• International Journal of Control, Automation, and Systems
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• 제6권6호
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• pp.948-953
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• 2008

In high dynamic situations, the GPS carrier tracking loop requires a wide bandwidth to track a carrier signal because the Doppler frequency changes more rapidly with time. However, a wide bandwidth allows noises within the bandwidth of the tracking loop to pass through the loop filter. As these noises are used in the numerical controlled oscillator(NCO), the carrier tracking loop of a GPS receiver shows a degraded performance in high dynamic situations. To solve this problem, an adaptive two-stage Kalman filter, which offers the NCO a less noisy phase error, can be used. This filter is based on a carrier phase dynamic model and can adapt to an incomplete dynamic model and a quickly changed Doppler frequency. The performance of the proposed tracking loop is verified by several simulations.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.454-457
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• 1995

In optical disc system, tracking actuator is consisted of coarse actuator and fine tracking actuator. This, two-stage actuator, requires many devices and two servos for large stroke and precisional displacement. These complicate configuration increases moving mass. So dynamic characteristics become bad, that is, sensitivity of high frequency gain decrease. In this paper, frequency performance is willing to be better as so one dimensional tracking actuator is designed. In order to investigate the performance of the proposed tracking actuator, the Bode diagram is plotted with Dynamic analyzer and friction characteristic is explained. Finally, tracking error performance is ins investigated into 0.1 .mu.m resolution with MATLAB simulation.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.435-438
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• 2002

In this paper, the effect of surface tension, wettability, flow rate of contaminants with varying surfactant content and frequency of applied voltage on the tracking breakdown of epoxy insulating materials were investigated. As the flow rate of contaminant is increased, the surface resistivity is decreased, and the leakage current is increased, the time to tracking breakdown is decreased. It is found that time to tracking breakdown depends on the surface tension of contaminant, that is difference of wettability And as the frequency of applied voltage is increased, time to tracking breakdown decreased.

• Journal of electromagnetic engineering and science
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• 제1권2호
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• pp.131-138
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• 2001

The DTV (Digital TV) tuner for an 8-VSB (Vestigial Side-Band) modulation was developed to meet the requirements of the ATSC (Advanced Television Systems Committee). The double frequency conversion and the active tracking filter in the front-end were used to cancel interferences between adjacent channels and multi-channels by suppressing the IF beat and the Image frequency. However, It was impossible to get frequency mapping between the tracking filter and the first VCO (Voltage Controlled Oscillator) in the existing DTV tuner structure which differs from the NTSC (National Television Systems Committee) tuner. This paper, therefore, suggests an assailable structure and a new method for the automatic frequency selection by mapping the frequency characteristics over the tracking voltage and the combined HW which is composed of a Micro-controller, an EEPROM (Electrically Erasable Programmable Read Only Memory), a DAC (Digital-to-Analog Converter), an OP amplifier, and a switch driver.

• Journal of Power Electronics
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• 제18권5호
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• pp.1470-1478
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• 2018

Recently, wireless power transfer (WPT) via coupled magnetic resonances has attracted a lot of attention owing to its long operation distance and high efficiency. However, the WPT systems is over-coupling and a frequency splitting phenomenon occurs when resonators are placed closely, which leads to a decrease in the transfer power. To solve this problem, an adaptive frequency tracking control (AFTC) was used based on a closed-loop control scheme. An improved particle swarm optimization (PSO) algorithm was proposed with the AFTC to track the maximum power point in real time. In addition, simulations were carried out. Finally, a WPT system with the AFTC was demonstrated to experimentally validate the improved PSO algorithm and its tracking performance in terms of optimal frequency.

• 한국음향학회지
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• 제21권3호
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• pp.256-263
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• 2002

본 연구에서는 백색 가우시안 잡음이 부가되는 환경 (AWGN)에서 측정 신호로부터 주파수와 진폭의 시간적 변동 특성을 추적하는 문제를 고려한다. 확장 칼만 필터는 여러 가지 응용분야에서 이용되고 있으며, 특히 시간적으로 변동하는 주파수를 추적하는 문제에도 응용되어 왔다. 기존의 확장 칼만 필터 주파수 추적기는 시간에 대한 신호 진폭의 변화폭이 적은 경우에 대해 유도되었거나 진폭의 시간적 변화폭이 큰 경우에는 부가적인 진폭 추적기가 요구된다. 본 연구에서는 시간에 따를 진폭의 변화폭이 상대적으로 큰 경우에 시변 주파수의 추적 성능을 높이기 위해 주파수와 진폭을 동시에 추적하는 확장 칼만 필터 주파수-진폭 추적기를 제안하고 수치모의 실험과 실제 실험을 통하여 그 성능을 확인한다.

• Bulletin of the Korean Chemical Society
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• 제18권12호
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• pp.1281-1285
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• 1997

The time-dependent tracking inversion method is developed to extract the potential of the excited state from frequency-domain measurements, such as the absorption profile. Based on the relay of the regularized inversion procedure and time-dependent wave-packet propagation, the algorithm extract the underlying potential piece by piece by tracking the time-dependent data which can be synthesized from frequency-domain measurements. We have demonstrated the algorithm to extract the potential of excited state for a model diatomic molecule. Finally, we describe the merits of the time-dependent tracking inversion method compared to the time-dependent inversion and discuss several extensions of the algorithm.

• 대한전자공학회논문지TC
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• 제39권8호
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• pp.14-25
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• 2002

본 논문에서는 제 3 세대 이동 통신인 WCDMA 기지국 모뎀의 실제 구현에 적합하도록 변형된 AFC(Automatic Frequency Control) 루프를 제안한다. 제안된 AFC 루프에는 구현상의 복잡도 감소를 위하여 기존의 CP-FDD(Cross Product Frequency Difference Detector) 알고리즘을 변형한 Normalized CP-FDD 알고리즘을 적용하였다. 제안된 Normalized CP-FDD는 입력 신호 진폭 변화에 민감한 기존 CP-FDD 출력 특성을 보완하며, FDD의 출력(S-curve)의 선형화 구간을 증가시킴으로써 안정적인 주파수 오차에 대한 추정을 가능하게 한다. WCDMA에서는 IS-95 시스템과 다르게 파일롯 심볼이 연속적으로 전송되지 않으므로, FDD 입력단에 이동 평균 필터(Moving Average Filter)를 도입하여 교차곱(Cross-product)의 수를 증가시킴으로써 잡음의 영향을 감소시키고 주파수 오차에 대한 추적 시간 성능과 안정성을 향상시켰다. 또한 다단 추적 모드를 적용함으로써 수신 신호의 주파수 오차의 크기에 대한 능동적인 보상이 가능하도록 하였으며, 루프 필터의 출력을 이용한 ROM table 도약 구조의 NCO(Numerical Controled Oscillator)를 적용하여 주파수 오차를 보상하였다. 본 논문에서 제안한 알고리즘은 WCDMA 기지국 모뎀 구현에서 성공적으로 적용되었다.

• Journal of Electrical Engineering and Technology
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• 제6권3호
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• pp.319-327
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• 2011

An iterative technique based on orthogonal filters and frequency tracking is proposed to estimate harmonic components in power systems. The technique uses frequency interpolation to estimate fundamental frequency and harmonics when the nominal frequency of the signal is a non-integer value. Due to the number of computations involved during the generation of filter coefficients, an offline computation is suggested. Beneficial features of the proposed technique include fixed sampling rate and fixed data window size. The performance of the proposed technique is examined by simulating different power system operating conditions and evaluating the data from these simulations. A technique based on Fast Fourier Transform is also used to estimate the harmonic components for all the simulated signals. These estimates are compared with those obtained from the proposed technique. Results show that the proposed technique can converge to the accurate fundamental frequency and therefore, provide accurate harmonic components even when the fundamental frequency is not equal to the nominal frequency.

• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.481-490
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• 2021

In the ultrasonic welding machine, when the load fluctuates, the L and C of the piezo element in the oscillation part change. As a result, the resonant frequency is changed, so it is necessary to match the operating frequency of the ultrasonic welding machine to the new resonant frequency. That is, in order to maximize the output of the oscillation unit of the ultrasonic welding machine, it is inevitable to follow the resonance frequency. Accordingly, many methods for following the resonant frequency are being actively studied. In addition, in order to check the effect of external inductance on the operation of the ultrasonic welding machine, The equivalent circuit of the piezo element was analyzed by including the external inductance for resonance in the equivalent circuit of the piezo element, and the method of selecting an appropriate inductance was described. In this paper, we propose a new system that allows the switching frequency of the inverter to tracking the resonance frequency even if the resonance frequency is changed due to the load of the ultrasonic welding machine.