• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.4
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• pp.131-139
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• 2004

This paper proposes a variable-Q digital graphic equalizer with the opposite filters. A method for designing the proposed equalizer is also presented. In the proposed variable-Q equalizer, we adjust the Q-factor of the equalizer filter depending on the gain, yielding an improved equalizer performance. Also, by increasing the Q-factor of the opposite filters gracefully as the gain becomes greater, the inter-band interference can be removed effectively. We shall show that the frequency response of the proposed equalizer can reproduce the user's gain setting faithfully.

• The Journal of the Acoustical Society of Korea
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• v.19 no.3
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• pp.63-71
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• 2000

A new type of second-order digital peaking filters for professional-quality digital audio system is proposed whose frequency response can be elaborately controlled throughout the composite structure of a standard band-pass filter and a 0-dB bypass gain. The proposed method for designing the peaking filter uses the Q-compensation technique to prevent the Q-distortion caused by the variation of the gain factor and is reduced into a compact form which is proper to the real-time implementation. Methods are examined for computing its coefficients, which are exact and very straightforward to compute with small amount of the system resources.

• Korean Journal of Optics and Photonics
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• v.6 no.3
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• pp.245-256
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• 1995

Rugate filters of inhomogeneous refractive index were designed using the Fourier transform and the effect of reflectance, stop bandwidth, optical thickness, and Q function on the rugate filter was investigated. An iterative correction process using a merit function was employed to fit an initial design to the target spectrum. Three Q functions derived by Sossi, Bovard, and Fabricius, respectively, were compared in terms of the number of iteration, merit function, and optimum optical thickness. The result shows that after a number of iterations the Q functions by Bovard and Fabricius produce high rejection rugate filters closer to the target spectrum than the Sossi's Q function and the optimal optical thickness is determined by the stop-band width of the rugate filter. ilter.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.79-83
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• 2000

When passband ripple α/sub p/ and stopband attenuation α/sub s/ at the w/sub s/ where the stopband begins are specified in filter design, △α/sub s/ usually exceeds the specification by △α/sub s/ due to the necessity that the order n of the filter function be an integer. In this paper, we apply a trade-off method to remove the excess stopband attenuation △α/sub s/ for reducing the value of pole-Q and improving the characteristics of the Chebyshev filter function. We also apply the trade-off method of pole-Q reduction to the modified Chebyshev function, and then the 4 types of function have been analyzed to compare in frequency and time domain characteristics. The trade-off method reduces the pole-Q which influences the filter characteristics to maximum 49.6% without increase of the order n. Thus implies that they have the improved characteristics such as the reduced passband ripple and flatter delay characteristics as compared Chebyshev filter function before trade-off. And the unit step response shows shorter delay time and settling time in time domain performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3425-3430
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• 2013

The fast-growing market in wireless communications has led to the development of multi-standard mobile terminals. In this paper, a frequency-tunable active RC bandpass filter for multi-standards wireless communication system is designed using an active inductor. The conventional bandpass filter design methods employ the high order filter or high quality factor Q to improve the stopband attenuation characteristics and frequency selectivity of the passband. The proposed bandpass filter based on the high Q active inductor has an improved frequency characteristics. The center frequency and gain of the designed bandpass filter is tuned by employing the tuning circuit. We have performed the simulation using TSMC $0.18{\mu}m$ process parameter to analyze the characteristics of the designed active RC bandpass filter. The bandpass filter with Q=20.5 has 90MHz half power bandwidth at the center frequency of 1.86GHz. Moreover, the center frequency of the proposed bandpass filter can be tuned between 1.86~2.38GHz for the multi-standards wireless communication system using the capacitor of the tuning circuit.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.11
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• pp.123-129
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• 2016

Disturbance Observer(DOB) based control is considered for the purpose of the balancing performance enhancement in a single-wheel robot. Design of DOB can be folded into two parts, the inverse model of the plant and the Q-filter. The inverse model is derived from the inverted stick model and a Q-filter is designed to stabilize the inverse model. In this paper, a Q31 filter is designed and its effect is evaluated by experimental studies. The time constant provides a complimentary characteristic between the disturbance suppression and the sensor noise immunity. Therefore, suitable selection of the time-constant must be considered. Comparative experiments are conducted to investigate the control performances when three different Q filters are respectively applied in the DOB. Through the analysis of the experimental results, a time constant is designed to have a proper value in the design of DOB for balancing control of a single-wheel robot.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.3-10
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• 2014

Direct conversion receiver(DCR) gets noticed for integration and cost reduction of wireless communication systems instead of the heterodyne receiver which uses complex filter. But DCR has several factors in performance degradation. One of them is I/Q imbalance phenomenon, that is amplitude and phase mismatch between real and imaginary part of receiver. Accordingly, researches are being carried to improve the I/Q imbalance problem. However, the tendency of the broaden bandwidth of communication systems, low pass filter(LPF) mismatch problem affects severely in I/Q mismatch phenomenon at the DCR. To study this problem, we generated 10MHz broadband signal and shifted it ${\pm}8MHz$ from the center frequency. The signal is affected by LPF mismatch and it appears as frequency selective distortion. Thus, LPF mismatch model is added to I/Q imbalance model which conventionally dealt with amplitude and phase mismatches. In addition, we proposed the compensation method for each factors of mismatch. As the simulation results, the proposed I/Q mismatch compensator resolves the frequency selective distortion which occurred by the existing LPF mismatch.

• 전기의세계
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• v.34 no.1
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• pp.19-23
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• 1985

LQG로 설계된 시스템이 LQR의 보증된 안정감도를 갖도록 $K_{f}$를 조정하는 한 LTR기법을 살펴보았다. q가 0이라면 필터는 실제의 프로세서 잡음의 Q = Q$_{0}$라는 점에서 최적이다. 그러나 q의 값이 증가함에 따라 $K_{f}$는 증가되고 x over ^에 따라서 시스템의 동특성은 관측에 의해 수정되는 항보다 상대적으로 소홀히 취급되어진다. 따라서 출력 y에 포함되어 지지않는 x의 추정치 xover^은 그 실제값과 차이가 많이 나타날 우려가 생긴다. 또한 관측잡음이 xover^에 크게 영향을 미치므로 잡음을 배척하는 필터의 성질도 모호해질 우려가 있다. 그러나 안정강도의 관점에서는 크게 개선되어진다는 것을 알 수 있다. 실제 설계에 있어서는 이 장점과 단점들을 잘 trade off시키는 단계가 필요할 것이다. 또한 추정치 xover^를 얻는데 정상상태의 칼만 필터를 이용하지 않고 극배치(Pole Placement)방법을 사용함도 고려할 수 있으며 이에 따른 LTR도 흥미있는 분야가 될 수 있을 것이다.다.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.271-275
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• 2014

A New Single Phase Active Power Filter Controller is proposed using Rotating Synchronous Frame d-q transformation. Instantaneous Active Power is calculated using d-q transformation. Average Value of Instantaneous Active Power is obtained using Low Pass Filter. Because power factor is corrected, source current is in phase with source voltage. Amplitude of source current is calculated using single phase power formula. Reference signal of compensated current of Active power filter is obtained from source current reference signal minus load current. Simulation is performed using hysteresis current controller in proposed new controller. Simulation result shows that because active power filter compensates load current, source current is in phase with source voltage and source current is sinusoidal. And Hilbert transformer is builded using all pass filter.

• Journal of Broadcast Engineering
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• v.8 no.1
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• pp.3-10
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• 2003

This paper proposes a variable-Q digital graphic equalizer in which each equalizer filter has different Q-factor depending on the band as well as the gain. The proposed equalizer demonstrates the symmetric frequency response over the audible frequency range. While maintaining the similar level of hardware complexity, the proposed equalizer yields an actual response that is quite close to the desired one, as compared with the conventional equalizers. Also, we investigate how the performance is affected by the center frequencies of the filters.