• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.8
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• pp.17-22
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• 2007

In this paper, we propose a threshold estimation algorithm for a noncoherent IR-UWB receiver using 1-bit sampler. The proposed method reduces the hardware complexity by using the information of binary data resulted from 1-bit sampler instead of measuring the energy level of a received signal. Besides, mathematical modeling shows that the performances are similar to those of theoretically optimal threshold in terms of bit error rate. Computer simulations based on the IEEE 802.15.4a channel model also demonstrate the superiority of the proposed algorithm.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.6 s.360
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• pp.24-30
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• 2007

In this paper, an energy detection-based low power, low complexity IR-UWB receiver in multipath impulse radio channel is presented. The proposed receiver has a simple 1-bit sampler for energy detection. Also, multipath signal received from multipath impulse radio channel is amplified and envelope of the signal is detected. Then, energy detection technique using integrator by summing multipath signals in certain period is adopted to minimize the BER loss by simple energy detection. In particular, in acquisition of a sample signal, SNR is additionally improved using a digital sampler. Symbol decision using several sampled signals is performed and thus the process of symbol synchronization is significantly simplified. Also, it is effectively designed to be compatible with influences of multipath and timing error. In addition, the proposed receiver complexity is reduced using pulse decision window. The performance of the proposed receiver is simulated based on IEEE 802.15.4a channel model and the algorithms are implemented on FPGA.

• Journal of the Institute of Convergence Signal Processing
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• v.18 no.1
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• pp.13-20
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• 2017

In this paper, we evaluate the basic test results of the 32 Gbps observational equipment introduced as the back-end system for the wideband VLBI (Very Long Baseline Interferometry) observation of KVN (Korean VLBI Network). Radio astronomers want to make a large radio telescope that has excellent performance in order to observe the superfine structure of a celestial body, but a lot of money is needed. Therefore, in order to increase the sensitivity, the performance improvement of the receiving system and the method of observing the wide frequency bandwidth are introduced. To do this, we adopted a wideband sampling method for converting analog signals to digital with ultra-fast speeds and a wideband sampler for performing digital filtering in order to observe a wide observational frequency bandwidth. The wideband sampler (OCTAD-K) supports up to 16 Gsps-2bits sampling and supports a variety of observational bandwidth using digital filtering techniques. In particular, it is designed to support KVN's 4-frequency simultaneous observation system and VERA(VLBI Exploration of Radio Astrometry)'s 2-beam observation system. It can also support polKVN(Korean VLBI Network), KaVA(KVN and VERA Array), 32Gbps Direct Sampler, Digital Filter, Widebandarization observations and supports the standard VDIF(VLBI Data Interchange Format) format of observed data. In this paper, the performance of the system and the problem solving are described in detail after performing the factory inspection and field test before the system is introduced.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.38-44
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• 2008

In this paper, we introduce an low complexity and low power IR-UWB (impulse radio ultra wideband) baseband transceiver for wireless sensor network. The proposed baseband, implemented by TSMC 0.18um CMOS technology, has a simple structure in which a simplified packet structure and a digital synchronizer with 1-bit sampler to detect incoming pulses are used. Besides, clock gating method using gated clock cell as well as customized clock domain division can reduce the total power consumption drastically. As a result, the proposed baseband has about 23K digital gates with an internal memory of 2Kbytes and achieves about 1.8mW@1Mbps power consumption.

• Publications of The Korean Astronomical Society
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• v.22 no.3
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• pp.63-73
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• 2007

In this paper, we introduce the performance test results of digital data processing system for KVN (Korean VLBI Network). The digital data processing system for KVN consists of DAS (Data Acquisition System) and high-speed recorder which called Mark5B system. DAS system performs the digitalization of analog radio signal through ADS-1000 gigabit sampler with 1 Gsps/2-bit and process the digital filtering of digital signal. Mark5B system records the output data of DFB (Digital Filter Bank) with about 1 Gbps. In this paper, we carried out the preliminary evaluation experiments of the KVN digital data processing system connected between DAS system and Mark5B with VSI (VLBI Standard Interface) interface which is designed for compatible in each VLBI system. We first performed all of the KVN digital data processing system connected by VSI interface in the world. In factory inspection phase, we found that the DAS system has a memory read/write error in DSM (Digital Spectrometer) by analyzing the recorded data in Mark5B system. We confirmed that the DSM memory error has been correctly solved by comparing DSM results with Mark5B results. The effectiveness of KVN digital data processing system has been verified through the preliminary experiments such as data transmission, recording with VSI interface connection and data analysis between DSM and Mark5B system. In future work, we will perform the real astronomical observation by using the KVN 21m radio telescopes so as to verify its stability and performance.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3651-3656
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• 2012

The size-segregated atmospheric aerosols have been collected at 1100 m site of Mt. Halla in Jeju, a background area in Korea, using 8-stage cascade impact air sampler during Asian dust and non-Asian dust storm periods. Their ionic and elemental species were analyzed, in order to examine the pollution characteristics and composition change between Asian dust and non-Asian dust periods. The major ionic species such as nss-$SO_4{^{2-}}$, $NH_4{^+}$, and $K^+$ were predominantly distributed in the fine particles (below $2.1{\mu}m$ diameter), and besides the $NO_3{^-}$ was distributed more in coarse particle fraction than fine particle. On the other hand, the typical soil and marine species i.e., nss-$Ca^{2+}$, $Na^+$, $Cl^-$, and $Mg^{2+}$, were mostly existed in the coarse particles (over $2.1{\mu}m$ diameter). As well in the elemental analysis of aerosols, the major soil-originated Al, Fe, Ca, and others showed prominently high concentrations in the coarse particle fraction, whereas the anthropogenic S and Pb were relatively high in the fine particle fraction. From the comparison of aerosol compositions between Asian dust and non-Asian dust periods, the concentrations of the soil-originated species such as nss-$Ca^{2+}$, Al, Ca, Fe, Ti, Mn, Ba, Sr have increased as 2.7-4.2 times during the Asian dust periods. Meanwhile the concentrations of nss-$SO_4{^{2-}}$ and $NO_3{^-}$ have increased as 1.4 and 2.0 times, and on the contrary $NH_4{^+}$ concentrations have a little bit decreased during the Asian dust periods. Especially the concentrations of both soil-originated ionic and elemental species increased noticeably in the coarse particle mode during the dust storm periods.