• ETRI Journal
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• v.30 no.4
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• pp.495-505
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• 2008

This paper presents a parallel processing searcher structure for the initial synchronization of a direct sequence ultra-wideband (DS-UWB) system, which is suitable for the digital implementation of baseband functionalities with a 1.32 Gsample/s chip rate analog-to-digital converter. An initial timing acquisition algorithm and a data demodulation method are also studied. The proposed searcher effectively acquires initial symbol and frame timing during the preamble transmission period. A hardware efficient receiver structure using 24 parallel digital correlators for binary phase-shift keying DS-UWB transmission is presented. The proposed correlator structure operating at 55 MHz is shared for correlation operations in a searcher, a channel estimator, and the demodulator of a RAKE receiver. We also present a pseudo-random noise sequence generated with a primitive polynomial, $1+x^2+x^5$, for packet detection, automatic gain control, and initial timing acquisition. Simulation results show that the performance of the proposed parallel processing searcher employing the presented pseudo-random noise sequence outperforms that employing a preamble sequence in the IEEE 802.15.3a DS-UWB proposal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3C
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• pp.237-244
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• 2006

I/Q phase unbalance caused by non-ideal circuit components is inevitable physical phenomenons and leads to performance degradation when we implement a practical coherent M-ary phase shift keying(M-PSK) demodulator. In this paper, we present an exact and general expression involving two-dimensional Gaussian Q-functions for the bit error rate(BER) of uniform M-PSK with I/Q phase unbalance over an additive white Gaussian noise(AWGN) channel. First we derive a BER expression for the k-th bit of 8, 16-PSK signal constellations when Gray code bit mapping is employed. Then, from the derived k-th bit BER expression, we present the exact and general average BER expression for M-PSK with I/Q phase unbalance. This result can readily be applied to numerical evaluation for various cases of practical interest in an I/Q unbalanced M-PSK system, because the one- and two-dimensional Gaussian Q-functions can be easily and directly computed using commonly available mathematical software tools.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.870-873
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• 1991

In this paper, We present demodulation and synchronization method of phase shift keying signal using Double Frequency Vector Technique for Reference Vector. 2nd Harmonic Vector for Reference Vector is utilized in discriminating between noise and carrier signal, and in producting correlation value for data bit logical level. And we applied this demodulator to Automatic Meter Reading System being communicated with electric distribution power lines.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1219-1225
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• 2001

In this Paper we describe the design of synchronization algorithms for burst QPSK receiver, which are applicable to BWLL uplink. The demodulator consists of digital down converter, matched filter and synchronization circuits. For symbol timing recovery we ufo Gardner algorithm. And we use forth power method and decision directed method for carrier frequency recovery and phase recovery, respectively. For the sake of performance analysis, we compare simulation results with the board implemented by FPGA which is APEX20KE series chip for Alter. The performance results show it works quite well up to the condition that a frequency offset equal to 4.7% of symbol rate.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.12
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• pp.9-15
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• 1994

In this paper, the linearized power amplifier using digital adaptive predistorter is implemented in order to restrict spectral spreading and adjacent channel interference. The linearized systems is composed of a DSP56001 processor that executes predistortion in baseband. 90.deg. phase shifter, power splitter/combiner, quadrature modulator/demodulator of 360MHz band, and nonlinear amplifier. A ${\pi}$/4-shift QPSK is used to modulate digital random signals. As the quantized power of baseband signal and the output of amplifier are fed to the predistorter, and predistorting values are calculated using an adaptive algorithm. In the experiment, a peak to sidelobe ratio of the linearized amplifier is improved up to 15dB in comparison with conventional nonlinear amplifier, which means that the distortion of transmitted signal is decreased and adjacent channel interference was reduced.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.857-860
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• 1999

It is made possible a removal of the preamble for carrier recovery and symbol-timing recovery by storing a burst in memory with low overhead QPSK demodulation and this demodulation method also effects frame efficiency improved by processed synchronization performance. In this paper, we have proposed that new algorithm for arc-tangent look-up table which transform the input I, Q data by phase. This I, Q data plays an important role in demodulation and makes demodulator with low-overhead by storing a burst in memory. To evaluate proposed new algorithm and symbol-timing recovery method, function simulation and timing verification have been done by using synopsys VHDL tool.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.1
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• pp.11-21
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• 1989

In this paper, a GMSK modulator was implemented with a gaussian lowpass filter using digital signal processing, a phase integration, D/A convers and auxiliary circuits. The relatively narrow bandwidth of power spectrum of the GMSK modulator is observed when the cut off frequency (B T) of the gaussian baseband filter is varied. In a demodulator, a discriminator type circuit is used. Using the above degital radio GMSK modem, BER is theoretically derived and experimentally measured when 16Kbps PRBS data is transmitted under Rayleigh fading and additive white gaussian noise conditions.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.4
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• pp.38-45
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• 1994

It is very imprtant and necessary to predict luminous enviroment in an interior space. This paper has de scribed about energy saving and evaluated interior visual environment in a office building having on/off turning control lighting system utilizing daylight. In order to predict the interior varior illumination distribution, the scale model w a m~a de and examined under various conditions, such ad difference of window glass, and color pattern of wall, floor, and also ceiling lighting system type. Ths paper suggests that basic fundamental data of lighting design ~rformancein the concept and schematic stages of design.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.481-487
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• 2013

To successfully accomplish a bit synchronization, a synchronizer should exploit a preamble pattern. A MFM (modified frequency modulation) flag is uses as a preamble in a PJM (phase jitter modulation) mode RFID standard. In the recent work, a synchronizer for a PJM mode tag was proposed, which is composed of several correlators. In this paper, we present a new bit synchronizer in which a coarse synchronization is done as in the previous work while a fine synchronization is performed via exploiting a violation bit included in the MFM flag. We show that the proposed synchronizer can significantly reduce the overall hardware complexity at the expense of slight burden to a demodulator structure. Through simulation, we also show that its performance is comparable to that of the previous system despite its hardware simplicity.

• Journal of IKEEE
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• v.22 no.3
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• pp.800-804
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• 2018

This paper presents a novel HF band differential quadrature phase-shift keying (DQPSK) orthogonal frequency-division multiplexing (OFDM) communication system. The system can deliver 3.6 kbps with a bandwidth of about 3 kHz. In a digital modem, OFDM with 32-point fast Fourier transform is used. In the system, each subcarrier uses DQPSK modulation. Hence, a demodulator does not require carrier phase recovery and symbol timing recovery. And, each subcarrier employs CRC error check code individually. By using CRC code for each subcarrier, bit error caused by multipath fading can be recovered simply.