• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.3
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• pp.319-332
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• 2014

Insertion loss is used as the character to express the efficiency of EMI filter. In this paper, we studied the better method that can measure the insertion loss of EMI filter exactly than the original method. For the achievement of this, the method measuring both common mode(CM) and differential mode(DM) insertion loss with arbitrary input/output impedance is accomplished using a 4-ports S-parameters system for consideration of unbalanced factor. Using this method, when input/output used in specific system is known, CM/DM insertion loss of EMI filter inserted in the system can be calculated. Finally, we applied 4-ports modeling method to 'X/Y capacitor part' and suggested the algorithm for selecting suitable the value of Y-capacitor using mixed mode S-parameters and mixed mode chain S-parameters.

• Journal of the Korean Institute of Telematics and Electronics
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• v.15 no.2
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• pp.15-18
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• 1978

The impedance step up ratio and variations of input admittances of the folded dipole antenna are calculated by the moment method. The results are compared with those calculated by Guertler's formula. The input admittance of the folded dipole antenna has the maximum value at the frequency somewhat lower than the resonance frequency and its susceptance which has periodic properly is null lot several different frequencies if radius ratio of two elements is not very large. Frequency characteristic of folded dipole antenna is improved when its radius ratio is increased.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.673-675
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• 2011

본 논문은 GHz 대역 소자 응용을 위한 프로그램 가능 보상 회로를 제안한다. 이러한 회로는 5.2GHz대에서 동작하는 고주파 회로의 칩 제작과정에서 예기치 않게 발생한 미세한 PVT (공정, 전압, 온도) 변동을 검출하여 미세 변동된 회로 성능 변수들을 자동으로 보상한다. 자동으로 보상 가능한 고주파 회로 성능 변수들은 중요한 요소인 입력 임피던스, 전압이득과 잡음지수를 포함한다. 이러한 회로는 미세 변동을 자동으로 보상할 수 있도록 고주파 신호를 직류 신호로 변환하는 DFT (Design-for-Testability) 회로를 포함한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1134-1138
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• 2008

In this paper, the synthesis of distributed impedance transformers is presented that is essential for power divider design, whereby a broadband power divider is designed. Transfer functions of distributed transformers are synthesized with Chebyshev approximation, and their element values are calculated for various minimum insertion losses(MIL) and ripples. Desired performance of transformers is obtained by optimizing MIL's and ripples of a transfer function. As an application example, a four-way power divider is designed that operates over 2 to 8GHz frequency range. Experimental results are shown to approach the design performance, so transformer design by distributed network synthesis proves to be useful to power divider design.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.455-464
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• 2005

We have proposed a model of a thermal voltage converter(TVC) using the trans-impedance of lossy transmission line and developed a calculation program for ac-dc transfer difference of the TVC. The proposed TVC consists of a thermo-element(f) and a range resistor wire connected in series at the center of coaxial cylinder. The range resistor wire is used to extend the measurement range of the n. The calculated ac-dc transfer differences of the proposed TVC by simulation agree well with the measured values within the uncertainties. The simulated and measured values are agreed within $1{\mu}V/V$ from 40 Hz to 10kHz, within $5{\mu}V/V$ from 20kHz to 100MHz, and within $12{\mu}V/V$ from 200kHz to 1 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.933-940
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• 2017

A wireless power transfer system with a negative impedance converter(NIC) was designed and tested. The system was investigated to identify the effects of ferrites and conductors. To improve the power transfer efficiency(PTE), the Q-factor of the transmitter was enhanced by the negative resistance generated by the NIC. The NIC was composed of an Op-Amp and resistors. The negative resistance was obtained with respect to a resistor connected in a feedback loop. The dimension of the Tx coil was $250mm{\times}250mm{\times}0.8mm$. The impedance and Q-factor were $31+j1874{\Omega}$ and 60, respectively. The negative resistance was selected to be $30{\Omega}$, and the Q-factor was increased to 900 by reduction of the transmitter resistance, which was about 15 times higher than that of a conventional transmitter. The measured PTE was greatly improved in comparison to that of a conventional system. These results demonstrate that the PTE is enhanced by using the NIC.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.15-23
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• 1998

In this paper, distributed mixer is studied at microwave frequency. The circuit of distributed mixer composed of gate 1,2, drain transmission lines, matching circuits in input and output terminal, DGFET's. For impedance matching of input and output port at higher frequency, image impedance concept is introduced. In distributed mixer, a DGFET's impedances are absorbed by artificial transmission line, this type of mixer can get a very broadband characteristics compared to that of current systems. A RF/LO signal is applied to each gate input port, and are excited the drain transmission line through transcondutance of the DGFET's. The output signals from each drain port of DGFET's added in same phases. We designed and frabricated the distributed mixer, and a conversion gain, noise figure, bandwidth, LO/RF isolation of the mixer are shown through computer simulation and experimentation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.5
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• pp.10-17
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• 1989

A new design method of lossy matching network for the microwave broadband ampilfier is presented by using seattering parameters instead od modeling of transistor. A lossy matching network is represented as the combination of 2 lossless networks between which lossy serial or parallel immittance is inserted without using specific topology, and so many useful matching cireuits can be realized. Also it is shown that linear transforming relation exists between gain and reflection coefficient of the amplifier, and the transforming equation is derived using scattering parameters. With this equation some constant gain circles can be drawn on reflection coefficient plane to get adequate reflection coefficient and gain. And since the relations between amplifier gain/reflection coefficient and the immittance of passive element are bilinear transformations. constant gain or reflection coefficients circles. Illustrative examples are presented to show the usefulness of proposed method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.6
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• pp.602-612
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• 2013

In this paper, a design and fabrication of miniaturized 5.3 GHz reflection type $360^{\circ}$ analog phase shifter with branch line coupler and $360^{\circ}$ variable reactance load. In order to miniaturize phase shifter, novel branch line coupler is proposed. The novel branch line coupler is miniaturized using transformation of transmission line to T and ${\pi}$ type equivalent circuit. The miniaturized branch line coupler has small size of above 50 % compared with conventional branch line coupler. For wide phase shift range, $360^{\circ}$ variable reactance load structure is adopted. Especially, the structure was improved for linear phase shift by adding transmission line which acts as an impedance transformer. The improved structure was miniaturized using the equivalent lumped-element of transmission line. The fabricated phase shifter with $15{\times}15mm^2$ shows wide phase shift of above $480^{\circ}$, the insertion loss of -4~-6 dB and the reflection loss of below -20 dB at 5.3 GHz under 0~10 V control voltage range.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.2
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• pp.239-244
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• 2004

In this paper, we have developed a frequency mixer which can be used as a microwave phase conjugator in the LS band retrodirective antenna system. The mixer as a phase conjugator must have an If signal of which frequency is nearly as high as that of an RF signal, so this fact brings difficulty in the combination of input signals and the design of impedance matching circuit. The circuit configuration is chosen to be of the gate mixer using a pseudomorphic HEMT device. The operating frequencies are 4.00 ㎓, 2.01 ㎓, and 1.99 ㎓ for LO, RF, and IF, respectively. Conversion gain is measured to be 12.5 ㏈ and 1 ㏈ compression point -34 ㏈m at the LO power of -7 ㏈m. The mixer fabricated in this research is the single-ended type, where RF leakage signal appears inevitably at the If port because RF and If frequencies are almost the same. The circuit topology suggested here can be applied directly to the design of balanced-type mixers and phase conjugators.