• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.1
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• pp.202-211
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• 2001

This paper deals with an analysis of multipath which affect a transmission performance in underwater acoustic channel. Underwater acoustic channel with multipath structure is introduced to mathematical modelling for a basin environment. In this paper, SMR(Signal to Multipath Ratio) which is defined as a parameter of multipath's effect is presented as a mathematical equation, and the equation of SMR is simulated by MATLAB program. Furthermore, this paper is also dealt with an implementation of modulation and demodulation system for acoustic transmission. Acoustic Transmission is limited by frequency bandwidth, so $\pi/4 QPSK$(Quadrature Phase Shift Keying) methods which is very useful at frequency ]imitation and FM(Frequency Modulation) are used at acoustic communication system. This implemented hybrid modulation/demodulation system is used as an analog board of image transmission system. In this system, adaptive equalization for reducing the multipath effect and baseline JPEG used for an image compressing are also stated.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2000.05a
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• pp.419-425
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• 2000

This paper deals with an analysis of multipath which affect a transmission performance in underwater acoustic channel. Underwater acoustic channel with multipath structure is introduced to mathematical modelling for a basin environment. In this paper, SMR(Signal to Multipath Ratio) which is defined as a parameter of multipath's effect is presented as a mathematical equation, and the equation of SMR is simulated by MATLAB program. Furthermore, this paper is also dealt with an implementation of modulation and demodulation system for acoustic transmission Acoustic Transmission is limited by frequency bandwidth so $\pi$/4 Quadrature Phase Shift Keying) methods which is very useful at frequency limitation and FM(Frequency Modulation) are used at acoustic communication system. This implemented hybrid modulation/demodulation system is used as an analog board of image transmission system

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.10C
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• pp.597-604
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• 2011

In this paper, we propose group Manchester code (GM) modulation scheme for medical in-body wireless body area network (WBAN) systems. In IEEE, the WBAN system is assigned as 802.15. Task Group 6 (TG 6), and the related standardization is being progressed, Recently, in this Group, group pulse position modulation (GPPM), which can obtain data rate increase by grouping pulse position modulation (PPM) symbols, is proposed as a new modulation scheme for low-power operation of WBAN system. However, the conventional method suffers from BER performance degradation due to the absence of gray coding and its demodulation characteristics. Therefore, in this paper, we propose a modified GM scheme which groups Manchester code instead of PPM. In the proposed GM scheme, a low-complexity maximum likelihood (ML) demodulation method is employed in order to maximize the BER performances, Also, log likelihood ratio (LLR) decision method is proposed to employ the Turbo code as forward error correction (FEC), Finally, we verified that the proposed method has a good performance and is an appropriate scheme for in-body WBAN system through extensive performance evaluation.

• Journal of Broadcast Engineering
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• v.12 no.1 s.34
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• pp.2-10
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• 2007

We analyzed the receiving performance of the DVB-S2 transmission system in the BC(Backward Compatibility) mode. The transmitter employs the hierarchical modulation, and the receiver can be implemented by the direct demodulation or the hierarchical demodulation. The performance of each demodulation scheme is analyzed by a statistical method and a computer simulation for the AWGN and nonlinear channels. The ratio of the LP/HP streams which is proper in the domestic satellite broadcasting environments, is also suggested.

• Journal of the Korean Institute of Navigation
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• v.6 no.1
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• pp.1-18
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• 1982

In this paper, author studied on the elementary data required for the design of the receiver of Pseudo Noise (PN) phase modulation communication adopted in Global Positioning System(GPS). By computer simulation technique, the phase modulator, filters, and PN generator are designed, and also required bandwidth of R-F amplifier for carrier frequency in phase modulation system is investigated. It is verified that the optimum bandwidth is about 3 times of the PN frequency and almost independent of the carrier frequency. And the low pass filter required for demodulation of slow Boolean data is also found to be about 60 times of the data signal frequency.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.5-8
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• 2001

SSB(Single Sideband) modulation scheme is high bandwidth efficient method in the mobile communication system compared with present DSB(Double Sideband) modulation scheme. Using the othogonality between inphase PN code and Hilbert transformed quadrature PN code, we propose phase estimation structure that enables coherent demodulation in the reverse link basestation receiver Several system characteristics, bit error rate and phase error variance, are simulated and compared with balanced QPSK DS/CDMA system. To verify system performance, SSB/BPSK-DS/CDMA test board is implemented using FPGA chips.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3C
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• pp.69-76
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• 2005

In this paper, we propose a biorthogonal modulation employing a constant-amplitude transmission of multi-code signals by introducing a simple constant-amplitude coding scheme with redundant bits. The proposed constant-amplitude biorthogonal multi-code (CABM) modulation can provide high spectral efficiency compared with a conventional direct sequence/spread spectrum (DS/SS) modulation. Nevertheless the proposed CABM modulation can keep up a constant-amplitude signal. Additionally, we propose various types of demodulation structures for the CABM modulation. Simulation results show that bit error rate (BER) performance and hardware complexity of the proposed CABM modulation are highly improved in comparison with those of a constant-amplitude orthogonal multi-code (CAOM) modulation.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1982.10a
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• pp.19-21
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• 1982

In ancient age of Korea, Fire and smoke beacon system is only one method which transmitted an information. This paper is dealt with several problems of modern communication analysis on it. For example informaiton analysis, networking, modulation, demodulation and encoding etc, of beacon System.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.54.4-54
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• 2002

1.Introduction 2. Channel Equalizer Using Adaptive Neural Network 3. Data Modulation and Demodulation Using Haar Transform 4. Binary Signal Transmission Using Haar Transform 5. Conclusion

• Journal of the Korean Society for Precision Engineering
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• v.24 no.9
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• pp.60-67
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• 2007

A signal conditioning circuit for capacitive displacement sensors was developed using a high frequency modulation/demodulation method, and its performance was evaluated. Since capacitive displacement sensors can achieve high resolution and linearity, they have been widely used as precision sensors within the range of several hundred micrometers. However, they inherently have a limitation in low frequency range and some nonlinearity characteristics and so a specially designed signal conditioning circuit is needed to handle these properties. The developed signal processing circuit consists of three parts: linearization, modulation/demodulation, and nonlinearity compensation. Each part was constructed discretely using several IC chips and passive elements. An evaluation system for precision displacement sensors was developed using a laser interferometer, a precision stage, and a PID position controller. The signal processing circuit was tested using the evaluation system in the respect of resolution, repeatability, linearity, and so on. From the experimental results, we know that a highly linear voltage output can be obtained successfully, which is proportional to displacement and the nonlinearity of output is less than 0.02% of full range. However, in the future, further investigation is required to reduce noise level and phase delay due to a low-pass filter. The evaluation system also can be applied effectively to calibration and evaluation of precision sensors and stages.