• Journal of the Korean Institute of Telematics and Electronics
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• v.13 no.5
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• pp.1-8
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• 1976

Microwave GaAs Metal Semiconductor Field effect Transistors (MESFET) with the gate-length of two micrometers are investigated. The scattering parameters of the transistors have been measured from 1GHz to 2GHz by Hp8545 Automatic network analyzer. From the measured data, an equivalent circuit is established which consists of an ntrinsic and. extrinsic transistor elements. In this paper, GaAb MESFET Amplifier is used in conjunction with conventional microstrip techniques to match into a 50 ohms high input/output impedances system. We found that Power gain is less than 8dB and VSWR is less than 1.5 in L-Band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.895-903
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• 2007

Design equations of DC blocks terminated in arbitrary impedances are newly suggested and a microstrip DC block is tested for the perfect matching. The DC block is a two-port passive component and the power excited at a port is transmitted into another port. However, all the excited power at the input can not be delivered to the output and therefore most of the conventional DC blocks can not be perfectly matched with arbitrary termination impedances. To solve the matching problem, its one-port equivalent resonant circuit model, front which design equations can be derived, is newly suggested. Using the derived design equations, any DC block can be designed, perfectly matched without any restriction of coupling coefficients. To verify the derived design equations, measurements were carried out and the results are in good agreement with prediction, showing insertion and return losses at 4.1 GHz are 0.82dB and -31dB, respectively.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.1
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• pp.70-78
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• 1995

In order to implement broadband RAM's(Radar Absorbing Materials) made up of multiple dielectricl layers, the design variables such as the dielectrci constaints, the depths and the loss tangents of dielectric are optimized. The wave impedances regarding the reflective wave are found in dielectrics, input impedances and reflection coefficients with multiple dielectric layers are derived from the transmission line circuit theory. Finally, minimum average reflective power and optimum design variables are obtained by applying the numerical technique, called modified Powell method. In case of four dielectric layers with inequality constraints in design variables, a quite favourable and feasible result with the total depth of 1.1 cm, the average reflective power of 0.85% over the bradband frequency range is obtained for a specific example.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.78-81
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• 2006

In this paper, the investigation of characteristic impedance on low voltage distribution system is described The residential area of LV distribution systems is researched for the modeling. At frequency range from 1MHz to 30Mhz, the input characteristic impedances of low-voltage distribution network are obtained with experiments. The low-voltage distribution system based on the model is built at the laboratory building. S parameters are measured by performing experiments. Finally, the characteristic impedances are reported.

• 전기의세계
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• v.18 no.5
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• pp.12-19
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• 1969

The sensitivity of transistorized d.c. amplifiers is mainly limited by drift at operating point caused by ambient temperature changes. A chopper-type transistorized amplifier is necessary to obtain a high sensitivity without recourse to drift compensation which requires the adjustment of several balancing controls. A chopper-stabilized system consisting of an electro-mechanical chopper for input and output and a high-gain a.c. amplifier is designed and analyzed. The gain of the a.c. amplifier, expressed as the ratio of voltages, is larger than 80db in the band of 50C/S - 100KC/S. The complete system gives an open-loop gain of 68db at direct current. The offset voltage is 20.mu.V referred in input and the voltage drift at the input is less than 10.mu.V/hr at 25.deg.C. This type of amplifier would be useful for the high-gain transistorized d.c. amplifier for analog computers. Also, due to the high input impedance, it is suitable for amplification of signals from wide range of source impedances.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.2
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• pp.18-25
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• 1994

In this papaer, the input impedance of the rectangular microstrip patch antennas with the multilayered structure is analysed by using the moment method technique in the spectral domain. The analysis is carried out for two different feeding structures : directfeeding structure and electromagnetic-feeding structure. In order to obtain the accurate input impedance, the current distribution on the microstrip feed line is modeled by the quasi-TEM travelling wave and the PWS(piecewise sinusoidal) mode. The input impedances of the designed microstrip antennas are measured and compared with the calculation. which shows a good agreement.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.271-274
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• 2000

In this paper, the distortion of an electrical pulse with rise/fall time resulting from dispersion and reflection as it propagates along a tapered microstrip line is investigated, and the delay time and distortion rate with respect to input and load impedances are analyzed on triangular and exponential tapered lines and analyzed the influence of the reflection and frequency dispersion on the distorted voltage wave in the tapered lines. The observed overshoot in front of the distorted wave is caused due to the frequency dispersion and the sustained tail of that comes from the reflection in the tapered line.

• Journal of KSNVE
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• v.6 no.6
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• pp.749-754
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• 1996

In this paper, a design method of matching layers is presented for the sandwich type broad band underwater acoustic vibrators. The characteristic impedances of matching layers are determined to be matched to the characteristic impedance of head mass material. For the dynamic characteristic analysis of the sandwich type transducers, one dimensional FEM technique is also introduced. A test vibrator with the quarter wave matching layers has been designed to verify the proposed method. And the wide band characteristics of the input impedance and transmitting voltage response (TVR) are investigated.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.135-138
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• 1999

In this paper, we designed each matching networks by given input and output impedances of power amplifiers. Mearsured results for IMD and gain flatness are -30㏈c and $\pm$0.2㏈ with 38㏈m output power PEP of PTE10119 at 2.10-2.20㎓ and are -30㏈c and $\pm$0.4㏈ with 42㏈m output power PEP of MRF284 at same frequency range.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.7
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• pp.9-16
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• 1998

The nput impedance of a patch-tupe dipole antenna for GPR is calculated by using the moment methods in case that the surrounding medium is modeled on a multi-layer structure consisting of lossy dielectircs. When the cone-type function equivalent to pulse basis function in employed, one of the double integration can be performed analytically. The remaining integration is excuted numerically in a finite rnage and analytically in asymptotic region. The current distributions and input impedances of those antennas are calculated numerically.