• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.735-741
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• 2003

A simplified view of array design and application process was introduced. Array design is critical to achieve a successful phased array measurements. A planar microphone array is designed to produce optimum performance and also to fit economic requirement in integrating data acquisition system. Certain performance characteristics are of primary concern when designing arrays. These characteristics include array resolution, spatial aliasing and array sidelobe suppression. Every array has its directional pattern that shows such characteristics. Assuming that a monopole source is located in center, beam-patterns have been simulated varying measurement conditions such as number of sensors. array aperture size, distance between array and source, frequency of interest and so on. Sensor correction was conducted on very channel using magnitudes and phased of FRF with respect to a reference microphone channel. Then with a spiral type array, measurements have been made with two point sources of same frequency in order to investigate array resolving abilities. It is observed that higher frequency source achieves better resolution than lower one does.

• Korean Journal of Optics and Photonics
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• v.11 no.3
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• pp.193-197
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• 2000

A polarized mode convertible, wavelength tunable optical filters with acoustic barriers and acousto-optic effect have been produced in LiNb03 substrate utilizing the Ti double diffusion technique. Polarization conversion in excess of 81 % and a spectral width of -200 kHz (-1.83 nm) were achieved at a wavelength of 1551.6 nm and RF frequencies of 173.07 kHz and 173.05 kHz for both transverse electric (TE) and transverse magnetic (lM) input polarizations, respectively. The electrical driving power was 10.97 mW and reduced to about 10% of one for an optical filter without an acoustic barrier. A linear tuning rate of 8.2 nmlMHz and sidelobe intensity of -4 dB was demonstrated. rated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.11
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• pp.1063-1070
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• 1991

A microstrip array antenna are designed to depend on the size of rectangular microstrip patch for the relative current destribution to be 1:2:2:1 or 1:1:2:2:1:1 using Tchebyscheff polynominals, and it consist of sharp beam pattern. Gain difference between the main lobe and sidelobe is calculated for theoritical values of 21.97 db or 29.54 db. The designed microstrip array antenna are measureed various characteristics, such as return loss, resonant frequency, radiation pattern, bandwidth, beamwidth, and agreed with each other and theoretical value. Also it is presented a process of phase variation of patch array antenna depend on relative current distribution for beam scanning.

• Journal of electromagnetic engineering and science
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• v.11 no.2
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• pp.97-104
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• 2011

A planar slotted waveguide array antenna has been designed at 9.37 GHz for X-band radar applications. The antenna consists of multiple branchline waveguides with broadwall radiating shunt slots and a main waveguide to feed the branch waveguides through a series of inclined coupling slots. The antenna feed point is located at the center of the main waveguide. Element weights in the array have been calculated bysampling a continuous circular Taylor aperture distribution at the 25 dB sidelobe level in both the E and Hplanes. A commercially available electromagnetic (EM) simulation tool has been used to characterize the individual isolated slot and that data hassubsequently been used to design the planar array. The array is finally analyzed in a CST Microwave studio and the measured and simulated results have been found to be in good agreement.

• Proceedings of the IEEK Conference
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• 2001.06d
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• pp.151-154
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• 2001

In this Paper, a new harmonic imaging technique is proposed and evaluated experimentally. In the proposed method, a weighted chin signal with a hanning window is transmitted. The RF samples obtained on each array element are individually compressed by correlating with the reference signal defined as the 2nd harmonic (2f0) component of a transmitted chirp signal generated in a square-law system. The proposed method uses the compressed 2f0 component to form an image, for which the crosscorrelation term with f0 component should be suppressed below at least -60dB. After experiment, the 6dB pulse width and peak sidelobe level of the compressed 2f0 component were 0.7us and -60dB, respectively. This result shows that the proposed method can successfully eliminate the f0 component with a single transmit-receive event and therefore is more efficient than the conventional pulse inversion (PI) method in terms of frame rate. We also observed that the 2nd harmonic compont starts to decrease for source pressure higher than 210kPa in water, which implies that SNR of the 2nd harmonic imaging using short pulses cnanot be incresed beyond a certain limit.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.9
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• pp.1025-1033
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• 2012

Fabry-Perot cavity(FPC) antennas with artificial magnetic conductor(AMC) surface are designed in order to provide scan capability by $4{\times}1$ array feed inside the cavity. The proposed antenna, excited by $4{\times}1$ thinned array, not only achieve higher directivities but also improve suppression of sidelobe level(SLL) relative to that of the thin array alone. The FPC antenna with the height of a quarter wavelength generate maximum gain of 19 dB, SLL suppression of 14 dB and maximum scan angle of $8^{\circ}$ under the feed phase difference of $90^{\circ}$ at the design frequency of 12 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.908-914
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• 2013

A shaped Cassegrain antenna is designed from the condition of the same path length at the equi-phase surface by using the conservation of energy and Snell's law. In order to improve the phase error efficiency of aperture surface, the surface profile of the main and sub-reflectors is found to satisfy the power distribution and the equi-phase condition at the aperture surface. The sidelobe levels of 36.4 dB and 33.9 dB are achieved at the AZ and EL planes, respectively from numerical calculation by physical optics method at Ku band and the directivity of designed antenna is 10 percent greater than that of conventional antenna.

• Journal of the Korea Society of Computer and Information
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• v.16 no.5
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• pp.101-107
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• 2011

The optimum weight vector is studied to remove interference and jamming signals in adaptive array antenna system. The optimum weight vector is calculated to apply a minimum variance algorithm and cost function in linearly constrained conditions, and accurately estimates target's signal. Adaptive array antenna system is the system which improves signal to noise ratio(SNR) and decreases interference and jammer power. Adaptive array antenna system delays at tap output of antenna array element. Each tap finally makes the complex signal of one in multiplier complex weight. In order to obtain optimum's weight calculation, optimum weight vector is used in this paper. After simulation, resolution is increased below $3^{\circ}$, and sidelobe is decreased about 10 dB.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.4
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• pp.161-168
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• 2009

We demonstrated $\check{S}$olc-type wavelength filters in periodically poled Ti-diffused lithium-niobate channel optical waveguide (Ti:PPLN). A $\check{S}$olc-type transmission spectrum based on the polarization-mode conversion was observed experimentally in PPLN with period 16.6${\mu}m$. A reasonable explanation of such a phenomenon was presented. A polarization-mode converted transmission peak was observed at wavelength 1272.49nm. The FWHM and sidelobe of spectrum are about 0.23nm and 7 dB, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.668-670
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• 2010

It is necessary to estimate the range and Doppler shifted spectrum for the extraction of useful information from the return echoes in the frequency modulated continuous wave radar systems used for the remote sending purpose such as detection of moving targets. However, the spectrum estimation using the FFT method causes the very large sidolobes of clutter masking the essential signal information if the acquisition time of an echo signal is pretty short. Therefore, in this paper, the efficient data windowing method is investigated to suppress the strong sidelobe levels of the clutter and results are analyzed.