• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.10a
• /
• pp.669-672
• /
• 2008

In this paper, we propose a constant-amplitude multi-rode trans-bi-orthogonal modulation scheme by introducing a simple constant-amplitude coding scheme with redundant bits and trans-code, which if a modified orthogonal modulation scheme. Generally speaking, the orthogonal modulation scheme is not appropriate for the high speed data transmission applications because of bad bandwidth efficiency. Therefore, we use the multi-rode trans-bi-orthogonal modulation with trans-code for high bandwidth efficiency. Moreover, redundant bits are used for constant-amplitude-coding. Finally, we compare the performance of the proposed scheme with the orthogonal modulation and constant-amplitude multi-code trans-orthogonal modulation by using the computer simulation.

• Korean Journal of Optics and Photonics
• /
• v.10 no.6
• /
• pp.448-452
• /
• 1999

The Gaussian impulse fUllction initially assumed in the inverse problem is $e^{-\sigma^2\chi^2}$. The modified Gaussian amplitude pupil function $e^{\frac-{\omega^2}{4\sigma^2}$ is obtained by the inverse Fourier transform of $e^{-\sigma^2\chi^2}$. A Gaussian amplitude modulation plate (GAMP) is designed and fabricated by using absorption and transparence glass which are the same refractive index. It is compared the experimental transmittance with theoretical that of GAMP. It is found that the linewidth of Gaussian optical imaging system obtained by wavelength is $0.365{\mu}m$ and NA is 0.07 is decrease 2/3 than that of Rayleigh.

• Korean Journal of Optics and Photonics
• /
• v.9 no.2
• /
• pp.59-62
• /
• 1998

One dimensional inhomogeneous aperture modulation effects on the MTF of optical system was investigated. The lens undertest was a doublet made in Korea. It was 10 mm effective diameter, 87.8 mm effective focal length. The ray-fans and spot diagrams were caluculated and presented on the picture for on-axis and off-axis (field of view, 1$^{\circ}$ and 2$^{\circ}$). Aperture modulation was carried out by positioning a aperture modulator close contacted with the lens undertest. We bought two modulators from Edmud Company in U.S.A. One was linear type and the other was stepped type. The MTFs were measured on the best of focus for unmodulated apertue where the MTF has the largest value for 60 c/mm and were compared with one another. The MTFs of modulated apertures had a little lower values than the MTF of unmodulated aperture for on-axis but in the case off-axis, the values are highly improved as much as the wider field of view by modulating on the aperture.

• Proceedings of the KAIS Fall Conference
• /
• 2008.11a
• /
• pp.215-218
• /
• 2008

본 논문에서는 다중 트랜스 신호를 정 진폭으로 전송하는 정 진폭 다중 트랜스 직교 변조 방식에서 이용할 수 있는 오류 정정 부호 방법을 제안한다. 격자부호를 사용한 다중 트랜스 직교 변조방식이 비트 오율 성능을 높이는 것에 적합함을 보인다. 정 진폭 다중 트랜스 직교 변조 방식에서는 정진폭을 유지하기 위하여 세로축의 패리티 비트를 이용하여 신호를 부호화시키며, 가로축의 패리티 비트를 부가하여 이것이 격자부호를 이루도록 하여 비트 오율 성능 개선을 최대화 하도록 한다. 제안된 시스템을 이용하여 여러 비트율의 성능을 비교해 보았을 때 시스템의 복잡도의 증가가 거의 없으므로 복조기의 복잡도도 간단히 구현할 수 있으며 격자부호를 사용하지 않은 시스템에 비하여 비트 오율의 성능이 더 개선됨을 알 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.24 no.3
• /
• pp.398-404
• /
• 2020

In this paper, we propose a new design method of signal constellation of the spiral quadrature amplitude modulation (QAM) exploiting a modified gradient descent search algorithm and its binary mapping rule. Unlike the conventional method, the new method, which uses and the constellation optimization algorithm and the maximum number of iterations as a parameter for the iterative design, is more robust to phase noise. And the proposed binary mapping rule significantly reduces the average Hamming distance of the spiral constellation. As a result, the proposed spiral QAM constellation has much improved error performance compared to the conventional ones even in a very severe phase noise environment. It is, therefore, considered that the proposed QAM may be a useful modulation format for coherent optical communication systems and orthogonal frequency division multiplexing (OFDM) systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.2
• /
• pp.182-190
• /
• 2011

A amplitude modulation(AM) range measuring system utilizes the phase difference of the modulated envelope of the reflected signal to measure the distance. It is known that the AM system has a problem in accuracy due to antenna leakage signals and spurious reflection signals, but an AM range measurement system using an active reflector, which shifts the frequency bands, has been proposed in order to minimize the measurement errors due to spurious signals. In this paper, a new phase measurement module for the AM range measurement system, which enables to measure long distance with good accuracy, is proposed. The modulation frequency is alternatively selected between 8 and 1 MHz, and the measured distance range with this module is up to 150 m within 2 cm accuracy. A JK flip-flop circuit is used for higher phase accuracy, and an XOR circuit is used to cover long distance.

• Journal of Broadcast Engineering
• /
• v.19 no.6
• /
• pp.967-970
• /
• 2014

An efficient peak detection algorithm in magnitude spectrum is proposed to distinguish the M-frequency shift keying(FSK) signals from other digitally modulated signal. In addition, recognition of the modulation order estimation of FSK signals is also studied based on the fact that the magnitude spectrum of FSK signals reveals the number of peaks equal to the modulation order. When no a priori information about the signals, we utilize the histogram of the magnitude spectrum to determine the threshold which is important factor in peak detection algorithm. The simulation results show high probability of classification under 500 symbols and signal-to-noise ratio(SNR) higher than 4dB.

• Korean Journal of Optics and Photonics
• /
• v.9 no.5
• /
• pp.277-281
• /
• 1998

One dimensional inhomogeneous aperture modulation effects on the MTF of optical system was investigated. The lens under test was a doublet made in Korea. It has 10 mm effective diameter, 87.8 mm effective focal length. The ray-fans and spot diagrams were calculated and presented on the picture for on-axis and off-axis (field of view, $1^{\circ}$ and $2^{\circ}$). Aperture modulation was carried out by positioning a aperture modulator close contacter with the lens under test. We bought two modulators from Edmud Company in U.S.A. One was linear type and the other was stepped type. The MTFs were measured on the best of focus for each modulated aperture where the MTF has the highest value for 60 line/mm and were compared with one another. For on-axis, the MTFs of some modulated apertures had higher values than the MTF of unmodulated aperture in the high frequency region. In the case of off-axis, at the field of view $1^{\circ}$, the MTF values of some modulated aperture are improved prominently and some other one are disimproved. At the field of view $2^{\circ}$ most of the MTFs of modulated apertures had lower values than the MTF of unmodulated aperture except the MTFs of linear and inverse linear type aperture in the high frequency area. But the values of MTFs in high frequency region were too low for actual use.

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

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.9 no.4
• /
• pp.1-6
• /
• 1972

A super widely amplitude modulating AM modulator system, utilizing the impedance trasformation characteristics of transmission line is presented. The analyses and oscillograms obtained from the AM modulator systems using VHF tube, FET or VVC diode as an active element are added to verify the principle of the system.