The direction of arrival (DOA) estimation problem is formulated in a compressive sensing (CS) framework, and an extended array aperture is presented to increase the number of degrees of freedom of the array. The ordinary least square adaptable least absolute shrinkage and selection operator (OLS A-LASSO) is applied for the first time for DOA estimation. Furthermore, a new LASSO algorithm, the minimum variance distortionless response (MVDR) A-LASSO, which solves the DOA problem in the CS framework, is presented. The proposed algorithm does not depend on the singular value decomposition nor on the orthogonality of the signal and the noise subspaces. Hence, the DOA estimation can be done without a priori knowledge of the number of sources. The proposed algorithm can estimate up to (false(M2−2false)/2+M−1)/2 sources using M sensors without any constraints or assumptions about the nature of the signal sources. Furthermore, the proposed algorithm exhibits performance that is superior compared to that of the classical DOA estimation methods, especially for low signal to noise ratios (SNR), spatially-closed sources and coherent scenarios.
In this paper, a novel wide axial ratio bandwidth (ARBW), high gain, and low profile lefthand circularly polarized [4 × 4] elliptical microstrip array suitable for Ku-band satellite TV reception applications is introduced. A careful study has been done to get the optimum design to be suited for these application requirements. A circularly polarized microstrip patch with two stubs opposite to each other to produce two orthogonal modes is presented. The proposed element has 1.49 GHz 10-dB return loss bandwidth (RLBW), 0.44 GHz 3-dB Axial-ratio band (ARBW), and 6.9 dBi gain. A novel substrate integrated waveguide (SIW) feeding structure is investigated. Using the advantage of the output ports phase response of the SIW feeding network, two structures have been investigated. First, a [2 × 2] circular array has been designed, and although it has reached a good RLBW, this structure does not achieve the required ARBW for the above-mentioned application. Further, a compact [2 × 2] sequential feeding network is designed to widen the ARBW. The measurement shows a very good result with about 12 dBi gain, 14.8% RLBW, and 12% ARBW. Finally, a [4 × 4] duple sequential feeding array is designed to increase the gain of the antenna to about 19 dBi, with 13% RLBW and 20.7% ARBW. In addition to that, the final antenna profile is 0.0184λ.
This paper presents the design of optimum miniatureized conformal smart antenna system using 1u8 switched Butler Matrix and the realization of its planar smart antenna system. The demands of wireless communication were increases, so the higher capacity, wider coverage and low attenuation are main characteristic to provide the better and quality services. Smart antenna systems provide a broad range of ways to improve the performance of wireless system through the increase of the number of voice calls and the amount of data throughput, to avoid interference and to ease network management. The proposed both planar and conformal smart antenna system structures radiation characteristics are obtained to demonstrate the excellent performance which has isolation up to -27 dB and coupling up to -52 dB with antenna return loss equals to -37 dB to meet the requirements for wireless communications applications.
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