high stability and quality factor. The designed modules performance is that has the characteristics of over 54dB conversion gain, 1.3dB noise figure.

• Journal of Broadcast Engineering
• /
• v.8 no.2
• /
• pp.126-135
• /
• 2003

To investigate the DTV coverage especially in downtown areas and improve the performance of DTV receivers, it is necessary to capture the receiving DTV signals that contain the complex characteristics of the real-world RF environments and regenerate them in a laboratory without the performance degradation. In this paper, we developed a DTV RF capture and regeneration system adapting digital signal processing and high speed hard disk storage techniques and analyze its characteristics. The system can capture and replay the DTV RF signals based on a real-time condition in a hard disk. There Is no time limit for capturing RF data within the installed storage capacity. We can expect various Possible applications for this system such as a tool for the development of the receiver performance analysis, design and analysis for the DTV coverage areas, etc.

• Journal of KIISE:Computer Systems and Theory
• /
• v.31 no.11
• /
• pp.617-625
• /
• 2004

We propose an efficient stream authentication scheme that is an improvement of PCC scheme by using information dispersal algorithm. The drawback of PCC scheme is that received packets for each group are verifiable only if the signature packet of the group is successfully received. The proposed scheme processes the signature packet by introducing some amount of redundancy and splitting the result into pieces, which are then transmitted. The receiver is able to reconstruct the signature packet if the number of the received pieces is larger than the threshold. It is shown that under the same communication overhead verification probability of the proposed scheme is higher than that of SAIDA. Moreover, its computational cost is lower than that of SAIDA.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.20 no.6
• /
• pp.43-48
• /
• 2006

In this paper, the rectenna converting 2.45[GHz] microwave into DC power is designed and fabricated for wireless power transmission using microwave and the methode for impedance matching and tuning are proposed in order to maximize RF-DC conversion efficiency. The fabricated rectenna can be easily tuned by using a broad open stub and has the RF-DC conversion efficiency up to 59[%] when the 5[dBm] input power is applied. The 2.2[V], 1.5[mW] DC level, in the 1[m] distance between the transmitter and the receiver can be obtained and this value is avaliable in the small power digital system.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.7 no.5
• /
• pp.852-857
• /
• 2006

This paper presents a precision method to calculate the electric field density of mountain area using digital terrain elevation data(DTED). Generally we calculate the electric field density of a point adding a direct field density and horizontal reflection field density between two points. In this paper, we consider a vertical reflection field density from vertical surface near the wave propagation line between transmitter and receiver. The vertical reflection electric field have different propagation path and polarization from a horizontal reflection field. And the total electric field density adding horizontal field density and vertical reflection value is more accurate than a direct path electrical field density or direct field density adding a horizontal reflection field density.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.8A
• /
• pp.771-778
• /
• 2002

We investigate the design of an interpolation filter of a MF-TDMA demodulator which is applied to DVB-RCS. If sampling is not synchronized to the data symbols, timing adjustment in digital receiver must be performed by interpolation. It is impossible that conventional sinc interpolation filter coefficients are actually extended to infinity. We propose a Kaiser window interpolation filter and a sinc interpolation filter using th Kaiser window. Simulation results show that the performance improvement is realized by employing the proposed interpolation filter.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.20 no.6
• /
• pp.562-567
• /
• 2000

Many pressure vessels for power and industrial plant are fabricated from low alloy carbon steels. The inner sides of pressure vessels are commonly weld-cladded with austenitic stainless steels to minimize problems of corrosive attack. Disbonding cracks are often detected at the transition region of welding interlayer, which is serious problem to reliability of pressure vessels. We have developed C-scan system to high speed inspection of overlay weld using DSP(digital signal processor). This system consists of signal processing parts (oscilloscope, pulser/receiver, digitizer, DSP), scanner, program and position controller. The developed system has been applied to a practical ultrasonic testing in overlay weld, and demonstrated high speed with precision

• Journal of the Optical Society of Korea
• /
• v.17 no.6
• /
• pp.494-499
• /
• 2013

In this paper, we present an optical encryption and information authentication of 3D objects considering wireless channel characteristics. Using the optical encryption such as double random phase encryption (DRPE) and 3D integral imaging, a 3D scene with encryption can be transmitted. However, the wireless channel causes the noise and fading effects of the 3D transmitted encryption data. When the 3D encrypted data is transmitted via wireless channel, the information may be lost or distorted because there are a lot of factors such as channel noise, propagation fading, and so on. Thus, using digital modulation and maximum likelihood (ML) detection, the noise and fading effects are mitigated, and the encrypted data is estimated well at the receiver. In addition, using computational volumetric reconstruction of integral imaging and advanced correlation filters, the noise effects may be remedied and 3D information may be authenticated. To prove our method, we carry out an optical experiment for sensing 3D information and simulation for optical encryption with DRPE and authentication with a nonlinear correlation filter. To the best of our knowledge, this is the first report on optical encryption and information authentication of 3D objects considering the wireless channel characteristics.

• Journal of Veterinary Science
• /
• v.19 no.6
• /
• pp.840-845
• /
• 2018

The purpose of this study was to propose a standard for differentiation between normal dogs and patients with hyperadrenocorticism (HAC) by measuring skin thickness via ultrasonography in small breed dogs. Significant changes in skin thickness of patients treated with prednisolone (PDS) or patients with HAC treated with trilostane were evaluated. Skin thickness was retrospectively measured on three abdominal digital images obtained from small breed dogs weighing < 15 kg that underwent abdominal ultrasonography. Mean skin thickness of normal dogs was $1.03{\pm}0.25mm$ (mean ${\pm}$ SD). Both the HAC and PDS groups showed significantly thinner skin than that in the normal group. Seven of the 10 HAC patients treated with trilostane had increased skin thickness. The area under the curve value of 0.807 was based on the receiver operating characteristics (ROC) curve for differentiating normal dogs from HAC patients. Sensitivity was 76% and specificity was 73% when skin thickness was less than the 0.83 mm cutoff value. In conclusion, measurement of skin thickness in small breed dogs by using ultrasonography is likely to provide clinical information useful in differentiating HAC patients from normal dogs. However, exposure to PDS, trilostane, and other conditions may have a significant effect on skin thickness.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.16 no.2
• /
• pp.113-119
• /
• 2006

Image steganography is a secret communication method used to transmit secret messages that have been embedded into an image. To accommodate a secret message in a digital image, the original cover image is modified by the embedding algorithm. As a result, a stego image is obtained. The sender hides the secret message in a cover image that has no meaning, and then transmits the stego image to the receiver. In this paper, we propose a steganographic method based on spatial domain to embed a secret message using a difference value of two consecutive pixels and a secret quantization range. Especially, we use the modular operation for increasing of insertion information. Through experiments, we have shown that the proposed method has much mon payload capacity, average 60 percent, than some existing methods by using modular operation.