• Composites Research
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• v.26 no.5
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• pp.279-288
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• 2013

In this paper, the delamination and deformed FSS caused by residual stresses in the Loop type FSS embedded composites and the transmission characteristic changes due to deformation of FSS by residual stresses were studied. FSS may have different electromagnetic characteristics depending on the type of element, design variables, and array. Therefore, design variables of square loop FSS embedded composites structures were determined to obtain the transmission characteristic for X-band (8~12 GHz). Then the design variables of other types of loops (triangular loop and circular loop) were determined based on the dimensions of square loop. Thereafter, the residual stresses and transmission characteristics of FSS embedded composite structures with various single and double loop FSS's, and stacking sequence of composite laminates were compared.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.5
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• pp.152-161
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• 2017

The CBTC(Communication based Train Control) system employed on 2.4GHz ISM band adopt the IEEE802.11.x standard. Therefor communication time delay, distortion and data losses will be produced. To overcome these problems, CPSK(Continuous Phase shift keying) modulated DS/SS(Direct Sequence Spread Spectrum) transmitter with 908MHz carrier frequency is proposed. Through the eye diagram and scatter diagram the performance is analysed. And the phase noise characteristic of the local oscillator is measured about 60dBc/Hz, this means that the phase noise performance is very good compared to the signal. Reference frequency suppression of the 2nd local oscillator is 50dB below compared to the signal. Through the polarities of the complementary signal equally probable, the line spectrum of the output spectrum is eliminated. The nonlinear effects which introduce the spectral spreading or spectral regeneration is reduced remarkably.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.607-615
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• 2019

In this paper, the electromagnetic effects on the discontinuity structures of the frequency selective radome in manufacturing process based on the X-band were analyzed. In order to fabricate a curved radome using a planar frequency selective surface structure, it is assumed that gaps, slanted gaps, pattern damage, and pattern misalignment between FSS patterns, which are discontinuous elements that can occur at the joint surface of the FSS panel. FSS specimens including continuous elements were fabricated and the frequency transmission characteristics were measured in a free space measurement environment. From the measurement results, resonance frequency shift, transmission performance degradation, and bandwidth variations were found to be the largest when the damaged pattern was bonded to the junction of FSS panels.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.12
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• pp.1167-1172
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• 2013

This paper presents a X-band doppler radar with high conversion gain using a self-oscillating-mixer(SOM) that oscillation and frequency mixing is realized at the same time. To improve phase noise of the SOM oscillator, a ${\lambda}/2$ slotted square patch resonator(SSPR) was proposed, which shows high Q-factor of 175.4 and the 50 % reduced circuit area compared to the conventional resonator. To implement the low power system, low biasing voltage of 1.7 V was supplied. To enhance the conversion gain of the SOM, bias circuit is configured near the pinch-off region of transistor, and the conversion gain was optimized. The output power of the proposed SOM was -3.16 dBm at 10.65 GHz. A high conversion gain of 9.48 dB was obtained whereas DC Power consumption is relatively low about 7.65 mW. The phase noise is -90.91 dBc/Hz at 100 kHz offset. The figure-of-merit(FOM) of the proposed SOM was measured as -181.8 dBc/Hz, which is supplier to other SOMs by more than about 7 dB.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.159-162
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• 2002

The eleventh-order coupled line lowpass filter(LPF) was designed to suppress harmonics and spurious signals. The microstrip type LPF was fabricated using a high-$T_{c}$ superconductor(HTS) $YBa_{2}$$Cu_{3}$$O_{7-x}$(YBCO) thin film with the $CeO_{2}$ buffer layer which was deposited on the sapphire ($Al_{2}O_{3}$) substrate of 30 x 30 $mm^{2}$. The coupled-line type LPF was designed for 1.2 GHz of cutoff frequency with 0.01 dB of ripple level at passband. The fabricated HTS LPF shows excellent attenuation characteristics in stopband of 1.2~9.5GHz (7-attenuation poles in the stopband), and shows low insertion loss (0.2 dB) and return loss (17.1 dB) in the pass- band. These measured results match well with those obtained by the EM simulation. This clearly demonstrates that the HTS LPF can suppress harmonics and spurious signals effectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.4
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• pp.535-540
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• 2013

We design a slotted waveguide antenna for X-band which a 1.4m length with slot depth variation. A 54 slot array is modeled and simulated by CST, and the side lobe level is suppressed effectively in a certain range of frequency. The experimental results of the antenna show that its gain, maximum sidelobe level and half power beam-width are 21.8dB, -31dB and 2.0deg, respectively.

• Proceedings of the IEEK Conference
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• 1998.06a
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• pp.405-408
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• 1998

Due to the large conduction band discontinuity between emitter base, OmGaAs HBT has an advantge to enable the hot electrons to inject into the base. In this paper, InAlGaAs/InGaAs HBT with the various emitter junction gradings and the modified collectors are simulated and analyzed by HMC(hybrid monte carlo) simulator in order to find a optimal structure for the shortest transit time. A minium base transit time (.tau.$_{b}$ ) of 0.21 ps was obtained for HBT with the grading layer, which is parabolically graded from x=1.0 to x=0.5. The minimum collector transit time (.tau.$_{c}$ ) of 0.31ps was found when the collector was modified by inserting p$^{[-10]}$ and p$^{+}$ layers. Thus HBT in combination with the emitter grading and the modified collector layer showed the cut-off frequency (f$_{T}$) of 183GHz.z.z.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.1 s.24
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• pp.144-151
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• 2006

A rectangular loop antenna for S-band radar is proposed. The proposed loop antenna is the modified type of folded monopole antenna. The feeding line is coplanar stripline with $180^{\circ}$ phase difference for operating in odd mode. The proposed antenna showed return loss of -15.57dB at the center frequency and bandwidth of about 790MHz (> 25%) under the condition of VSWR < 2. The gains of single, 1x2, and 1x4 array loop antennas are 4.3, 7.0, and 10.2dBi, respectively.

• Journal of the Korea Society of Computer and Information
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• v.5 no.2
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• pp.105-114
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• 2000

In this Paper in order to break with real-time position of signal source which have first dimension motion, the N antenna is arrayed with half-circle, the incident angle of signal source from receiving power pattern to receive at receive antenna is estimated and measured, and the system that measure horizontal moving distance of signal source is designed. Signal source is constructed by 10-20dBm transmitter power which frequency is 10.52GHz of X band, and on horizontally moving the position of signal source. validity of new method is confirmed.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.58-59
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• 2011

Microstrip line on dielectric substrate depending on the type of its configuration can be applied to be antenna, communication filters, and resonators. When driving frequency is considered more than X-band, unnecessary signal leakage should be occurred because of flowing through the planar circuit at banding position. So leakage signal will affect other planar circuit, and then EMC problem has to be introduced. In this paper, the affection of banding planar circuit on dielectric substrate was investigated.