• Journal of Magnetics
• /
• v.18 no.2
• /
• pp.178-182
• /
• 2013

We have developed a new non-conventional electron paramagnetic resonance (EPR) spectrometer, in which no resonant cavity was used. We previously demonstrated a wide frequency range operation of an EPR spectrometer using two loop antennas, one for a microwave transmission and the other for signal detection [1]. In contrast to Ref. [1], the utilization of a microstrip antenna as a transmitter enhanced a capability of wide-band operation. The replacement of conventional capacitors with varactor diodes makes resonance condition easily reproducible without any mechanical action during tuning and matching procedure since the capacitance of the diodes is controlled electronically. The operation of the new EPR spectrometer was tested by measuring a signal of 1,1-diphenil-2-picrylhydrazyl (DPPH) sample in the frequency range of 0.8-2.5 GHz.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.12A
• /
• pp.1759-1765
• /
• 2000

공기 갭을 갖는 일축성 기판위에 마이크로 패치 안테나의 공진 주파수가 full-wave approach와 모멘트 계산법을 이용하여 연구되었다. 일축성 매질내의 구성관계식을 통하여 제안된 구조에서의 파수영역 다이애딕 그린 함수를 유도하였으며 이 결과로부터 전계 적분 방정식을 수식화하였다. 갤러킨 모멘트법을 사용하여 전계 적분 방정식을 이산화 하였으며 기저함수의 선택은 수치 해석적 수렴을 고려하여 패치 위의 실제 전류밀도와 가장 유사한 형태인 정현적 기저함수를 선택하였다. 전사모의 실험 결과의 타당성을 검증하기 위해서 기존의 결과와 비교하여 일치된 결과를 얻었다. 공기 갭의 두께와 패치 길이, 이방성 비의 변화에 따른 공진 주파수가 제시되고 분석되었다.

• Proceedings of the IEEK Conference
• /
• 2000.07a
• /
• pp.175-178
• /
• 2000

The resonance characteristic of microstrip antenna with an airgap between the substrate layer and ground plane is investigated. The study is performed by using a rigorous Green’s function formulation in the spectral domain and Galerkin’s moment method calculation. The numerical convergence using sinusoidal basis functions, the unknown surface current distribution in the rectangular patch, is discussed. Numerical result for the effects of airgap and patch length on the complex resonant frequencies of the rectangular microstrip structure are also presented

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.2254-2256
• /
• 2000

This paper presents an implantable telemetry LC resonance-type pressure sensor for the measurement of the ventricle pressure. This sensor consists of a capacitor and an inductor. This resonant circuit is magnetically coupled with an external antenna coil. The resonance frequency of the circuit decreases as the sensor capacitance is increased by the applied pressure. The inductance and the capacitance are 428nH and 0.98${\mu}F$, respectively. The resonance frequency is 245.7MHz when the differential pressure is zero. The sensitivity of the sensor is 9.477kHz/Pa.

• Journal of Advanced Navigation Technology
• /
• v.22 no.5
• /
• pp.449-455
• /
• 2018

For the size reduction, we propose a microstrip-fed monopole antenna with half X-slot in the radiation patch and cover WLAN dual band 2.4 GHz band (2.4 ~ 2.484 GHz) and 5 GHz band (5.15 ~ 5.825 GHz). The frequency characteristics such as impedance bandwidth and resonant frequencies were satisfied by optimizing the numerical values of various parameters, while the reflection loss in 5 GHz was improved by using defected ground structure (DGS). The proposed antenna is designed and fabricated on a FR-4 substrate with dielectric constant 4.3, thickness of 1.6 mm, and size of $24{\times}41mm^2$. The measured impedance bandwidths (${\mid}S_{11}{\mid}{\leq}-10dB$) of fabricated antenna are 450 MHz (2.27 ~ 2.72 GHz) in 2.4 GHz band and 1340 MHz (4.79 ~ 6.13 GHz) in 5 GHz band which sufficiently satisfied with the IEEE 802. 11n standard in dual band. In particular, radiation patterns which are stable as well as relatively omni-direction could be obtained, and the gain of antennas in each band was 1.31 and 1.98 dBi respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.12
• /
• pp.1327-1336
• /
• 2012

In this paper, the dual-faced monopole antenna, which is arranged by numerous rectangular ring patches in sequence for the multi-bands is proposed. The ring type structure of the patch can be increased the bandwidth. Therefore the bandwidth and beam width are improved by using multiple arrayed patches. When the ring type patches are inserted serially, the resonance frequencies are occurred by the current flow from the first ring patch. It is possible because the gap between the patches is very narrow. In addition, if the patches are composed on the same plane as the feed-line, fabrication could be very difficult because the gap between the patches is extremely narrow. The thickness and permittivity of the antenna, moreover, are very important parameters because both sides of the substrate are used. We finally found the optimal thickness and permittivity to generate the coupling effect by simulation. All patches are consisted of 4-steps which the patch size was decreased 85 % by each step. In conclusion, the resonant frequency bands are 1.75~2.6 GHz(850 MHz), 3.24~3.46 GHz(220 MHz), 3.8~4.0 GHz(200 MHz), and 4.4~4.9 GHz(500 MHz).

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.37 no.2
• /
• pp.83-90
• /
• 2000

In this paper, a stacked circular-disk microstrip 1${\times}$4 array antenna was designed and manufactured and tested to apply in next generation mobile communication, on IMT-2000 system(up-link: 1.885 GHz∼2.025 GHz, down-link: 2.11 GHz∼2.2 GHz) base station which has dual frequency, broadband and high-gain characteristics. The experimental results are as follows : resonant frequency of 1.885 GHz and 2.178 GHz VSWR (1.064 , 1.432), return loss (-30.19 dB , -24.99 dB), band width (VSWR<2) are 402 MHz, -3dB beam width at radiation pattern are ${\alpha}$E-16.8$^{\circ}$, ${\alpha}$H-69$^{\circ}$(1.885 GHz) and ${\alpha}$E-l5.2$^{\circ}$, ${\alpha}$H-51.5$^{\circ}$(2.178 GHz), gain(13.7 dBi∼15.21 dBi).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.10 no.2
• /
• pp.277-290
• /
• 1999

A simulation using the finite-difference time-domain method to analyze the electromagnetic interactions between a cellular phone and the human body was conducted, and a synthesis of a bone-equivalent material to make a human head phantom was performed. A test model of the cellular phone was fabricated to measure its reflection coefficient and radiation pattern in the free space. Various effects of the human body on the characteristics of the phone, such as input impedance, reflection coefficient, radiation pattern, and radiation efficiency are analyzed as the distance between the head and the phone antenna varies. When the phone was operated close to the head, the resonant frequency of the antenna decreased by up to 12%. With the output power of 0.6W, as long as the distance was larger than 30mm, the 1-g averaged peak SAR was below the ANSI/IEEE safety guideline, 1.6 W/kg. To synthesize the bone-equivalent material, an epoxy with hardener and a graphite powder were used as basis ingredients, and a small amount of a conducting epoxy was added to control the conductivity of the material. A material having a relative permittivity of 18.04 and a conductivity of 0.347, which are close to those of the bone at 850 MHz, was synthesized.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.61 no.12
• /
• pp.1892-1897
• /
• 2012

Modern electronic circuits are of importance for the function of communication, traffic systems and security systems. An intentional threat to these systems could be of big casualties and economic disasters. This study has examined susceptibility of electronic circuits inside the cavity by HPEM(High Power Electromagnetics). The UWB measurements were done at an anechoic chamber using a RADAN voltage source, which can generate a transient impulse of about 200 kV. The HPEM wave penetrated inside the metal case appeared to the long damped ringwave of pulse length compared with the incident wave. In addition, the resonant frequency generated inside the metal case occurred primarily in the range of 1~3 GHz. The frequency band of 1~3 GHz was influenced on the electronic circuit, which was confirmed by an external antenna and an internal absorber. The electronic circuit was influenced by HPEM infiltrated into the cavity at the 86 kV/m out of the metal cases. Also in case of an absorber the susceptibility of an electronic circuit was smallest among other cases(aperture, antenna). It is considered that absorber has a function absorbing electromagnetic wave infiltrated into the cavity and simultaneously limiting resonance by varying a boundary condition inside the cavity. Based on the results, electronic equipment systems could be applied to protection that has suited system requirements.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.12C
• /
• pp.1606-1616
• /
• 2004

This paper introduces a technique for generating an appropriate template signal via modeling of minimum-phase stable ARMA (Auto-Regressive Moving Average) system for coherent impulse communication systems. It has been well known that the transmitted impulse signal becomes deformed because of dispersive and resonant characteristics. Accordingly, in spite of using ideal template signal at the correlator, these impairments degrade overall performance attributed to low level of coherence. To increase the degree of coherence, our proposed scheme realizes A3U system derived by Gaussian pulse signal, which simulates the overall characteristic of transfer function in between transmit and receive wideband antennas so as to generate an appropriate template signal in a form of output. The performance of proposed scheme will be shown in results from computer simulations to verify its affirmative impact on impulse communication system with regarding several distinctively shaped antennas.