SDR 시스템을 위한 Complex Bandpass Sampling 기법 및 일반화 공식의 유도

배정화,하원,박진우,Bae, Jung-Hwa,Ha, Won,Park, Jin-Woo 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.7C

차세대 통신기술인 Software-Defined Radio (SDR)시스템은 단일 하드웨어 플랫폼에 소프트웨어 변경만으로 다양한 통신표준을 수용할 수 있는 시스템이다. 시스템의 융통성(flexibility)과 적응성(adaptability)을 위하여 RF와 관련된 하드웨어의 최소화가 필요하며, 이를 위해 ADC를 사용으로 기저대역(baseband) 또는 낮은 IF단으로 직접하향 변환(downconversion)을 할 수 있는 bandpass sampling 기법이 필수적이다. 이 논문에서는 complex bandpass sampling 방식을 이용하여 두 가지의 통신 표준이 한 시스템에서 동시에 직접 하향 변환하는 새로운 방법을 제안하였다. 이에 따른 sampling 가능 영역, 보호대역(guard-band)을 고려한 sampling 가능 최소 주파수 그리고 이동된 신호의 위치를 구하는 수식들을 유도한 뒤 그래프를 통해 비교 분석하였다. 또한 제안한 sampling방식이 모의실험을 통해 기존에 제안되었던 real bandpass sampling방식보다 SDR시스템에 더욱 적합하다는 것을 입증하였다. A bandpass sampling technique, which is a method directly downconverting a bandpass signal to a baseband or a low IF signal without analog mixers, can be an alterative choice for the SDR system to minimize the RF front-end. In this paper, a complex bandpass sampling technique for two bandpass-filtered signals is proposed. We derived generalized formulae for the available sampling range, the signal's IF and the minimum sampling frequency taking into consideration the guard-bands for the multiple RE signals. Thru the simulation experiments, the advantages of the . complex bandpass sampling over the pre-reported real bandpass sampling are investigated for applications in the SDR design.

다중 대역통과 신호의 하향변환을 위한 Complex Bandpass Sampling 기법

배정화,하원,박진우,Bae, Jung-Hwa,Ha, Won,Park, Jin-Woo 한국통신학회 2005 韓國通信學會論文誌 Vol.30 No.9C

A complex bandpass sampling technique can provide a more flexible architecture for designing a software- defined radio(SDR) system, because it has several advantageous features of larger sampling range and lower minimum sampling frequency than a real bandpass sampling method. In spite of the potential advantages of the complex bandpass sampling, solid investigation for the direct downconversion of multiple signals by the complex sampling theory has not been reported yet. Thus, we propose in this paper a novel scheme for the downconversion of multiple signals using the complex bandpass sampling, and develop the formulae related to the complex bandpass sampling for practical usage, such as the valid sampling range, the intermediate frequency (If), and the minimum sampling frequency of the downconversion of multiple RE signals. Such derived formulae are verified from simulations. 일반적인 bandpass sampling 방법인 real bandpass sampling 기법은 하향변환(downconversion)을 시행할 때 음의 주파수 대역의 RF 신호와의 에일리어싱(aliasing) 현상을 피해야 하므로 신중한 sampling 주파수 선택이 요구된다. 더욱이 다중신호(multiple signals)가 하향변환 될 경우에 이 sampling 방법은 더욱 많은 제약이 따르게 된다. 그러나 Hilbert 변환을 사용하는 complex bandpass sampling 방법은 음의 주파수 영역의 신호를 제거함으로써, real bandpass sampling 기법보다 유연하고 넓은 sampling 주파수 범위를 제공하며, 또한 더욱 낮은 sampling 주파수를 얻을 수 있는 장점이 있다. 본 논문에서는 이러한 complex bandpass sampling의 특징을 사용하여, 다중 신호를 하나의 통신 기기에서 동시에 하향 변환하는 수신기의 구조를 제시한다. 그리고 하나 또는 2개 신호의 하향변환에 관한 내용으로 제한하지 않고 N개의 신호로 확장하여 유효 sampling 주파수 영역 및 보호대역(guard-band)이 고려된 sampling 가능 최소 주파수에 관한 수식들을 일반화한다. 또한 모의실험을 통해 유도된 수식들을 증명한다.

Atmospheric Bioaerosol, Bacillus sp., at an Altitude of 3,500 m over the Noto Peninsula: Direct Sampling via Aircraft

Kobayashi, Fumihisa,Morosawa, Shinji,Maki, Teruya,Kakikawa, Makiko,Yamada, Maromu,Tobo, Yutaka,Hon, Chun-Sang,Matsuki, Atsushi,Iwasaka, Yasunobu Korean Society for Atmospheric Environment 2011 Asian Journal of Atmospheric Environment (AJAE) Vol.5 No.3

This work focuses on the analysis of bioaerosols in the atmosphere at higher altitudes over Noto Peninsula, Japan. We carried out direct sampling via aircraft, separated cultures, and identified present isolates. Atmospheric bioaerosols at higher altitudes were collected using a Cessna 404 aircraft for an hour at an altitude of 3,500 m over the Noto Peninsula. The aircraft-based direct sampling system was devised to improve upon the system of balloon-based sampling. In order to examine pre-existing microorganism contamination on the surface of the aircraft body, bioaerosol sampling was carried out just before takeoff using the same method as atmospheric sampling. Identification was carried out by a homology search for 16S or 18S rDNA isolate sequences in DNA databases (GenBank). Isolate sampling just before takeoff revealed Stretpomyces sp., Micrococcus sp., and Cladosporium sp. One additional strain, Bacillus sp., was isolated from the sample after bioaerosol collection at high altitude. As the microorganism contamination on the aircraft body before takeoff differed from that while in the air, the presence of additional, higher atmosphere-based microorganisms was confirmed. It was found that Bacillus sp. was floating at an altitude of 3,500 m over Noto Peninsula.

Atmospheric Bioaerosol, Bacillus sp., at an Altitude of 3,500 m over the Noto Peninsula: Direct Sampling via Aircraft

Fumihisa Kobayashi,Shinji Morosawa,Teruya Maki,Makiko Kakikawa,Maromu Yamada,Yutaka Tobo,Chun-Sang Hon,Atsushi Matsuki,Yasunobu Iwasaka 한국대기환경학회 2011 Asian Journal of Atmospheric Environment (AJAE) Vol.5 No.3

This work focuses on the analysis of bioaerosols in the atmosphere at higher altitudes over Noto Peninsula,Japan. We carried out direct sampling via aircraft,separated cultures, and identified present isolates. Atmospheric bioaerosols at higher altitudes were collected using a Cessna 404 aircraft for an hour at an altitude of 3,500 m over the Noto Peninsula. The aircraft-based direct sampling system was devised to improve upon the system of balloon-based sampling. In order to examine pre-existing microorganism contamination on the surface of the aircraft body, bioaerosol sampling was carried out just before takeoff using the same method as atmospheric sampling. Identification was carried out by a homology search for 16S or 18S rDNA isolate sequences in DNA databases (GenBank). Isolate sampling just before takeoff revealed Stretpomyces sp., Micrococcus sp., and Cladosporium sp. One additional strain,Bacillus sp., was isolated from the sample after bioaerosol collection at high altitude. As the microorganism contamination on the aircraft body before takeoff differed from that while in the air, the presence of additional, higher atmosphere-based microorganisms was confirmed. It was found that Bacillus sp. was floating at an altitude of 3,500 m over Noto Peninsula.

현장에서의 바이오가스 포집방법이 실록산 측정값에 미치는 영향 분석

김다은 ( Da-eun Kim ),박성범 ( Sungbeom Park ),박대원 ( Daewon Pak ),김낙주 ( Nackjoo Kim ) 한국환경분석학회 2016 환경분석과 독성보건 Vol.19 No.3

Siloxanes are volatile silicon compounds found in biogas that need to be removed in the process of utilizing biogas as an energy source. Therefore, optimal detection of siloxanes in biogas is essential. In this study, two different configurations of a direct sampling method using methanol for solvent absorption are compared. The two configurations are on-site and off-site direct sampling. The on-site direct sampling involves trapping gas directly from the biogas source in impingers filled with methanol, and the off-site method involves absorbing gas in impingers from gas bags filled with biogas previously sampled and homogenized under controlled temperature and pressure conditions. The absorption methodology used is originally from Air Toxics Ltd. and ESS Laboratories. A change in flow rate was considered in order to keep the same composition of biogas throughout multiple sampling events. Also, GC/MS and ESTD methods were applied. To minimize instrumental errors, different GC capillary columns were tested to find the optimal GC/MS conditions. Polysiloxane coated columns (HP-1MS, HP-5MS) showed better peak separation and quantification when compared to a polyethylene glycol-coated column (HP-INNOwax). Finally, the two sampling configurations were statistically compared and it was determined that there are no significant differences in detection results between them.

등속 튜브연소로 출구에서의 직접 샘플링 방법을 이용한 연기입자 입경분포 측정

구재학(Jaehark Goo) 한국화재소방학회 2023 한국화재소방학회논문지 Vol.37 No.6

The size distribution of smoke particles, influenced by varying fire conditions, constitutes a significant research focus in the firefighting domain concerning fire detection and the impact on lung deposition which is a major contributor to both short- and long-term casualties among residents and firefighters. Currently, the ISO/TS 19700 method is commonly employed to measure characteristics of combustion products, including composition and concentration, primarily for gaseous substances. However, due to measurement challenges, limited research results exist on particulate substances using this method, and outcomes vary significantly among researchers. The particle size distribution which is the typical characteristics of particulate materials is crucial factor leading to discrepancies in measurements at the combustion furnace outlet. This distortion is influenced by factors such as particle collision, temperature changes, and residence time in the mixing chamber installed for cooling and dilution. This study unveils the disparity in particle size distribution between using a mixing chamber and direct sampling. A solution is proposed by replacing the mixing chamber at the outlet of the steady-state tube furnace specified in the existing ISO/TS 19700 method with a direct sampling approach. Smoke particles generated under combustion conditions at various temperatures and equivalence ratios were directly sampled at the furnace exit. These samples underwent a two-stage dilution process, and the real-time particle size distribution was measured using an electrostatic low-pressure impactor. This approach minimizes distortion of the particle size distribution attributable to the mixing chamber. 화재 조건에 따라 달라지는 연기 입자의 크기 분포는 화재 현장에서 발생하는 연기로 인한 거주자 및 소방관의 장단기 인명 피해의 주요 원인인 폐침전뿐만 아니라 화재 감지와 관련하여 소방 분야에서 중요한 연구 주제이다. 현재 연소 생성물의 성분, 농도 등의 특성은 ISO/TS 19700 방법을 이용하여 측정하는 경우가 많은데, 이 방법은 가스상 물질에 주로 사용되며 측정의 어려움으로 이 방법을 이용한 입자상 물질에 대한 연구 결과는 많지 않고 그 결과는 연구자에 따라 많은 차이를 보인다. 입자상 물질의 특성 중 대표적인 것이 크기분포이며 이 측정값이 연소로 출구에서의 실제 분포와 다르게 나타나는 이유로서 중요한 것 중 하나는 냉각, 희석을 위해 설치된 혼합상자에서 입자의 충돌, 온도 변화, 체류시간 등의 인자에 의해서 이 크기분포 특성이 왜곡되기 때문으로 판단된다. 본 연구에서는 기존의 ISO/TS 19700 방법에 명시된 등속 튜브연소로 출구에서의 혼합상자를 직접 샘플링 방법으로 대체함으로써 혼합상자를 사용하는 경우와 직접 샘플링하는 경우의 입경분포 차이를 밝히고 해결책을 제시하였다. 이를 위하여 각 온도 및 당량비 변화에 따른 연소조건에서 발생한 연기 입자를 등속연소로 출구에서 직접 샘플링한 후 2단 희석장치를 거쳐 정전저압임팩터로 실시간 입경분포를 측정함으로써 혼합상자로 인한 입자 크기분포 왜곡을 최소화하였다.

Analysis of Residual Monomers in Poly(acrylonitrile-co-butadiene-co-styrene)

최성신,김윤기 한국고분자학회 2012 Macromolecular Research Vol.20 No.6

Residual monomers in poly(acrylonitrile-co-butadiene-co-styrene) (ABS) were extracted using direct thermal desorption as well as solvent extraction, and were analyzed using gas chromatography (GC). Headspace sampling and liquid injection were employed as an injection method. For the solvent extraction/liquid injection method, the solvent peak covered the residual monomer peaks. For the solvent extraction/headspace sampling method, the solvent peak was almost not overlapped with the residual monomer peaks, but the peak intensities of the residual monomers were small compared to the liquid injection. Using the direct thermal desorption method,clear chromatograms were obtained. The residual monomers were extracted by heating at 75-150 oC for 5 h, and the thermally desorbed materials were injected to GC by headspace sampling. Amounts of the residual monomers increased with increase of the heating temperature. The recommendable method to analyze the residual monomers in ABS was that the extraction method was direct thermal desorption at 150 oC for 5 h, and the injection method was headspace sampling.

Sampled-data observer-based output-feedback fuzzy stabilization of nonlinear systems: Exact discrete-time design approach

Kim, D.W.,Lee, H.J. North-Holland 2012 Fuzzy Sets and Systems Vol. No.

This paper presents a new direct discrete-time design methodology of a sampled-data observer-based output-feedback fuzzy controller for a class of nonlinear system that is exactly modeled in Takagi-Sugeno's form at least locally. A fundamental yet challenging issue in this direction is the unavailability of the exact discrete-time model of the nonlinear plant in a closed form. In contrast to the earlier works that are based on an approximate discrete-time model thus the stability obtained in the design step is not preserved in the implementation step, we employ an exact discrete-time fuzzy model in an integral form. Sufficient asymptotic stabilization conditions are investigated in the discrete-time Lyapunov sense. We then show that the resulting sampled-data controller indeed asymptotically stabilizes the nonlinear plant. An example is provided to illustrate the effectiveness of the proposed methodology.

Effect of Opening on the Shear Behavior of Granular Materials in Direct Shear Test

김병수,Satoru Shibuya,박성완,Shoji Kato 대한토목학회 2012 KSCE Journal of Civil Engineering Vol.16 No.7

This paper examines the effect of the opening between the shear boxes on the shear behavior in the direct shear box test (H=20 mm×D=60 mm) under a constant vertical stress using seven types of granular material. It is observed that the magnitude of shear strength and dilatancy decreases due to the outflow of sample with an increase in the opening. The two notions of the Threshold Point (TP) as the limit opening size and the Threshold Line (TL) offering the guideline of opening size is defined according to the mean particle size of soil samples. However, similar shear behaviors were observed regardless of the opening size because there was no outflow of sample through applying the Teflon sheet in the direct shear box tests for Toyoura sand. Finally, the shear mode on the circular specimen applying the Teflon sheet is also examined in comparison with the results from other tests.

Detecting Sensor Fault for Nonlinear Systems in T-S Form Under Sampled-Data Measurement: Exact Direct Discrete-Time Design Approach

지성철,이호재,김도완 제어·로봇·시스템학회 2016 International Journal of Control, Automation, and Vol.14 No.2

A direct discrete-time design methodology for sampled-data sensor fault detection for nonlinear systemsin Takagi–Sugenos form is proposed. Contrary to the conventional schemes in this way that rely on an approximatediscrete-time model of the nonlinear system, our result is established based on an exact one. Condition to designthe observer and the residual gain under anH =H∞ performance criterion is presented in matrix inequality format. An example is given to illustrate the effectiveness of the proposed methodology.