• International journal of advanced smart convergence
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• 제8권3호
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• pp.61-68
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• 2019

Spatial modulation (SM) is the first proposed space modulation technique. By further utilizing the quadrature spatial dimension, quadrature spatial modulation (QSM) has been developed as an amendment to SM system to enhance the overall spectral efficiency. Both techniques are capable of entirely eliminating interchannel interference (ICI) at the receiver. In this paper, we propose a simple adaptive hybrid switching transmission scheme to obtain better system performance than SM and QSM systems under a fixed transmission date rate. The presented modulator selection criterion for switching between spatial modulator and quadrature spatial modulator is based on the larger received minimum distance of spatial modulator and quadrature spatial modulator to exploit the spatial channel freedom. It is shown through Monte Carlo simulations that the proposed hybrid SM and QSM switching system yields lower error performance than the conventional SM and QSM systems under the same fixed data rate and thus can provide signal to noise ratio (SNR) gain.

• 전자공학회논문지A
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• 제33A권6호
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• pp.32-41
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• 1996

We propose the improved GMSK (gaussian-filtered minimum shift keying) quadrature modulator using the FIR(finite impulse response )filter whose coefficients are obtained form the differnce of phase response, and design its ASIC (applicaton specific integrated circuit) which can be used for GSM (global system for mobile communication) digital cellular system and DCS 1800 (digital cellular system at 1800MHz) personal communication system. Input data become quantized I and Q channel 10 bit signal through cosine and sine ROM mapping after being filtered by the FIR filter whose normalized bandwidth is 0.3 and designed by considering intersymbol interference as well as sampling ratio. These two signals become the GMSK modulated I and Q channel signal through DAC (digital-to-analog converter) and 7th order analog chebyshev LPF(low pass filter) respectively. The difference between the ideal analog signal and its digitized signal is analyzed in terms of sampling noise, quantization noise, truncation noise and coefficient noise. And the effect of the LPF following the DAC is considered. The ASIC design of the GMSK quadrature modulator is also confirmed by an experiment.

• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.570-575
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• 2012

In a wireless communication RF transmitter, the output of a quadrature modulator (QM) is distorted by not only the linear imperfection features such as in/quadrature-phase (I/Q) input gain imbalance, local phase imbalance, and local gain imbalance but also the nonlinear imperfection features such as direct current (DC) offset and mixer nonlinearity related to in-band spurious signal. In this paper, we propose the unified QM model to analyze the combined effects of the linear and nonlinear imperfection features on the performance of the QM. The unified QM model consists of two identical nonlinear systems and modified I/Q inputs based on the two-port nonlinear mixer model. The unified QM model shows that the output signals can be expressed by mixer circuit parameters such as intercept point and gain as well as the imperfection features. The proposed approach is validated by not only simulation but also measurement.

• 대한전자공학회논문지SD
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• 제41권3호
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• pp.31-38
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• 2004

광섬유격자 센서어레이의 복조에 사용할 목적으로 광섬유레이저의 파장변화 검출방법을 제안하였다. 삼각파로 변조된 광섬유레이저의 출력 파장을 Mach-Zehnder 간섭계와 시간지연샘플링 기법으로 분석하였다. 피크간의 시간차를 측정하는 기존의 방법과 달리 파장변조 메카니즘의 비선형 특성에 무관하게 항상 선형적인 출력을 얻을 수 있었으며 6.5 ㎚의 스캔범위에서 약 20 pm의 파장분해능을 얻을 수 있었고, 이는 응답특성이 뛰어난 위상변조기를 사용할 경우 크게 개선될 수 있음을 보였다.

• Current Optics and Photonics
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• 제2권2호
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• pp.134-139
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• 2018

A novel approach for frequency-tripling vector signal generation via balanced detection without precoding and optical filter is proposed. The scheme is mainly utilizing an integrated dual-polarization quadrature phase shift keying (DPQPSK) modulator. In the DPQPSK modulator, one QPSK modulator is driven by an RF signal to generate high-order optical sidebands, while the other QPSK modulator is modulated by I/Q data streams to produce baseband vector signal as an optical carrier. After that, a frequency-tripling 16-quadrature-amplitude-modulation (16QAM) vector millimeter-wave (mm-wave) signal can be obtained by balanced detection. The proposed scheme can reduce the complexity of transmitter digital signal processing. The results show that, a 4 Gbaud baseband 16QAM vector signal can be generated at 30 GHz by frequency-tripling. After 10 km single-mode fiber (SMF) transmission, the constellation and eye diagrams of the generated vector signal perform well and a bit-error-rate (BER) below than 1e-3 can be achieved.

• 한국통신학회논문지
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• 제21권8호
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• pp.2055-2062
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• 1996

This paper presents a method of compensating for the gain and phase imbalance of quadrature modulator and demodulator. The gain and phase imbalance are compensated using the received power after the compensation pattern was transmitted at tranceiver. The proposed method is less vulnerable to changes in the transmission channel than the conventional method because compensation is made possible within the tranceiver system, and even the change in phase mblance in accordance with frequency can be compensated utilizing the adaptive algorithm. According to numerical results, a normalized eye opening and a bit error rate are improved by 1.8dB and 3.8dB, respectively.

• 한국전자파학회논문지
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• 제29권5호
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• pp.383-388
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• 2018

본 논문은 CMOS 공정을 이용하여 1.8 GHz 대역에서 임의의 부하 임피던스를 스위치 제어를 통해 가변 하는 6-포트 기반의 임피던스 변조기에 관한 연구이다. 1.8 GHz 대역 임피던스 변조기는 전력 분배기(Wilkinson power divider), $90^{\circ}$ 하이브리드 결합기(quadrature hybrid coupler), 그리고 각각의 서로 다른 부하 임피던스 선택을 위한 SP3T 스위치들로 구성하였다. 제안된 임피던스 변조기는 1.4~2.2 GHz에서 -13 dB 삽입손실과 10 dB 이상의 입/출력 반사손실 결과를 얻었다. 또한, 3.3 V의 안정적인 전원공급을 위한 LDO(Low Drop Output) 레귤레이터와 디지털 회로 제어가 간편하도록 SPI(Serial Peripheral Interface)를 집적화했으며, 칩 크기는 패드를 포함하여 $1.7{\times}1.8mm^2$이다.

• 전기전자학회논문지
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• 제22권4호
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• pp.1019-1024
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• 2018

In this paper, we suggest a combined cost function to find out the optimal operation of an envelope tracking system, and evaluated its performance with Quadrature Amplitude Modulation (QAM) waveform, with which envelope tracking coefficients for the peak drain efficiency and the bandwidth of power amplifiers are determined. Based on the classical envelope tracking theory, the operation of the supply modulator, which is a key part of the envelope tracking process, is modeled and analyzed mathematically. Then characteristics of the modulator by setting envelope shaping function as a cubic polynomial and sweeping the coefficients of this function was analyzed. By sweeping the coefficients, efficiency and bandwidth at each condition with 64-QAM signal was used to obtain optimal point of the supply modulator. Compared to the conventional shaping functions, the optimized function showed the bandwidth reduction by 12.7 percent point while the efficiency was maintained.

• ETRI Journal
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• 제26권4호
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• pp.307-314
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• 2004

The application of a discrete pseudomorphic high electron mobility transistor (p-HEMT) as a grounded switch allows for the development of low cost phase shifters and phase modulators operating in a Ku band. This fills the gap in the development of phase control devices comprising p-i-n diodes and microwave monolithic integrated circuits (MMICs). This paper describes a discrete p-HEMT characterization and modeling in switching mode as well as the development of a low-cost four-bit phase shifter and direct quadrature phase shift keying (QPSK) modulator. The developed devices operate in a Ku band with parameters comparable to commercially available MMIC counterparts. Both of them are CMOS compatible and have no power consumption. The parameters of the QPSK modulator are very close to the requirements of available standards for satellite earth stations.

• 대한전자공학회논문지TC
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• 제45권3호
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• pp.1-6
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• 2008

본 논문에서는 2.4GHz 및 5GHz의 이중대역에서 동작하는 I/Q 모듈레이터를 설계하였다. 광대역 믹서에 $90^{\circ}$ 위상천이기를 이용하여 quadrature 신호를 입력하여 베이스밴드 신호를 변조된 RF 신호로 출력한다. 제안한 I/Q 모듈레이터의 변환 손실은 2.4GHz에서 약 15dB이고 5.8GHz 대역에서 약 16dB이다. 사이드밴드 억압특성은 2.4GHz/5GHz에서 각각 15dBc, 16dBc이며, carrier suppression은 두 대역에서 약 40dBc이다. 또한 11Mbps 의 QPSK 신호입력시의 EVM 특성은 2.4GHz에서 약 8.5%, 5GHz에서 10% 이며, 반송파 억압은 두 대역에서 40dB 이상으로, 무선 랜 신호를 인가시 출력 스펙트럼 규격을 만족하였다.