• The Korean Journal of Applied Statistics
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• v.22 no.1
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• pp.171-179
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• 2009

In this paper we studied the effective approximations to the distribution of the sum of products of normal variables. Based on the saddlepoint approximations to the quadratic forms, the suggested approximations are very accurate and easy to use. Applications to the FSK (Frequency Shift Keying) communication are also considered.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.879-886
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• 2003

Agile frequency synthesizers are the common device used for commandable, wide-band frequency hopping in frequency-hopped (FH) communications. In this paper, synthesizer phase transient effect and its compensation methods in an FH/FSK(Frequency Hopped Frequency Shift Keying) system are studied. Models for these analysis are developed and resulting performance degradations are computed. The basic PLL is difficult to implement for fast frequency hopping in narrowband radio communication systems. To solve this problem, digital frequency synthesizer/CPM (Continuous Phase Modulation)modulator is proposed. And it's performance is analyzed theoretically. The analysis show that fast frequency hopping is possible in frequency hopping system that use digital frequency synthesizer/CPM modulator.

• Journal of Advanced Navigation Technology
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• v.14 no.3
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• pp.367-374
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• 2010

In this paper, the frequencies sharing possibility between TA(TalkAround) Radios and RFID system in 900MHz frequency band have been studied. The modulation technic for FHSS(Frequency Hopping Spread Spectrum) of TA is digital FSK and RFID system adapts digital ASK modulation technic. The communication mode of the tested RFID system for frequencies sharing possibility was FHSS. The field test was performed by five scenarios. The RFID field testing system for the frequencies sharing possibility was composed of four tags and two main devices made in USA. Four TA and Egilant spectrum analyzer was used for testing. The frequencies sharing possibility by differentiated modulation was theoretically analyzed. As result of simulation, it was proved that the frequencies sharing between each other modulation system is possible. And also as result of field testing it was confirmed that the signal of TA Radios have no effect on the signal of RFID system.

• Journal of Radiation Protection and Research
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• v.20 no.2
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• pp.85-95
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• 1995

Radiation measuring system using wireless communication method with single channel has been diveloped and tested. In this system, radiation signals from GM tube are transformed into digital pulses in pulse processing circuit and modulated in FSK (frequency shift keying) circuit for digital communication and then wirelessly transmitted to a receiving unit. The digital pulses received are then demodulated in FSK circuit and converted into radiation dose/dose rate in the data acquisition unit to display on the screen of a personal computer. The performance of this system was evaluated by using both a pulse generator and a standard radiation source(Cs-137). In both cases, digital pulses with 5V were observed in pulse processing circuit without distortion of their shape through wireless communication system. The experimental results of radiation measurement by this system after several test-irradiation of GM detector to a standard radiation source(Cs-137), showed good agreement with irradiation dose rate within 10% difference, and proved that this system could be effectively utillized as radiation measuring instrument. It is expected that this wireless radiation measuring system developed for the first time in Korea, can be used as a radiation monitor as well as a personal dosimeter if we can further improve this system to adopt wireless multichannel communication system.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.370-381
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• 2021

This paper presented an efficient transceiver structure of multiband Frequency Shift Keying (FSK) signals with direct sequence spread spectrum for maintaining covertness and performance. In aspect to covertness, direct sequence spread spectrum method, which multiplying by Pseudo Noise (PN) codes whose rate is much higher than that of data sequence, is employed. In aspect to performance, in order to overcome performance degradation caused by multipath and Doppler spreading, we applied multiband, turbo equalization, and weighting algorithm are applied. Based on the simulation results, by applying 4 number of multiband and number of chips are 8 and 32, experiments were conducted in a lake with a distance of moving from 300 m to 500 m between the transceivers. we confirmed that the performance was improved as the number of bands and chips are increased. Furthermore, the performance of multiband was improved when the proposed weighting algorithm was applied.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.579-585
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• 2006

In this study, we analysis an optical receivers using the optical preamplifier in a spectrum-sliced WDM systems. The average numbers of photons/bit, for an $10^{-9}$ error probability, counts using the OOK and FSK transmission. As a result, the theoretical sensitivity for PIN receiver and optical preamplifier receiver are approximately $9.2\times10^4\;and\;7.2\times10^2$ in the m=20, respectively. Also, the average numbers of photons/bit, for and given error probability, theoretical receiver sensitivity for Gaussian method and k-square method are approximately $9\times10^2\;and\;2.16\times10^2$ in the m=40, respectively. And the average numbers of photons/bit, for an given error probability, theoretical receiver sensitivity, OOK and FSK transmission are approximately $1.9\times10^2\;and\;3.1\times10^2$ in the m=20, respectively.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.295-302
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• 2016

Underwater acoustic communication channel is often defined as a multipath fading channel since the multipath arrivals from various paths interfere with each other and cause frequency dependent constructive or destructive interference in received signals. Therefore signal-to-noise ratio (SNR) of received signal fluctuates as a function of frequency. In addition, sea surface fluctuation induces frequency dependent time variant signal fading due to coherent component variation of surface bounce path. The frequency shift keying (FSK) system is known to be less sensitive and more robust under these interference and fading, and M-ary frequency shift keying (MFSK) system is adopted to increase a data rate. In this study, a bit error rate (BER) of 4 channels 4FSK system are examined in shallow sea multipath channel. Experimental results show that RS code reduces efficiently the BER of 4FSK system since frequency dependent time-varying fading is characterized to give burst errors. The BER of a different data rate or different source-to-receiver range depends on not only the channel coherent bandwidth but also frequency dependent multipath fading.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.284-290
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• 1999

This paper describes a Frequency Shift Keying (FSK) modulator and demodulator and the experimented underwater data ommunication equipment to transfer the analog echo signal in real-time from an underwater vehicle to the mother ship. The system consists of an echo signal transfer unit equipped to the vehicle and an ultrasonic receiver equipped on the ship. The former includes an ultrasonic transceiver unit of 180kHz for echo detection and a continuous wave transmitter of 50kHz with a FSK modulator for echo transmission to the ship. The latter includes an ultrasonic receiver of 50kHz and the FSK demodulator. The results of experiment are as follows. 1. The characteristics of the FSK modulating and demodulating circuits designed with the use of C-MOS IC 4046 was good and confirmed its usefulness in underwater data communication system.2. The prototype ultrasonic transceiver unit shows profitable driving power while the pulse duration was short less than 3 msec, but it was found that the driving power is not sufficient while the long pulse duration or continuous wave is used. The gain of the ultrasonic receiver was 80 dB and the receiving bandwidth 700Hz (at - 3 dB point).3. It was found that the system designed by the author has some possibility to use in underwater echo transfer.4. At the FSK modulator, the widths of voltage and frequency which represent linearity were 3.5 V, 1600Hz, respectively, at the FSK demodulator 2.6 V, 700Hz, respectively.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.35 no.3
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• pp.285-285
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• 1999

This paper describes a Frequency Shift Keying (FSK) modulator and demodulator and the experimented underwater data ommunication equipment to transfer the analog echo signal in real-time from an underwater vehicle to the mother ship. The system consists of an echo signal transfer unit equipped to the vehicle and an ultrasonic receiver equipped on the ship. The former includes an ultrasonic transceiver unit of 180kHz for echo detection and a continuous wave transmitter of 50kHz with a FSK modulator for echo transmission to the ship. The latter includes an ultrasonic receiver of 50kHz and the FSK demodulator. The results of experiment are as follows. 1. The characteristics of the FSK modulating and demodulating circuits designed with the use of C-MOS IC 4046 was good and confirmed its usefulness in underwater data communication system.2. The prototype ultrasonic transceiver unit shows profitable driving power while the pulse duration was short less than 3 msec, but it was found that the driving power is not sufficient while the long pulse duration or continuous wave is used. The gain of the ultrasonic receiver was 80 dB and the receiving bandwidth 700Hz (at - 3 dB point).3. It was found that the system designed by the author has some possibility to use in underwater echo transfer.4. At the FSK modulator, the widths of voltage and frequency which represent linearity were 3.5 V, 1600Hz, respectively, at the FSK demodulator 2.6 V, 700Hz, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.1
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• pp.80-86
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• 2010

This paper describes the development result of S-band Transmitter of STSAT-3 by satellite research center(SaTReC), KAIST. STSAT-3 has two kinds of communication channels, S- band for Telemetry & Command and X-band for mission payload. S-band Transmiiter(STX) consist of modulator, frequency synthesizer, power amp and DC/DC converter. The modulation scheme of STX is FSK(Frequency Shift Keying). The interface between spacecraft OBC and STX is RS-422. The STX is based on modular design. The RF output power of STX is 1.5W(31.7dBm) and BER of STX is under 1E-5. The Test of STX is completed successfully such as functional Test and environmental(vibration, thermal vacuum) Test.