• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.108-113
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• 2011

In this paper, we propose QAPM(Quadrature Amplitude Position Modulation) modulation scheme for improving power efficiency and we compare existing PSSK(Phase Silence Shift Keying) and QAPM. An existing PSSK Modulation is extension from PSK modulation technique. The conventional PSSK modulation technique can be regarded as an extension from PSK modulation. And this PSSK has better power efficiency than PSK modulation. The Bandwidth efficiency of PSSK is half than PSK, but improved BER(Bit Error Rate) performance. A propose QAPM scheme is build on QAM. And BER performance of QAPM is better than PSSK because BER performance of QAM is better than PSK. In this paper, we compare PSSK and QAPM regard to bit error rate and throughput.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.8
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• pp.41-46
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• 2012

A quadrature voltage controlled oscillator(QVCO) for X-band is presented in this paper. The QVCO has fabricated in Charted $0.13{\mu}m$ CMOS process. The QVCO consists of two cross-coupled differential VCO and two differential buffers. The QVCO is controlled by 4 bit of capacitor bank and control voltage of varactor. To have a linear quality factor of varactors, voltage biases of varactors are difference. The QVCO generates frequency tuning range from 6.591 GHz to 8.012 GHz. The phase noise is -101.04 dBc/Hz at 1MHz Offset when output frequency is 7.150 GHz. The supply voltage is 1.5 V and core current 6.5-8.5 mA.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.529-530
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• 2008

The proposed CMOS Quadrature VCO for WLAN application was designed in TSMC $0.18\;{\mu}m$ RF CMOS technology. The QVCO based on NMOS back-gate as a coupling transistor and switched capacitors array without tail transistors is designed to generate quadrature output signals. The simulated results show that the QVCO core consumed 3.67 mA and 6.6 mW from a 1.8 V supply. The QVCO is tunable between $4.76\;GHz\;{\sim}\;6.35\;GHz$ and has a phase noise lower than -116.8 ㏈c/Hz at 1 MHz offset over the entire tuning range

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9A
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• pp.835-843
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• 2010

Energy spreading transform (EST) based equalization is a very effective technique to remove inter symbol interference (ISI) in frequency selective channel. EST based system uses cyclic prefix (CP) similar to orthogonal frequency division multiplexing (OFDM) system. Since CP is a redundancy, it degrades the data transmission rate. RISIC is an algorithm that removes an inter block interference (IBI) caused by insufficient CP length and reconstructs CP. In this paper, we propose a system that combines the existing EST system with quadrature phase shift keying (QPSK) modulation and RISIC algorithm to enhance the efficiency of the transmission. Also we extend the proposed system to 16 quadrature amplitude modulation (QAM) modulation. The proposed system is shown to performance close to matched filter bound (MFB) even with insufficient CP.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.6 s.360
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• pp.18-23
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• 2007

In this Paper, we consider multiple input multiple output Feher-patented quadrature phase shift keying (MIMO-FQPSK) system supporting high spectral efficiency and throughput. Based on the fact that the complex baseband signal sampled at every bit duration has only eight phase values and its signal can be considered as 8-phase-shift keying signal, FQPSK demodulation with maximum likelihood sequence estimation(MLSE) is considered and it is extended to MIMO system. The performance of MIMO-FQPSK receiver is analyzed by computer simulation and by considering the union upper bounds for zrero forcing detection and minimum mean square error detection.

• The Journal of the Korea Contents Association
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• v.7 no.12
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• pp.254-261
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• 2007

In this paper, we propose a blind equalization method for advanced terrestrial digital multimedia broadcasting (AT-DMB) systems which use hierarchical modulation. The AT-DMB system adopts hierarchical 16-ary quadrature amplitude modulation (16-QAM) to ensure backward-compatibly with the differential quadrature phase shift keying (DQPSK) signal of the legacy terrestrial digital multimedia broadcasting (T-DMB) systems and to support higher transmission rate. Due to the hierarchical modulation, the conventional T-DMB signal and the additional signal have different error rate at same signal to noise ratio (SNR). By weighting the decided symbols differently according to the reliability of the symbols, i.e., high priority symbol with low error rate and low priority symbol with high error rate, we can improve the channel estimation accuracy. In this paper, we analyze SNR loss by hierarchical modulation and confirm it through simulations. Moreover, through simulations, we verify that the proposed weighting method improve BER compared to the no-weighting method.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.296-299
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• 2003

This paper shows a novel and simple IIR/FIR QMF(quadrature mirror filter) filter banks, mixed IIR and FIR structure. Here, FIR filters used for phase compensation. In this paper, we introduced analysis and synthesis filter banks, which used FIR linear phase filters and all pass filters. In result, phase response of analysis and synthesis filter banks become approximately linear characteristic. Simultaneously, a liasing distortion can be completely canceled.

• ETRI Journal
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• v.42 no.4
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• pp.562-574
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• 2020

Quadrature spatial modulation (QSM) utilizes the in-phase and quadrature spatial dimensions to transmit the real and imaginary parts of a single signal symbol, respectively. The improved QSM (IQSM) transmits two signal symbols per channel use through a combination of two antennas for each of the real and imaginary parts. The main contributions of this study can be summarized as follows. First, we derive an upper bound for the error performance of the IQSM. We then design constellation sets that minimize the error performance of the IQSM for several system configurations. Second, we propose a double QSM (DQSM) that transmits the real and imaginary parts of two signal symbols through any available transmit antennas. Finally, we propose a parallel IQSM (PIQSM) that splits the antenna set into equal subsets and performs IQSM within each subset using the same two signal symbols. Simulation results demonstrate that the proposed constellations significantly outperform conventional constellations. Additionally, DQSM and PIQSM provide a performance similar to that of IQSM while requiring a smaller number of transmit antennas and outperform IQSM with the same number of transmit antennas.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.114-119
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• 2019

The transmitted acoustic signals are severely influenced by multiply reflected signals from boundaries, such as sea surface and bottom in the shallow water. Very large reflection signals from boundaries cause inter-symbol interference so that the performance of the underwater acoustic communication is degraded. Usually, the waveform shaping filters are used to prevent the reflected signals under this kind of acoustic channel. Especially, the raised cosine filter is widely used, which can also be used to restrict the bandwidth of the transmitted signal. In this study, we evaluate the raised cosine filter for image data transmission in the shallow water, and propose a new modified raised cosine filter. The QPSK (Quadrature Phase Shift Keying) system is used for the underwater acoustic communication simulations with different distances and symbol rates. As a result, the bit error rate was reduced from the minimum 1.0 % to the maximum 32 %.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.8
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• pp.867-873
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• 1988

The degradation due to channel distortion in a quadrature modulation system from the ideal constant values over the bandwidth of a direct sequence spread spectrum signal are considered. Through using series expansion for the channel gain and phase response, the degradation in the correlator output at the receiver is found as a function of the parameters involved , including phase error, delay error, linear gin variation, quadratic gain variation, and quadratic phase variation.