• Journal of the Korea Society of Computer and Information
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• v.15 no.10
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• pp.99-104
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• 2010

In this paper, the internal antenna for mobile communication handset which is able to control both coupling coefficient and resonant frequency without any major modification of radiator and ground plane of PIFA(Planner Inverted F Antenna). The resonant frequency as well as amount of coupling between feeding point and shorting post can be adjusted by changing inductance. Because the inductor is connected on shorting post where the strength of electric field is weak, the performance reduction of the proposed antenna is very small enough to neglect. For the variation of the inductance value within 3.3nH, the resonant frequency of antenna can have operating range of 1650MHz ~ 1830MHz. And as be increased the inductance, the coupling coefficient of antenna is over coupled. This means that it can be electrically controlled the resonant frequency and input impedance of antenna by inductance and minimized the mismatch loss. Size reduction of 10% for PIFA is obtained without any major modifications of antenna elements. For the frequency range from 1650 to 1830MHz, reduction of the measured antenna gain is within 0.93dB as varying the value of inductance from 0 to 3.3nH.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.7
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• pp.597-605
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• 2015

Negative impedance converter(NIC)-based non-Foster impedance matching is proposed for an electrically small antenna. The antenna considered in this work is a resistively loaded vee dipole(RVD) antenna, which has considerable reflection at the feed point because of its large negative input reactance. The non-Foster matching circuit built near the feed point consists of two-stage NIC circuit and a capacitor connected between the stages. The NIC is realized by using operational amplifiers(op-amps) and resistors. The circuit is designed by considering of the input impedance according to the finite open-loop gain of the practical NICs. The stability test of the impedance-matched RVD antenna is performed. The non- Foster matching circuit is implemented with the RVD antenna. The measured impedance demonstrates that the proposed non-Foster matching circuit effectively reduces the input reactance of the RVD antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.10-18
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• 2014

In this paper, we propose a new frequency reconfigurable dual-band antenna. By using an electronically compact eighth-mode substrate-integrated-waveguide(EMSIW) resonator, we have designed a compact antenna, which performs dual-band movement by additionally loading a complementary split ring resonator(CSRR) structure. The EMSIW and CSRR structures are designed to satisfy the bandwidths of 1.575 GHz(GPS) and 2.4 GHz(WLAN), respectively. We load the CSRR with a varactor diode to allow a narrow bandwidth and to enable the resonance frequency to continuously vary from 2.4 GHz to 2.5 GHz. Thus, we realize a channel selection function that is used in the WLAN standards. Irrespective of how a varactor diode moves, the EMSIW independently resonates so that the antenna maintains a fixed frequency of the GPS bandwidth even at different voltages. Consequently, as the DC bias voltage changes from 11.4 V to 30 V, the resonance frequency of the WLAN bandwidth continuously changes between 2.38 GHz and 2.5 GHz, when the DC bias voltage changes from 11.4 V to 30 V. We observe that the simulated and the measured S-parameter values and radiation patterns are in good agreement with each other.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.5
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• pp.407-411
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• 2005

A simulation investigation on the circular cylindrical reentrant cavity with axial ridges and a cylindrical circumferential slot is presented. This study indicates that by properly adjusting the dimensions of the ridge sand the slot, the size of the cavity can be miniaturized to around $\lambda_0$ The simulation results using CST MWS show good agreement with past theoretical predictions and provide useful insight into fundamental concerns associated with electrically small antennas.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.91-96
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• 2018

In this paper, dual axes waveguide rotary joint, which operates at high power and has low loss characteristic, is designed and fabricated for a Ka-band millimeter-wave small radar. Its electrical performance is verified through the S-parameter at room temperature, high power and operation temperature test. Rotary joint functionally consists of the mode converter transforming rectangular waveguide into circular waveguide and the choke at the rotation part. At the configuration design, linking a fixed transmitter to an antenna rotating dual axes electrically for minimum loss and light weight body are considered. In Fc(center frequency)${\pm}500MHz$, the designed rotary joint has VSWR 1.5:1 below return loss, -2.0 dB above insertion loss. It is found that rotary joint characteristics is similar to design results.