• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.134-137
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• 2001

A variable bandwidth filter (VBF) is proposed for cleaning signals with known instantaneous bandwidth (IB). Also, the behaviors and the characteristics of the VBF are examined in time-frequency domain (TFD). The proposed VBF clips a noisy signal along the boundaries of IB and rejects noise in the outside of the IB of the signal in TFD. It is possible to construct four kinds of VBF that are low-pass VBF, high-pass VBF, band-pass VBF and band-stop VBF.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.138-141
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• 2001

In this paper, a VBF(variable bandwidth filter) is suggested and analyzed in time-frequency domain. There are four kinds of VBF, which are low-pass VBF, high-pass VBF, band-pass VBF and band-stop VBF. The proposed VBF can extract the components of signals within variable instantaneous bandwidth at a specific time instant. Instantaneous bandwidth is estimated in time-frequency domain. The VBF is represented by rational form in extended Fourier frequency domain.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.751-754
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• 2002

This paper introduces a way to realize biquadratic transfer functions using Operational Amplifiers (OAs) and Operational Transconductance Amplifiers (OTAs). The basic circuit configuration is constructed with two OAs and five OTAs. It is shown that low-pass, band-pass, high-pass, band-stop and all-pass transfer functions can be realized by suitably choosing the input terminals. And the circuit parameters can also be set by the transconductance gains of the OTAs independently. An example is given together with simulated results by PSPICE.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.8
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• pp.42-51
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• 1998

An 8th-order elliptic low-pass filter with cutoff frequency of 3.13kHz is presented. The design procedure is based on teh 1/s impedance transformation which is applied to a minimum capacitor LC ladder network.The tranformed network is implemented with resistors and high Q frequency-dependent negative resistors (FDNR's). The high Q FDNR is realized with two transadmittance amplifiers. Detailed SPICE simulations show that the iflter has pass-band ripple of 0.18dB, stop-band attenuation over 100dB, cutoff frequency of 3.13 khz, and cutoff frequency temperature coefficient of 8.5ppm/.deg. C at supply voltage of .+-.5V.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2001.11a
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• pp.464-468
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• 2001

In this paper, we propose a robust watermarking technique that accepts time scaling, pitch shift, add noise and a lot of lossy compression such as MP3, AAC, WMA. The technique is developed based on digital filtering. Being designed according to critical band of HAS (human auditory system), the digital filters nearly affect audio quality. Furthermore, before implementing digital filtering, wavelet transform decomposes the audio signal into several signals that is composed of specific frequencies. Designed digital filters scan the decomposed signal. The designed digital filter, band-stop filter, distorts and eliminates specific frequencies of audio signals. Watermarking detection can be accomplished by FFT (Fast Fourier Transform). Firstly, segments of audio signal are transformed by FFT. Then, the obtained amplitude spectrum by FFT is summed repeatedly. Finally the watermark detector can find filters used to watermark encoding based on eliminating frequencies. The suggested technique can embed 4bits/s in a robust manner.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.207-210
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• 2000

This paper introduces a voltage-mode biquadratic circuit using only Operational Amplifiers (OTAs) and Operational Transconductance Amplifiers (OTAs). The proposed circuit can realize low-pass, band-pass, high-pass, band-stop and all-pass transfer functions by suitably choosing the input and output terminals. And the circuit characteristics can be electronically tuned through adjusting the transconductance gains of OTAs. Some examples are given together with simulated results by PSpice. The circuit configuration is very suitable for implementation in both bipolar and CMOS technologies.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.200-201
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• 2002

Recently, a countermeasure for the electromagnetic noise emission on RF integrated transmission line using the loss generation of ferromagnetic thin films is briefly suggested$\^$1,2/. Without the magnetic film, the noise harmonics of the signal pass through the transmission line with only a little attenuation. The ideal role of magnetic film is not to raise insertion losses in the pass-band and to give as large attenuation as possible to eliminate the noise harmonics at the stop-band, the frequency range higher than the meaningful signal as shown in Fig. 1. and Fig. 2. (omitted)

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.7-11
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• 2002

A novel microstrip type law-pass filter using thin or thick film resistors is proposed to efficiently eliminate harmonic spurious response in stop-band. The proposed low-pass filter shows the spurious suppression enhancement of 20 dB over a conventional one. The designed low-pass filter could be used as a harmonic rejection filter of a local oscillator for Ku-band satellite payload system.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.258-259
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• 2007

In this paper, the secant method is adopted to improve a transfer function required by specific filtration properties. It is advantageous over the conventional and widely used 'Template method' in that it enables users to seek the position of a pole which will turn out to meet well the requirements of in-band insertion loss as well as stop-band rejection even after a small number of iterative steps. For validating the proposed method, the transfer function of a 4-pole waveguide filter is targeted.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.11
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• pp.2242-2246
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• 2009

In this paper, a homogeneous dual composite right/left-handed (D-CRLH) transmission line (TL) is proposed by using a defected ground structure (DGS) on the ground plane. In order to satisfy a homogeneity condition of metamaterial, a subwavelength unit cell is designed by way of a spiral DGS and a meander stub. From a dispersion diagram, it is expected that the frequency bands for the left-handed (LH) property is 3.5 - 4.4 GHz. At 3.8 GHz in the LH band, backward propagating phenomenon is observed from full-wave analysis. The experimental results show that the proposed TL has a stop-band in 1.75 - 3.6 GHz.