• Journal of information and communication convergence engineering
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• 제7권3호
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• pp.304-308
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• 2009

This paper proposes a new concept of a signal constellation of the recently introduced half-symbol-rate-carrier phase-shift keying (HSRC-PSK) modulations for bandwidth-efficient high speed data communications. Since the HSRC-PSK modulations contain different symbol energies representing the same bit sequences due to the loss of orthogonality of their HSRC signals, it is very hard to represent the symbol using the conventional signal constellation. To resolve the problem, two different energies are assigned to represent one symbol for the HSRC offset quadrature phase shift keying (OQPSK) modulation. Similarly, the different energies exist to display the different symbol for HSRC minimum shift keying (MSK) modulation. With the proposed signal space representation, HSRC-PSK symbol can easily be shown with a two-dimensional scatter plot which provides helpful information of evaluating HSRC-PSK signal's quality.

• Journal of Power Electronics
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• 제14권6호
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• pp.1197-1207
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• 2014

Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.

• 한국정보통신학회논문지
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• 제5권1호
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• pp.52-60
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• 2001

본 논문에서는 나카가미 페이딩 환경에서 다중 반송파 MFSK-DPSK/DS-CDMA 합성 변조기법을 제안하였다. 또한, 다중경로 페이딩에 강한 특성과 주파수 이용 효율이 높은 다중반송파 DS-CDMA 합성변소 방식을 같이 사용하여 분석하였다. 그러한 변조방식은 비동기식 MFSK와 MFSK에 기반한 DPSK를 이용한 결합 주파수 위상 합성변조 방식이다. 결과로부터 전력효율과 대역폭 효율이 일반적인 통신 시스템보다 다중캐리어 합성 변조시스템이 효율을 개선시킬 수 있음을 알았다.

• ETRI Journal
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• 제34권6호
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• pp.800-806
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• 2012

Transmission performances of direct detection-based 100-Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal-to-noise ratio sensitivity, chromatic dispersion, cross-channel nonlinearity, and transmission distance on the performance of differential 8-ary phase-shift keying (D8PSK), differential phase-shift keying plus three-level amplitude-shift keying (DPSK+3ASK), and dual-carrier differential quaternary phase-shift keying (DC-DQPSK) are evaluated. The performance of coherent dual-polarization quadrature phase-shift keying (DP-QPSK) with block phase estimation and coherent DP-QPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100-Gb/s signal over several hundred kilometers of a single-mode fiber link. The results also show that DC-DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC-DQPSK is comparable to that of coherent DP-QPSK with digital differential detection. The maximum transmission distance of DC-DQPSK is over 1,000 km, which is enough distance for metro applications.

• 한국통신학회논문지
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• 제15권10호
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• pp.797-810
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• 1990

The error rate equations of digitally modulated signals transmitted through the Gaussian noise and tone multiple interference channel have been derived. Using the derived equations of error probabilities in the environments of Gaussian noise tone interferer and Gaussian noise multiple interferer, the error rate performances of various digitally modulated signals have been evaluated, and compared in graphs as a function of average carrier to tone interferer power ratio(CIR), average carrier to multiple interferer power ratio(CIT) and the average carrer-to-Gaussian noise powr ratio(CIR). In this paper, the modulation schemes such as amplitude shift keying (ASK), phase shift keying(PSK), frequency shift keying(FSK), minimum shift keying(MSK), quadrature amplitud modulation(QAM) and amplitude phase shift keying(APK) have been selected for the study of performance comparison. The results of comparison show us that, in low bits/sec/Hz, PSK is superior to the other schemes, but in high bits/sec/Hz, mixed multi ary type is better than single multi ary type. And in strong noise evironment, the multiple interferer has much influence than tone interferer, however, in low noise environment. the mojor error factor is tone interferer. But tone interference effect nearly disappears over specified CIR level about 20[dB]. And the modulation schemes using amplitude are heavily influenced by multiple interference.

• Journal of Positioning, Navigation, and Timing
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• 제11권3호
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• pp.147-156
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• 2022

In this paper, we propose Time-Division-Multiplexing Tertiary Offset Carrier (TDMTOC), a novel GNSS modulation based on Tertiary Offset Carrier (TOC) modulation. The TDMTOC modulation multiplexes two three-level signals (i.e., -1, 0, and 1) while crossing over time, and is a type of TOC modulation designed specifically for signal multiplexing. The proposed modulation generates TDMTOC subcarriers of two different phases by simply combining two Binary Offset Carrier (BOC) subcarriers by addition or subtraction. TDMTOC has better correlation and spectral properties than conventional BPSK, BOC, and MBOC modulation techniques, and has good power and spectral efficiency since it can multiplex signals without power loss similar to time division multiplexing. To prove this, we introduce the multiplexing process of TDMTOC, and compare TDMTOC with Binary Phase Shift Keying (BPSK), BOC, Composite BOC (CBOC), and Time Multiplexed BOC (TMBOC) that are currently serviced in GNSS by simulations of various aspects. Through the simulation results, we prove that TDMTOC has better correlation property than modulations currently used in GNSS, less intersystem interference due to its wide spectrum property, and robustness in multipath and noise channel environments.

• 한국해양공학회지
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• 제20권3호
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• pp.1-6
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• 2006

Modulation theory describes propagation of surface waves with deep wave number and frequency modulation. Locally spectrally narrow wave packet can have accumulated large scale frequency shift of carrier wave during propagation. Some important nonlinear modulation effects, such as negative frequencies, phase kinks, crest pairing, etc., often observed experimentally at long fetch propagation of finite amplitude surface wave trains, are reproduced by the proposed theory. The presented model permits also to analyze the appropriately short surface wave packets and modulation periods. Solutions show the wave phase kinks to arise on areas' of relatively small free surface displacement in complete accordance with the experiments.

• Journal of information and communication convergence engineering
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• 제7권2호
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• pp.152-156
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• 2009

This paper examines the BER performance of the recently proposed half-symbol-rate-carrier (HSRC) offset quadrature phase-shift-keying (OQPSK) receiver for high-speed data communication. A modified demodulation technique using a bit-time period signal integration, the bit-error-rate (BER) performance of the HSRC-OQPSK signal improves more than 4dB compared to that of a demodulation technique using a symbol-time period integration. This paper also examines the BER performance of modified demodulation with various band-limited channels modeled using low-pass filters, and the three different data-rate systems are simulated and compared with the performance of the system using the conventional demodulation technique.

• 한국정보통신학회논문지
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• 제14권5호
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• pp.1155-1163
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• 2010

기존의 웨이브릿 편이 변조 시스템은 스케일링 함수(scaling function)를 1로, 웨이브릿(wavelet)을 0으로 하는 1비트 변조방법이 있고, 스케일링 함수와 웨이브릿 그리고 이 두 신호를 반전시켜서 생성된 4개의 반송파를 사용하는 2비트 변조방법이 있다. 본 논문에서는 2비트 변조방법인 4-ary 스케일링 웨이브릿 편이변조(4-ary SWSK : 4-ary scaling wavelet shift keying) 시스템을 정의하고, QPSK 시스템으로부터 정의된 시스템의 비트 에러 확률과 부호 에러 확률을 유도한다. 제안한 4-ary SWSK 성능을 분석하기 위하여, 기존의 QPSK(quadrature phase shift keying), MFSK(M-ary frequency shift keying), 그리고 제안한 방법의 비트 에러 확률 및 부호 에러 확률을 구한다. 실험결과 제안한 방법의 비트 에러 확률과 부호 에러 확률이 좋은 성능을 보였다.

• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 제13회 정기총회 및 2002년도 동계학술발표회
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• pp.192-193
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• 2002

In this paper we investigate the phase modulation efficiency in the electrooptic phase modulator using PPpinNN GaAs/AlGaAs W-type waveguide. The phase change is affected by the refractive index change taking place inside the depletion region. The behavior of the modulator can be understood in terms of two electric field-related and two carrier-related effects linear electrooptic, quadratic electrooptic, plasma, and bandgap shift. As a result, the phase modulation efficiency was measured about 34.6($^{\circ}$/V$.$mm) for the TE polarized light. The quadratic electrooptic coefficient R 5.82${\times}$10$\^$-15/($\textrm{cm}^2$/V$^2$) is Obtained ant the Phase efficiency Caused by the quadratic electrooptic effect is about 10 times larger than that from the conventional linear electrooptic effect.