A new double L-shaped multiband patch antenna on a polymer resin material substrate

The design and prototyping of a new double L-shaped patch antenna on substrate of available low cost polymer resin composite material is presented. The designed microstrip line fed compact antenna consists of a planar double L-shaped slotted radiating patch, 1.6 mm thick substrate and ground plane. The proposed small antenna was designed and analyzed using a finite-element method-based, commercially available, high frequency structure simulator, and fabricated on a printed circuit board. The measured ?10 dB return loss bandwidths were 220 MHz and 650 MHz at 4.85 GHz and 8.10 GHz center frequencies. The corresponding symmetric and almost steady radiation patterns have peak gains of 7.6 dBi and 4.1 dBi, making the proposed antenna suitable for C and × band wireless applications, especially for WLANs, mobiles and satellites. The radiation efficiency, input impedance and current distribution of the proposed antenna were also analyzed.     

Compact wideband implantable antenna for biomedical applications

Wideband miniaturized antenna along with high gain is much needed for biomedical implantable applications. Square patch with loop structure of 51.2 mm³ (8 mm × 8 mm × 0.8 mm) volume is printed on RT Duroid 5880 (ε_r = 2.2) low permittivity substrate. Parametric study is conducted to optimize the antenna structure. Tissue model is used to take the simulation results and Body Equivalent Solution is used for measuring the antenna performance. Good radiation performance is confirmed by obtaining a gain of −16.7 dBi at 2.45 GHz and a low SAR value of 35.03 W/kg over 10g tissue with input power 1W is obtained. Proposed antenna gives a 64.9% measured wide impedance bandwidth. This study reveals that simple antenna structure can provide good performance when it is placed in complicated environment.     

Antenna gain enhancement by using metamaterial radome at THz band with reconfigurable characteristics based on graphene load

The reconfigurable concept of a graphene loaded patch antenna with increasing gain is proposed in this paper. We have developed the patch antenna with inset feed for THz band application for which graphene load is used to obtain the reconfigurable characteristic. It has been shown that by increasing the graphene chemical potential, the antenna resonant frequency shifted and the gain increased drastically up to 4 dBi. Additionally, we have shown that antenna efficiency is improved up to 78% which shows more than 100% of enhancement in comparison to basic antenna by increasing the graphene chemical potential. Finally, considering the antenna gain improvement, we have implemented the metamaterial layer over the antenna. In this case, the gain is increased more than 5–6 dBi. In addition, when we put the metamaterial layer over the antenna, the graphene layer shows more linear characteristics. By using parametric studies, we have defined the best point for metamaterial layer around 0.58λ. The final antenna gain is more than 11 dBi, which is useful for THz communication and THz medical imaging systems.     

一种新型宽带定向性贴片天线设计

利用超材料概念,通过在接地面上蚀刻条形缝隙图案,并引入"八木"天线中的反射器和引向器的设计思想,设计并且制作了一种超宽带强定向型贴片天线.仿真结果表明,天线相对带宽为65.3%(6.9—13.6 GHz),带内回波损耗均在-10 d B以下,整个频段内天线的增益均在4.4 d Bi以上.由于接地板上蚀刻的超材料结构的左手特性影响了天线介质基底的等效媒质参数,天线电磁场的传播方向被改变,天线辐射场主要集中在水平方向而不是传统贴片天线的垂直方向.在传统的贴片天线上引入反射器和引向器增强了天线的方向性.实验结果与仿真结果有较好的一致性.     

一种辐射零点可控的紧凑型滤波贴片天线

提出了一种辐射零点可控的紧凑型滤波贴片天线。该滤波天线以基本的微带贴片天线为原型,主要由一个简单的金属辐射贴片和两个对称的分割形槽组成。两个分割形槽蚀刻在金属贴片上,使得高/低频段分别产生两个宽边辐射零点,从而引入滤波选频功能。该结构未引入额外滤波电路和其他寄生单元,节省了空间尺寸,结构更加紧凑;两个辐射零点独立可控,提高了设计的灵活度。且在实现滤波选频功能的同时,对天线增益的影响很小。利用HFSS仿真软件优化滤波天线结构,制作了一个实物模型并进行了测试。测试结果与仿真结果基本一致。测试结果表明,提出的滤波天线工作在2.40 GHz,两个独立可控的辐射零点分别位于1.96 GHz和2.66 GHz,平均实际增益约为7.0 dBi,带外抑制水平超过39 dB。     

Coplanar waveguide-fed compact planar ultra-wideband antenna with inverted L-shaped and extended U-shaped ground for portable communication devices

To simultaneously cover multiple wireless services and protocols, the antenna in communication devices should operate over a wide and ultra-wide frequency band. The use of wide/ultra-wideband antennas not only lessens the number of antennas necessary to cover multiple frequency bands but also decreases the system complexity, size, and costs. To operate over the ultra-wide frequency band, in this paper a CPW-fed small antenna is reported for portable communication devices. The anticipated antenna comprises a bow-tie-shaped patch and two ground planes. One inverted L-shaped and one extended U-shaped ground plane are asymmetrically placed with the main radiator which helps the antenna prototype to realize a functional band of 3.05 – 11.25 GHz (VSWR ≤ 2). In the functional band, the studied antenna accomplished a maximum peak gain of 4.98 dBi and maximum efficiency of 94.4%. Moreover, it exhibits symmetric omnidirectional radiation patterns and good time-domain behavior. The lucrative characteristics such as simple design, very small size (24.5 × 20 mm²), ultra-wide operating band, good gain and efficiency, stable radiation characteristics, and good time-domain characteristics make it a potential candidate to be used in portable communication devices.     

High gain and circularly polarized substrate integrated waveguide cavity antenna array based on metasurface

Two substrate integrated waveguide (SIW) cavity antenna arrays based on metasurface are proposed in this paper. By rotating the metasurface element, circularly polarized and high gain antennas are achieved respectively. Firstly, multi-mode resonance theory is employed to broaden the bandwidth of the slot antenna. And then, an SIW cavity composed of 4×4 cornercut elements is added on the top of the slot antenna to achieve the circular polarization and improve the front-to-back ratio. Thirdly, the metasurface elements are sequentially rotated and a high gain antenna with 2-dBi enhancement on average in the operation band is obtained. Based on the two antenna units, two 2×2 antenna arrays are designed. The circularly polarized and high gain antenna arrays are both fabricated to verify the correctness. Furthermore, the novel wideband phase shifter is employed in the circularly polarized antenna to obtain an operating bandwidth of 38% (4.05 GHz-5.95 GHz) and AR bandwidth of 24.9% (4.4 GHz-5.65 GHz). The bandwidth of the high gain antenna can reach 42.7% (3.95 GHz-6.1 GHz) and with the gain enhancement of 2 dBi compared with that of the circularly polarized antenna. The gain remains steady in most of operating band within a variation of 1 dBi. It is remarkable that the rotating of the metasurface element has a great influence on the antenna performance, which provides a new explication for the multi-function antenna design.     

A compact square loop patch antenna on high dielectric ceramic–PTFE composite material

Design and prototyping of a low profile, compact square loop microstrip line fed miniature patch antenna on 1.9 mm thick ceramic-polytetrafluoroethylene (PTFE) high dielectric composite material substrate is presented in this paper. The measured ?10 dB return loss bandwidths of the antenna are 300 MHz (0.75–1.05 GHz) and 800 MHz (2.4–3.2 GHz) with 3.4 dBi, 8.86 dBi and 7.42 dBi at 900 MHz, 2.5 GHz and 3.0 GHz, respectively. The measured symmetric and almost stable radiation pattern makes the proposed antenna suitable for RFID, GSM, ZIGBEE, WBAN, LR-WPAN etc. integrated mobile devices.     

Analysis of single band and dual band graphene based patch antenna for terahertz region

A microstrip patch antenna is designed using a very thin layer of graphene as the radiating patch, which is fed by a microstrip transmission line. The graphene based patch is designed on a silicon substrate having a dielectric constant of 11.9, to radiate at a single frequency of 2.6 THz. Further, this antenna is made to resonate at dual frequencies of 2.48 THz and 3.35 THz, by changing the substrate height, which is reported for the first time. Various antenna parameters such as return loss, VSWR, gain, efficiency and bandwidth are also determined for the single and dual band operation. For the single band operation, a bandwidth of 145.4 GHz and an efficiency of 92% was achieved. For dual band operation, a maximum bandwidth of 140.5 GHz was obtained at 3.35 THz and an efficiency of 87.3% was obtained at the first resonant frequency of 2.48 THz. The absorption cross section of the antenna is also analysed for various substrate heights and has maximum peaks at the corresponding resonating frequencies. The simulation has been carried out by using a full wave electromagnetic simulator based on FDTD method.     

Analysis on effect of low dielectric permittivity on indium-doped tin oxide based optically transparent terahertz patch antenna

Indium-doped tin oxide based optically transparent rectangular patch antennas are designed to resonate at 750 GHz; one on the glass substrate and the other on the polyimide substrate. Characteristics of both the transparent antennas such as impedance bandwidth, radiation efficiency, directivity and gain are analyzed and compared. Polyimide substrate has a lower dielectric permittivity than the glass substrate. The effect of low dielectric permittivity substrate on the radiation characteristics of the terahertz transparent patch antenna is analyzed. The transparent antenna on polyimide substrate is shown to have gain greater than 3.97dB in 714–795 GHz. The proposed transparent antennas are designed and simulated by using finite element method based electromagnetic solver, Ansys–HFSS.     

A multi-frequency circularly polarized metasurface antenna array based on quarter-mode substrate integrated waveguide for sub-6 applications

A miniaturized multi-frequency circularly polarized array is designed in this paper. The antenna array is composed of three independent sub-arrays employing modified quarter-mode substrate ntegrated aveguide (QMSIW) to achieve three circularly polarized frequency bands. By introducing strip-slot, the impedance bandwidth of the antenna array is broadened while the dimension is decreased by 75% to realize miniaturization. Meanwhile, metasurface causes the impedance bandwidth of the sub-array to be further enhanced. Moreover, the metal vias are employed in the antenna array design to further achieve miniaturization. The antenna array is manufactured and measured to verify the design. Both the measured and simulated results display that the array achieves the impedance bandwidths of 10%, 11.7%, and 14.8% and axial ratio bandwidths of 8.8%, 8.0%, and 8.5% at 2.5, 3.5, and 4.8 GHz, respectively. The gain is stable in the operating band within an uncertainty of 0.7 dBi. The whole dimension is 0.92λ×0.63λ×0.04λ, where λ₀ is the wavelength at the lowest resonant frequency. Furthermore, the simple structure and miniaturization provides great convenience in sub-6 applications.     

Microstrip patch array antenna on photonic crystal substrate at terahertz frequency

Recent advancement in the fabrication and packaging technology has led to the micrometer and nanometer-scale device modeling. This technological development and subsequent reduction in the dimension of devices like modulators, detectors and antennas has brought a thought of increasing the operating frequency of the system to the extent of sub-millimeter wavelength. In the view of the technical breakthrough in the area of fabrication and packaging, we have explored a printed antenna array on the photonic crystal in the terahertz spectrum in this paper. An equivalent circuit model of the antenna has been proposed and a methodology to investigate various electrical parameters is discussed. Tunable parameters of the structure have been explored to optimize the electrical performance of the proposed antenna. The analysis is also compared by using two simulators: (a) CST Microwave Studio based on finite integral technique and (b) Ansoft HFSS based on finite element method. The effect of the photonic crystal as substrate to enhance the gain of this kind of the antenna has also been demonstrated. The gain, directivity, front-to-back ratio (F/B ratio), and the radiation efficiency of the proposed antenna at 600 GHz is 16.88 dBi, 17.19 dBi, 14.77 dB and 89.72%, respectively. Finally, the performance of the antenna has been compared with the reported literature.     

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.     

A High-gain Wideband Antenna with Double Fabry-perot Cavities

A high-gain wideband antenna, using the electromagnetic resonances of double Fabry-Perot (F-P) cavities, is proposed. The two cavities are excited by a patch antenna placed in the cavities on top of the ground plane. One of the double F-P cavities is formed by a ground plane and a single metallic strips array, and the other consists of the patch and the metallic strips array. The two F-P cavities have different resonance points which yield the frequency bandwidth of 7% between 13.0 and 14 GHz with S₁₁ ≤ 10 dB, meanwhile, in this frequency region high gain is also obtained. Moreover, the center frequency and bandwidth could be adjusted by changing the cavity length. The high-gain wideband antenna was manufactured and measured. The measured VSWR is less than 2 from 13.3 GHz to 15.2 GHz, the measured gain is 13.5 dB at 13.5 GHz. In addition to that, a considerable improvement of 7 dB in terms of gain is obtained when compared to the same antenna without metallic strips.     

Compact wideband antenna above a wideband non-uniform artificial magnetic conductor

A compact wideband antenna place above a non-uniform artificial magnetic conductor (AMC) is presented. The antenna is composed of a wideband coplanar waveguide fed antenna, with wideband harmonic suppression characteristic using non-uniform defected ground structure. Besides, a non-uniform wideband AMC is designed. The AMC unit cell is composed of a square patch into which a four arms spiral shape is etched. It exhibits a wider ±90° bandwidth than the spiral unit cell and a smaller size than the square patch unit cell. The antenna is placed above the proposed AMC structure formed by 6 × 5 unit cells. The overall dimensions of the complete structure are 0.7 × 0.6 λ ₀ ² , where λ ₀ is the free-space wavelength at the lowest frequency. It offers a low-profile configuration with a total thickness of λ ₀/14.3, and it is matched between 2.5 and 5.4 GHz (73.5 %). Furthermore, it has a stable main lobe radiation pattern in the E- and H-planes within the operating frequency band. Moreover, compared with the antenna without AMC, the broadside realized gain is significantly increased. A prototype has been realized, and there is a good agreement between simulated and measured results. Furthermore, the proposed structure presents a size reduction of about 34 %, and better radiation characteristics in comparison with the conventional square AMC.     

Study on composite photonic crystal patch antenna

The paper investigated a composite photonic crystal patch antenna by using the method of finite difference time domain (FDTD). The results show that there exists a wave resonance state at 2.635 GHz, where the real part of the permittivity and permeability are all negative; its refraction index is –1. The effect has largely enhanced the electromagnetic wave’s resonance intensity, and has improved the localized extent of electromagnetic energy obviously in such photonic crystal structure (PBG), resulting in a higher antenna gain, a lower return loss, and a better improvement of the antenna’s characteristics. Due to such the advantages, the use of patch antennas can be extended to such fields as mobile communication, satellite communication, aviation, etc.     

High-gain composite microstrip patch antenna with the near-zero-refractive-index metamaterial

A high-gain rectangular microstrip patch antenna which is covered by a single layer metamaterial (MTM) superstrate with the near zero refractive index is proposed. The refraction of the metamaterial at frequency 3.51 GHz–3.57 GHz is very close to zero. The metamaterial with the near zero refractive index is placed 42 mm above an ordinary rectangular microstrip patch antenna. The effectively zero refractive index behavior of metamaterial superstrate can gather the wave emitted from the microstrip patch antenna and collimate it toward the normal direction of the antenna. The finite element method (FEM) and the finite difference time domain (FDTD) method are used to study the characteristics of this antenna. The results of the two methods indicate that the realized gain of the proposed antenna is increased by more than 6 dB, and the antenna has a flatness high gain in the predicted frequency band, where the proposed MTM is designed to have a near zero index of refraction. Therefore, the high-gain antenna is effectively enhanced based on the near-zero-refractive-index metamaterial.     

Broadband metamaterial absorber on a single-layer ultrathin substrate

In this article, a broadband metamaterial microwave absorber on a low-cost FR-4 Epoxy substrate is proposed. The unit cell of the absorber consists of a staircase shape metallic patch placed on the top of the metal-backed ultrathin dielectric substrate having a thickness of 1.9 mm (0.07 λ₀). The absorption of more than 90% is achieved with this proposed low profile single-layer microwave absorber throughout the operation band from 8.86 to 15.5 GHz. The performance is analyzed for different values of incident angle, polarization angle, substrate height, and dielectric constant. The surface current and the power loss density at the top and bottom planes at the two absorption peaks of 9.46 and 13.90 GHz are also analyzed to elaborate the absorption mechanism of the structure. Experimental result closely follows the simulated one. The broadband characteristics of the design with relative absorption bandwidth (RAB) of 54.51% at both TE and TM polarizations of incident wave for a wide incident angles makes it versatile for applications in the X and Ku bands of microwave frequencies. The proposed work is very compact (unit cell size: 0.22 λ₀) with ultrathin substrate height (0.07 λ₀) and giving RAB performance of 54.51% comparable with that of others. Thus with this single-layer low-cost substrate material a broadband absorber is achieved.     

Analysis of graphene based optically transparent patch antenna for terahertz communications

With and without multi walled carbon nanotube (MWCNT) loaded graphene based optically transparent patch antennas are designed to resonate at 6 THz. Their radiation characteristics are analyzed in 5.66–6.43 THz band. The optically transparent graphene is deployed as the patch and ground plane of the antennas, which are separated by a 2.5 μm thick flexible polyimide substrate. By shorting the microstrip line and ground plane of the antenna with a MWCNT via, the return loss of the antenna is improved. The peak gain of 3.3dB at 6.2 THz and a gain greater than 3dB in 5.66–6.43 THz band is obtained for antenna loaded without MWCNT. Both the antennas achieved a −10dB impedance bandwidth of 12.83%. Gain, directivity and radiation efficiency of the proposed antennas are compared with conventional transparent patch antennas and graphene based non-transparent antennas. The antenna structures are simulated by using finite element method based electromagnetic simulator-Ansys HFSS.     

Radiation properties of microstrip patch antenna covered with an anisotropic dielectric layer and a plasma sheath

By using SO-FDTD method, radiation properties of microstrip patch antenna covered with an anisotropic dielectric layer and a plasma layer are investigated. Simulation results show that the resonant frequency of antenna covered with a plasma layer varies with different plasma parameters. It has been indicated that the frequency offset of antenna is as high as 120 MHz when plasma frequency changes from 1 GHz to 8 GHz. The effect on antenna covered with an anisotropic dielectric layer is analyzed, while altering the dielectric constant or thickness of dielectric layer. Finally, the peak gain of antenna in complex plasma environment is presented in detail.