Microstrip Antennas Integrated with Electromagnetic Band-Gap (EBG) Structures: A Low Mutual Coupling Design for Array Applications

Dept. of Electr. Eng., Univ. of California, Los Angeles, CA, USA
IEEE Transactions on Antennas and Propagation (Impact Factor: 2.46). 11/2003; 51(10):2936 - 2946. DOI: 10.1109/TAP.2003.817983
Source: IEEE Xplore

ABSTRACT Utilization of electromagnetic band-gap (EBG) structures is becoming attractive in the electromagnetic and antenna community. In this paper, a mushroom-like EBG structure is analyzed using the finite-difference time-domain (FDTD) method. Its band-gap feature of surface-wave suppression is demonstrated by exhibiting the near field distributions of the electromagnetic waves. The mutual coupling of microstrip antennas is parametrically investigated, including both the E and H coupling directions, different substrate thickness, and various dielectric constants. It is observed that the E-plane coupled microstrip antenna array on a thick and high permittivity substrate has a strong mutual coupling due to the pronounced surface waves. Therefore, an EBG structure is inserted between array elements to reduce the mutual coupling. This idea has been verified by both the FDTD simulations and experimental results. As a result, a significant 8 dB mutual coupling reduction is noticed from the measurements.

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    • "Therefore, the isolation between antenna elements is one of the key issues for the design of the MIMO systems. A number of techniques have been reported to enhance the isolation of two antenna elements, they can be classified as the introduction of offsetting branches [6], [7], the usage of modified ground [8], the utilization of metamaterials [9]–[12], as well as the adoption of decoupling networks [13]. Regarding the four-element antenna system, the reported techniques include the utilization of decoupling networks [14]– [17], optimization of antenna system configurations [18], [19], introduction of metamaterial structures including split-ring resonators (SRRs) [20]–[22] and planar mushroom [23], as well as any combination of the decoupled methods mentioned earlier [24], [25]. "
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    ABSTRACT: A double-layer mushroom structure is proposed to enhance the interelement isolation of a four-element antenna system, wherein four closely positioned substrate-integrated cavity-backed slot (SICBS) antenna elements are configured for multiple-input multiple-output (MIMO) applications. A wall with a double-layer mushroom structure is positioned in between the four antenna elements. An antenna prototype with a ground plane size of ${mathbf{0}}.{mathbf{96}};{{mathbf{lambda }}_{mathbf{0}}} times 0.96;{{mathbf{lambda }}_{mathbf{0}}}$ (${{mathbf{lambda }}_{mathbf{0}}}$ is the free space-wavelength at 2.4 GHz) demonstrates an enhanced interelement isolation of 16 dB for parallel-directed antenna element pairs, while the isolation of the orthogonally directed antenna element pairs remains unchanged over the operating bandwidth ($vert {{mathbf{S}}_{{mathbf{11}}}}vert < - {mathbf{10}};{text{dB}}$) of 2.396 –2.45 GHz. With the enhanced isolation larger than 42 dB between each antenna element pair, the envelope correlation coefficient (ECC) is lower than 0.02 across the operating bandwidth. The simulated and measured results validate the good MIMO diversity performance of the proposed antenna system.
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    • "Due to the in-phase reflection characteristics, the mushroomtype HIS has been used as the ground plane or reflector of various antennas to achieve low-profile design [2−3]. The mushroom-type HIS structures also exhibit electromagnetic band-gap (EBG) properties, and are usually integrated in between antenna elements to suppress undesired surface waves and thus reduce the inter-element mutual coupling [4] [5]. On the other hand, the mushroom structures have been utilized to implement composite right/left-handed (CRLH) transmission-line structures [6]. "
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    The 9th European Conference on Antennas and Propagation (EuCAP 2015); 04/2015
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    • "The reason is that the cloak structure for an antenna is needed to be designed in a way that provides drastic scattering reduction, and at the same time, preserves the electromagnetic performance of the antenna. In this regard, in [32], a mushroom-like electromagnetic band-gap (EBG) structure has been proposed in the design of microstrip antenna arrays in order to reduce the strong mutual coupling caused by the thick and high-permittivity substrates . In [33], the concept of cloaking a sensor (a short dipole antenna) without affecting its ability to receive an incoming signal has been presented. "
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