• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.1
• /
• pp.76-84
• /
• 2012

In this paper, two kinds of E-plane microstrip-to-waveguide transitions are optimally designed and fabricated for combining output power from multiple small-power amplifiers in a WR-28 waveguide because conventional K connectors cause unnecessary insertion loss and adaptor loss. The transition design is based on target specifications such as a center frequency of 35 GHz, bandwidth of ${\pm}500MHz$, 0.1 dB insertion loss and 20 dB return loss. Performance variation caused by mechanical tolerance and assembly deviation is fully evaluated by three dimensional electromagnetic simulation. The fabricated back-to-back transitions with 16 mm and 26.57 mm interstage microstrip lines show insertion loss per transition of ~0.1 dB at 35 GHz and average 0.2 dB over full Ka band. Also the back-to-back transition shows return loss greater than 15 dB, which implies that the transition itself has return loss better than 20 dB.

• Polymer(Korea)
• /
• v.27 no.3
• /
• pp.201-209
• /
• 2003

DC and AC electrical conductivity and electromagnetic interference shielding effectiveness of milled carbon fiber/nylon composites were investigated with the kind of nylon matrix. Percolation transition at which the conductivity is sharply increased was observed at about 7 vol% of milled carbon fiber. Nylon 46 as a matrix was more effective to obtain high electrical conductivity than nylon 6, and the difference in conductivity was occurred by the treatment of coupling agent. Frequency dependence of AC conductivity could be explained by relaxation phenomenon at just below percolation and resonance phenomenon at 40 vol% of carbon fiber, respectively. Negative temperature coefficient phenomenon was found in all composites. Electromagnetic interference shielding effectiveness was increased with the concentration of carbon fiber. At a high conductivity region the return loss was more dominant to the total shielding effectiveness than the absorption loss.

• Earthquakes and Structures
• /
• v.19 no.5
• /
• pp.379-393
• /
• 2020

The purpose of this study is to first evaluate the seismic behavior of ageing arch bridges by using the Intensity Measure - based demand and DCFD format, which is referred to as the fragility-hazard format. Then, an investigation is performed for their seismic vulnerability. Analytical models are created for bridges concerning different features and these models are subjected to Incremental Dynamic Analysis (IDA) analysis using a set of 22 earthquake records. The hazard curve and results of IDA analysis are employed to evaluate the return period of exceeding the limit states in the IM-based probabilistic performance-based context. Subsequently, the fragility-hazard format is used to assess factored demand, factored capacity, and the ratio of the factored demand to the factored capacity of the models with respect to different performance objectives. Finally, the vulnerability curves are obtained for the investigated bridges in terms of the loss ratio. The results revealed that decreasing the span length of the unreinforced arch bridges leads to the increase in the return period of exceeding various limit states and factored capacity and decrease in the displacement demand, the probability of failure, the factored demand, as well as the factored demand to factored capacity ratios, loss ratio, and seismic vulnerability. Finally, it is derived that the probability of the need for rehabilitation increases by an increase in the span length of the models.

• Journal of electromagnetic engineering and science
• /
• v.11 no.2
• /
• pp.83-90
• /
• 2011

In this paper, we present the design method for a low-pass type inverter, which can effectively suppress the spurious response associated with band-pass filters. The inverter has a length of ${\lambda}/4$ and employs not only a stepped-impedance configuration but also asymmetrical and bending structures in order to improve frequency selectivity and compactness. The inverter is applied as an impedance/admittance inverter to the ultra-wideband (UWB) band-pass filter. The UWB band-pass filter configuration is based on a stub band-pass filter consisting of quarter-wavelength impedance inverters and shunt short-circuited stubs ${\lambda}/4$ in length. The asymmetrical stepped-impedance low-pass type inverter improves not only the spurious responses, but also the return loss characteristics associated with a UWB band-pass filter, while a compact size is maintained. The UWB band-pass filter using the proposed inverters is fabricated and tested. The measured results show excellent attenuation characteristics at out-band frequencies, which exceed 18 dB up to 39 GHz. The insertion loss within the pass-band (from 3.1 to 10.6 GHz) is below 1.7 dB, the return loss is below 10 dB, and the group delay is below 1 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.3 s.118
• /
• pp.257-264
• /
• 2007

In this paper, we have designed and fabricated a wide-band and high gain antenna which can integrate a standard of IEEE 802.1la$(5.15\sim5.25\;GHz,\;5.25\sim5.35\;GHz,\;5.725\sim5.825\;GHz)$. We inserted a parallel dual slot into a rectangular patch to have wide-band, and we offset an element of capacitance from the slot by using coaxial probe feeding method. We also designed a converter of $\lambda_g/4$ impedance with taper type line so that wide-band impedance can be matched easily. We finally designed structure with $2\times2$ array in order to improve the antenna gain, and the final fabricated antenna could have a good return loss(Return loss$\leq$-10 dB) and a high gain(over 13 dBi) at the range of $5.01\sim5.95\;GHz(B/W\doteqdot940\;MHz)$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.11 no.5
• /
• pp.748-754
• /
• 2000

A novel single feed wide band CP stacked microstrip antenna using crossed slots has been designed, fabricated and measured. For the single rediating element the designed 10dB return loss bandwidth is 34.5%99.45~13.54 GHz), 3dB axial ratio bandwidth is 18.7%(11.17~13.39GHz), and 6 dB gain bandwidth is 29%(10.21~13.64GHz). For the 2$\times$2 array designed using a sequential rotation method, the 10dB return loss bandwidth is 35.9%(9.69~13.94GHz), 3dB axial ratio bandwidth is 34.6GHz (9.93~14.03GHz), and 6dB gain bandwidth is 27.4%(10.35~13.6GHz). For the fabricated 8$\times$8 array antenna, the 10dB return loss bandwidth is 27.3%(10.17~13.41GHz), 3dB axial ratio bandwidth is 27.9GHz(10.1~13.4GHz), and the radiation pattern is good agreement with theory. This antenna can be used for broadband applications for communications or broadcasting in Ku band.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.27 no.2
• /
• pp.101-107
• /
• 2016

This paper presents the characteristics of a double-cone broadband antenna with compact and three-dimensional structure that can be used in UWB system. The theoretical analysis is conducted using a finite difference time domain(FDTD) method. The parameters are the radius, a height of broadband double-cone antennas with shorting plate, and the number of plates on a ground plane. This paper examines influence of structural parameters on return loss. The results show that a condition for an optimum structure of broadband double-cone antennas with shorting plate exists. It also shows that the broadband double-cone antennas with shorting plate have radiation patterns similar to those of a dipole antenna. To verify the theoretical analysis, computed results are compared to experimental results.

• 전자공학회논문지 IE
• /
• v.45 no.4
• /
• pp.54-59
• /
• 2008

In this paper, circularly polarized patch antenna with 2-stage LNA for the reception of S-DMB is presented. It used teflon didelectric substrate of ${\in}_r$=2.2 and the size is $40{\times}40{\times}15\;[mm]$. Experimental results of fabricated antenna show that bandwidths of input return loss and axial ratio are about 22 [MHz] and 25 [MHz]. Input return loss, output return loss, gain, and noise figure of the fabricated 2-stage LNA are $S_{11}$=-14 [dB], $S_{22}$=-18 [dB], $S_{21}$=26.8 [dB], and NF=1.14 [dB] respectively. The fabricated active type antenna has total gain of 30.4 [dB] at 2.642 [GHz].

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.45 no.8
• /
• pp.35-40
• /
• 2008

This paper proposes a dual-band balun which is based on Wilkinson power divider. By inserting $\lambda/2$ transmission line between port 2 and 3, this balun shows good matching at all ports and improved isolation. We use matamaterial(CRLH, D-CRLH) structure for a miniaturization of the circuit implementation and dual-band operation at TDMB frequency range(195MHz) and DVB-H frequency range(670MHz). The proposed balun is designed with return loss larger than -12.98dB at all port, and isolation larger than -12.4dB, the amplitude imbalance between output signals less than 0.08dB, also phase differences of outputs less than $2.8^{\circ}$.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.18 no.10
• /
• pp.2359-2366
• /
• 2014

In this paper, the characteristics of a inset fed rectangular microstrip patch antenna for S-band applications is studied. The variations of return loss along inset length and inset width are investigated on the inset fed rectangular microstrip patch antenna. From the investigated results, the optimized inset fed antenna is designed. At the resonant frequency 2.3 GHz, the optimized dimension of the patch is $45.0mm{\times}40.9mm$. The inset length and width are 14 mm and 1 mm, respectively. The designed antenna is fabricated on the substrate which has a dielectric constant and thickness with 2.5 and 0.787 mm. Simulation results are obtained by a 3D EM(Electromagnetic) solver. The resonant frequency and return loss are measured 2.3025 GHz and -21.11 dB, respectively. The measured and simulated results of the fabricated antenna are in good agreement.