• Journal of Korea Society of Industrial Information Systems
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• v.27 no.5
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• pp.49-59
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• 2022

The SHAPE algorithm has the advantage of being able to shape the pulse spectrum as desired and design it not to distort other characteristics, so it was used in the active sonar pulse design. In this paper, we propose a pulse design using the SHAPE algorithm for a multi-static sonar system to reduce the cross-correlation between frequency-adjacent pulses and prevent the performance degradation of the pulses themselves. The boundary function of the SHAPE algorithm is set to be limited to the pulse bandwidth. As a result of applying the proposed design method to the sinusoidal frequency modulated pulse, the peak cross-correlation level (PCCL), which means the degree of cross-correlation, was reduced by 44.23 dB. Although the PCCL decreased by several tens of dB, no significant change in the ambiguity function was observed, and the integrated sidelobe level (ISL), which means the average value of the side lobe, increased by 11.64 dB.

• 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.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.83-90
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• 2009

A new IRF (Impulse Response Function) analysis technique in high resolution SAR image is presented by taking into account the real clutter environment. In order to investigate the realistic effect of clutter background on the impulse response function of SAR image, an ideally generated impulse response function is superimposed with a large number of background clutter data which are extracted from the various regions of an actual SAR image. As a performance measure, PSLR (Peak Sidelobe Ratio) of the clutter-contained IRF is presented in the various groups of clutter background, and finally the results are compared with the stochastic model.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.483-486
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• 1998

한국해양연구소 온누리호에 장착된 에어건 배열에서 건 간격에 따른 빔 패턴 변화를 확인하였으며 남극해역에서 획득된 탐사자료와 비교하였다. 컴퓨터 모의과정과 배열 이론을 이용하여 신호진폭 및 빔 폭 변화 등을 시간 및 주파수 영역에서 분석하였다. 154 Hz에서 송이배열 (cluster array) 및 폭 배열 (wide array)의 빔 폭 변화는 배열 형태보다는 건 간격에 큰 영향을 받고 있어 배열 형태가 달라도 빔 폭은 서로 유사하게 변한다. 건 간격이 클수록 송이배열이 90$^{\circ}$의 빔 패턴에서 주엽 (mainlobe)이 최대치가 되는 것과는 달리 폭배열은 0$^{\circ}$에서 최대치를 나타내며 부엽 (sidelobe)은 건 간격과 무관하게 나타난다. 두 배열의 선형간섭이 점차 줄어드는 건 간격은 2.43 m이다. 남극해 탐사자료는 건 간격이 증가함에 따라 주신호 진폭은 약하게 기포는 강하게 증가한다. 이러한 결과는 빔 패턴 변화에서도 마찬가지로 나타나는데 건 간격이 클수록 주엽의 빔 폭이 점차 좁아져 강한 빔 패턴을 나타냄으로서 남극 탐사자료와 서로 잘 일치한다.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4
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• pp.78-83
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• 1999

This paper concerns a least square method for pattern optimization of a thinned sensor array in which the squared error between a desired pattern and a synthesized one is minimized. A weighting function is applied in the function with respect to the array visual range for a symmetric and asymmetric configuration for sensor spacing. An exponential weighting function is proposed to control the sidelobes efficiently around the mainbeam and to generate a uniform sidelobe. The resulting pattern may be employed to eliminate incoming interferences distributed uniformly around the array visual range.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.152-159
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• 1996

We have designed and implemented an optoelectronic hardware of binary phase extraction joint transform correlator (BPEJTC) which provides higher peak-to-sidelobe ratio than many other versions of JTC that has been published so far and does not produce correlation peaks due to intra-class association, to construct a multi-target tracking system. The digital processing unit controlling the entire system plays the part of modifying and binarizing the joint transform power spectrum (JTPS) and the optical processing unit is mainly used to take fourier transform operations. Some experimental results conducted by designed system along with its architecture showed the processing rate of 6 frames per second, thereby the potential applicability of the proposed system to real-time multitarget tracking system is given.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.10a
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• pp.40-44
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• 1986

The cassegrain antenna, 32metor , diameter, is designed for the satellite earth station at Boun. It is fed by a beam waveguide of type. The results of measurements G/T (Gain to Noise Temperature ratio) is 40.86dB/K at the elevation elevation angle 5˚ for 4GHz. And the average transmit and receive gain are 64.62dB and 61.3dB, respectively. They satisfy the values designed for the antenna. The sidelobe levels of the pattern also are in good accord with the recommendation of C.C.I.R.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.39 no.4
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• pp.408-417
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• 2002

Gabor cosine and sine functions have widely been used to describe the human visual filters. This paper presents a new method to locally represent image frequency components using these functions. The parameters of basis functions are determined based on dc ripple and the sidelobe strength of step response. The resultant transform consisting of Gabor cosine and sine functions is compared with existing transforms by computing the joint effective width and by applying to the image reconstruction with the limited number of transformed coefficients. The experimental results show that the proposed transform has better performance than DGT and DCT.

• Journal of the Korean Institute of Navigation
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• v.3 no.2
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• pp.21-30
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• 1979

Echo sounder and Doppler sonar are to theultra-sonic transducers for measuring the depth and the ship's speed respectively. To measure the depth and speed with a single transducer, it is required to control the ultra-sonic beam to optional direction. In the past, the direction of the transducer itself is varied, but such a method provoked much problems in the mechanical design of the equipment. This paper deals with the method to control beam direciton by the phase control of the plural arrangement of transducers, and the results are studied by a computer simulation. The remarkable results of the study is condensed as follows; 1. The greater the interval of arrangement between transducers, the sharper the radiation pattern is, but in this case, the level of undesired sidelobe is also increased. 2. The control of radiation pattern up to 60 degree can be achieved by an adequate arrangement of more than 10 transducers. 3. It is shown that a simultaneous measurement of both depth and speed can be achieved by alternating directivity of the pulse by the method proposed in this paper.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.10
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• pp.16-23
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• 1990

In this paper, the shaped offset Cassegrain antenna with low sidelobe, low cross-polar level, and high efficiency is designed. The design data is presented for shaping scheme. The validity of radi-ation characteristics is accomplished by comparing the result of measurement with numerical calculation and design goal. Experimental results of designed antenna are in good agreement with design goal except efficiency.