• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.6
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• pp.599-604
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• 2002

In this paper, a digital potentiometer is used as a load resistor of a wireless optical differential detector with a polarizer, to improve the noise reduction capability. In this structure, the noise voltages of the two photodiodes are made equal by controlling a digital potentiometer and the optical noise is cancelled out. With a digital potentiometer, the signal to noise ratio is enhanced by about 23 dB.

• Journal of electromagnetic engineering and science
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• v.15 no.1
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• pp.59-61
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• 2015

A wideband H-band detector operating near 300 GHz has been developed based on SiGe HBT technology. The detector consists of an on-chip antenna and a HBT differential pair for square-law detection. It showed responsivity of more than 1,700 V/W and noise equivalent power (NEP) smaller than $180pW/Hz^{0.5}$ for the measured frequency range of 250-350 GHz. The maximum responsivity and the minimum NEP were 5,155 V/W and $57pW/Hz^{0.5}$, respectively; both were obtained at 330 GHz with DC power dissipation at 9.1 W.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1990.10a
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• pp.52-57
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• 1990

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1131-1143
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• 2016

Differential detection schemes do not require any channel estimation, which can be employed under user mobility with low computational complexity. In this work, a soft-input soft-output (SISO) differential detection algorithm is proposed for amplify-and-forward (AF) over time-varying relaying channels based cooperative communications system. Furthermore, maximum-likelihood (ML) detector for M-ary differential Phase-shift keying (DPSK) is derived to calculate a posteriori probabilities (APP) of information bits. In addition, when the SISO is exploited in conjunction with channel decoding, iterative detection and decoding approach by exchanging extrinsic information with outer code is obtained. Finally, simulation results show that the proposed non-coherent approach improves detection performance significantly. In particular, the system can obtain greater performance gain under fast-fading channels.

• ETRI Journal
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• v.29 no.2
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• pp.143-152
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• 2007

In this paper, we propose a time-varying modified minimum mean-squared error (MMSE) detector for the detection of higher data rate signals in a multirate asynchronous code-division multiple-access (CDMA) system which is signaled in a fast Rayleigh fading channel. The interference viewed by a higher data rate symbol will be periodic due to the presence of a lower data rate symbol which spans multiple higher data rate symbols. The detection is carried out on the basis of a modified MMSE criterion which incorporates differential detection and the ratio of channel coefficients in two consecutive observation intervals inherently compensating the fast variation of the channel due to fading. The numerical results obtained by the MMSE detector with time-varying detection show around 3 dB (M=2) and 6 dB (M=4) performance improvement at a BER of $10^{-3}$ in the AWGN channel, while introducing more computational complexity than the MMSE detector without time-varying detection. At a higher $E_b/N_0$, the proposed scheme can achieve a BER of approximately $10^{-3}$ in the presence of fast channel variation which is an improvement over other schemes.

• Fire Science and Engineering
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• v.23 no.3
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• pp.67-72
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• 2009

This paper is for response feature of fire detectors not only to analysis response feature of fire detector, but also to observe flame spread of inside-building and fire enlargement by using the row house which is supposed to be broken up. Many kinds of popular detectors such as heat type detector(differential type, fixed temperature type, Analogue type)and smoke type(light scattered type, Analogue type, single alarm type) were installed in the house in order to check for the change of temperature by installing of thermocouples. As a result, smoke detectors are better than heat detectors when it comes to making effective fire-detect system in the row house.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.104-109
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• 2001

The time to measure the size distribution using Condensation Nuclei Counter(CNC) and Differential Mobility Analyzer(DMA) can be shortened by classifying particles ramping the DMA voltage exponentially and continuously. In measurement, particles sampled at different time are mixed together going through sampling tube and CNC. Because the size distribution is inversed by using detector responses to sampling time intervals in this accelerated method, the mixing effects give inversion errors to the size distribution. The mixing effects can be considered by appling the transfer function with mixing effects to the data inversion. The inversion considering this effects gives birth to the size distribution shifted to the opposite direction of the size scanning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.11
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• pp.1095-1102
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• 1991

In this paper, we proposed the differential demodulation technique of 2-h CPM and analyzed its error performances. We derived the sets of modulation indices of 2-h phase codes adequate to the differential detection. The power spectra of 2-h CPM signals with various sets of mudulation indices are illustrated and compared, Besides, the error performances for the differential detectors are calculated and detectors using Viterbi algorithm are compared and analyzed by computer simulations.

• Nuclear Engineering and Technology
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• v.49 no.4
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• pp.776-780
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• 2017

To avoid imaging artifacts and interpretation mistakes, an improvement of the uniformity in gamma camera systems is a very important point. We can expect excellent uniformity using cadmium zinc telluride (CZT) photon counting detector (PCD) because of the direct conversion of the gamma rays energy into electrons. In addition, the uniformity performance such as integral uniformity (IU), differential uniformity (DU), scatter fraction (SF), and contrast-to-noise ratio (CNR) varies according to the energy window setting. In this study, we compared a PCD and conventional scintillation detector with respect to the energy windows (5%, 10%, 15%, and 20%) using a $^{99m}Tc$ gamma source with a Geant4 Application for Tomography Emission simulation tool. The gamma camera systems used in this work are a CZT PCD and NaI(Tl) conventional scintillation detector with a 1-mm thickness. According to the results, although the IU and DU results were improved with the energy window, the SF and CNR results deteriorated with the energy window. In particular, the uniformity for the PCD was higher than that of the conventional scintillation detector in all cases. In conclusion, our results demonstrated that the uniformity of the CZT PCD was higher than that of the conventional scintillation detector.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.746-752
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• 2005

In this paper, optical noise effect is reduced by using the loss characteristics of plastic fibers in an optical wireless system. The attenuation coefficient of a plastic fiber for the signal is different from that f3r the noise light, and the length difference between two fibers to the 2PD's behaves like a discriminative element. It is possible to eliminate the optical noise effect and detect only the signal without optical filters. The signal to noise ratio in a differential detector using fibers was 9.7 dB higher than in a single photodiode without optical fiber.