• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.43-48
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• 2021

We propose 2-channel filter bank method instead of FFT method to decrease sub-channel interference for using of efficient frequency resource in MC-CDMA method. Since a prototype filter of filter bank having wavelet characteristic is designed having more less side-lobe, the nearest co-channel interference and inter symbol interference are decreased efficiently. Since the spreading signal of suggesting MC-CDMA system is being demanded for less chip rate and is not being considering for autocorrelation characteristic, the Walsh code can be used as a optimal orthogonal signal set. We consider bit error rate and signal to noise ratio to estimate the performance of suggested system on condition that white noise channel and arbitrary sinusoidal jammer are existing. As a result of comparing to traditional FFT-based MC-CDMA simulation result, our suggested system has shown better performance than traditional MC-CDMA method on the side of minimizing interference effect.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1176-1179
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• 2011

In this paper, design of series-fed microstrip antennas with sum and difference patterns is presented for millimeter-wave applications. The antenna was designed to exhibit high-gain and low side-lobe level(SLL) below -20 dB. A conventional transmission-line model, Taylor and Bayliss distributions were employed to determine current distribution for sum and difference patterns. Moreover, connecting lines between microstrip patches were tuned to achieve an optimized design. The measurement was also performed to validate the designed antennas.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.77-82
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• 2013

The filtering characteristics of planar distributed feedback (DFB) waveguides composed by gratings with different period are solved using equivalent transmission-line network. To analyze explicitly its band-pass and resonance properties, a longitudinal modal transmission-line theory (L-MTLT) based on Floquet's theorem and Babinet's principle is newly developed. The numerical results reveal that this approach offers a simple and analytic algorithm to analyze the filtering characteristics of cascaded DFB structure with different period, and the bandwidth and side-lobe suppression of cascaded DFB filter are sensitively dependent on the variation of aspect ratio and the number of grating at each region.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1019-1025
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• 2004

The X-band 10${\times}$10 waveguide slot array antenna for SAR is designed, fabricated and measured. The array antenna is designed using the equivalent circuit model based on the field distribution of the dominant mode, TE$\sub$10/, and EM simulation. The method to decide optimum angle of the centered inclined slot(coupling slot) and the optimum of offset of the longitudinal slot(radiating slot) is provided. The designed antenna structure is EM simulated and fabricated. The measured return loss bandwidth is 180 MHz at 9.15 GHz , the side lobe level is below -25 dB, HPBW is about 9$^{\circ}$, and the gain is 25.5 dB. These results are similar to the simulation data.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.317-322
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• 2005

Synthetic Aperture Radars(SAR) are used mainly for high-resolution imaging of the terrain. This paper describes the 16$\times$16 array antenna designed for an X-band, automobile-based SAR(AutoSAR) system. This antenna has the structure of several layers such as radome, radiators, slots, feed network, and honeycomb cores. Each layer is adhesively bonded to meet different combination of structural and electrical design requirements. Using the Strip-Slot-Foam-Inverted-Patch(SSFIP) structure and dogbone slots, a wide bandwidth and a structural hardness were achieved. Measurement results were compared with simulation results. It was observed that the SAR antenna had a bandwidth of 1.7 GHz, side-lobe levels of less than -20 dB, half-power beamwidth of 5$^{\circ}$, and gains of 25.0 dBi. The observed results show that the designed array antenna is suitable for the broadband AutoSAR system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1282-1290
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• 2000

The LHCP circularly polarized antenna operating at the satellite broadcast receiving band is developed by employing the sequential-rotation technique in which each truncated-corner patch square element is arranged in the triangular lattice type. Antenna designed with sequentially rotated technique of triangular lattice type has the effect of improved axial-ratio bandwidth, cross-polarization etc., and the degradation of radiation pattern can be reduced significantly by minimizing the radiation loss of feeding line structure. Characteristics of antenna designed is satisfied with specifications of array antenna for DBS that is -27 dB of side lobe level and -20 dB of cross-polarized level at $\Phi$=45$^{\circ}$ plane.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.829-835
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• 2006

In this paper, new structure of the Cassegrain reflector antenna whose spill-over is efficiently reduced by modified reflectors is proposed for high power. It can be achieved by designing the geometry of subreflector in Cassegrain system using two hyperbolic curves in order to be suitable a lager beamwidth of feeding pattern without broadening main reflector. Finally, radiation efficiency and side lobe level of the proposed Cassegrain reflector antenna can be improved respectively 9 %, 10 dB than conventional one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.865-872
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• 2002

The conventional Rotman lens antenna using a waveguide lens has the bended waveguide from the inner lens contour to the antenna element. However in this paper the improved Rotman lens antenna having a straight waveguide is proposed. By applying this technique, the beam steering antenna for BMWS application which has 3 input ports and 6 antenna elements consisted of open-ended waveguide has been designed and fabricated. From the measurement, the gain of the beam steering antenna is 15.4 ~ 17.2 dB. The direction angle is 0$^{\circ}$, +14$^{\circ}$~ +16$^{\circ}$, -15$^{\circ}$~ -16$^{\circ}$ and the side lobe level is -l0 ~ 20 dB.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.4 s.19
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• pp.53-60
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• 2004

In this paper, the radar antenna of navigation radar on helicopter was suggested to Ka-band lens antenna. It is type of the streamlined convex lens to reduce the air resistivity when helicopter was navigated. Although aperture area is smaller than the standard antenna just like horns, the gain is higher and beamwidth is smaller than standard horns. We made the lens by using maximum flare angle of the horn and dielectric constant of the lens. As a result, when aperture diameter was 280mm and focal length was 145mm, the return loss -21.25dB, the gain was 32.2dBi, E and H beamwidth was $1.8^{\circ}$(E-plane), $1.4^{\circ}$(H-plane), nearly $1.5^{\circ}$, and side-lobe level was -18.4 dB(E-plane), -19.5dB(H-plane) lower were presented. So this suggested type can be used for the radar antenna of navigation radar on helicopter, and it will possible just a little some sidelobe suppression by using the choked horn as a feeder horn.

• The Journal of the Acoustical Society of Korea
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• v.6 no.3
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• pp.43-51
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• 1987

In this work an implementation of SAW based serial type AWQPSK modulator is studied. The SAW AWQPSK modulator consisting of input apodized IDT and output uniform IDT with center frequency of 20 MHz and bit rate of 4MHz has been designed and fabricated on $YZ-LiNbO_3$ substrate. Measured center frequency and null-to-null bandwidth are 20MHz, respectively. The sidelobe suppression is achieved 60dB below the peak mainlobe level. Measured responses meet the theoretical values with tolerable amount of deviation. SAW-based modulator simplifies the implementation of AWQPSK which uses complex pulse shape as a baseband pulse.