• Journal of the Korean Institute of Navigation
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• v.23 no.1
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• pp.23-28
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• 1999

With a rapid progress in electronic industry we enjoy various conveniences of life. As many kinds of information equipments are supplied even to most of individuals as to be called an information society, we are exchanging much information with one another surprisingly. Consequently the occupation density of microwave frequency band is highly increased, and electromagnetic environment is getting more seriously bad. It often gives fatal blow to even human life and thus becomes serious social problems. Electromagnetic wave absorbers for anechoic chamber are needed to broaden the effective frequency bandwidth, reduce the thickness, and decrease the weight. There are various absorbers proposed for the above conditions, but they could not decisively solve it the alone requirements. The Electromagnetic wave absorber made by a conventional ferrite tile has, for example, broadened the useful frequency bandwidth by the way of forming air layer(practically use urethane foam, etc.) on the ferrite tile. Therefore, an air layer is formed between a reflection plate and a sintered Ni-Zn ferrite tile of 7 mm in thickness, which has reflectivity less than -20 dB from 30 MHz to 400 MHz in bandwidth. Accordingly, in this paper, a broadened electromagnetic wave absorber are designed, which has the reflection characteristics less than -20 dB from 30 MHz to 6,000 MHz in the bandwidth. Then we achieved the goal by design the inserting square Ferrite Cylinders with the thickness less than 17.5 mm on existing grid type Ferrite absorber. The purpose of this research is on the development of very wide-band electromagnetic absorber for a universal anechoic chamber for measuring radiated electromagnetic wave or immunity of electronic equipments, GTEM-cell, wall material for preventing TV ghost, etc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.7A
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• pp.511-519
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• 2003

In this paper, to achieve a broad-band and high-gain antenna, we thus designed and analyzed the CRLPDA(Corner Reflector Antenna feeding by Log-Periodic Dipole Antenna) made up of 90$^{\circ}$corner reflector, which is trough-reflector type installed a planar reflector at the folded line. CRLPDA for operating frequency band of 1,400 MHB ~ 2,400 MHz was designed and radiation characteristics of the designed antenna were analyzed by moment method. To verify the analysis results, CRLPDA was fabricated and the calculated results were compared with the measured results. The measured results showed good agreement with the calculated results. As the result of measurements, bandwidth(VSWR＞2) for 1,000 MHz was achieved and gain was 13 dBi.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.827-836
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• 2001

The L-shaped strip is shown to be an attractive feed for the thick microstrip antenna (thickness around 10% of the operating wavelength). The L-strip incorporated with the radiating patch introduces a capacitance suppressing some of the inductance introduced by the strip itself. In this paper, a wideband microstrip patch antenna fed by L-strip for the PCS (1,750~1,850 MHz) and IMT-2000 (1,920~2,170 MHz) broad-band is presented. A two-element array fed by L-strip is also proposed. Both the antennas have stable radiation patterns across the passband. The impedance bandwidth is over 31% (VSWR < 1.5, 615 MHz) of the center frequency. Moreover, both the antennas have about 7 dBi average gain.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.399-409
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• 1998

In this paper, the broad-band design theory for weakly-coupled Tap-Off for CATV systems has been described and the transmission line impedance matching method has been proposed. The fabricated weakly-coupled Tap-Offs based on the above theory and method have been much improved in the frequency characteristics compared with conventional ones. Thus, the useful bandwidth of weakly-coupled Tap-Offs have been extended from 5 to 2000 MHz. It is also recognized that turn numbers of the coils composing the transformer are not integers but 0.9, 1, 1.9, 2, 2.9, etc., in the actual circuits. Further, the practical measurements of the frequency characteristics for a fabricated weakly-coupled Tap-Off show very good agreements with theoretical results, and hence, the validity of the proposed design theory and transmission line impedance matching method have been confirmed.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.297-300
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• 2006

In this paper, the EM wave absorbers were designed and fabricated for X-band sensors using Carbon of dielectric material with CPE. The complex relative permittivity of samples is calculated by the measured S-parameter data. We simulated the double-layered type EM wave absorber with broad bandwidth using the measured complex relative permittivity by changing the thickness and layer, which was fabricated based on the simulated design. The fabricated EM wave absorber consist of 1mm first layer sheet facing metal with Carbon composition ratio 70 vol% and 1.5 mm second layer sheet with Carbon composition ratio 60 vol%. The comparisons of simulated and measured results are good agreement. As a result, the optimized absorption ability of double-layered type EM wave absorber with thickness of 2.5 mm is higher than 10 dB from 7.8 GHz to 13.3 GHz.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.84-87
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• 2000

In this paper, a high gain-broad bandwidth MMIC distributed amplifier was designed using cascaded single section distributed amplifier configuration. The PHEMT for this studies was fabricated at our lab The PHEMT has a 0.2 $\mu\textrm{m}$ gate length. a 80 $\mu\textrm{m}$ unit gate width and 4 gate fingers. A designed MMIC amplifier have higher S$\sub$21/ gain than the common distributed amplifier using the same number of active devices. From the simulated result, we obtained that the S$\sub$21/ gain of DC ∼ 20 GHz bandwidth was 15.6 dB and flatness was ${\pm}$0.9 dB, and input and output reflection coefficient were lower than -8 dB. The simulated gain shows an improvement 7.3 dB compared with those of conventional distributed amplifier. And the chip size is 2.0 ${\times}$ 1.2 $\textrm{mm}^2$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.7
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• pp.653-660
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• 2004

This paper presents monopole antenna with electromagnetically coupled feed and its equivalent circuit model. The proposed structure is consists of a rectangular disk-loaded monopole and a probe with rectangular spiral strip line feed. The rectangular disk-loaded monopole is represented by parallel RLC resonant circuit and the probe with rectangular spiral strip line feed is represented by series RLC resonant circuit. Therefore broad bandwidth can be achieved through electromagnetic coupling between these structures that generate two resonances within close frequency range. The antenna with electrical dimensions of only 0.075λ$\sub$0/${\times}$0.075λ$\sub$0/${\times}$0.075λ$\sub$0/ has 16.5 % fractional bandwidth for VSWR$\leq$2 at a center frequency of 2.038GHz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.432-436
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• 1999

The development of Electromagnetic Communication technology have made our life abundant. However, the countermeasure of EMI(Electromagnetic Interference) are more important socially as increase of a main cause on electromagnetic waves occurrence. It is required that the absorbing ability of an electromagnetic wave absorber is above 20 dB, the bandwidth of which is required from 30 MHz to 1,000 MHz for satisfying the international standard about EMI and also will be required from 30 MHz up to 5,000 MHz in the bandwidth. In this paper, we proposed the square projection type absorber satisfying the above requirements and carried out broadband design using the equivalent material constants method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1183-1187
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• 2005

In this paper, a weathercock-shaped microstrip patch antenna for application in 5.25GHz band wireless LAN is designed and fabricated. To obtain sufficient bandwidth in VSWR<2, the T-slot is inserted on the patch, the coaxial probe source is used. The measured result of fabricated antenna obtained 350MHz or about $7.62\%$ bandwidth in VSWR<2 referenced to the center frequency, the gain of 5.25${\~}$6.70dBi. The experimental 3-dB beam width is shown to be broad across the pass band in azimuth and elevation at $80.32^{\circ}$ and $83.88^{\circ}$, in several.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.65-71
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• 2009

In this paper, we propose an aircraft on-glass antenna for FM radio reception. To obtain broad matching bandwidth, we employed a multiple loop as the basic antenna structure, and the shape of the loops mimics the frame of a window in order to ensure pilots' field of view as large as possible. The detailed design parameters of the multi-loop structure were determined using a Pareto genetic algorithm with a full wave EM simulation tool. The optimized on-glass antenna was built and installed on a Korean utility helicopter (KUH) The measurement results showed a half power matching bandwidth of about 63.3 %, average vertical bore-sight gain of about -12.98 dBi in the FM band.