• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.190-193
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• 2003

The DOA(Direction Of Arrival) estimation to select a best beam for receiving a particular signal in switched beam antenna systems, and to shape the optimal beam in adaptive array antenna systems, is typically performed under the assumption that the target user motion is almost negligible. In this paper, we model the user as the time-varying source and adopt the LPA(Local Polynomial Approximation) tracking algorithm, proposed by Katkovnik, to solve the time-varying DOA estimation problem. Then, we compare the power spectrum functions between the LPA beamformer and the conventional beamformer, also, the normalized SNRs of each beamformer. The results show that the LPA beamformer is robuster than the conventional beamformer in tine-varying environments. In addition, in case of the conventional beamformer, more array elements give rise to more degradation in the aspect of SNR.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.7
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• pp.989-1002
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• 1995

In this paper, we propose a new algorithm, so called the Signal Decorrelation via Virtual Translation of Array (SDVTA) algorithm, for estimating the directions of arrival(DOA's) of narrowband coherent signals incident on a general array. An effective procedure is composed of transforming the steering matrix of the original array into that of the virtually translated sensor array and taking the average of the transformed covariance matrices in order to decorrelate the coherent signals. The advantage of this approach is in that 1) it can estimate the DOA's of m-1 coherent signals(M : the number of array sensors) since the effective aperture size is never reduced. 2) a geometry of array is unrestricted for solving the narrowband coherency problem. 3) the efficiency of signal decorrelation does not depend on the phase differences between coherent signals unlike the Coherent Signal Subspace Method (CSM). Simulation results are illustrated to demonstrate the superior performance of this new algorithm in comparison with the normal MUSIC and examine the comparative performance with the various choices of the optimal transformation matrix under coherent signal environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1534-1542
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• 1997

In this paper, we present a performance improvement method for the direction-of-arrival (DOA) estimation algorithm of the narrowband signals incident on a uniform circular array. It is very important to estimate the covariance matrix effectively because the performance of DOA algorithm mainly depends on the exactness of the sampel coveriance matrix which is computed from the received samples of signals. In case of uniform circular array with the even number sensors, the structure of the arrray has a useful geometrical property. Therefore we present the method which can estimate covariance matrix more effectively using this property. The simulation results are shown to demonstrate the superior perfodrmance obtained by the proposed covariance matrix estimation method relative to that of the conventional estimation method.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.322-327
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• 2007

Dedicated outdoor air-conditioning(DOA) system that utilizes pre-cooling and desiccant dehumidification can be superior to conventional cooling and reheating system with respect to energy consumption and indoor thermal comfort. In this work, simulation has been conducted to study various factors that affect the performance of DOA. Dynamic simulation shows the transient variation of temperature and humidity as the on/off control logic is imposed. Exit humidity of process air and flow rate are varied to study the effect on exit temperature of process air, dehumidification quantity, required regeneration temperature and exit humidity of regeneration air. For an outdoor air condition of $28.5^{\circ}C$ temperature, 16 g/kg humidity ratio and 2000 cmh flow rate, the dehumidification efficiency is increased by 4.6% as the flow rate is doubled.

• The Journal of the Acoustical Society of Korea
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• v.17 no.8
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• pp.64-67
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• 1998

여러 해 동안 많은 연구자들에 의해서 코히런트한 간섭신호가 있는 환경에서 신호 의 도래각을 추정하는 방법에 대한 연구가 진행 되어왔다. 이런 방법들은 대부분 공간 평활 (Spatial Smoothing)류의 방법을 사용하고 있으나 Pillai에 의해서 각 센서에 들어오는 신호 의 평균을 이용한 방법이 제안되었다. 이 방법에서는 특별히 복소수의 입력에 대해서는 대 칭형 배열을 사용하도록 했기 때문에 실수 입력을 다룰 때 보다 약 2배의 센서 개수가 필요 하다[S.U.Pillai,Array Signal Processing,Springer-Verlang New York, 1989]. 본 논문에서는 Pillai의 방법을 사용할 때 복소수 입력에서도 실수 입력의 경우와 같은 개수의 센서를 사용 하는 방법을 제안한다.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.445-450
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• 2018

Reliable detection and parameter estimation of a radar cross section(RCS) fluctuating target have been known as a difficult task. To reduce the effect of RCS fluctuation, various diversity techniques have been considered. This paper presents a new method for synthesizing a covariance matrix applicable to a coherent multi-input multi-output(MIMO) radar with frequency diversity. It is achieved by efficiently combining covariance matrices corresponding to different carrier frequencies such that the signal-to-noise ratio(SNR) in the combined covariance matrix is maximized. The value of a synthesized covariance matrix is assessed by examining the phase curves of its entries and the improvement on direction of arrival(DOA) estimation.

• Journal of Information Processing Systems
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• v.16 no.4
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• pp.774-783
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• 2020

For the issue of subsurface target localization by reverse projection, a new approach of target localization with different distances based on symmetric sub-array multiple-input multiple-output (MIMO) radar is proposed in this paper. By utilizing the particularity of structure of the two symmetric sub-arrays, the received signals are jointly reconstructed to eliminate the distance information from the steering vectors. The distance-independent direction of arrival (DOA) estimates are acquired, and the localizations of subsurface targets with different distances are realized by reverse projection. According to the localization mechanism and application characteristics of the proposed algorithm, the grid zooming method based on spatial segmentation is used to optimize the locaiton efficiency. Simulation results demonstrate the effectiveness of the proposed localization method and optimization scheme.

• ETRI Journal
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• v.45 no.3
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• pp.492-504
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• 2023

Researchers have recently shown an increased interest in estimating the direction-of-arrival (DOA) of wideband noncircular sources, but existing studies have been restricted to subspace-based methods. An off-grid sparse recovery-based algorithm is proposed in this paper to improve the accuracy of existing algorithms in low signal-to-noise ratio situations. The covariance and pseudo covariance matrices can be jointly represented subject to block sparsity constraints by taking advantage of the joint sparsity between signal components and bias. Furthermore, the estimation problem is transformed into a single measurement vector problem utilizing the focused operation, resulting in a significant reduction in computational complexity. The proposed algorithm's error threshold and the Cramer-Rao bound for wideband noncircular DOA estimation are deduced in detail. The proposed algorithm's effectiveness and feasibility are demonstrated by simulation results.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.164-171
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• 2012

ESPRIT(Estimation of Signal Parameter via Rotational Invariance Techniques) estimates DOAs(directions of arrival) of the incident signals on a sensor array by exploiting the shift invariance between its two subarrays. This paper suggests an efficient DOA estimation method based on ESPRIT when coherent signals impinge on the sensor array. When applying ESPRIT, it is necessary to find a signal subspace. Though the widely known SS(spatial smoothing) method allows us to obtain a signal subspace in the presence of coherent signals, its computational complexity is very high. Recently a CV(correlation vector) based method has been presented which is computationally simple. However, the number of resolvable signals in the method is smaller than that in the SS based method when multiple coherent signal groups are present. The proposed method in this paper, which obtains a signal subspace by utilizing only part of the correlation matrix, significantly reduces the computational complexity as compared with the SS based one, while the former is resolving the same number of coherent signals as the latter,

• Journal of Advanced Navigation Technology
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• v.6 no.3
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• pp.181-187
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• 2002

In this paper, we propose a resolution enhancement method for estimating direction-of-arrival(DOA) of narrowband incoherent signals incident on a general array. The resolution of DOA algorithm is dependent on the aperture size of antenna array. But it is very impractical to increase the physical size of antenna array in real environment. We propose the method that improves resolution performance by virtually expanding the sensor spacing of original antenna array and then averaging the spatial spectrum of each virtual array which has a different aperture size. Superior resolution capabilities achieved with this method are shown by simulation results in comparison with the standard MUSIC for incoherent signals incident on a uniform circular array.