Mushroom-like Electromagnetic Band Gap Research Articles

MINIATURE ELECTROMAGNETIC BAND-GAP STRUCTURE USING SPIRAL GROUND PLANE

An important application of electromagnetic band-gap (EBG) structures is reducing the mutual coupling and eliminating the scan blindness for array antennas. However, some array antennas have small element spacing, and traditional mushroom-like EBG materials are too large. Under this condition, miniature EBG structures are desired for these array antennas. In this paper, a novel method using spiral ground plane is proposed to reduce EBG structure sizes. A low frequency band-gap can be obtained by adjusting the width and length of the spiral arms. An experimental prototype is fabricated to validate the analysis. The measurement results show a good agreement with the simulation data. Compared with traditional mushroom-like EBG structures, the proposed EBG achieves more than 77% size diminution.

STUDY THE EFFECTS OF ELECTROMAGNETIC BAND-GAP (EBG) SUBSTRATE ON TWO PATCH MICROSTRIP ANTENNA

Utilization of electromagnetic band-gap (EBG) structures is becoming attractive in the electromagnetic and antenna community. In this paper, the effects of a two-dimensional electromagnetic band- gap (EBG) Structures on the performance of microstrip patch antenna arrays are investigated using the Ansoft High Frequency Selective Simulator (HFSS TM ). A mushroom-like EBG structure is compared with 2-DEBG Structures. HFSS TM is employed to determine the effects of different Structures on two element microstrip patch antennas array. Two element microstrip patch antenna array on a uniform substrate suffer from strong mutual coupling due to the pronounced surface waves. Therefore, diverse forms of 2-DEBG Structures like: little number of holes, large number of holes, defect mode and different number of mushroom-patches columns structure are discussed. The two element microstrip patch antennas array placed on a defect in the electromagnetic (EBG) substrate that localizes the energy under the antennas. The excitation frequency of the two element microstrip patch antennas array near the resonance frequency of the defect mode can be used to control the coupling between antennas that are placed in an array. The mutual coupling improved by using large number of mushroom-patches columns structure.

Design of Three-layer Circular Mushroom-like EBG Structures

In this paper two types of three-layer mushroom-like electromagnetic band-gap (EBG) surfaces with circular patches are investigated. One of them consists of a square array of circular patches and the other one consists of a triangular array of circular patches in upper and lower layers. Guidelines for designing a ground plane for low proflle antenna applications are presented using the re∞ection phase characteristics. The efiect of some parameters of the three-layer structures on the re∞ection phase characteristic is studied. The frequency band in which a wire antenna adjacent to the three-layer EBG surface has good matching is determined by investigating the re∞ection phase characteristics of the EBG ground plane.

Investigation of EBG surface performance for high-precision GPS applications

A mushroom-like electromagnetic bandgap (EBG) surface for interference mitigation in GPS L2 and L1 band is presented. This printed metallo-dielectric structure is designed to act like commercially available choke rings (cylindrically corrugated surface). Measurements exhibit comparable performance, while weight and thickness are significantly reduced.

Characteristics and Applications of a Novel Compact Spiral Electromagnetic Band-Gap (EBG) Structure

In this paper a novel compact electromagnetic band-gap (EBG) structure in a spiral shape is presented and investigated. This EBG cell introduces spiral structure to enlarge the capacitance between neighboring elements much, and get an extremely compact size. The simulations and experimental results have proved that the length of the spiral structure is only 30.9% of the conventional mushroom-like EBG structure. The structure also presents some merits to design multi-band EBG structure only by adjusting the length of capacitance and without changing the periodical size. Two applications are demonstrated, including radiation pattern improvement of patch antenna with novel EBG structure and steerable array with a linearly discrete beamsteering of 20° in steps of 10° at 3.0 GHz.

Reduction of Mutual Coupling in a Microstrip Patch Array Fed by a Triplate Waveguide with EBG Elements

This letter presents mutual coupling reduction in an E-plane arranged microstrip patch array fed by a triplate waveguide. Five mushroom-like electromagnetic band-gap (EBG) elements arranged in one column are embedded both between two radiating patches and between the feeding lines for suppression of the surface wave and the parallel plate mode, respectively. Validity of the proposed EBG elements is confirmed by the measurement.

Locally Resonant Cavity Cell Model for Electromagnetic Band Gap Structures

Mushroom-like electromagnetic band gap (EBG) structures exhibit unique electromagnetic properties that have found a wide range of electromagnetic device applications. This paper focuses on the local resonance behaviors of EBG structures, and a simply locally resonant cavity cell (LRCC) model for mushroom-like EBG structures is presented to gain insight to the physical mechanism of the EBG structures and the interaction of electromagnetic waves with EBG structures. The LRCC model proposes two kinds of main resonance modes: One is the mono-polarized mode that accurately predicts the position of the surface wave suppression bandgap, which is equivalent to the LC parallel resonance based on quasistatic assumption in principle, and the other is the cross-coupling polarized mode that exhibits some interesting resonant phenomena, which has not been observed previously. Parametric studies including the radius effect of the metal plated vias are effectively performed by using the LRCC model. Some numerical simulations and experiments of EBG structures, such as square, triangle, and hexagon lattices, are given to illustrate the applications and validation of LRCC model proposed by this paper.

Analysis and Design of Waveguide Slot Antenna Array Integrated With Electromagnetic Band-Gap Structures

Utilization of electromagnetic band-gap (EBG) structures becomes more attractive in the electromagnetic and antenna community. This letter investigates the performance of a waveguide slot antenna array integrated with mushroom-like EBG structures. Some novel and efficient EBG array configurations are proposed, and a waveguide broadside resonant slot array of 5 times 5 elements was designed, built and tested. The tradeoffs and design considerations of EBG structures are discussed to obtain optimum performance

Reflection Phase and Frequency Bandgap Characteristics of EBG Structures with Anisotropic Periodicity

An anisotropic mushroom-like electromagnetic bandgap (EBG) structure is studied. Different to the conventional EBG structures with square unit cell, the presented EBG structures are with anisotropic periodicity. The periodic spacing or the metal patch length is different along the two periodic directions. So the reflection phase and the frequency bandgap will show distinct characteristics compared to the conventional EBG structures. These two features of the anisotropic EBG structures have been calculated numerically using FDTD method. The results show that the frequency of in-phase reflection is dependent on the polarization of incident plane wave, and the frequency bandgap along the two orthogonal directions could be designed to be similar or even overlapped.

A novel compact electromagnetic-bandgap (EBG) structure and its applications for microwave circuits

A novel electromagnetic-bandgap (EBG) structure in a fork-like shape is investigated. This structure has an extremely compact size. A comparison has been carried out between the new structure and the conventional mushroom-like EBG structure. Simulations and experimental results have verified that the area of the fork-like structure is less than 40% of the latter. The presented structure also provides an additional degree of freedom to adjust the bandgap position, which is applied to design a novel reconfigurable multiband EBG structure. Several application examples have been demonstrated, including a double-element microstrip antenna array with low mutual coupling, notch-type antenna duplexer, and steerable array with a linearly discrete beamsteering of 20/spl deg/ in steps of 10/spl deg/ at 2.468 GHz.

Reflection phase characterizations of the EBG ground plane for low profile wire antenna applications

Mushroom-like electromagnetic band-gap (EBG) structures exhibit unique electromagnetic properties that have led to a wide range of electromagnetic device applications. This paper focuses on the reflection phase feature of EBG surfaces: when plane waves normally illuminate an EBG structure, the phase of the reflected field changes continuously from 180/spl deg/ to -180/spl deg/ versus frequency. One important application of this feature is that one can replace a conventional perfect electric conductor (PEC) ground plane with an EBG ground plane for a low profile wire antenna design. For this design, the operational frequency band of an EBG structure is defined as the frequency region within which a low profile wire antenna radiates efficiently, namely, having a good return loss and radiation patterns. The operational frequency band is the overlap of the input-match frequency band and the surface-wave frequency bandgap. It is revealed that the reflection phase curve can be used to identify the input-match frequency band inside of which a low profile wire antenna exhibits a good return loss. The surface-wave frequency bandgap of the EBG surface that helps improve radiation patterns is very close to its input-match frequency band, resulting in an effective operational frequency band. In contrast, a thin grounded slab cannot work efficiently as a ground plane for low profile wire antennas because its surface-wave frequency bandgap and input-match frequency band do not overlap. Parametric studies have been performed to obtain design guidelines for EBG ground planes. Two novel EBG ground planes with interesting electromagnetic features are also presented. The rectangular patch EBG ground plane has a polarization dependent reflection phase and the slotted patch EBG ground plane shows a compact size.

Microstrip antennas integrated with electromagnetic band-gap (EBG) structures: a low mutual coupling design for array applications

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.