• Journal of IKEEE
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• v.27 no.1
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• pp.71-77
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• 2023

In this paper, a dual-band stopband frequency selective surface that can be applied to Wi-Fi 6E systems is designed to block external interfering signals with adjacent operating frequency spectrum in indoor wireless LAN environments. The proposed frequency selective surface structure has frequency blocking characteristics in the 2.4GHz and 6GHz bands, and is realized through a modified crossed dipole structure and an interlocking puzzle form between unit structures. The proposed structure is designed to have stable frequency response characteristics with respect to incident angle and polarization, and the experimental results show good agreement with the simulation results for incident waves from 0° to 45°.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.393-400
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• 2003

This paper deals with the design and manufacturing technique of EQM(Engineering Qualification Model) of input multiplexer(IMUX) for the Ku-band satellite transponder. Channel dropping method by circulator chain structure is adopted for demultiplexing each channel. External equalizers are attached behind channel filters fur reduction of group delay variation and amplitude variation simultaneously. Both channel filters and equalizers adopted dual-mode technique in design f3r mass and volume reduction. Channel filters are designed to have 8-pole elliptic response and equalizers to be of 2-pole reflection type. For good temperature stability characteristics, INVAR36 material is used for channel filters and external equalizers. Vibration test, Thermal Vacuum Test, and EMC test have been performed on input multiplexer and it is shown to be suitable for Ku-band satellite transponder.

• Journal of Broadcast Engineering
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• v.12 no.5
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• pp.516-524
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• 2007

In order to use limited frequency resources efficiently, a single frequency network using digital on-channel repeater(DOCR) has been studied and would be implemented. The DOCR generates strong pre-ghosts to ATSC DTV receivers. The forward filter of equalizer in ATSC DTV receivers compensates the distortion made by pre-ghosts. This process induces noise enhancement and colored noise, thereby results in the performance degradation. In this paper we propose to use a dual-feedback equalizer to combat strong pre-ghosts. The proposed equalizer has two feedback filters. One is the decision feedback filter and the other is non-decision feedback filter. The additional non-decision feedback filter decreases the noise by whitening the noise and preventing the generation of colored noise in pre-ghost channel. Thus the equalization technique of dual-feedback structure has performance enhancement in pre-ghost channel in comparison with conventional decision feedback equalizer(DFE). By simulation we analyzed the performance enhancements of DTV receiver using dual-feedback equalization structure.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.10
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• pp.138-142
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• 2016

Dual-energy digital radiography (DEDR) has been used for detecting lesions within the body using energy subtraction methods. The purpose of this study was to acquire optimal bone and tissue image by changing physical factors such as Tube voltage (kVp) and add filters, and then we compared with the predicted values using SRS-78 program and experimental results. For that purpose, we acquired images according to changes in physical parameters of various materials since we had to acquire the optimal bone and tissue image using energy subtraction. Used phantom consists of aluminum and polymethyl methacrylate (PMMA) and a comparison of image optimization was measured by contrast-to-noise ratio (CNR). In results, first of all, we confirmed that a subtraction image from 50 kVp image and 120 kVp image is optimal bone and tissue image. Also when we added a 10 mm Aluminum add filter, we expected it is a result of the optimal bone and tissue image. Besides, we confirmed these results are consistent with the predicted optimized condition by SRS-78 program.. In conclusion, we indicated that we can acquire optimal bone and tissue image by controling physical factors such as kVp, add filters through this study. Also we expected that DEDR will contribute to the field of medical imaging technology.

• Journal of IKEEE
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• v.13 no.4
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• pp.110-115
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• 2009

The motion compensation is the most time-consuming and complex unit in the H.264 decoder. The performance of the motion compensation is determined by the calculation of pixel interpolation. The quarter-pixel interpolation is achieved using 6-tap horizontal or vertical FIR filters for luminance data and bilinear FIR filters for chroma data. We propose the architecture for interpolation of luminance and chroma data in H.264 decoders. It is composed of dual-channel pipelined processing elements and can interpolate integer-, half- and quarter-pixel data. The number of the processing cycles is different depending on the position. The processing elements are composed of adders and shifters to reduce the complexity while the accuracy of the pixel data are maintained. We design interpolators for luminance and chroma data using Verilog-HDL and verify the function and performance by implementing using an FPGA.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.85-92
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• 2017

Recently, electric propulsion systems are used for unmanned surface vehicle, fish finder boat, etc. Some of these propulsion systems can be constructed of two electric motors and propellers for advanced impellent force. In this case, the speed difference generated between two propellers, namely, the synchronous error has a bad influence on the energy efficiency and course error. In this study, a synchronous control system is designed to restrain synchronous error caused by disturbance and mismatched dynamic characteristics. The control system is composed of the reference model, pre-filters, speed controllers, and synchronous controllers. The reference model is used for calculating the decoupled synchronous error and control input for each propulsion system. The pre-filters and speed controllers are designed in order that the propulsion system may follow the reference signal without overshoot and input saturation. And the synchronous controllers are designed from the viewpoint of stable and quick synchronization through root locus mothed approach. Finally, the simulation results show that the designed control system is effective for the disturbance.

• 전자공학회논문지 IE
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• v.47 no.2
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• pp.60-65
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• 2010

In this paper, we propose a dual-band filtering method optimized to DBO-CSS systems which are alternatively transmitted in low and high bands. The conventional channel filter which passes entire signal bandwidth causes a problem that excessive noise in neighboring sub-band is added while one of signals in two sub-bands is received. The dual-band filtering proposed in this paper can overcome the performance degradation in the conventional filtering method without increase of hardware complexity. The proposed method is based on two filters to be matched with DBO-CSS signals receiving alternatively and can exclude the undesired noise in neighboring sub-band. Simulation results for the proposed method show better performance about 2.5dB than the conventional one.

• Journal of Advanced Navigation Technology
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• v.15 no.1
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• pp.97-103
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• 2011

This paper presents a dual-band balanced mixer using nonlinear phase characteristic of composite right/left-handed (CRLH) transmission line. This metamaterial structure provides low LO leakage and high RF to LO isolation without additional filters for LO and RF path. The balanced mixer consists of balun and Wilkinson divider with dual-band characteristic of unit-cell which behaves like a CRLH metamaterial. Experimental results are used to verify the proposed metamaterial functions. The balanced mixer design results in an operating frequency of 870 MHz and 1660 MHz with an optimum mixer conversion loss of 15.2 dB at 870 MHz and 21.2 dB at 1660 MHz.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.7 s.349
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• pp.162-169
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• 2006

A Micorstrip Bandpass Filter Using DBRs for WLAN ($2.3{\sim}2.4GHz$) applications is designed and an EBG structure is employed in the ground plane of the filter to suppress the stopband responses of the filter. The number of DBRs is chosen as two in consideration of low insertion loss and small size of two filter. The center frequency of the filter to be designed is 2.35GHz and its bandwidth is 140MHz. The responses of two kinds of DBR filters (one with EBG and the other without EBG) are calculated and compared with the measurements. The experimental results are in good agreement with the calculations: The bandwidth and insertion loss of the filter with EBG structure are 3.8% and 1.7dB respectively, while those of the filter without EBG structure are 7% and 1.23dB. It is shown that the insertion loss of the filter is increased and its bandwidth is deceased due to the EBG structure. Also the stopband responses of the filters with EBG structures are shown to be much improved compared with those without EBG.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.599-605
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• 2003

A dual-mode asymmetric canonical filter is widely used in an input demultiplexer for satellite transponder. This paper deals with a simple synthesis method fur an asymmetric canonical filter. The coupling matrix of an asymmetric canonical filter is obtained by applying plane rotation technique to the coupling matrix of a symmetric canonical filter. This paper gives a list of pivots and rotation angles to obtain the coupling matrix of asymmetric canonical structure filters. The coupling matrix of 8th and 10th order asymmetric canonical filter is obtained by this proposed method. It is shown that the frequency response of asymmetric canonical filter is identical to that of symmetric canonical filter.