Preface 1. Introduction 2. FDTD Method for periodic structure analysis 3. EBG Characterizations and classifications 4. Design and optimizations of EBG structures 5. Patch antennas with EBG structures 6. Low profile wire antennas on EBG surfaces 7. Surface wave antennas Appendix: EBG literature review.

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Electromagnetic Band Gap Structures in Antenna Engineering

A compact decoupling network for enhancing the port isolation between two closely spaced antennas is proposed in this paper. In the network, we first connect two transmission lines (TLs) individually to the input ports of two strongly coupled antennas. The length of the TLs is designed so that the trans-admittance between ports changes from a complex one at the antenna inputs to a pure imaginary one. A shunt reactive component is then attached in between the TL ends to cancel the resultant imaginary trans-admittance. Finally, a simple lumped-element circuit is added to each port for input impedance matching. The even-odd mode analysis is adopted to investigate the currents excited on the antennas for predicting the radiation pattern of the two-element antenna array. Two examples of printed antennas at 2.45 GHz are tackled by using the proposed decoupling structure. The measurement results agree quite well with the simulation ones. High antenna isolation and good input return loss are simultaneously achieved in both cases, which demonstrates the feasibility of the structure. The decoupled antenna array in each example radiates, as prediction, toward different but complementary directions when the input power is fed in turn to the two input ports. The array efficiency is estimated better than 75% in each example. This pattern diversity effect is helpful for reducing the channel correlation in a multiple-input multiple-output (MIMO) communication system.

https://ir.nctu.edu.tw:443/bitstream/11536/8064/1/000263032000006.pdf

A Decoupling Technique for Increasing the Port Isolation Between Two Strongly Coupled Antennas

Periodic structures can help in the reduction of mutual coupling by using their capability of suppressing surface waves propagation in a given frequency range. The purpose of this work is to show the viability of using a planar electromagnetic band gap (EBG) structure based on a truncated frequency selective surface (FSS) grounded slab to this aim. The goal is to use it in patch antenna arrays, keeping both the element separation smaller than for grating lobes avoidance (assuming broadside case) and the patch antenna size large enough to have a good antenna directivity. To this aim, a multilayer dielectric substrate composed of high and low permittivity layers is convenient. This allows the use of a planar EBG structure made of small elements printed on the high permittivity material and, at the same time, the low permittivity layer helps the bandwidth and the directivity of the antenna to be increased. The EBG structure was designed under these premises and optimized for the particular application via an external optimization algorithm based on evolutionary computation: ant colony optimization (ACO). The mutual coupling reduction has been measured and it is larger than 10 dB with a completely planar structure.

Mutual Coupling Reduction in Patch Antenna Arrays by Using a Planar EBG Structure and a Multilayer Dielectric Substrate

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.

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

A broad bandwidth and high gain rectangular patch antenna was specifically designed in this paper using planar-patterned metamaterial concepts. Based on an ordinary patch antenna, the antenna has isolated triangle gaps and crossed strip-line gaps etched on the metal patch and ground plane, respectively. Demonstrated to have left-handed characteristics, the patterned metal patch and finite ground plane form a coupled capacitive-inductive circuit of negative index metamaterial. It is shown to have great impact on the antenna performance enhancement in terms of the bandwidth significantly broadened from a few hundred megahertz to a few gigahertz, and also in terms of high efficiency, low loss, and low voltage standing wave ratio. Experimental data show a reasonably good agreement between the simulation and measured results. This antenna has strong radiation in the horizontal direction for some specific applications within the entire band.

/pdf/a-broadband-and-high-gain-metamaterial-microstrip-antenna-5drz20moav.pdf

A broadband and high-gain metamaterial microstrip antenna

This paper presents an electromagnetic band-gap (EBG) structure in a fork-like shape. The period of the EBG lattice is only 0.07/spl lambda//sub 0/ at the desired stopband frequency, resulting in the most compact EBG lattice over achieved. A comparison has been carried out between the new structure and the 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. Also a double element microstrip antenna array inserted with the new EBG structure has been simulated, showing that a 6.51 dB mutual coupling reduction is achieved.

A novel compact electromagnetic band-gap (EBG) structure and its application in microstrip antenna arrays

A new concept is presented for a switched-sector planar antenna using parasitic elements with switches loaded. The antenna array provides multiple radiation patterns with a single RF signal port without the need for RF switches or phase shifters in the direct RF signal path. Measured and simulated patterns are used to demonstrate the performance improvement.

https://ieeexplore.ieee.org/iel5/9253/29352/01329805.pdf

A novel switched-sector planar antenna using parasitic elements

In this paper two multi-feed reconfigurable pattern antennas (MFRPA) have been proposed; a multi-feed with phase switching method was introduced to achieve a reconfigurable pattern for single microstrip ring or central grounded circular patch antenna; by controlling the phase of exciting source of each port, several reconfigurable beams can be achieved, and simulation and fabrication experiments have been carried out to verify the design.

Multi-feed reconfigurable pattern antenna implemented by switches

In this paper a novel Yagi V-dipole has been proposed for pattern reconfiguration, and the Yagi structure is to obtain a unidirectional beam. Simulation and measurement results both validated the performance of this design.

Fanglu Chen

Papers

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

A novel compact electromagnetic band-gap (EBG) structure and its application in microstrip antenna arrays

A novel switched-sector planar antenna using parasitic elements

Multi-feed reconfigurable pattern antenna implemented by switches

Yagi V-dipole reconfigurable antenna