Earticle

Perturbation analysis of direction of arrival (DOA) estimation has been studied mostly on one-dimensional arrays rather than planar arrays, which remains room for exploration. For uniform circular arrays with various model errors, we establish the corresponding system model. Then a performance analysis of the two-dimensional MUSIC algorithm is proposed by first-order error analysis and verified by simulation. The results show that the root-mean-squared error of DOA estimation is proportional to the standard deviation of the model errors, including gain-phase errors, sensor position errors, and mutual coupling effect.

본 논문에서는 원형배열 안테나의 위상차와 위상차 배열 패턴을 비교하여 전파 신호원의 방향을 찾는 방법을 연구 하였다. 위상비교 방향탐지 방식에서는 안테나 기준선 길이가 입사신호의 0.5파장보다 길면 같은 위상차에서 두 개 이상의 방위가 계산되는 방위각 모호성이 발생한다. 본 논문에서는 0-360도 방위각에서 전파 신호가 입사될 때 5개 안테나에서 검출된 위상차 패턴을 융합하여 방위각 모호성을 제거한다. 개발된 모호성 제거 기법은 안테나가 5개인 균일원형배열 구조 에서 안테나 기준선이 입사신호의 1.236파장 이하이면 방위각 모호성 없이 방향탐지를 정확하게 수행하였다. 본 알고리즘은 조난구조와 전자정보시스템의 방향탐지 장치 설계에 잘 활용할 수 있을 것으로 판단된다.

In this paper, we have studied a direction finding method of the radio signal by comparing the phase difference and its pattern from the uniform circular array antenna. In the phase comparison direction finding, if the length of the antenna baseline is longer than 0.5 wavelength of the incident signal, azimuth ambiguity occurs in which two or more azimuth angles are calculated in the same phase difference. The azimuthal ambiguity is removed by fusing the phase difference of the 5 antennas. The developed ambiguity elimination technology reduces the azimuth error where the antenna baseline is shorter than 1.236 wavelength in the uniform circular array with five antennas. This algorithm is very useful for the design of direction finder of an electronic information system.

본 논문에서는 원형 배열 안테나를 장착한 차량이 이동하면서 메쉬 네트워크 환경을 구성할 때 다중 노드 빔 형성을 위한 안테나 선택 방식과 전력 제어 알고리즘을 제안한다. 제안한 안테나 선택 방법은 안테나의 방사 이득을 고려하여 빔 형성을 위한 안테나를 선택하고, 두 개 이상의 노드가 인접할 경우 배열 이득을 최대화하기 위해 안테나를 중복으로 선택한다. 제안한 전력 제어 알고리즘은 중복 안테나 선택 시 SIR이 최대가 되도록 각 안테나의 전력을 제어한다. 전산 모의 실험을 통하여 제안한 알고리즘을 적용하여 기존의 방식과 비교하여 두 노드가 15°로 인접했을 때 최대 2.5 dB의 SIR 향상을 보인다.

This paper proposes the antenna selection scheme and power control algorithms of multiple nodes beamforming when the vehicles equipped with circular array antennas is moving and construct mobile mesh networks. The proposed antenna selection scheme chooses beamforming antenna elements considering antenna radiation gain and allows duplicated antenna selection for multiple adjacent nodes. The proposed power control algorithms maximize SIR for the duplicated antenna selection. The simulation demonstrates that the proposed antenna selection and power control achieve 2.5dB higher SIR gain than that of conventional methods when two nodes are apart from 15°.

Recently, Compressive Sensing (CS) has been applied to array signal processing. In theory, Direction-of-Arrival (DOA) estimation based on CS recovery can work well in correlated environments. However, a large number of sensors (i.e., linear measurements) are still needed for CS recovery. To improve on this, we propose a new CS-based DOA estimation method with a recently designed antenna structure called the Asymmetric Antenna without Phase Center (Asym-AWPC). The best reconstruction is achieved by solving the l1-norm optimization problem, which is cast as an l1-regularized least-squares program. Simulated results indicate the effectiveness of the proposed CS-based Asym-AWPC DOA estimator in a multipath environment over a recent Asym-AWPC DOA estimator but using the Multiple Signal Classification (MUSIC) rather than CS. Further improvement on the resolution can be achieved by tuning the degree of asymmetry in designing the Asym-AWPC.

In modern wireless communication systems including beamformers or location-based services (LBS), which employ multiple antenna elements, estimating the number of signals is essential for accurately determining the quality of the communication service. Representative signal number estimation algorithms including the Akaike information criterion (AIC) and minimum description length (MDL) algorithms, which are information theoretical criterion models, determine the number of signals based on a reference value that minimizes each criterion. In general, increasing the number of elements mounted onto the array antenna enhances the performance of estimating the number of signals; however, it increases the computational complexity of the estimation algorithm. In addition, various configurations of array antennas for the increased number of antenna elements should be considered to efficiently utilize them in a limited location. In this paper, we introduce an efficient signal number estimation algorithm based on the beamspace based AIC and MDL techniques that reduce the computational complexity by reducing the dimension of a uniform circular array antenna. Since this algorithm is based on a uniform circular array antenna, it presents the advantages of a circular array antenna. The performance of the proposed signal number estimation algorithm is evaluated through computer simulation examples.

For a wireless communication system, the angle-of-arrival (AOA) of the signal has a variety of applications. The signal AOA is estimated utilizing various antenna array structure such as Uniform Linear Array (ULA), Uniform Rectangular Array (URA), and Uniform Circular Array (UCA). In this paper, we introduce a cascade AOA estimation algorithm based on the UCA, which is consisted of CAPON and Beamspace MUSIC. CAPON is employed to estimate approximate AOA groups including multiple AOA signals and Beamspace MUSIC is employed to estimate detailed signal AOAs in the estimated AOA groups. In addition, we provide the computer simulation results for verifying and analyzing the performance of the cascade AOA estimator based on UCA.

An algorithm is presented for estimating the 3-D location (i.e., azimuth angle, elevation angle, and range) of multiple sources with a uniform circular array (UCA) consisting of an even number of sensors. Recently the rank reduction (RARE) algorithm for partly-calibrated sensor arrays was developed. This algorithm is applicable to sensor arrays consisting of several identically oriented and calibrated linear subarrays. Assuming that a UCA consists of M sensors, it can be divided into M/2 identical linear subarrays composed of two facing sensors. Based on the structure of the subarrays, the steering vectors are decomposed into two parts: range-independent 2-D direction-of-arrival (DOA) parameters, and range-relevant 3-D location parameters. Using this property we can estimate range-independent 2-D DOAs by using the RARE algorithm. Once the 2-D DOAs are available, range estimation can be obtained for each source by defining the 1-D MUSIC spectrum. Despite its low computational complexity, the proposed algorithm can provide an estimation performance almost comparable to that of the 3-D MUSIC benchmark estimator.

본 연구는 단일 원주의 와여기 진동특성에 관한 연구의 연속연구로서 풍동내 에 직렬로 배열된 두 원주의 직교유동에 의한 두 가지 경우의 동적 거동을 조사하였다. 첫째는 상류측 탄성지지 원주의 후류내에 가깝게 놓여진 하류측 고정원주의 간섭에 의한 상류측 원주의 진동(proximity-induced vibration)이며, 둘째는 상류측의 고정원 주의 후류내에 가깝게 놓여진 하류측 탄성지지 원주의 공기역학적 진동(wake-induced vibration)이다. 본 연구의 목적으로 직렬로 배열된 동일 직경의 두 원주에 있어서 어느 한 쪽의 원주가 탄성지지가 되어 있을 경우, 두 원주사이의 간격과 유속변화에 따른 와여기 진동과 유력탄성 불안정 진동의 진동특성 및 후류내에서의 와유출 특성을 명확히 하기 위해 실험적으로 조사, 연구하였다.

The wake-induced vibration and proximity-induced vibration of two interfering circular cylinders in tandem are investigated experimentally, using an elastically supported cylinder and a fixed cylinder in uniform crossflow. Dynamic responses and flow periodicity in wake are measured to investigate the effect of system parameters on aerodynamic instability. The parameters include the free stream wind velocity and the position of two interfering circular cylinders. The oscillating behavior of the amplitude of the elastically supported cylinder is changed by varying the position, the relative gap spacing between two interfering circular cylinders and the reduced velocities. In small gap spacing between the elastically supported cylinder located to upstream and the circular cylinder fixed to downstream, the fluidelastic instability is founded. The vibration amplitude decreases notably as gap spacing between two interfering circular cylinders becomes large. The dynamic behavior at g/D-4.0 is similar to that of the single circular cylinder.