• Title, Summary, Keyword: candidate frequency band

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Feasibility Study on Tropospheric Attenuation Effect of Ku/V Band Signal for Korean Satellite Navigation System

  • Park, Jungkeun;Lee, Young Jae;Choi, Moonseok;Jang, Jae-Gyu;Sung, Sangkyung
    • 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.

Proposal of Wireless Communication Method and Candidate Frequency Band for Constructing the Integrated Radio Networks for Railroads (철도통합 무선망 구축을 위한 무선통신방식과 후보주파수대역 제안)

  • Park, Duk-Kyu;Lee, Sang-Yun;Yoon, Byungsik;Kim, Yong-Kyu
    • Journal of the Korean Society for Railway
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    • v.16 no.6
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    • pp.510-518
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    • 2013
  • These days, interest in radio networks for railways has increased both at home and abroad. In response to this trend, not only the existing radio networks which focus on railway control signals but also the next-generation integrated radio network that can send videos and manage mass storage data are actively being investigated. This paper proposes wireless communication methods to establish integrated radio networks for railways. The paper further suggests a candidate frequency band that could be allocated as the frequency band for railways among the frequency bands currently used in Korea. Based on this paper, we can expect that the domestic railroad will operate more efficiently and that security and convenience of the railroad will reach a superior level. In addition, the Korean integrated radio networks for railways, which cope with the changes in the global technology market, will be established.

Distorted Image Database Retrieval Using Low Frequency Sub-band of Wavelet Transform (웨이블릿 변환의 저주파수 부대역을 이용한 왜곡 영상 데이터베이스 검색)

  • Park, Ha-Joong;Kim, Kyeong-Jin;Jung, Ho-Youl
    • IEMEK Journal of Embedded Systems and Applications
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    • v.3 no.1
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    • pp.8-18
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    • 2008
  • In this paper, we propose an efficient algorithm using wavelet transform for still image database retrieval. Especially, it uses only the lowest frequency sub-band in multi-level wavelet transform so that a retrieval system uses a smaller quantity of memory and takes a faster processing time. We extract different textured features, statistical information such as mean, variance and histogram, from low frequency sub-band. Then we measure the distances between the query image and the images in a database in terms of these features. To obtain good retrieval performance, we use the first feature (mean and variance of wavelet coefficients) to filter out most of the unlikely images. The rest of the images are considered to be candidate images. Then we apply the second feature (histogram of wavelet coefficient) to rank all the candidate images. To evaluate the algorithm, we create various distorted image databases using MIT VisTex texture images and PICS natural images. Through simulations, we demonstrate that our method can achieve performance satisfactorily in terms of the retrieval accuracy as well as the both memory requirement and computational complexity. Therefore it is expected to provide good retrieval solution for JPEG-2000 using wavelet transform.

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Analysis of 1.7GHz Frequency Interference for Domestic Digital Cordless Phone (1.7GHz 대역 국내 디지털 코드리스폰 도입을 위한 주파수 간섭 분석)

  • Kim, Jong-Ho;Kang, Gun-Hwan;Park, Duk-Kyu
    • 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.

A Study on the Analysis of 1.7GHz Frequency Interference for Domestic Digital Cordless Phone (1.7GHz 국내 디지털 코드리스폰 도입을 위한 주파수 간섭 분석에 관한 연구)

  • Kang, Gun-Hwan;Kim, Jong-Ho;Park, Duk-Kyu
    • Proceedings of the Korea Contents Association Conference
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    • pp.52-57
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    • 2006
  • This research studies and analyzes the current trends and the frequency allocation bands for digital cordless phone(DCP) in other county. 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.

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Study on the Selection of Optimal Candidate Bands for the Spectrum Sharing (주파수 공동사용을 위한 최적의 후보 대역 선정방안 연구)

  • Choi, Joo-Pyoung;Lee, Won-Cheol
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.25 no.10
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    • pp.1005-1019
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    • 2014
  • In this paper, we proposed the frequency candidates band for the spectrum sharing through researching and analyzing the current status of the policy and the economic values which is actively conducted on the United States and Europe. To this end, we investigated to the status and problems with the frequency reallocation and arrangement in respond to the current frequency demand. To solve these frequency reallocation and arrangement method problems, we introduce to the concept and current status of policy for the frequency method progress by advanced countries mainly. Also the results of the economic value analysis introduced in terms of the operators. In addition, we proposed the assessment terms and criteria for the selection of frequency candidates band through joint research and analysis results.

Comparison Analysis of Time and Frequency Resource of Candidate Waveforms for 5G Mobile Communications (5세대 이동통신을 위한 후보 변조기술들의 시간과 주파수 자원 비교 분석)

  • An, Changyoung;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.27 no.11
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    • pp.987-995
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    • 2016
  • One of evaluation indicators of candidate waveforms for 5G mobile communication is spectral efficiency improvement by OOB(Out of Band) power reduction technique. In this paper, time-frequency resource allocation characteristic of UFMC(Universal Filtered Multi-Carrier), FBMC(Filter Bank Multi-Carrier), and W-OFDM(Weighted Orthogonal Frequency Division Multiplexing) system is evaluated and analyzed. As simulation results, spectral efficiency characteristic of these systems have been improved according to time resource allocation. In this paper, we can confirm that each system has similar time-frequency efficiency characteristic when the number of transmission bit is same and four symbols are transmitted with the linear system condition. Also, we can conclude that FBMC system has the lowest time-frequency resource efficiency under the nonlinear condition.

Band Structure Engineering of Monolayer MoS2 by Surface Ligand Functionalization

  • Lee, Sang Yoon;Ramzan, Sufyan
    • Proceeding of EDISON Challenge
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    • pp.367-370
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    • 2015
  • Monolayer transition metal dicalcogenide (TMDC) materials are currently attracting extensive attention due to their distinctive electronic, transport, and optical properties. For example, monolayer $MoS_2$ exhibits a direct band gap in the visible frequency range, which makes it an attractive candidate for the photocatalytic water splitting. For the photoelectrochemical water splitting, the appropriate band edge positions that overlap with the water redox potential are necessary. Similarly, appropriate band level alignments will be crucial for the light emitting diode and photovoltaic applications utlizing heterojunctions between two TMDC materials. Carrying out first-principles calculations, we here investigate how the band edges of $MoS_2$ can be adjusted by surface ligand functionalization. This study will provide useful information for the realization of ligand-based band engineering of monolayer $MoS_2$ for various electronic, energy, and bio device applications.

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Segmentation of continuous Korean Speech Based on Boundaries of Voiced and Unvoiced Sounds (유성음과 무성음의 경계를 이용한 연속 음성의 세그먼테이션)

  • Yu, Gang-Ju;Sin, Uk-Geun
    • The Transactions of the Korea Information Processing Society
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    • v.7 no.7
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    • pp.2246-2253
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    • 2000
  • In this paper, we show that one can enhance the performance of blind segmentation of phoneme boundaries by adopting the knowledge of Korean syllabic structure and the regions of voiced/unvoiced sounds. eh proposed method consists of three processes : the process to extract candidate phoneme boundaries, the process to detect boundaries of voiced/unvoiced sounds, and the process to select final phoneme boundaries. The candidate phoneme boudaries are extracted by clustering method based on similarity between two adjacent clusters. The employed similarity measure in this a process is the ratio of the probability density of adjacent clusters. To detect he boundaries of voiced/unvoiced sounds, we first compute the power density spectrum of speech signal in 0∼400 Hz frequency band. Then the points where this paper density spectrum variation is greater than the threshold are chosen as the boundaries of voiced/unvoiced sounds. The final phoneme boundaries consist of all the candidate phoneme boundaries in voiced region and limited number of candidate phoneme boundaries in unvoiced region. The experimental result showed about 40% decrease of insertion rate compared to the blind segmentation method we adopted.

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A Study on Characteristics of the Transmission Line Employing Periodically Perforated Ground Metal on GaAs MMIC and Its Application to Highly Miniaturized On-chip Impedance Transformer Employing Coplanar Waveguide (GaAs MMIC상에서 주기적으로 천공된 홀을 가지는 접지 금속막 구조를 이용한 전송선로 특성연구 및 코프레너 선로를 이용한 온칩 초소형 임피던스 변환기에의 응용)

  • Yun, Young
    • Journal of the Korean Society of Marine Engineering
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    • v.32 no.8
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    • pp.1248-1256
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    • 2008
  • In this paper, basic characteristics of transmission line employing PPGM (periodically perforated ground metal) were investigated using theoretical and experimental analysis.According to the results, unlike the conventional PBG (photonic band gap) structures, the characteristic impedance of the transmission line employing PPGM structure showed a real value, which exhibited a very small dependency on frequency. The transmission line employing PPGM structure showed a loss (per quarter wave length) higher by $0.1{\sim}0.2\;dB$ than the conventional microstrip line. According to the investigation of the dependency of RF characteristic on ground condition, the RF characteristic of the transmission line employing PPGM structure was hardly affected by the ground condition in the frequency lower than Ku band, but fairly affected in the frequency higher than Ku band, which indicated that coplanar waveguide employing PPGM structure was optimal for RF characteristic and reduction of size. Considering above results, impedance transformer was developed using coplanar waveguide with PPGM structure for the first time, and good RF characteristics were observed from the impedance transformer. In case that {\lambda}/4$ impedance transformer with a center frequency of 9 GHz was fabricated for a impedance transformation from 20 to10 {\Omega}$, the line width and length were 20 and $500\;{\mu}m$, respectively, and its size was only 0.64 % of the impedance transformer fabricated with conventional microstrip lines. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on MMIC.