• ETRI Journal
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• v.40 no.5
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• pp.592-603
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• 2018

In order to obtain better target identification performance, an efficient waveform design method with high range resolution and low sidelobe level for orthogonal frequency division multiplexing (OFDM) multiple-input multiple-output (MIMO) radar is proposed in this paper. First, the wideband CP-based OFDM signal is transmitted on each antenna to guarantee large bandwidth and high range resolution. Next, a complex orthogonal design (COD) is utilized to achieve code domain orthogonality among antennas, so that the spatial diversity can be obtained in MIMO radar, and only the range sidelobe on the first antenna needs suppressing. Furthermore, sidelobe suppression is expressed as an optimization problem. The integrated sidelobe level (ISL) is adopted to construct the objective function, which is solved using the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm. The numerical results demonstrate the superiority in performance (high resolution, strict orthogonality, and low sidelobe level) of the proposed method compared to existing algorithms.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.4
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• pp.673-682
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• 2010

This paper describes and analyzes a various generation methods of the mutually orthogonal polyphase sequences with low cross-correlation peak sidelobe and low autocorrelation peak sidelobe levels. The mutual orthogonality is the key requirement of multi-static or MIMO(Multi-Input Multi-Output) radar systems which provides the good target detection and tracking performance. The polyphase sequences, which are generated by SA(Simulated Annealing) and GA(Genetic Algorithm), have been analyzed with ACF(Autocorrelation Function) PSL(Peak Sidelobe Level) and CCF(Crosscorrelation Function) level at the matched filter output. Also, the ambiguity function has been introduced and simulated for comparing Doppler properties of each sequence. We have suggested the phase selection rule for applying multi-static or MIMO systems.

• Journal of the Korea Institute of Military Science and Technology
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• v.9 no.3
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• pp.95-100
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• 2006

The pulse compression technique using Linear FM signal is commonly used for improving the performance of both the detection range and range resolution in radar system. In general, the compressed LFM waveform has relatively large sidelobe level which may prevent a target from being detected when strong jammer or clutter signal is near the target signal. In this paper, we propose a new weighting method which uses the square-root weight to suppress the sidelobe level. Typical applications are missile seekers and tracking radar systems where target tracking range is available prior to the signal processing. By computer simulation, we show that the performance of the proposed method is better than that of the conventional weighting methods in terms of sidelobe suppression.

• ETRI Journal
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• v.29 no.1
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• pp.95-98
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• 2007

A low-profile phased array antenna with a low sidelobe was designed and fabricated using a genetic algorithm (GA). The subarray distances were optimized by GA with chromosomes of 78 bits, a population of 100, a crossover probability of 0.9, and a mutation probability of 0.005. The array antenna has 24 subarrays in 14 rows, and is designed as a mobile terminal for Ku-band satellite communication. The sidelobe level was suppressed by 6.5 dB after optimization, compared to the equal spacing between subarrays. The sidelobe level was verified from the far-field pattern measurement by using the fabricated array antenna with optimized distance.

• ETRI Journal
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• v.43 no.4
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• pp.650-659
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• 2021

Multi-carrier waveforms have several advantages over single-carrier waveforms for radar communication. Employing multi-carrier complementary phase-coded (MCPC) waveforms in radar applications has recently attracted significant attention. MCPC radar signals take advantage of orthogonal frequency division multiplexing properties, and several authors have explored the use of MCPC signals and the difficulties associated with their implementation. The sidelobe level and peak-to-mean-envelope-power ratio (PMEPR) are the key issues that must be addressed to improve the performance of radar signals. We propose a scheme that applies pattern-based scaling and geometric progression methods to enhance sidelobe and PMEPR levels in MCPC radar signals. Numerical results demonstrate the improvement of sidelobe and PMEPR levels in the proposed scheme. Additionally, autocorrelations are obtained and analyzed by applying the proposed scheme in extensive simulation experiments.

• The Journal of the Acoustical Society of Korea
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• v.23 no.8
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• pp.570-575
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• 2004

In the underwater acoustic systems. we can receive signals and retrieve information about a target by using a beamforming method. The most important thing in the beamforming is finding the way to optimize the mainlobe beamwidth and the sidelobe level to the desired value. One of the prominent results of beamforming method. which has been studied. is Philip's weighting function method(1) . Philip's method adaptively adjusts its weights of array to meet the desired mainlobe beamwidth and sidelobe level. It is very similar to the design method in adaptive filter. However. this method cannot easily bring us to the desired sidelobe level due to complementary relation between mainlobe beamwidth and sidelobe level. In this paper, we propose a new algorithm using partial constrained adaptation. This method makes us circumvent the above problem and meet the specification of design easily. The proposed algorithm presents a Pattern synthesis that designer can easily control the mainlobe beamwidth and the sidelobe level to the desired value while calculation time to converge is decreasing.

• Proceedings of the Acoustical Society of Korea Conference
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• 1991.06a
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• pp.151-156
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• 1991

In this paper, we propose a new algorithm for designing the R-G filter that has optimum performance in terms of mean square sidelobe level(MSSL) for the Barker code. The advantage of the conventional R-G filter lies in its simple structure so that it can be easily implemented. However, the conventional R-G filter dose not have optimum performances in terms of peak sidelobe level(PSL), mean sidelobe level(MSL), and MSSL. Recently, a(R-G)LP filter of which filter coefficients are obtained by the linear programming algorithm was proposed and known to have optimum performance in PSL. The proposed (R-G)LS filter keeps the simple structure of the conventional R-G filter and has the filter coefficients that minimizes the sidelobe in the least square sense. The analytic results show that the proposed (R-G)LS filter has better performances than the conventional R-G filter in terms of PSL, MSL, and MSSL. Compared with (R-G)LP filter, the proposed (R-G)LS filter has better performances in terms of MSL and MSSL. The proposed filter design algorithm can be applied to the other binary codes such as truncated pseudonoise(PN) codes and concatenated codes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.43-48
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• 2018

Offset parabolic antenna have been widely used for satellite communication system. To locate feedhorn on antenna system, it requires arbitrary structure which forces to fix on system. However, arbitrary scatterer increases sidelobe level of elevation axis. To solve this problem, we need to predict which angle level is increased by arbitrary scatterer simply. Because conventional simulation method takes a long time to simulate parabolic antenna system and needs exclusive software. In this paper we can calculate sidelobe angle simply by using raytracing method, check coincidence between calculated and simulated result and show how arbitrary scatterer affects sidelobe lavel of elevation axis of offset parabolic antenna depending on angle and location of arbitrary structure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1493-1510
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• 2000

Theoretical models that can be used to predict the range of main lobe widths and the probability distribution of the peak sidelobe levels of two-dimensionally sparse arrays are presented here. The arrays are considered to comprise microphones that are randomly positioned on a segmented grid of a given size. First, approximate expressions for the expected squared magnitude of the aperture smoothing function and the variance of the squared magnitude of the aperture smoothing function about this mean are formulated for the random arrays considered in the present study. By using the variance function, the mean value and the lower end of the range i.e., the first I percent of the mainlobe distribution can be predicted with reasonable accuracy. To predict the probability distribution of the peak sidelobe levels, distributions of levels are modeled by a Weibull distribution at each peak in the sidelobe region of the expected squared magnitude of the aperture smoothing function. The two parameters of the Weibull distribution are estimated from the means and variances of the levels at the corresponding locations. Next, the probability distribution of the peak sidelobe levels are assumed to be determined by a procedure in which the peak sidelobe level is determined as the maximum among a finite number of independent random sidelobe levels. It is found that the model obtained from the above approach predicts the probability density function of the peak sidelobe level distribution reasonably well for the various combinations of two different numbers of microphones and grid sizes tested in the present study. The application of these models to the design of random, sparse arrays having specified performance levels is also discussed.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.428-431
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• 2003

In this paper, distances between elements are optimized for low sidelobe level (SLL) microstrip patch array using Genetic Algorithms. Genetic Algorithms are "global" numerical-optimization methods, it's advantages are very simple coding and fast optimization. This paper show how to optimize the maximum SLL using Genetic Algorithms. In the results, although mutual coupling is neglected, it's maximum SLL is 3.5 dB lower than Uniformly Spaced Array(distance=$0.5{\lambda}$).