Mushroom-like Electromagnetic Band Gap Research Articles

Mushroom-Like EBG to Improve Patch Antenna Performance For C-Band Satellite Application

In order to suppress the surface waves excitation that are caused by thick substrate in a patch antenna, a mushroom-like EBG (Electromagnetic Band Gap) structure is used. Such structures enhance its characteristics of gain, directivity, bandwidth and efficiency. Firstly, we determined frequency band gap characteristics of mushroom like EBG unit cell value by using CST software with 3mm (0.06λo) for covering 6 GHz. The periodic arrangement of such mushroom-like EBG structures was not limited by any interconnecting microstrip lines. Four columns of EBGs shifted inwards to antenna edges by 0.3mm (0.06λo) or a gap of its design around the patch from the left and right sides. Different configurations were also examined in order to get the better improvement in antenna performance. The final design of this mushroom-like shifted periodic structure shows an effective increase in the directivity by 77%, gain by 108%, bandwidth by 29% and the efficiency by 20% for the antenna. This structure has diversified application possibility for wireless and satellite communications.

Reduction of Mutual Coupling between Closely Spaced Microstrip Antennas Arrays Using Electromagnetic Band-gap (2D-EBG) Structures

Reducing mutual coupling is a key research area in design of compact microstrip antennas arrays. To minimize the overall size of the antennas arrays, the distance between them must be very small, as a result a strong mutual coupling is appears. Periodic structures can help to design a low profile of antennas arrays and enable to improve their performances by the suppression of surface waves propagation in a given frequency range. This paper proposes a novel configuration of mushroom-like electromagnetic band-gap (2D-EBG) structure created by microstrip technology placed between two antennas arrays to reduce the mutual coupling more than -33.24dB. When 13×2 EBG structures are used, the mutual coupling reduces to -59.36dB at the operation frequency 5.8GHz of the antennas arrays. A 26.12dB mutual coupling reduction is achieved, which proves that the surface wave is suppressed. The proposed configuration is designed, optimized, and miniaturized by using electromagnetic software CST Microwave Studio. The measured results show that there is a good agreement with the computed results.

Mushroom-like Electromagnetic Band Gap based Polarization Converters for Millimeter Wave Applications

Developments in radar navigation and remote sensing required rugged and inexpensive location markers and calibration targets with very large radar cross sections and a specified polarization response. Passive radar targets derived from corner reflectors were considered for this application. These targets require polarization converters for their operation. Conventional converters suffer from heavy weight, complicated structure, losses, and/or limited bandwidth. Polarization converters made of electromagnetic band gap materials are low profile, light weight, efficient, and have large bandwidth. The work presented here is a development of a simple procedure for the design of these converters. The requirements for polarization transformation are derived. The design procedure is outlined. Mushroom-like electromagnetic band gap materials using square patches are used. These materials are made polarization dependent through making single slot or two slots in the square patches. Detailed parametric study was conducted to see the effect of different parameters upon reflection phase difference. Polarization converters to transform linear polarization to linear polarization with the reflected electric field perpendicular to the incident electric field were designed.

Pattern reconfigurable antenna using electromagnetic band gap structure

In this paper, a single rectangular patch antenna incorporated with an array of electromagnetic band gap (EBG) structures is proposed. The proposed antenna features radiation pattern agility by means of connecting the shorting pin vias to the EBG unit cells. The proposed design consists of 32 mm × 35.5 mm rectangular patch antenna and 10.4-mm-square mushroom-like EBG unit cells. The EBGs are placed at both sides of the antenna radiating patch and located on the thicker substrate of thickness, h. The copper tape which represents the PIN diode is used to control the connection between the EBG’s via and the ground plane as reconfigurable mechanism of the antenna. The simulated result shows by switching the ON and OFF EBG structures in either sides or both, the directional radiation pattern can be tilted from 0 to +14°. The proposed antenna exhibits 7.2 dB realized gain at 2.42 GHz. The parametric study on EBG and antenna is also discussed.

A Low Mutual Coupling Design for Array Microstrip Antennas Integrated with Electromagnetic Band-Gap Structures

Developing and employing methods to reduce the mutual coupling between elements of an antenna array has become a hot topic in the design of antenna arrays. The utilization of electromagnetic band-gap (EBG) structures is an attractive way to reduce surface wave excitation in printed antenna geometries so to mitigate the mutual coupling problem. This paper investigates the performance of a microstrip antenna phased array embedded in an EBG. A novel EBG array configuration is proposed, the band-gap feature of mushroom-like EBG has been studied, its band-gap feature of surface-wave suppression is demonstrated by plotting variations of the transmission coefficient S12 with frequency and dispersion diagram. The antenna design is verified by High Frequency Structural Simulator (HFSS), the simulating results show that the EBG design approach is a good candidate for a reduction in mutual coupling at certain frequencies between radiator elements, which in turn increases antenna directivity.

Low-profile Circularly Polarized Antenna Exploiting Fabry-Perot Resonator Principle

We designed a patch antenna surrounded by a mushroom-like electromagnetic band-gap (EBG) struc- ture and completed it by a partially reflective surface (PRS). EBG suppresses surface waves and creates the bottom wall of the Fabry-Perot (FP) resonator. PRS plays the role of a planar lens and forms the top wall of the FP resonator. The novel PRS consists of a two-layer grid ex- hibiting inductive and capacitive (LC) behavior which allows us to obtain a reflection phase between -180° and +180°. Thanks to this PRS, we can control the height of the cavity in the range from λ/2 to λ/300. Obtained results show that the FP resonator antenna ena- bles us to achieve a low profile and a high-gain. The patch is excited by a microstrip transmission line via the cross- slot aperture generating the circular polarization. Functionality of the described concept of the FP antenna was verified at 10 GHz. The antenna gain was 15 dBi, the impedance bandwidth 2.3% for |S11| < -10 dB, and the axial ratio bandwidth 0.6% for AR < 3.0 dB. Hence, the antenna is suitable for narrowband applications. Computer simulations show that the microwave FP an- tenna can be simply redesigned to serve as a source of circularly polarized terahertz waves.

Low‐profile high‐gain slot antenna with Fabry‐Pérot cavity and mushroom‐like electromagnetic band gap structures

A novel low-profile high-gain slot antenna based on a modified Fabry-Perot cavity (FPC) and a mushroom-like electromagnetic band gap (EBG) structure is proposed and discussed. The low-profile FPC composed of a planar artificial magnetic conductor and frequency selective surfaces is utilised to enhance gain. Moreover, the mushroom-like EBG structure rather than a traditional reflector is used to reduce the profile and to increase gain. Eventually, an antenna prototype operating at the WLAN system coverage IEEE 802.11a (5.15–5.35 GHz) is fabricated and exemplified to validate high radiation performance. The measured results show that the proposed antenna achieves a high gain of up to 10.6 dBi at 5.25 GHz and an −10 dB impendence bandwidth for S 11 ranging from 5.08 to 5.51 GHz.

A Dual Band Patch Antenna with a Pinwheel-Shaped Slots EBG Substrate

A dual band microstrip patch antenna integrated with pinwheel-shaped electromagnetic band-gap (EBG) structures is proposed. The patch antenna consists of a pair of spiral slots on the patch and is fed by using coaxial line. Its full-wave simulation predicts dual bands from 4.43 GHz to 4.56 GHz and from 4.96 GHz to 5.1 GHz in the C-band. The designed EBG with eight pinwheel-shaped slots addresses smaller frequency drift compared with the traditional square mushroom-like EBG when applied to the patch antenna. With the help of designed EBG structure, the impedance bandwidth, radiation efficiency, and gain of the patch antenna are improved significantly. The 10 dB impedance bandwidth is extended by 3.4% and 6.5% at the low- and high-frequency bands, respectively. The radiation efficiency is increased by 5% and 17.8%, and the realized gain is enhanced by 1.87 dB and 1.56 dB at 4.57 GHz and 5.06 GHz, respectively. The designed EBG structure may have many applications in other types of planar antennas.

A Novel Microstrip Antenna With Composite Patch Structure for Reduction of In-Band RCS

A novel kind of composite patch antenna is proposed, in which the mushroom-like electromagnetic band-gap (EBG) structure is integrated onto the conventional patch. Due to the high impedance property of the EBG structure, the scattering fields from EBG structure and the rest of antenna can be out of phase and cancel each other. The composite patch antenna exhibits a natural low in-band radar cross section (RCS) property and keeps the compact planar size as the conventional patch antenna. When radiating, the composite patch as a whole acts as the radiating part of the antenna; while scattering, the composite patch antenna can significantly reduce the in-band RCS within the main scattering beam direction, and the maximum reduction can reach 8 dBsm when plane wave is impinging from normal direction.

Design of Compact 4 × 4 UWB-MIMO Antenna with WLAN Band Rejection

A compact 4 × 4 UWB-MIMO antenna with rejected WLAN band employing an electromagnetic bandgap (EBG) structure is presented in this paper. The MIMO antenna is electrically small (60 mm × 60 mm), printed on a FR4_epoxy substrate with the dielectric constant of 4.4 and a thickness of 1.6 mm. A mushroom-like EBG structure is used to reject the WLAN frequency at 5.5 GHz. In order to reduce the mutual coupling of the antenna elements, a stub structure acting as a bandstop filter is inserted to suppress the effect of the surface current between elements of the proposed antenna. The final design of the MIMO antenna satisfies the return loss requirement of less than −10 dB in a bandwidth ranging from 2.73 GHz to 10.68 GHz, which entirely covers UWB frequency band, which is allocated from 3.1 to 10.6 GHz. The antenna also exhibits a WLAN band-notched performance at the frequency band of 5.36–6.34 GHz while the values of all isolation coefficients are below −15 dB and the correlation coefficient of MIMO antenna is less than −28 dB over the UWB range. A good agreement between simulation and measurement is shown in this context.

A Design of EBG-PIFA for RFID Applications in UHF Band

One of the longstanding problems in planar inverted F antenna (PIFA) is its efficiency, which reduces as PIFA is placed too close to the ground. In this paper a kind of mushroom-like Electromagnetic band gap (EBG) structure with three conductor layers is designed In the UHF band, which has smaller unit cells and thinner thickness compared to classical ones. This kind of mushroom-like EBG structure is used as the reflector of PIFA with capacitor structure. It is demonstrated that PIFAs with EBG grounds have higher radiation efficiency than those with PEC ground. At the same time, no significant changes in the antenna resonance frequency and the radiation patterns are found. The theoretical prediction is well verified by results of both simulation and experiment.

Model and Mechanism of Miniaturized and Stopband-Enhanced Interleaved EBG Structure for Power/Ground Noise Suppression

An interleaved electromagnetic bandgap (EBG) structure is investigated to be with a compact size and wide stopband bandwidth for suppressing power/ground noise in power distribution networks. A design concept of the interleaved EBG structure is given to improve both lower and upper bound cutoff frequencies through varying the pitch of the power and ground vias and validated by measured results. An equivalent circuit model of the 1-D EBG structure is established using transmission-line sections to precisely predict the lower and upper bound cutoff frequencies. Based on the 1-D model, a physical mechanism is found to explain why the interleaved EBG structure can reduce the size and broaden the stopband. As an example, the bandgap of the interleaved EBG structure is in the range from 1.9 to 4.54 GHz. The electrical size, which is normalized to the wavelength in the substrate, and relative bandwidth are 0.071 λ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">gL</i> and 139%, respectively. Unlike other works with tradeoff between size and bandwidth, the interleaved EBG structure can simultaneously achieve substantial improvements on the bandwidth of 51.1% and on the miniaturization of 61.2% compared with the conventional mushroom-like EBG structure.

DUAL-LAYER EBG STRUCTURES FOR LOW-PROFILE ``BENT'' MONOPOLE ANTENNAS

We propose in this paper the design, realization and experimental characterization of a low-proflle metamaterial \bent monopole antenna with a total height of 0.027‚0 and a fractional bandwidth of 24.4% around 1.3GHz. The metamaterial (MTM) structure is a dual-layer mushroom-like electromagnetic band gap (DL- EBG) conceived and optimized to improve the antenna's operating bandwidth. Moreover, a \Sabre-Type antenna composed by two identical \bent monopole metamaterial antennas placed on both sides of a composite thin slab material has been simulated and realized. The \sabre antenna provides a vertically polarization and omnidirectional radiation patterns in the elevation plane while its radiation patterns are almost directional in the azimuth plane. A maximum gain of 8.7dB is obtained by measurement at 1.45GHz. A remarkable agreement is obtained between the measured and the simulated results.

Novel Design of Electromagnetic Bandgap Using Fractal Geometry

A novel electromagnetic bandgap (EBG) structural design based on Fractal geometry is presented in this paper. These Fractals, which are the Sierpinski triangles, are arranged to repeat each 60° to produce the hexagonal unit cells. By changing the gap between two adjacent Sierpinski triangles inside EBG unit cell, we can produce two EBG structures separately that have broadband and dual bandgap. By using the suspending microtrip method, two arrays 3 × 4 of EBG unit cells are utilized to investigate the bandgap of the EBG structures. The EBG operation bandwidth of the broadband structure is about 87% and of the dual-band structure is about 40% and 35% at the center bandgap frequencies, respectively. Moreover, a comparison between the broadband EBG and the conventional mushroom-like EBG has been done. Experimental results of the proposed design show good agreement in comparison with simulation results.

Bandwidth Enhancement Based on Optimized Via Location for Multiple Vias EBG Power/Ground Planes

The ground surface perturbation lattice (GSPL) structure is investigated to suppress power noise in the power distribution network of mixed signal circuits. In order to enhance the bandwidth of the noise suppression, the GSPL structure is implemented by using multiple vias in the mushroom-like electromagnetic bandgap structure. Under the concept of multiple vias, the lower and upper bound cutoff frequencies of the bandgap are influenced by the position of the vias. An optimum position for the vias is found to achieve maximum stopband bandwidth. In this paper, the stopband mechanism of GSPL structure is investigated and the corresponding equivalent circuit model is proposed to quickly predict the lower and upper bound cutoff frequencies. Suitable test boards are fabricated and measured to demonstrate the accuracy of the design concept. The result shows that there is a good consistency between simulated, modeled, and measured results.

Transmit–Receive Isolation Improvement of Antenna Arrays by Using EBG Structures

The mushroom-like electromagnetic band-gap (EBG) structure combined with a choke structure is applied to improve the transmit-receive (T/R) isolation of two X-band large antenna arrays. The basic idea presented is to suppress the surface wave propagation between the T/R arrays by utilizing EBG walls formed through a vertical configuration of the EBG cells, so as to improve the T/R isolation. The isolation level of the arrays with the EBG walls and a metal choke is measured and compared to other isolation methods applied. The experimental results show that by using this combined structure, the isolation level can be improved by at least 30 dB in the radar's operation band, which shows its high efficiency.

RCS Reduction of Patch Array Antenna by Electromagnetic Band-Gap Structure

In this letter, electromagnetic band-gap (EBG) structure is used to reduce the radar cross section (RCS) of the patch array antenna. The proposition of this method is based on the high impedance characteristic of the mushroom-like EBG structure. The basic patch array antenna is designed with a central frequency of 5.0 GHz while replacing the substrate of the array with the mushroom-like EBG structure. The frequency band in which RCS of the patch array antenna reduced significantly can be adjusted by parameters of the EBG. The backward RCS of the patch array antenna with EBG can be reduced as much as 10 dB compared to that of the conventional array antenna, and the degradation of the antenna performance is not significant.

A Novel Tri-Band Circular Slot Patch Antenna with an Ebg Structure for Wlan/WiMAX Applications

In this paper, an electromagnetic band-gap (EBG) structure is proposed to achieve tri-band operation for a novel circular slot patch antenna, which is suitable for WLAN and WiMAX applications. The proposed antenna consists of a rectangular radiation patch with an etched circular slot, a circular ring, and a mushroom-like EBG structure, all of which are printed on the top side of the substrate. By embedding a circular ring in the circular slot, the antenna can generate two impedance bandwidths. With the use of EBG structure, the proposed antenna can operate in three separate bands. Simulation results are compared with the measurements, and a good agreement is obtained. The measured results show that the 10 dB return loss bandwidths of the proposed antenna are 530 MHz (2.28–2.81 GHz), 470 MHz (3.29–3.76 GHz) and 1250 MHz (4.87–6.12 GHz), which can cover all the 2.4/5.2/5.8 GHz WLAN bands and 2.5/3.5/5.5 GHz WiMAX bands. In addition, a design evolution and a parametric study of the proposed antenna are presented to provide information for designing, modifying, and optimizing such an antenna. At last, good omnidirectional radiation patterns with appreciable gain are obtained over the operating bands.

Investigated new embedded shapes of electromagnetic bandgap structures and via effect for improved microstrip patch antenna performance

Three novel shapes of mushroom-like electromagnetic bandgap (EBG) structures are presented in this paper. The three shapes are based on a rectangular metal strip with different combinations. The performances of the three-shape structures are studied by using both an incident plane wave method and transmission coefficient approach. The effect of height and via location is also studied to achieve multi or wide bandgap. These shapes are embedded in microstrip patch antenna substrates. The performance of the MPA is improved as increasing the antenna gain by 5 dBi, decreasing the surface current so improving the antenna radiation pattern as well as reducing the antenna size by more than 70% compared to the original size. The new shapes of EBG structures are integrated with MPA as a ground plane, where the conducting ground plane is replaced by a high impedance surface EBG layer. Parametric studies are conducted to maximize their impedance bandwidth and gain. It is found that the antenna bandwidth increased by approximately four times than the original band and its gain is similarly increased. Sample of these antennas are fabricated and tested to verify the designs.

UWB Monopole Antenna With Stable Radiation Pattern and Low Transient Distortion

In this letter, an ultrawideband (UWB) microstrip-fed planar monopole antenna with stable radiation pattern is presented. Although compact and simple structure of the planar antennas made them a good candidate in UWB applications, due to unwanted current distribution on the ground section, they suffer from transient distortion and radiation pattern rotation in different frequencies. To alleviate this effect, a metallic staircase plane is placed in the bottom of the substrate. In addition, a mushroom-like electromagnetic band-gap (EBG) structure is embedded on the top layer of the substrate to increase the gain in higher frequencies. Measurement results show 2.2-6 dB gain in broadside direction in 3-10-GHz frequency. A new definition of pattern stability factor (PSFII) is proposed, which is proper for both directional and omnidirectional radiation patterns. Calculated PSFII for the proposed antenna is higher than 95%, which shows a stable radiation pattern. Furthermore, it shows a low distortion manner where the fidelity factor in the main beam direction is more than 95%. In comparison to similar antennas presented in literature, PSFII and gain have been improved noticeably.