• Journal of Advanced Navigation Technology
• /
• v.12 no.2
• /
• pp.139-145
• /
• 2008

There has been lots of studies on communication systems using millimeter wave recently in many countries, specially in newly assigned 57GHz ~ 64GHz ISM band. Among those studies, IEEE 802.15.3c standard proposes OFDM (Orthogonal Frequency Division Multiplexing) systems for high data rate transmission support. But OFDM method has the PAPR (peak-to-Average Power Radio) problem The PAPR problem is to decline the performance of the transmission system due to signals distorted severely when passing through nonlinear components such as ADC/DAC and power amplifiers. In order to solve the problem of P APR, this paper suggests SSC (Sine Soft Clipping) and analyzes the PAPR, CCDF, PSD, BER by applying SAW(Surface Acoustic Wave) filter and power amplifiers to IEEE 802.15.3.c OFDM WPAN systems.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.36D no.1
• /
• pp.8-14
• /
• 1999

The active devices used at microwave frequency have the different phase shift according to input power. Especially, The difference of the phase shift is large in the saturation region of the amplifier. In this paper, we disigned the phase control system for fixing the different phase shift at device. With the high frequency nonlinear amplifier, we fabricated such system that the phase shift to be fixed automatically using the varible phase shifter. The variable phase shifter fixed total phase variation of the circuit using the information that was obtained from the comparison of imputsignal phase with output signal phase. Even though the input signal is 2-tone or FM type, we could estimate and also fix the phase variation on DUT Dynamic range is about 10dB. It has been experimented at 1960MHz using Teflon (H=31mil, ${\varepsilon}r$=3.2)

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.1
• /
• pp.76-79
• /
• 2017

This paper presents the electromagnetic shielding structure for low frequency wireless power transfer system with magnetic induction method using soft magnetic materials. Soft magnetic materials have advantages such as high permeability and low magnetic loss, but have undesirable effect of power loss by eddy current. To overcome this, we proposed the patterned soft magnetic material to suppress the eddy current path. For validity of this paper, we simulated the coil transfer efficiency and the radiated electromagnetic field, and fabricated the proposed structure using 79-permalloy. The measured results shows good agreements with the simulated results and reduction of the radiated electromagnetic field compared to commercial ferrite plate.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.2
• /
• pp.24-30
• /
• 2009

In this paper, the FPGA modem platform complying with 3GPP Release 7 eHSPA specifications and its regularized verification flow are proposed. The FFGA platform consists of modem board supporting physical layer requirements, MCU and DSP core embedded control board to drive the modem board, and peripheral boards for RF interfacing and various equipment interfaces. On the other hand, the proposed verification flow has been regularized into three categories according to the correlation degrees of hardware-software inter-operation, such as simple function test, scenario test call processing and system-level performance test. When it comes to real implementations, the emulation verification strategy for low power mobile SoC is also introduced.

• Journal of the Korean Home Economics Association
• /
• v.28 no.2
• /
• pp.91-106
• /
• 1990

This study focuses on consumers' advertising discriminatory competencies and the influencing facors. So the objects of this study are as follows : 1) to identify the overall level of advertising discriminatory competencies. 2) to examine if consumer attitude variables have significant effects on the ads. discriminatory competenceis. 3) to examine if the frequencies of contacting advertising variable have significant effects on the ads. discriminatory competencies. 4) to examine if socio-economics variables-age, educational level, monthly family income, occupational status-have significant effects on the ads. discriminatory competencies. 5) to find out the independent influence of variables related to the ads. discriminatory competencies. For this purpose, a survey was conducted using questionaires and advertisement papers. The data used in this study included 194 Homemakers living in Seoul. The ads. used in this study included ads. of diary products like foods, drinks, medicine, cosmetic, detergent in TV, radio, newspaper and magagine. Statistics were Frequency Distribution, Mean, percentile, ANOVA, Scheff -test, Pearsons' Correlation, Multiple Regrassion Analysis. Major findings were as follows : First, in 26 items(70%) of 37 items measured consumers' ads. discriminatory competencies, the rate of right answer was below 50%, so over the half of consumers were misleaded by the deceptive ads. Second, consumers' ads. discriminatory competencies differed significantly according to consumer attitude variables but no according to the frequency of contacting advertising. Third, according to socio-demographic variables-age, educational level, monthly family income, occupational status-advertising discriminatory competencies differed significantly. In group of lower age, higher educational level, higher income and professional occupation status, the level of ads. discriminatory competencies were high. Forth, the most influencing variabel on ads. disciriminatory competencies were eudcational level and in turn general attitude toward ads., attitude toward consumerism. This three variables explain 22.9% of dependent variable's variance. From these findings, the following suggestions are made, First, the consumer education offering informations and learing practical ads. discriminatory competencies should be conducted for all consumers wheather they are educated or not. Also the education to improve the consumer attitude must be. Second, considering misleading level, the business must make the regulatory standards and reinforce the regulation voluntarily, and by enforcing the regulation of ads. and deciding more diverse, objective and exact standards, the government should keep the consumer's right to know.

• Journal of Broadcast Engineering
• /
• v.16 no.5
• /
• pp.693-704
• /
• 2011

As mobile devices become multi-functional, and converge into a single platform, there is a strong need for a codec that is able to provide consistent quality for speech and music contents. MPEG-D USAC standardization activities started at the 82nd MPEG meeting with a CfP and approved Study on DIS at the 96th MPEG meeting. MPEG-D USAC is converged technology of AMR-WB+ and HE-AAC V2. Specifically, USAC utilizes three core codecs (AAC, ACELP, and TCX) for low frequency regions, SBR for high frequency regions, the MPEG Surround for stereo information, and window transition technology for smoothing transition between various core coder. USAC can provide consistent sound quality for both speech and music contents and can be applied to various applications such as multi-media download to mobile devices, digital radio, mobile TV and audio books.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.16 no.7
• /
• pp.1344-1349
• /
• 2012

The Korean DGPS station transmits the 200 bps GPS enhancement signal using the MSK modulation in frequency range of 283.5 kHz to 325 kHz. The land-based stations of 6 sites provide the service area of 80 km with the output power of 500 W. The ocean-based stations of 11 sites provide the output power of 300 W, which provide the DGPS service to 185 kM. Some places are serviced from two or three DGPS stations. The interferences among the DGPS stations using the high power can be occurred. Also, the performances of the user terminasl in dual service area can be degraded. In this paper, the protection ratios for the DGPS service are defined. Using the MF wave propagation model, the interferences among the DGPS stations and the adjacent wireless ground stations are analyzed. Also, the performances of DGPS user terminals are analyzed in the viewpoint of interference.

• Water for future
• /
• v.28 no.6
• /
• pp.183-191
• /
• 1995

Applying microwave, a velocity measurement system has been developed in order to measure the velocity of stream water surface. It's main purpose is the measurement for high velocity of flood water. It is under the developing stage of experimental measurement system. The microwave surface velocity meter uses Doppler effects of microwave. It consists of a radio frequency(RF) part and that of signal processing. Thr RF part has the function of microwave oscillation, reception of reflected wave, and determination of Doppler frequency, etc. Signal processing designates amplification, fast Fourier transform, etx. Various measuring experiments were performed at bridges and a spillway of Taechong re-regulation dam with the microwave velocity meter. Verification test was also made through water tank of ship model test at Research Institute of Ships and Ocean Engineering. It shows 4% error inherent in A/D converter and additional several percentage errors from measurement circumstance. The measuring ranges are from 0.5 to 3.5 m/s. The result shows good linear relationship between carriage velocity and measured velocity, thus proves usefulness as a measuring instrument for flood water velocity. The instrument requires overall re-engineering procedure and number of data should be accumulated and analyzed to treat wind effects and random fluctuations of water surface.

• Publications of The Korean Astronomical Society
• /
• v.27 no.3
• /
• pp.71-80
• /
• 2012

We have developed superconducting mixer receivers for 129 GHz VLBI observation in Korean VLBI Network (KVN). The developed mixer has a radial waveguide probe with simple transmission line L-C transformer as a tuning circuit to its 5 series-connected junctions, which can have 125 - 165 GHz as the operation radio frequency (RF). For intermediate frequency (IF) signal path a high impedance quarter-wavelength line connects the probe to one end of symmetric RF chokes. The double side band (DSB) receiver noise of the mixer was about 40 K over 4 - 6 GHz IF band, whereas we achieved the uncorrected single side band (SSB) noise temperature of about 70 K and better than 10 dB image rejection ratio in 2SB configuration with 8 - 10 GHz IF band. Insert-type receiver cartridges employing the mixers have been under commission for KVN stations.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.26 no.8
• /
• pp.1222-1230
• /
• 2022

As the number of signal sources with low detectability by using various modulation techniques increases, research to classify signal modulation methods is steadily progressing. Recently, a Convolutional Neural Network (CNN) deep learning technique using FFT as a preprocessing process has been proposed to improve the performance of received signal classification in signal interference or noise environments. However, due to the characteristics of the FFT in which the window is fixed, it is not possible to accurately classify the change over time of the detection signal. Therefore, in this paper, we propose a CNN model that has high resolution in the time domain and frequency domain and uses wavelet transform as a preprocessing process that can express various types of signals simultaneously in time and frequency domains. It has been demonstrated that the proposed wavelet transform method through simulation shows superior performance regardless of the SNR change in terms of accuracy and learning speed compared to the FFT transform method, and shows a greater difference, especially when the SNR is low.