Probe‐fed microstrip antennas loaded with very high‐permittivity ceramics

This article reports the feasibility study of miniaturizing probe‐fed microstrip patch antennas by dielectric loading. The loading materials are barium tetratitanate ceramics of very high dielectric constant (ε_r = 38, 80). It is shown that, simply through loading, the antenna sizes are greatly reduced; however, the antenna performances are deteriorated. For instance, the antenna gain becomes lower. Then enhancement of the antenna performances follows. A substrate–superstrate structure is used to recover the gain. Both the experiments and the finite‐difference time‐domain (FDTD) simulations demonstrate that the gain and impedance bandwidth can be retrieved such that they are comparable to those of conventional microstrip antennas loaded with low permittivity materials (ε_r < 3). © 2006 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2006.     

Performance characterization of wideband,wide‐angle scan arrays of cavity‐backed U‐slot microstrip patch antennas

This work looks at the use of wideband cavity‐backed U‐slot microstrip antennas in finite phased arrays. This configuration retains the single‐patch and single‐layer characteristics of conventional microstrip antenna arrays and provides a good impedance matching over wider scan angles when electrically thick substrates are used to improve the frequency bandwidth. The characteristics of finite phased arrays of U‐slot rectangular microstrip patches enclosed in cylindrical cavities are analyzed from a validated hybrid methodology based on the finite element method, the modal analysis, and the properties of spherical waves. The results are compared with those obtained using an infinite array model. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Cross‐polarization reduction of microstrip antenna using microwave absorbers

In this article, a metamaterial inspired microwave absorber is used to reduce the cross‐polarization (XP) level of the radiated wave in microstrip antenna (MSA). A microwave absorber unit‐cell has been analyzed and implemented to reduce the cross polarization (XP) level in a single element and a 2 × 2 microstrip patch array antennas. The antennas have been designed on a FR‐4 substrate of thickness 0.8 mm at 10.1 GHz center frequency. The 2 × 2 patch array antenna with and without the absorbers have been experimentally verified for the S11 parameter, the radiation pattern, and the XP suppression in H‐plane and a good comparison has been found.     

一种分形结构微带天线的设计和馈点的优化

微带贴片天线是一种低材料、体积小、易于制作的天线。为了实现天线的多频带特性,在微带贴片天线中引入了sierpinski模型结构。分形结构是在一个递归的过程中产生的,它们可以在有限的空间产生很长或很宽的表面积,因此,分形结构可以使宽带天线在小型化的同时又能保持和大天线相似的辐射模式和输入阻抗特性。这种sierpinski分形结构的微带天线可以用在WLAN,BLUETOOTH和WIMAX中。本文详细研究了sierpinski分形结构的迭代设计以及馈带线的馈点位置,并分析了对于此类天线的最佳馈电点     

Direct and electromagnetically coupled compact microstrip antenna design with modified fractal DGS

This article proposes ultra‐miniature microstrip patches with direct and electromagnetically coupled feeding mechanism for wireless communications at 10 GHz. Antenna size reduction is achieved here by loading a modified Minkowski fractal (type‐2) defected ground structure (MFDGS‐II) exactly beneath the radiating patch. The proposed method involves the selection of best DGS configuration through sensitivity analysis of the antenna structure. From different applications point of view, three different designs: a single layer direct fed patch and two electromagnetically coupled fed multi‐layered microstrip patch antennas are proposed here and designed with MFDGS‐II. The resonant frequencies of the antenna designs are reduced in a significant manner incorporating MFDGS‐II without any change in the physical size of the antenna. The prototypes of the proposed antennas are fabricated, and the performance parameters are measured. Compared with other existing structures, with a lower patch size of 0.20 λ₀ × 0.15 λ₀, the proposed single layered antenna with microstrip feed achieves a patch size reduction up to 67% and an overall volumetric reduction of 84%, respectively. Similarly, the proposed multi‐layered patch with proximity feed exhibits a maximum impedance bandwidth of 600 MHz and the aperture coupled fed patch has a realized gain of 6.2 dBi with radiation efficiency of 91% centered at 10 GHz. All three proposed compact antenna structures are best in three different aspects and have the potential to meet the practical requirements for X‐band portable wireless applications.     

Resonant frequency of a microstrip patch in the vicinity of an identical radiator

The resonant frequency of a microstrip patch (rectangular, square, and circular) changes as soon as an identical patch is brought closer than 0.2λ to it. Closed-form expressions are presented for the H-plane-coupled configuration (the two adjacent patches are excited by same phase excitation) from which this altered resonant frequency may be easily computed. From the same expression the resonant frequency of an isolated patch antenna may also be calculated. A procedure utilizing these closed-form expressions for the design of microstrip patch antennas which will resonate at the desired frequency is also outlined. These expressions may be readily used in the computer-aided design of microstrip antenna arrays. © 1996 John Wiley & Sons, Inc.     

Low profile coupling feed circularly polarized antennas for WLAN applications

This article presents two designs of circularly polarized antenna with simple circular‐shaped radiator and circular slotted ground plane. An arc‐shaped microstrip line coupling feed mechanism is used to excite the circular radiating patch. The 3‐dB axial ratio bandwidth of the proposed antenna‐1 and proposed antenna‐2 are 3.33% and 18%, respectively. The proposed design has several advantages such as easy matching, fabrication simplicity, compact size, and wide axial ratio bandwidth. Both the antennas have been designed on FR‐4 substrate with dielectric constant 4.4 and thickness 1.59 mm. Simulated and measured results are presented to validate the working of the proposed antennas.     

Radio frequency response of flexible microstrip patch antennas under compressive and bending loads using multiphysics modeling approach

This research article studies the effect of compression and bending loads on resonant frequency of microstrip patch antennas using COMSOL Multiphysics software (will be called COMSOL hereafter). In this study, copper microstrip patch antenna of dimension 30 mm × 25 mm on polydimethylsiloxane (PDMS) substrate of dimension 50 mm × 50 mm is considered. The interface bonding is assumed to be ideal between the patch and substrate. Both Ansoft HFSS and COMSOL are used to model and analyze the original geometry of the microstrip patch antenna without applying physical load to make sure that the design and the impedance match is satisfactory. Then, COMSOL is used to find deformed shape of the microstrip patch antenna under different values of compression and bending loads. The deformed geometries are reanalyzed using COMSOL radio frequency (RF) simulation. The resonant frequencies at different load levels are obtained and the effect of loading and boundary conditions on the resonant frequency shift is discussed.     

Generalized design approach to compact wideband multi‐resonant patch antennas

In this work, a generalized design approach to compact, wideband multi‐resonant microstrip patch antenna is proposed. Theoretical criterion of the length of the prototype dipole is laid down based on the simplest dipole model and the associated eigenmodes at first. Then, the criterion is employed to reveal the general relationship between the prototype dipole length, operational modes, sizes, and radiation behaviors of the resultant multi‐resonant circular sector patch antennas. Next, a compact wideband, dual‐resonant circular sector patch antenna is designed accordingly. It is operating at the TM_3/4,1 and TM_9/4,1 modes within a 240° circular sector patch radiator with its radii short circuited. The antenna fabricated on a single‐layered air substrate exhibits an available radiation bandwidth of 25.0%, with a profile as small as 0.043 guided wavelength at the center frequency. It is evidently verified that the approach can be employed to realize compact, dual‐resonant wideband microstrip patch antennas without increasing antenna profile, inquiring multiple radiators or employing reactance compensation techniques. In addition, it may lead to a series of novel wideband patch antenna designs with diverse performances.     

A compact filtering antenna using dielectric strip resonator and parallel microstrip feed line

A filtering antenna using dielectric strip resonator and parallel microstrip feed line is proposed to achieve compact dielectric size and filtering response without gain reduction. The compact dielectric size is contributed by the dielectric strip resonator with high permittivity operated in the TM_δ1 cavity mode, whose electric field distribution along the short side is far less than half‐wavelength distribution. Therefore, the size of the proposed dielectric strip resonator is smaller than the traditional dielectric patch resonator operated in the TM₁₁ cavity mode. Additionally, the parallel placed microstrip line not only can excite the dielectric strip resonator for filtering response without gain reduction, but also can provide one upper‐edge radiation null for frequency selectivity enhancement. Compared with the reported filtering dielectric antennas, the proposed design exhibits the features of compact dielectric size, simple structure and wide stopband. For demonstration, one prototype operating at 4.9 GHz is fabricated, achieves the dielectric size of 0.00078 λ3 0 (λ₀ is the wavelength in the free space at the center frequency), the measured peak gain of 7.1 dBi, the 10‐dB impedance matching bandwidth of 4%, the stopband (> 16 dB) up to 1.84 f₀, and the cross‐polarization level of 20 dB within 3‐dB beam range.     

硅基微带天线损耗机理分析

硅基微带天线存在损耗大、效率低、增益不足等问题。其成因在于以下五种损耗:1.金属贴片及匹配微带线的导体损耗。2.介质的介电损耗。3.表面波损耗。4.半导体基底的电阻性损耗。5.由基底与绝缘层交界面上的载流子运动导致的界面损耗。在深入分析各种损耗的形成机理的基础上,研究了相应损耗的计算模型及其在总损耗中所占的地位,并提出了降低损耗的有效途径。实验结果显示,采用微机械(MEMS)工艺,在高阻硅与低介电常数介质的混合衬底上,生长一层多晶硅薄膜的方法,可有效降低损耗,使硅基微带天线单元的效率达到87%,增益达到8dB。     

Bacterial foraging optimization technique to calculate resonant frequency of rectangular microstrip antenna

Resonant frequency of rectangular microstrip antenna having various substrate thicknesses are generally calculated using the standard expressions presented in literatures. But these equations suffer from errors when compared with the experimental values due to Quasi‐TEM propagation in the microstrip structure and fringing field. A number of researchers used soft computing approach such as neural networks and genetic algorithm on those equations to minimize the error for better accuracy. Bacterial foraging, an evolutionary optimization technique conceived in recent times, has many advantages over genetic algorithm and is yet to be applied on the design of microstrip patch antenna. In this article, a novel technique is developed to apply bacterial foraging optimization technique in conjunction with the expressions developed to calculate accurately the resonant frequency of rectangular microstrip antenna of any dimension and of any substrate thickness. Further, bacterial foraging is applied to the calculatation of the feed point of microstrip antenna. The technique developed in this article can be a generalized soft computing tool to calculate resonant frequency of rectangular microstrip antenna. Similarly, the idea of the article can be used for calculating the various parameters of microstrip antennas of different structure and geometry. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.     

Closed-form expressions for computer-aided design of microstrip ring antennas

This article presents closed-form expressions for the resonant frequency and radiation characteristics of microstrip ring antennas to assist in the computer-aided design of such antennas. Radiation fields are obtained using the vector electric potential calculated from the magnetic currents flowing along the inner and outer edges of the planar waveguide model for the microstrip ring structure. Expressions for radiated power, conductor and dielectric loss factors, resonant resistance, efficiency, and directivity are derived. The smaller the radius of curvature of the ring, the larger is the spacing between the magnetic currents flowing along the inner and outer edges and thus the radiation efficiency is higher. The effect of a dielectric layer covering the ring antenna is also included. Experimental results for the resonant frequency and the radiation patterns agree well with the theoretical predictions. © 1992 John Wiley & Sons, Inc.     

Use of the FDTD method in the design of microstrip antenna arrays

The finite-difference time-domain (FDTD) method is a widely used numerical technique for computer-aided design (CAD) of printed antennas and arrays. This technique can accurately predict performance characteristics of complex microstrip antennas, including the effects of parasitic elements and aperture-coupled feeds. In the case of arrays, mutual coupling effects between closely packed elements can also be modeled. This article will examine the advantages and limitations of the FDTD method for CAD of microstrip arrays. Calculated results are compared with experiment for a 3-patch coplanar parasitic patch array.     

Design and development of microstrip patch antenna with circular and rectangular slot for structural health monitoring

Structural health monitoring (SHM) is the technique to identify the damage in the building or physical structures. Several structural health monitoring has been proposed in recent years. Increase in number of sensors and its wiring mechanism causes issue in signal processing demand, efficiency, and unreliability. In current state, already present sensors cannot be used for Structural Health Monitoring because of its high cost and low battery capacity, although none of these techniques are capable of monitoring the condition of complex physical structures. The measurement of strain can be done by using patch antenna as strain sensors. In currently available sensors only the wireless range. The main objective of this paper is to investigate the feasibility of using circular and rectangular slotted microstrip patch antenna as a strain sensor for structural health monitoring without these afore mentioned problems. These antenna sensors’ (slotted rectangular and circular microstrip patch antennas) simulation results are confirmed. From the simulation results, the sensor provides information about crack orientation.     

Design of 4-element microstrip array of wideband reflector antenna with stable high gain characteristics

In this paper, three microstrip antennas with and without reflector are proposed with stable and high gain characteristics. The proposed antennas are simple to design and do not involve loading of any active elements on the patch or ground plane. The designed antennas cover the total frequency range of 10.5–44.5 GHz and operate well within the 5G communication frequency band of 27–30 GHz; consequently, making proposed antennas suitable for upcoming wireless technology. Furthermore, a 2 × 2 antenna array with phase diversity is proposed which offers an almost stable gain of about 14 dBi within the operating band. The proposed antennas are analyzed by finite element method based Ansys HFSS simulator. The fabricated prototypes of the optimized designs are made and simulated results are found in good agreement with the measured results.

     

Theoretical and experimental studies of a microstrip antenna with two parasitic patches

The variations of the dimensions and locations of two stacked parasitic elements on the input impedance SWR bandwidth and radiation patterns of aperture-coupled rectangular microstrip antennas are analyzed. It is found that the SWR bandwidth can be improved by selecting appropriate sizes and locations of the parasitic patches. A 45% bandwidth of patch antennas was attained for SWR≤2.2. Experimental results are obtained to verify the theory. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 49–55, 1998.     

Fast simulation‐driven optimization of planar microstrip antenna arrays using surrogate superposition models

A technique for simulation‐driven design of excitation tapers for planar antenna arrays is presented. Our methodology exploits antenna array models constructed as a superposition of simulated radiation and reflection responses of the array under design, with only one radiator active at a time. Low computational costs of these models are ensured by using iteratively corrected electromagnetic‐simulation data computed with coarse meshes. Our technique allows for simultaneous control of the radiation pattern and the reflection coefficients of the array. Numerical efficiency as well as scalability of the technique is demonstrated using the design examples of various sizes and topologies, including a sixteen element and hundred element microstrip patch antenna arrays of the Cartesian lattice and a hundred element microstrip antenna array of the hexagonal lattice. The proposed technique is versatile as it also can be applied for simulation‐based optimization of antenna arrays comprising other types of individually fed elements, e.g., wires, strips, or dielectric resonator antennas. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:371–381, 2015.     

Wideband linear microstrip array antenna with high efficiency and low side lobe level

In this letter, the design and fabrication of the linear microstrip array antenna by series fed are presented. The array antenna consists of 16 reflector slot‐strip‐foam‐inverted patch (RSSFIP) antennas. The gain and efficiency of the linear array antenna is 16.6 dBi and 61% at 10 GHz, respectively. The antenna has a bandwidth (BW) of 45% from 8.1 to 12.8 GHz (S₁₁ < ?10 dB) and side lobe level (SLL) of ?25.6 dB across the BW of 19.2% from 9.4 to 10.4 GHz. These are achieved by using a microstrip series fed with defected ground structure (DGS) to feed the patch array antenna. Good agreement is achieved between measurement and simulation results.