• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.2
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• pp.837-856
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• 2016

Underwater image enhancement has received considerable attention in last decades, due to the nature of poor visibility and low contrast of underwater images. In this paper, we propose a new automatic underwater image enhancement algorithm, which combines nonsubsampled contourlet transform (NSCT) domain enhancement techniques with the mechanism of the human visual system (HVS). We apply the multiscale retinex algorithm based on the HVS into NSCT domain in order to eliminate the non-uniform illumination, and adopt the threshold denoising technique to suppress underwater noise. Our proposed algorithm incorporates the luminance masking and contrast masking characteristics of the HVS into NSCT domain to yield the new HVS-based NSCT. Moreover, we define two nonlinear mapping functions. The first one is used to manipulate the HVS-based NSCT contrast coefficients to enhance the edges. The second one is a gain function which modifies the lowpass subband coefficients to adjust the global dynamic range. As a result, our algorithm can achieve contrast enhancement, image denoising and edge sharpening automatically and simultaneously. Experimental results illustrate that our proposed algorithm has better enhancement performance than state-of-the-art algorithms both in subjective evaluation and quantitative assessment. In addition, our algorithm can automatically achieve underwater image enhancement without any parameter tuning.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.2
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• pp.159-164
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• 2004

In this paper, we have proposed the folded feed structure for the spurious harmonic suppression and we have designed the SIR CPW bandpass filter using this feed structure. The characteristic of the proposed feed structure was similar to that of the lowpass filter has wide stopband region and this can be used usefully to the spurious harmonic suppression of the bandpass filter. From the simulation and the measurement result, SIR CPW bandpass filter with folded feed structure has good harmonic suppression characteristics up to 5.8 f$\sub$0/ with -20 dB suppression level.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.2
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• pp.237-246
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• 1999

A miniaturized waveguide bandpass filter is designed by combining a corrugated lowpass structure and a highpass configuration based on the cut-off effect of waveguides. It is smaller than the conventional waveguide bandpass filter composed of half-wavelength resonators and has wider spurious free characteristics. Optimized design data for a seven-order waveguide bandpass filter with the symmetrical structure are given at the center frequency of 10 GHz with 800 MHz bandwidth. Measured bandwidth of the center frequency of 9.97 GHz is 840 MHz and measured insertion loss is 0.97dB, The length of the bandpass filter is 64.38mm. The first spurious response is produced at 26.1 GHz.

• Journal of Biomedical Engineering Research
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• v.22 no.4
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• pp.311-319
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• 2001

Statistical reconstruction methods in the context of a Bayesian framework have played an important role in emission tomography since they allow to incorporate a priori information into the reconstruction algorithm. Given the ill-posed nature of tomographic inversion and the poor quality of projection data, the Bayesian approach uses regularizers to stabilize solutions by incorporating suitable prior models. In this work we show that, while the quantitative performance of the standard filtered backprojection (FBP) algorithm is not as good as that of Bayesian methods, the application of spline-regularized smoothing to the sinogram space can make the FBP algorithm improve its performance by inheriting the advantages of using the spline priors in Bayesian methods. We first show how to implement the spline-regularized smoothing filter by deriving mathematical relationship between the regularization and the lowpass filtering. We then compare quantitative performance of our new FBP algorithms using the quantitation of bias/variance and the total squared error (TSE) measured over noise trials. Our numerical results show that the second-order spline filter applied to FBP yields the best results in terms of TSE among the three different spline orders considered in our experiments.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.6
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• pp.6-10
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• 1983

In this paper, an implementation method for digital filters using the residue arithmetic is proposed. This method can be used for processing digital signals with larger number of bits by applying the idea of the bit-slice algorithm, while previous residue digital filters can process digital signals with only a small number of bits. Furthermore, high-speed residue addition, subtrac-tion, and multiplication using look-up tables make it possible to get more flexible filters. Everything that is mentioned above is proved by implementing a cascade fourth-order Butterworth lowpass digital filter using this method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.697-706
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• 2000

In this paper, new bandpass filters that are composed of microstrip ring resonators with the center frequency of 5.775 GHz and the bandwidth of 100 MHz are presented. For the suppression of the unnecessary harmonics, lowpass filters are inserted into the feedlines and ring resonator itself, respectively These bandpass filters show good microwave characteristics with the harmonic suppression ratio of about 39 dB and 35 dB, respectively. Also, the varactor-tuned microstip ring bandpass filter with harmonic suppression is suggested and the tuning bandwidth of more than 450 MHz is obtained.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.10
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• pp.1122-1128
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• 2008

A novel tunable bandstop filter was proposed. It is composed of a right-handed transmission line, which has lowpass characteristics, and a left-handed transmission line which has highpass characteristics. Dispersion relations for the unit cells of RHTL and LHTL were derived by the method of ABCD parameter analysis. Varactor diodes and chip inductors were used to make the unit cells of RHTL and LHTL. A tunable bandstop filter was designed and fabricated by the parallel connection of RHTL and LHTL. The measured results of the proposed tunable bandstop filter are agreed well with the simulated results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.7
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• pp.1424-1428
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• 2004

In this paper, CMOS analog filters for use in the Analog front End of digital subscriber loop(DSL) chip set are proposed. Designed filters contain receiver continuous-time filters which are composed of lowpass and highpass functions. And their cutoff frequency are 138H1z and 1.1MHz respectively. A low-voltage gm-c integrator is improved and used to design filters. Desisned filters are verified by HSPICE simulation with the 0.25${\mu}m$ CMOS n-well parameter.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.05
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• pp.14-17
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• 1996

Evoked Potentials signals occur as a result of neuroelectric responses of the brain to sensory stimulation. In this paper, to analysis such signals we utilize a time-frequency analysis technique called wavelet transform. The wavelet analysis is performed based on a single prototype function,which can be thought of as a bandpass filter. Because the wavelet transform in a fine temporal analysis decomposes time-varying signals in EP into a dilated lowpass and a contracted highpass components, EP signal fetures can be obtained and analysed quantitatively at the levels of resolution. In the results, we analyze the VEP signal with the wavelet transform.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.10
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• pp.4745-4750
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• 2012

In this paper a $6^{th}$ 1MHz~30MHz bandpass filter for Power line communication(PLC) modem receiver is designed using current mode synthesis method which is good to design the low-voltage and low-power filter. The designed bandpass filter is composed of cascade connecting between $3^{rd}$ Butterworth highpass filter and $3^{rd}$ Chebychev lowpass filter. As a core circuit in the current-mode filter, a current-mode integrator is designed with new architecture which can improve gain and unity gain frequency of the integrator. The gain and the unity gain frequency of the designed integrator is each 32.2dB and 247MHz. And the cutoff frequency of the designed $6^{th}$ bandpass filter can be controlled to 50MHz from 200KHz according to controlling voltage and the power consumption is 2.85mW with supply voltage, 1.8V. The designed bandpass filter was verified using a $0.18{\mu}m$ CMOS parameter.