• The Journal of the Korea Contents Association
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• v.7 no.3
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• pp.60-67
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• 2007

This research studies and analyzes the current trends and the frequency allocation bands for digital cordless phone(DCP) in other country. From these results, we propose 1.7GHz & 2.4GHz as a effective candidate frequency band for domestic DCP. A proposed 1.7GHz is expected to introduce DECT system of Europe. Therefore it is necessary to make an analysis of interference between 1.7GHz band and an adjacent IMT-2000 band. In this paper, we proposed the allocation of channel for 1.7GHz on the basis of the analysis of frequency interference between 1.7GHz band and an adjacent IMT-2000 band.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1076-1082
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• 2013

The frequency bands were discovered which maximize the slopes of autocovariances of speech signals in frequency domain to increase the possibility of segregation between speech signals and background noise signal. A speech signal is divided into blocks which include multiples of sampled data, then those blocks are transformed to frequency domain using Fast Fourier Transform(FFT). To find linear equation by Linear Regression, the coefficients of autocovariance within blocks of some frequency band are used. The slope of the linear equation which is called the slope of autocovariance is varied from band to band according to the characteristics of the speech signal. Using speech signals of a man which consist of 200 files, the coefficients of the slopes of autocovariances are analyzed and compared from band to band.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.1
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• pp.80-88
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• 2016

For next generation global navigation satellite systems, new carrier frequencies in Ku/V band are expected to emerge as a promising alternative to the current frequency windows in L band as they get severely congestive. In the case of higher frequency bands, signal attenuation phenomenon through the atmosphere is significantly different from the L band signal propagation. In this paper, a fundamental investigation is carried out to explore the Ku/V band as a candidate frequency band for a new global satellite navigation carrier signal, wherein specific attention is given to the effects of the dominant attenuation factors through the tropospheric propagation path. For a specific application, a candidate orbit preliminarily designed for the Korean regional satellite navigation system is adapted. Simulation results summarize that the Ku band can provide a promising satellite navigation implementation considering the present satellite's power budget, while the V band still requires technical advances in satellite transceiver system implementations.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.4
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• pp.685-694
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• 2018

In this paper, we designed and fabricated the frequency mixer, which is the core parts of high frequency head in Ku-band tracking radar. To overcome the problem of single-ended and single-balanced resistive structure, we designed the fine-line structure with balanced mixer, to generate IF signal without distortion in L-band, after receiving the RF signal of the Ku-band. The prototype mixer showed a Noise Figure Max of 6.823dB, Gain of 4.1598~4.676dB and Band Pass of 61MHz in 5 Ku-band samples frequency.

• Journal of the Korean Institute of Navigation
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• v.19 no.2
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• pp.99-106
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• 1995

A wide band design method of an electromagnetic wave absorber with square ferrite cylinders in the second layer, which has very wide band frequency characteristics, is proposed and discussed. A theoretical model using the equivalent material constants method is also evaluated and proposed for its accuracy by comparison with Hashin-Shtrikman formulas. Based on the developed model, wide band electromagnetic wave absorbers with excellent reflective frequency characteristics in the frequency range of 30MHz to 3, 690MHz were designed.

• Journal of electromagnetic engineering and science
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• v.18 no.4
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• pp.254-260
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• 2018

In this study, we suggest an emulator for generating multiple heterogeneous interference signals in the Korean radio frequency identification/ubiquitous sensor network (RFID/USN) frequency band. The proposed emulator uses only one universal software radio peripheral to generate multiple heterogeneous interference signals more economically. Moreover, the physical and media access control parameters can be adjusted in real time using the LabVIEW program, thereby making it possible to create various time-varying interference environments easily. As an example showing the capability of the proposed emulator, multiple interference signals consisting of a frequency-hopping RFID signal and two LoRa signals with different spreading factors were generated. The generated signals were confirmed in both frequency and time domains. From the experimental results, we verified that our emulator could successfully generate multiple heterogeneous interference signals with different frequency and time domain characteristics.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.745-748
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• 1998

Recently, image and voice processing part is using wavelet transform. We propose thining algorithm using wavelet tranform. Wavelet transform consists of low frequency and high frequency in the spatial and frequency domain. After the wavelet decomposition, more than 90 percents of energy are contained in lowest frequency band. Therefor, for images with large difference of gray value between foreground and background like character images, we can more accurately in the lowest frequency band. Lowest frequency band has wavelet transform significant coefficient(WTS) that is required for the thinning algorithm we proposed Paper [3][5][7][8] can not separate consonants and vowels of korean characters. Becuase korean characters have structural feature. This paper can separate consonants and vowels. Simulation executed low frequency image and data compression can reduce 1/4$^{n}$ with level n. we can redcue time complexity 3/8.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.444-448
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• 2006

In this paper, a frequency synthesizer for X-band FMCW radars is proposed. Some X-band FMCW radars have been used as a level sensor for tanker ship and the resolution of the level sensor may be mainly depend on linearity of frequency sweep. For a linear frequency sweep. the proposed synthesizer employs a phase-locked loop using prescalars and a high speed digital PLL chip. The measured results show that the linear frequency sweep range is from 10 GHz to 11 GHz and the output power of the synthesizer is minium 7 dBm. and the phase noise is about -80 dBc/Hz at 100 KHz offset from 11 GHz.

• ETRI Journal
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• v.33 no.5
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• pp.818-821
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• 2011

A D-band subharmonically-pumped resistive mixer has been designed, processed, and experimentally tested. The circuit is based on a $180^{\circ}$ power divider structure consisting of a Lange coupler followed by a ${\lambda}$/4 transmission line (at local oscillator (LO) frequency). This monolithic microwave integrated circuit (MMIC) has been realized in coplanar waveguide technology by using an InAlAs/InGaAs-based metamorphic high electron mobility transistor process with 100-nm gate length. The MMIC achieves a measured conversion loss between 12.5 dB and 16 dB in the radio frequency bandwidth from 120 GHz to 150 GHz with 4-dBm LO drive and an intermediate frequency of 100 MHz. The input 1-dB compression point and IIP3 were simulated to be 2 dBm and 13 dBm, respectively.

• Journal of Broadcast Engineering
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• v.20 no.1
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• pp.82-91
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• 2015

The purpose of this paper is to propose the frequency allocation plan for the terrestrial UHDTV in 700MHz frequency band. Currently 700MHz frequency band is being requested by broadcasting, communication, and public safety sites for the use of UHDTV, LTE/LTE-A and PPDR (Public Protection and Disaster Relief) by each site. Validity and proper timing of each request is examined by references, and the frequency allocation plan is proposed. As results 9 channels and guard bands are allocated for the UHDTV service, under the consideration of two 10MHz frequency bands of the PPDR in700MHz band.