Novel Microstrip Antenna Design Upon Transformation Medium

This paper proposed a method based on transformation optics, implicit function, and level set methods to solve the challenge of multi-physics simulation of a microwave heating cavity with two different motion modes. A 3D computation model with a rotating turntable, a lifting support rod, and a sample is proposed as a detailed demonstration. Based on the theory of transformation optics, the rotating turntable is surrounded by two circles with a time-varying, inhomogeneous and anisotropy medium, and the electric field in the moving region is rotated by controlling the two mediums. The implicit function and level set methods compute the lifting motion by setting the properties of the lifting region as a function of space and time. The correctness of the proposed method is verified by comparing the proposed method’s results with the discrete position’s results, and then its accuracy is further verified by experiment. Subsequently, compared with the implicit function and level set methods only, the proposed method is more accurate. Finally, the effects of lifting motion, rotating motion and lifting motion (i.e., spiral motion) on microwave heating uniformity and heating efficiency were analyzed, respectively.

Based on the theory of transformation optics (TO), a new and simple method for generating multimodal orbital angular momentum (OAM) carrying beams in 3-D space is proposed in this letter. The proposed 3-D arbitrary-way multimodal OAM generator only requires an electric dipole as the source. It consists of a four-way plane waves converter and four multimodal OAM generators. Since this method only requires the operation of radial scaling map, different topological charge modes can be easily obtained by appropriately setting the sizes of the physical geometries.

Generation of vortex beam carrying orbital angular momentum (OAM) is a popular field of research in recent years. Based on the theory of complex transformation optics, a standing-wave current distribution along the circumference of a conventional circular patch is transformed into a uniform traveling current distribution instead, thus leading to the generation of vortex beams. Compared to the other designs of generating vortex beams, our design takes a patch antenna as a single radiator, thus, it has incomparable advantage in the compact structure.

Natural in-plane hyperbolic crystals (such as α-MoO3) and natural monoclinic crystals (such as β-Ga2O3) have recently drawn great research focus. Despite their obvious similarities, however, these two kinds of materials are usually studied as separate topics. In this Letter, we explore the intrinsic relationship between materials like α-MoO3 and β-Ga2O3 under the framework of transformation optics, providing another perspective to understand the asymmetry of hyperbolic shear polaritons. It is worth mentioning that we demonstrate this novel, to the best of our knowledge, method from theoretical analysis and numerical simulations, which maintain a high degree of consistency. Our work not only combines natural hyperbolic materials with the theory of classical transformation optics, but also opens new avenues for future studies of various natural materials.

Based on transformation optics theory, a kind of N-sided irregular polygonal cavity camouflage coating is proposed in this paper. The constitutive tensors of the camouflage coating are derived, and the functionality of the proposed coating is validated by full wave simulations. Simulation results show that the designed camouflage coating all has the same near and far field distributions with that of the bare PEC cavity in different incident angles and directions. In addition, this approach can be further to design N-sided irregular polygonal ground plane cloak with homogeneously anisotropic parameters. In order to apply at optical wavelength, the performance of the nonmagnetic camouflage coating is also verified. The simulations show that the reflective fields of nonmagnetic camouflage coating well agree with that of ideal coating except for incident direction because of the boundary impedance mismatching. Since the parameters of the designed camouflage coating are homogeneously anisotropic, it is expected that the proposed camouflage coating may find potential applications in the electromagnetic field engineering.

The approach in this book is historical and practical. It covers basic designs in more detail than other microstrip antenna books that tend to skip important electrical properties and implementation aspects of these types of antennas. Examples include: quarter-wave patch, quarter by quarter patch, detailed design method for rectangular circularly polarized patch, the use of the TM11 (linear and broadside CP), TM21 (monopole CP pattern) and TM02 (monopole linear) circular patch modes in designs, dual-band antenna designs which allow for independent dual-band frequencies. Limits on broadband matching are discussed. The appendix contains useful simple matching approaches, design details (gain, matching, sidelobes) of the little-studied omnidirectional microstrip antenna (OMA), limits and properties of common single and dual band Planar Inverted F Antenna (PIFA) antenna designs. The second edition has numerous additions to the earlier text which will make the concepts presented clearer. New cavity model analysis equations of circular polarization bandwidth, axial ratio bandwidth and power fraction bandwidth have been included. The section on omnidirectional microstrip antennas is expanded with further design options and analysis. This is also true of the section on Planar Inverted F (PIFA) antennas. The discovery and description of the fictious resonance mode of a microstrip slot antenna has been added to that section. Appendix A, on microstrip antenna substrates has been expanded to provide more detail on the types of substrate and their composition. This is often neglected in other texts. An appendix on elementary impedance matching techniques has been added as these methods have proven useful in my industrial work.

This paper introduces the flexible design of the Microstrip antenna (MSA) with a single band, coaxial feed circular polarization for wearable application. The proposed antenna has been designed for 1.57GHz frequency on flexible Kapton substrate with dielectric constant 3.4 and loss tangent 0.002, with dimensions of 50X 36X 0.8mm3• It exhibits resonating operations at the Global Positioning System (GPS) frequency L1 band (1.56 GHz-1.585GHz). Zigzag slotting along both lengths of the patch changes current distribution at the periphery and results in area minimization. The zigzag structure has been introduced to achieve the desired GPS band frequency with diagonal feed to achieve circular polarization (CP) with reduced patch area. The simulation results on a high-performance electromagnetic simulator (HFSS) obtained for this antenna show that it exhibits acceptable return loss (RL), voltage standing wave ratio (VSWR), radiation pattern along with minimal Specific Absorption Rate (SAR) for the specified frequency.

In this letter, we show by the theoretical analysis and computer simulation that the polarization of microstrip antenna can be changed using metamaterial with homogeneous constitutive parameters by applying the transformation optics approach, which is used to design the invisible cloak. We demonstrate that, the distribution of electric field between patch and ground-plane will be altered by filling in some properly designed metamaterial instead of traditional substrate, then, according to the cavity mode theory, some features of antenna's radiation will be also changed, such as polarization. As examples, we design a layout of metamaterial by coordinate transformation, which can make the microstrip antenna realize dual-band or circular polarization.

Lightning is one of the natural threats to an aircraft. Laboratory tests are usually limited to aircraft component levels and scaled prototypes. For small aircraft, sometimes the whole aircraft could be subjected to the lightning current specified in the relevant standards. Lightning current injection tests are carried out with standard components A to D. This is in anticipation of producing expected levels of fields and current values during a lightning strike. However, generating a current waveform with a rise time and magnitude the same as component A is very difficult in practice. Further, standards specify a return conductor (RC) arrangement for testing. Fields generated due to RC current can affect the current and field distribution. Hence, the emulated current and field in such tests could differ from that in an actual strike. The present work evaluates the current distribution for different lightning current waveforms suggested in standards and that realised in the laboratory. Also, the effect of the return cage on the current/field distribution is studied. The current and voltage distribution on aircraft skin is obtained by employing the impedance network method. A discretised model of Standard Dynamics Model (SDM) aircraft is employed for the present study. It is found that the surface current distribution on aircraft during a laboratory test can differ from that during the actual strike. Owing to the inductance of the aircraft, the rise time of the lightning current realised in the laboratory could be slow compared to that specified in standards; hence, it could also affect the current distribution on aircraft. This work is intended to provide insight into the inherent limitations of laboratory-level testing, which could be helpful for designers.

Numerous medical devices are implanted in the body for medical use. These include pacemakers and defibrillators, hormone pumps, nerve stimulators, and more. With the advancement and miniaturization of bio-electronics it is likely that the array of implantable medical devices will continue to expand in the years to come. Medical implants are intended to stay in the body for many years or decades, and it is often necessary to communicate with the device to download data about the health of the device or its batteries or the health of the patient, or to upload changes in settings or new procedures specified by the doctor. The design of antennas that can communicate with implantable devices is an interesting and challenging problem. The antenna must be small and long-term biocompatible, preferably able to be mounted on existing implant hardware or to utilize part of the hardware itself. The antenna must be electrically insulated from the body so as not to short out and be ineffective, and it must be efficient so as not to excessively drain the batteries. This paper describes the design and optimization of a spiral-shaped microstrip antenna attached to the 2x2x1/2 titanium battery pack of an implantable device imbedded in the body. The battery pack acts as the ground plane for the microstrip antenna and is in direct contact with the body. Two methods were used to optimize this antenna. The first was to simply try several designs in order to find the one that provided the best performance. This resulted in the antenna. The second method was to interface the XFDTD software (from Remcom, Inc.) which was used to simulate the antenna performance with iSIGHT (from Engineous, Inc.), an integration and optimization design program. Both antennas were prototyped and tested. The performance of both antennas is virtually identical. The use of optimization software saved significant man-hours in the optimization of this design.

Decoupling microwave heating efficiency from food property variations: A reduced-gradient index metamaterial strategy for superior efficiency and uniformity

Radar cross-section reduction through invisibility cloaking concept have been explored as a futuristic stealth technology. This novel concept upon realization can provide the optimal version of stealth to the aerospace domain. This chapter provides a technical insight to the design of ideal cylindrical and spherical cloaking structures in accordance with the transformation optics theory along with the feasibility study of this concept to aerospace platform. The simulations shown in this chapter are performed by using FEM based COMSOL Multiphysics software. The performance of the designed ideal spherical cloak is analyzed by comparing the radar cross-section of PEC sphere without cloaking and with multilayer cloaking shells. The multilayer spherical cloak shows reduced radar cross-section in C band as compared to PEC sphere.

Variations in load shape, volume, and permittivity significantly impact microwave energy conversion efficiency within multimode heating cavities. This study introduces a wedge dielectric plate that enables asymmetric microwave propagation when being in contact with a load, thereby enhancing heating efficiency and robustness under load variations. First, based on the transformation optics theory, an asymmetric waveguide is established by the wedge dielectric plate. Experimental results show varying microwave transmission efficiencies in both forward and reverse directions. Second, a microwave multimode cavity with a dielectric substrate is designed. When the dielectric wedge, dielectric substrate, and load are in physical contact, an efficient microwave transmission path will be formed to enable directed propagation toward the load via surface waves. Simulation results show over 90% heating efficiency with loads of varying volumes, dielectric properties, and shapes. Finally, microwave heating experiments are conducted and compared with a domestic oven using different loads. The proposed method achieves approximately 40% higher temperature increase at 750 W. This method is advantageous due to its low manufacturing cost, high power, robustness, and versatility, making it highly suitable for industrial applications.

Design and finite element simulation of information-open cloaking devices

Microstrip antennas or patch antennas are popular for their attractive features such as low profile, low weight, low cost, ease of fabrication and integration with RF devices. Micro strip antennas have been found favorable because they are inexpensive to manufacture and compatible with monolithic microwave integrated circuit designs (MMIC). They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonance frequency. A Microstrip or patch antenna is a narrowband, wide-beam antenna fabricated by etching the antenna element pattern in metal trace bonded to an insulating dielectric substrate with a continuous metal layer bonded to the opposite side of the substrate which forms a ground plane. The most commonly employed microstrip antenna is a rectangular patch. The major disadvantages of Microstrip antennas are lower gain and very narrow bandwidth. Microstrip patch antennas have some drawbacks of low efficiency, narrow bandwidth (3-6%) of the central frequency. Millimeter wave technology being an emerging area is still much undeveloped. As micro strip antennas have found wide variety of application areas, a number of techniques are evolved to improve its limited bandwidth. A good approach to improve the bandwidth is increasing the thickness of substrate supporting the micro strip patch. However problems exist on the ability to effectively feed the patch on a thick substrate and the radiation efficiency can degrade with increasing substrate thickness. A substantial research needs to be done in this area as its applications are numerous. The radiation patterns and S11 performance are used for the analysis of the different configurations. In the present endeavor a rectangular patch antenna is designed on thick substrate and simulated using MATLAB software and configuration on different dielectric susbstrates was used .