• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.95-97
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• 2000

배열 안테나에서 안테나 소자의 개수의 증가는 안테나의 이득을 증가시킬 수 있으므로 열악한 채널 환경에서도 채널이 필요로 하는 링크 마진을 얻을 수 있다. 그러나, 기존 빔 형성기에서 사용되는 배열 안테나 기법은 많은 계산량과 소모 메모리량 때문에 배열 소자의 개수에 제한이 따르게 된다. 이러한 문제를 해결하기 위하여 본 논문에서는 배열 안테나의 구조에 따른 위상차이를 보상하여 적은 계산량과 메모리를 갖는 배열 위상 차이 보상을 이용한 평행 구조 빔 형성기를 제안한다 배열 위상 차이를 보상하는 기법으로 적은 계산량과 메모리로 개수가 많은 긴 배열 안테나에서 얻을 수 있는 분해능과 안테나 이득을 얻을 수 있다. 제안된 기법의 성능을 비교하기 위해 기존의 빔 형성기법으로delay-sum 빔 형성기와 공분산 행렬의 고유치 해석을 통한 고유벡터 기법의 빔 스펙트럼과 연산량을 비교하였다. 제안된 기법으로 빔 형성을 하면, 배열 안테나의 소자의 개수가 늘어나도 기존의 방법보다 최소 30%의 연산량으로 스펙트럼 상 비슷한 성능을 얻을 수 있다.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.33B no.3
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• pp.142-150
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• 1996

Monopulse technique has been widely used for a bearing estimation of a desired signal. This method can estimate the bearing of the signal with only one pulse, so computational load and complexity are low and its processes are simple. But if the desired signal incidents with interferences or multiple signals exist in the beams, the method fails to estimate correct signal angle. To solve this problem, the method to use adaptive array was proposed. In conventional adaptive array methods, sum beam was formed with fixed weights and ifference beam was formed with adaptive weights determined to minimize beamformer output power with one or more linear constraints, or an algorithm to minimize each sum beam and difference beams simultaneously using adaptively formed one basic beam. Theroretical analyses and simulation results show that the performance of the proposed method is superior to that of conventional algorithms.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.179-182
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• 2004

수중음향통신을 위한 빔형성 알고리듬은 수중음향통신 신호가 상대대역폭(대역폭에 대한 반송주파수 비)이 큰 광대역 신호 특성을 고려해야한다. 우리는 본 논문에서 위상동기식 디지털 수중음향통신을 위한 협대역 신호 가정을 하지 않은 기저대역 배열 신호 모델을 유도하고 RLS 알고리듬을 이용하여 가중치를 갱신하는 FTR 필터 구조의 광대역 적응 빔형성 알고리듬에 대해서 전산 모의실험을 통하여 FIR 필터 길이, tap간 간격 등과 같은 최적의 FIR 필터 파라미터를 제시하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.459-464
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• 2001

We propose a transmit beamforming algerian for array antenna in FDD (Frequency Division Duplex) environments. The proposed method estimates the directions and spectra of the users, and constructs the spatial covariance matrix of the interferences at the downlink frequency. The weights are computed by that covariance matrix and desired user's direction vector Simulations are performed under Rayleigh fading environments. The proposed method don't need the data feedback, has the enhanced performance in BER (Bit Error Rate).

• Journal of Positioning, Navigation, and Timing
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• v.6 no.2
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• pp.43-51
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• 2017

In this study, the effect of the steering vector model mismatch due to array uncertainties on the performance of array processing was analyzed through simulation, along with the alleviation of the model mismatch effect depending on array calibration. To increase the reliability of the simulation results, the actual steering vector of the array antenna obtained by electromagnetic simulation was used along with the Jahn's channel model, which is an experimental channel model. Based on the analysis of the power spectrum for each direction, beam pattern, and the signal-to-interference-plus-noise ratio of the beamformer output, the performance deterioration of array processing due to array uncertainties was examined, and the performance improvement of array processing through array calibration was also examined.

• Journal of Communications and Networks
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• v.7 no.3
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• pp.258-262
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• 2005

An adaptive beamforming system based on code filtering and differential correlation approaches is proposed. The differential correlation method was originally proposed for time delay estimation of direct sequence code division multiple access (DS-CDMA) systems under near-far ratio conditions and the code filtering correlation algorithm, on the other hand, was proposed for array response estimation in DS-CDMA systems under perfect power control. In this paper, by combining differential correlation concept with the code filtering beamforming technology, an accurate estimate of the beam forming weights and an enhanced performance of DS-CDMA systems under sever near-far ratio conditions is achieved. The system performance in terms of beam pattern and bit-error-rate (HER) shows that the proposed adaptive beamformer outperforms the conventional code filtering correlation technique.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.287-291
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• 2003

This paper analyzes Bit Error Rate (BER) performance of a wireless communication system using BPSK modulation technique with a smart antenna at base station. The channels under consideration are Additive White Gaussian Noise (AWGN) channel or a slow, flat Rayleigh lading channel with AWGN. Under the assumptions that the MMSE beamformer is used and the time delays of all users are approximately equal, we first analytically derive closed-form expressions for the BER of the desired user. Then, computer simulation is carried out to verify the theoretical results.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.19-29
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• 2008

Underwater acoustic(UWA) communication is one of the most difficult field in terms of severe channel environments such as multipath propagation, high temporal and spatial variability of channel conditions. Therefore, it is important to model and analyze the characteristics of underwater acoustic channel such as multipath propagation, transmission loss, reverberation, and ambient noise. In this paper, UWA communication channel is modeled with a ray tracing method and applied to image transmission. Quadrature phase shift keying(QPSK) and multichannel decision feedback equalizer(DFE) are utilized as phase-coherent modulation method and equalization technique, respectively. The objective is to improve the performance of the image transmission using vertical sensor array instead of single sensor in the viewpoint of bit error rate(BER), constellation diagram, and received image quality.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.567-570
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• 1997

In a conventional digital beamformer received signal were sampled at least Nyquist rate of its maximum frequency. But it is wide band signal and its coherent sum must be obtained, the sampling clock of about $8f_o$ and $16f_o$ is necessary or high quality images. This paper described how image qualities are varied according to sampling clock. Mainly, we compared the SDF(Sampled Delay Focusing) that had maximum precision of $8f_o$ with $16f_o$ sampling system and analyze its characteristics.

• Journal of KSNVE
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• v.10 no.5
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• pp.886-891
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• 2000

In this paper, an iterative array shape estimation technique is presented, which is based on the use of the least squares polynomial fitting to the data from heading sensors. The estimated polynomial shape model is then used for calculating the hydrophone positions on the assumption that the arc distances between sensors are constant. In order to verify the applicability of the proposed algorithm, numerical simulations are performed using two types of non-linear array shapes. In addition the noise effects of heading sensors on the array shape estimation results and the performance of beamformer are also investigated.