• Journal of Communications and Networks
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• v.12 no.6
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• pp.529-532
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• 2010

Multi-carrier demultiplexer/demodulator (MCDD) in an on-board processing (OBP) satellite used for digital multimedia services has two typical architectures according to the channel demultiplexing procedure: Multistage multi-carrier demultiplexer (M-MCD) or poly-phase fast Fourier transform (PPF). During the channel demultiplexing, phase and quantization errors influence the performance of MCDD; those errors affect the bit error rate (BER) performance of M-MCD and PPF differently. In this paper, we derive the phase error variances that satisfy the condition that M-MCD and PPF have the same signal to noise ratio according to quantization bits, and then, with these results, analyze the BER performances of M-MCD and PPF. The results provided here may be a useful reference for the selection of M-MCD or PPF in designing the MCDD in an OBP satellite communications system.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.179-182
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• 1998

Carrier recovery, the process of recoverying the carrier in receiver, removes the phase difference between VCO and the received signal. However, the conventional structure of carrier recovery cannot be applied to multi-level QAM demodulator because of the increasing decision interval and the complexity of control as the number of symbol increases. In this paper, we suggest a new carrier recovery algorithm using $\theta-matching$ algorithm for multi-level QAM demodulation to overcome this problem and analysis the performance and implement it.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.7
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• pp.23-29
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• 1997

The performance degradation of CMOS differential amplifiers due to hot carrier effect has been measured and analyzed. Two-state CMOS amplifiers whose input transistors are PMOSFETs were designed and fabriacted using the ISRC CMOS 1.5.mu.m process. It was observed after the amplifier was hot-carrier stressed that the small-signal voltage gain and the input offset voltage increased and the phase margin decreased. The performance variation results from the increase of the transconductances and gate capacitances of the PMOSFETs used as input transistors in the differential input stage and the output stage and also resulted from the decrease of their output conductances. After long-term stress, the amplifier became unstable. The reason might be that its phase margin was reduced due to hot carrier effect.

• Journal of Institute of Control, Robotics and Systems
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• v.3 no.6
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• pp.602-612
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• 1997

With GPS carrier phase measurements from more than two antenna which attached to the vehicle, precise attitude can be easily obtained if the integer ambiguity included in carrier phase measurement is resolved. Recently some special products which use dual frequencies or has one receiver engine with multiple antenna are announced. But there are still strong requirements for the conventional single frequency off-the-shelf receiver. To meet these requirements, an efficient integer ambiguity resolution technique is indispensable. In this paper, a new technique to resolve integer imbiguity with single frequency receivers is proposed. The proposed method utilize the known baseline length as a constraint of independent elements of integer ambiguities. With this constraints, the size of search volume can be greatly reduced. Thus the true integer ambiguity can be easily determined with less computational burden and number of measurements. The proposed method is applied to real data to show its effectiveness.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.307-313
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• 2021

Modernized GNSS signal structures tend to use tiered codes, and all GNSSs use binary codes as secondary codes. However, recently, signals using polyphase codes such as Zadoff-Chu sequence have been proposed, and are expected to be utilized in GNSS. For example, there is Tiered Differential Polyphase Code (TDPC) using polyphase code as secondary code. In TDPC, the phase of secondary code changes every one period of the primary code and a time-variant error is added to the carrier tracking error, so carrier tracking ambiguity exists until the secondary code phase is found. Since the carrier tracking ambiguity cannot be solved using the general GNSS receiver architecture, a new receiver architecture is required. Therefore, in this paper, we describe the carrier tracking ambiguity and its cause in signal tracking, and propose a receiver structure that can solve it. In order to prove the proposed receiver structure, we provide three signal tracking results. The first is the differential decoding result (secondary code sync) using the general GNSS receiver structure and the proposed receiver structure. The second is the IQ diagram before and after multiplying the secondary code demodulation when carrier tracking ambiguity is solved using the proposed receiver structure. The third is the carrier tracking result of the legacy GPS (L1 C/A) signal and the signal using TDPC.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.6
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• pp.617-624
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• 2008

In general, RTK-GPS(Real Time Kinematic GPS) based on the single reference station is able to determinate the high accurate position of rover on the spot using error correction information of transmitted carrier phase from the base station via wireless modem. However, single reference station method has some weak points to decrease positioning accuracy because it must be obtained carrier phase from the each satellite continuously, allowed to transmit without obstacle and limited to short base line distance between base and rover station. This paper aims to attempt network based GPS carrier phase differential positioning using three multi reference stations to overcome the method of single reference station and RTK network is realized by real time monitoring program with Visual C++. The optimum error correction value of three multi reference stations by RTK networking is selected automatically to correct the position of rover station. In this paper, this algorithm is applied to determine sea water level using GPS buoy, and the accuracy results of water level change were analyzed and compared with each other using single and multi reference stations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1048-1054
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• 2012

This paper presents a Carrier phase fault detection (FD) method for GPS RTK (Global Positioning System Real Time Kinematic) in dynamic environment. There are various error sources in dynamic environment and these errors decrease the reliability of FD results. Due to the reason, Carrier phase measurements are separated into satellite induced signal, user induced signal and other remaining errors. Especially the user-induced signal is computed by user dynamic which is estimated by time-differenced Carrier phase (TDCP) and Doppler shift. TDCP makes it possible to avoid integer ambiguity resolution. Computer simulation is conducted to verify the suggested method. By applying impulse, step and ramp faults, the FD performance is analyzed.

• Journal of the Korean Institute of Navigation
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• v.6 no.1
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• pp.1-18
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• 1982

In this paper, author studied on the elementary data required for the design of the receiver of Pseudo Noise (PN) phase modulation communication adopted in Global Positioning System(GPS). By computer simulation technique, the phase modulator, filters, and PN generator are designed, and also required bandwidth of R-F amplifier for carrier frequency in phase modulation system is investigated. It is verified that the optimum bandwidth is about 3 times of the PN frequency and almost independent of the carrier frequency. And the low pass filter required for demodulation of slow Boolean data is also found to be about 60 times of the data signal frequency.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.101-102
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• 2006

Similar to Orthogonal Frequency Division Multiplexing (OFDM), a Single Carrier with Frequency Domain Equalization (SC-FDE) system is computationally efficient since equalization is performed on a block of data in the frequency domain. In coherent QAM schemes, the mean phase rotation error caused by the residual carrier frequency offset may lead to serious degradation. When the frequency equalizer is combined with the mean phase error tracking algorithm, its performance can be enhanced noticeably.

• Journal of Power Electronics
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• v.14 no.6
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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.