• International journal of advanced smart convergence
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• v.10 no.4
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• pp.45-51
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• 2021

Polar transmitter can support multi-band and multi-mode operation. The efficiency of frequency usage can be increased if polar transmitters can transmit multi-carrier signals. In this paper the configuration of polar transmitters is investigated to generate multi-carrier signals. Spectrum and CCDF Simulation results of two-carrier signals generated by the polar transmitter can be used to design of PM and AM path in a polar transmitter.

• Journal of the Korea Institute of Military Science and Technology
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• v.8 no.4 s.23
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• pp.102-109
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• 2005

In this paper, we propose a new listen-in technique to overcome the problems and the shortcomings which could possibly meet in the previous listen-in methods to deal with the blind signal manually according to operator's decision. In the proposed listen-in method, receiving the signals, classifying the modulation types, and demodulating the signals can be done automatically without operator's intervention. We realize the listen-in technology by developing the high speed frequency tuner, the automatic modulation recognizer, and the signal demodulator. In conclusion, we confirm and show that the developed equipment has a good performance in classifying the modulation type through the computer simulation and the field test.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.39-42
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• 2008

In this paper, we analyze the performance of ultra wide band (UWB) systems in indoor wireless channel in accordance with the number of pulses per bit at transmit signals and the decision types of receiver. The indoor channel is modeled as the modified Saleh and Valenzuela (SV) model which has been proposed as a UWB channel model by the IEEE group, IEEE 802.15.SG3a. Two types of UWB signals are considered One is the pulse position modulation-time hopping (PPM-TH) signal. And the other is the pulse amplitude modulation-direct sequence (PAM-DS) signal. It is assumed that the receiver is an ideal receiver which can receive all signals of the multipath.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.7
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• pp.399-406
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• 2000

We propose an nonlinear demodulation algorithm for undersampled multicomponent AM(Amplitude Modulation), FM(Frequency Modulation) and AM-FM signals. First, we derive respectively undersampling frequency of the AM, FM and AM-FM using undersampling scheme, and separate respectively monocomponent signals from multicomponent signals using periodic algebraic separation algorithm. In this case augmented separation matrix is very regular and sparse, it has a special structure. The proposed demodulation algorithm detects respectively message signals of the IA(Instantaneous Amplitude) and IF(Instantaneous Frequency) from descrete monocomponent AM, FM and AM-FM signals with an undersampling frequency to be controllable. Verifying the RMS(Root Mean Squares) errors of the detected signals, we show that the performance is excellent.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.1-6
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• 2006

By comparing video-overlay method where digital and SCM signal are modulated in different optical source, we experimentally investigated the performance of simultaneous modulation of data and broadcasting signals using a single LD for broadcasting in PON based optical access network. The experimental results show that by increasing the minimum value of injected current for LD modulation above about 1.5 times of threshold current of LD, data and broadcasting signals can modulate without mutual interference. We also proposed and demonstrated the scheme of optical transmitter optimized for simultaneous modulation of data and broadcasting signals where anode and cathode of LD are separately used as signal interface for data and broadcasting signals, respectively.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3761-3779
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• 2022

The performance of existing recognition algorithms for binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) signals degrade under conditions of low signal-to-noise ratios (SNR). Hence, a novel recognition algorithm based on features in the graph domain is proposed in this study. First, the power spectrum of the squared candidate signal is truncated by a rectangular window. Thereafter, the graph representation of the truncated spectrum is obtained via normalization, quantization, and edge construction. Based on the analysis of the connectivity difference of the graphs under different hypotheses, the sum of degree (SD) of the graphs is utilized as a discriminate feature to classify BPSK and QPSK signals. Moreover, we prove that the SD is a Schur-concave function with respect to the probability vector of the vertices (PVV). Extensive simulations confirm the effectiveness of the proposed algorithm, and its superiority to the listed model-driven-based (MDB) algorithms in terms of recognition performance under low SNRs and computational complexity. As it is confirmed that the proposed method reduces the computational complexity of existing graph-based algorithms, it can be applied in modulation recognition of radar or communication signals in real-time processing, and does not require any prior knowledge about the training sets, channel coefficients, or noise power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10B
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• pp.1769-1776
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• 2000

In this paper a new method is proposed to identify a modulation method in the case of unknown digitally modulated input signals. The proposed identification method is implemented with an artificial neural network which is based on characteristic feature extracted from the instantaneous amplitude the instantaneous phase and the instantaneous frequency of the input signals. The proposed method was simulated with 9 type signals (ASK2, FSK2, FSK4, PSK2, PSK4, PSK8, QAM8, QAM16) in a noisy communication environment. The results show that the artificial neural network can accurately recognize all kinds of patterns.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.7
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• pp.86-98
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• 1996

Modulation and demodualtion circuits of chaos frequency shift keying have been implemented using chua's circuits. The modulatin circuit, which is designed ot perform the frequency-doubling by coupled synchronization wihtout changing the intrinsic characteristics of its two chaos signals generated, modulates the digital input signals. The demodulation circuit detects the digital input signals form carrier by drive synchronization. these circuits, which are simplest until now and have no restriction to their digital input amplitudes, perform the aimed functions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.1986-1995
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• 2013

The ELINT system which derives intelligence from electromagnetic radiations plays an important role in modern electric warfares. Among radar characteristics inferred from the signals, intra-pulse modulation scheme is a useful feature to identify modern radars. This paper proposes the method to classify intra-pulse modulation schemes such as UM, PSK, BFSK, QFSK, LFM and NLFM based on the fuzzy algorithm. The proposed method defines fuzzy membership functions to characterize input signals, and then it calculates accordance rates for each modulation scheme with fuzzy inference rules. The experimental results show that the probability of correct recognition is more than 95% for SNR > 10dB.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.600-605
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• 2002

The keyhole formed by high energy density laser-material interaction periodically collapses due to surface tension of the molten metal in partial penetration welds. The collapse sometimes traps a void at the bottom of the keyhole, and it remains as welding defects. This phenomenon is seen as one cause of the instability of the keyhole during laser beam welding. Thus, it seems likely that improving the stability of the keyhole can reduce voids and uniform the penetration depth. The goal of this work is to develop techniques for controlling laser weld keyhole dynamics to reduce weld defects such as voids and inconsistent penetration. Statistical analysis of the penetration depth signals in glycerin determined that keyhole dynamics are chaotic. The chaotic nature of keyhole fluctuations and the ability of laser power modulation to control them have been demonstrated by high-speed video images of laser welds in glycerin. Additionally, an incident leading beam angle is applied to enhance the stability of the keyhole. The quasi-sinusoidal laser beam power of 400Hz frequency and 15$^{\circ}$ incident leading beam angle were determined to be the optimum parameters for the reduction of voids. Finally, chaos analyses of uncontrolled signals and controlled signals were done to show the effectiveness of modulation on the keyhole dynamics. Three-dimensional phase plots for uncontrolled system and controlled system are produced to demonstrate that the chaotic keyhole dynamics is converted to regular periodic behavior by control methods: power modulation and incident leading beam angle.