• Proceedings of the Korea Institute of Convergence Signal Processing
• /
• 2003.06a
• /
• pp.217-221
• /
• 2003

In this paper, the Viterbi decoder containing new branch metrics of the squared Euclidean distance with multiple order phase differences is introduced in order to improve the bit error rate (BER) in the differential detection of the trellis-coded MDPSK-OFDM. The proposed Viterbi decoder is conceptually same as the multiple Phase differential detection method that uses the branch metric with multiple phase differences. Also, we describe the Viterbi algorithm in order to use this branch metrics. Our study shows that such a Viterbi decoder improves BER performance without sacrificing bandwidth and power efficiency. Also, the proposed algorithm can be used in the single carrier modulation.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.54.3-54
• /
• 2001

This paper presents a controller design technique for standard 2nd-order system satisfying user-specified phase margin. A simple method is presented to meet stability margin for the 2nd-order system, which is important since the 2nd-order plant models are frequently encountered in the practical plant models such as actuators of the optical drive systems. Through the comparison of the specified stability margin and achieved stability margin, it is shown in the simple example that the proposed technique is useful in the initial design of control systems with stability margin specifications.

• Journal of Positioning, Navigation, and Timing
• /
• v.1 no.1
• /
• pp.7-14
• /
• 2012

Due to inaccurate safe navigation estimates, maritime accidents have been occurring consistently. In order to solve this, the precise positioning technology using carrier phase information is used, but due to high buildings near inland waterways or inclination, satellite signals might become weak or blocked for some time. Under this weak signal environment for some time, the GPS raw measurements become less accurate so that it is difficult to search and maintain the integer ambiguity of carrier phase. In this paper, a method to generate code and carrier phase measurements under this environment and maintain resilient navigation is proposed. In the weak signal environment, the position of the receiver is estimated using an inertial sensor, and with this information, the distance between the satellite and the receiver is calculated to generate code measurements using IGS product and model. And, the carrier phase measurements are generated based on the statistics for generating fractional phase. In order to verify the performance of the proposed method, the proposed method was compared for a fixed blocked time. It was confirmed that in case of a weak or blocked satellite signals for 1 to 5 minutes, the proposed method showed more improved results than the inertial navigation only, maintaining stable positioning accuracy within 1 m.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.44 no.2 s.314
• /
• pp.32-38
• /
• 2007

This paper represents a Doherty amplifier (DPA) with analog predistorter (PD) to improve the linearity of the DPA while preserving the high efficiency. A third-order PD cancels fifth-order intermodulation (IM5) as well as third-order intermodulation (IM3) components by their same phase difference in the PD and DPA. This is accomplished by independently controlling their phase by using the phase-controlled error generator in the PD. Also, we confirm the phase-control ability of the error generator experimentally with a simple and accurate phase measurement setup. For experimental verification, a third-order PD has been implemented and tested in a 180-W DPA at the wide-band code division multiple access (WCDMA) band of 2.11-2.17 GHz. Two-tone test results show that significant cancellation of IM3 and IM5 components can be obtained. For four-carrier WCDMA applications, significant adjacent channel leakage ratio (ACLR) improvement is achieved over a wide range of output power levels. This technique is cost-effective and convenient due to its simple structure, compact size, and three control parameters.

• ETRI Journal
• /
• v.26 no.3
• /
• pp.277-280
• /
• 2004

The distributions of electric field and induced second-order nonlinearity are analyzed in the periodic poling of optical fibers. A quasi-phase matching efficiency for the induced nonlinearity is calculated in terms of both the electrode separation distance between the applied voltage and generalized electrode width for the periodic poling. Our analysis of the quasi-phase matching efficiency implies that the conversion efficiency can be enhanced through adjusting the separation distance, and the electrode width can be maximized if the electrode width is optimized.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1996.04a
• /
• pp.221-226
• /
• 1996

Structural vibrations of adjacent buildings, manufacturing factories and engines on the stationary diesel power plant were increased by the variation of phase angle between two engines sometimes. In this paper, top bracings and synchrophaser have been introduced in order to reduce these vibrations. As a result, all of structural vibrations were greatly improved by the phase adjustment of 6th order X-mode vibration with these.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.10
• /
• pp.1831-1836
• /
• 2016

Phase noise spectrum distributions of signal generators for next-generation VSAT satellite system based on DVB-RCS2 were analyzed in this paper. The forward link of VSAT system utilizes the APSK higher-order modulation methods based on the DVB-S2 ACM, the modulation methods of the return link utilizes the higher-order PSK and QAM based on the DVB-RCS2. In digital satellite system using the higher-order modulation techniques, the phase noise have an effect on transmission performance, the transmission performance is dominantly degraded by the phase noise of signal generators in the transmission system. The phase noise spectrum distribution of signal generators are analyzed by considering the ACM conditions that adopts the modulation techniques and data rates due to satellite transmission environment. The proper phase noise spectrum distribution for next-generation VSAT system based on DVB-RCS2 are proposed from the analyzed phase noise spectrum characteristics.

• Proceedings of the KIEE Conference
• /
• 2007.04a
• /
• pp.113-118
• /
• 2007

In this paper, a new method is proposed for robust proportional- integral - derivative (PID) control that is to ensure specified phase margin and iso - damping property using reduction model. This method is based on the second order plus dead time(SOPDT) reduction model of the high order model. Reduction model used to ensure iso-damping property in the feature frequency. Simulation results gives proof of effectiveness of proposed method.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.4
• /
• pp.1597-1609
• /
• 2015

This paper introduces the fundamentals of the conventional LC low-pass filter circuit in the fractional domain. First, we study the new fundamentals of fractional-order LC low-pass filter circuit including the pure real angular frequency, the pure imaginary angular frequency and the short circuit angular frequency. Moreover, sensitivity analysis of the impedance characteristics and phase characteristics of the LC low-pass filter circuit with respect to the system variables is studied in detail, which shows the greater flexibility of the fractional-order filter circuit in designs. Furthermore, from the filtering property perspective, we systematically investigate the effects of the system variables (LC, frequency f and fractional orders) on the amplitude-frequency characteristics and phase-frequency characteristics. In addition, the detailed analyses of the cut-off frequency and filter factor are presented. Numerical experimental results are presented to verify the theoretical results introduced in this paper.

• Journal of Communications and Networks
• /
• v.7 no.3
• /
• pp.248-257
• /
• 2005

In this paper, we develop design procedures for carrier tracking loop for orthogonal frequency division multiplexing (OFDM) systems or other systems of blocked data. In such communication systems, phase error measurements are made infrequent enough to invalidate the traditional loop design methodology which is based on analog loop design. We analyze the degradation in the OFDM schemes caused by the tracking loop and show how the performance is dependent on the rms phase error, where we distinguished between the effect of the variance in the average phase over the symbol and the effect of the phase change over the symbol. We derive the optimal tracking loop including optional delay in the loop caused by processing time. Our solution is general and includes arbitrary phase noise apd additive noise spectrums. In order to guarantee a well behaved solution, we have to check the design against margin constraints subject to uncertainties. In case the optimal loop does not meet the required margin constraints subjected to uncertainties, it is shown how to apply a method taken from control theory to find a controller. Alternatively, if we restrict the solution to first or second order loops, we give a simple loop design procedure which may be sufficient in many cases. Extensions of the method are shown for using both pilot symbols and data symbols in the OFDM receiver for phase tracking. We compare our results to other methods commonly used in OFDM receivers and we show that a large improvement can be gained.