A SIZE-REDUCED LOG PERIODIC DIPOLE ANTENNA

A rectangle capacity patch was adopted as the resonance unit of the Log Periodic Dipole Antenna (LPDA) so as to realize the miniaturization of this aerial in this paper. Fifteen rectangle capacity patch units of different parameters were analyzed in this paper and three design laws of size-reduction were found. Accord-ing to these design laws, a 70% miniaturization ratio LPDA was designed and fabricated. The Voltage Standing Wave Ratio (VSWR) and pattern of the fabricated LPDA were measured. The results indicate that this size-reduction method do not deteriorate performance.

Novel Balun Structure for Dipole Antenna

A novel balun structure for dipole antenna,which is based on the current distribution on parallel microstrip lines and the emission cancellation characteristic of close equal and opposite currents,is proposed.The principle of the balun structure is first elaborated and verified.Then,a dipole antenna with resonance at 2.45 GHz is constructed using the balun and its radiation pattern is measured.The simulated and measured reflection coefficients(S_(11))of the antenna are in good agreement 2—3 GHz.The relative bandwidth with an S_(11) of below-10 dB is more than 25%.The antenna also shows a good radiation pattern at 2.45 GHz.The proposed structure can provide a new balun design method for dipole antennas.

Wideband dipole antenna with inter-digital capacitor

A dipole antenna with wideband characteristics is presented. The proposed antenna consists of a dipole with periodic capacitive loading and a pair of coplanar striplines （CPSs） as an impedance transformer. By adding interlaced coupling lines at each section, periodic capacitive loading is realized. The periodic interlaced coupling lines divide each arm of the dipole into five sections, and currents are distributed on different sections at different frequencies, which is useful to achieve a wide impedance bandwidth. By parametric study using HFSS, the optimized parameters of this dipole antenna are obtained. In order to validate the simulation results, a prototype of the proposed dipole antenna is fabricated and tested. The results show that the proposed antenna can achieve a gain of 3.1 dB–5.1 dB and bandwidth of 51% for ｜S 11 ｜ 10 dB over the band of 3.9 GHz–6.6 GHz, indicating its good radiation performance and radiation efficiency.

RESEARCH ON INPUT IMPEDANCE OF DIPOLE ANTENNA IN GTEM CELL

The formula of input impedance of dipole antenna in Gigahertz Transverse ElectroM agnetic(GTEM) cell based on the dyadic Green's function is first obtained in this paper. The validation of the formula is verified by the results of theoretical derivation and simulation with well agreements. In comparison with the formula of input impedance in free space, the relationship between the change of input impedance with the length of antenna and the position of antenna in GTEM cell is obtained. In addition, some meaningful conclusions are presented, which not only can be referred by the further research of ElectroM agnetic Interference(EMI) measurements in GTEM cell, but also provide the theoretical basis for testing compensation and error analysis.

Fabrication of THz Dipole Antenna Using Lift-off Method

The microfabrication technique for THz dipole antenna,"lift-off" was studied in this paper.Its procedure has been examined in detail,and discreetly tweaked.Particularly,Chlorobenzene is suggested to assist the formation of undercut indispensible for fulfilling "lift-off".The experimental results of fabricated antennas confirm the effectiveness of this method.

Design of a Metasurface Antenna Based on Characteristic Mode Theory

A novel metasurface antenna consisting of 5×5 rectangular patch elements is presented.Thestructure with and without the central element are both analyzed by the Characteristic Mode Theory(CMT).The developed mutually orthogonal principal modes of the optimized periodic patch structure areexcited by a center-feed dipole.A differential feeding network is employed to realize impedance matching.Prototype with profile height of 0.07λ_(0)(λ_(0)is the wavelength in free space at the lowest operatingfrequency)is fabricated and assembled to verify the simulation results.The measured results show that thereflectance coefficient of proposed matesurface antenna is less than-10 dB in the whole operating bandrange from 4.2 GHz to 5.5 GHz,a relative bandwidth of 26.8%is achieved,and the maximummeasured realized gain is more than 9 dBi with a maximum radiation efficiency of 90%.The designprovides a guideline on the application of characteristic modes(CMs)to radiation problems.

Terahertz generation from Si3N4 covered photoconductive dipole antenna

We observe enhanced terahertz (THz) radiation generated from a Si3N4 film-coated GaAs photoconductive dipole antenna. Compared to an uncoated antenna with identical electrode geometry and optical excitation power, the Si3N4 film-coated antenna has a higher effective DC resistance and larger breakdown voltage. As a result, the peak amplitude of generated THz radiation is significantly enhanced due to the Si3N4 film-coated layer.

Characteristics of on-chip dipole antenna using diamond for intra-chip wireless interconnect

In this paper,a 2-mm long on-chip dipole antenna pair on silicon substrate is simulated to investigate the transmission characteristics.A novel technique is proposed by employing a 0.35-mm thick diamond layer between silicon substrate and heat sink to improve antenna performance.The simulated transmission gain of this antenna pair with 1 mm separation on a 10-Ω cm silicon substrate increases by 9 dB at 20 GHz.A modified plane wave model involving diamond layer is also presented to explain gain improvement.Effects of dielectric variety,diamond thickness,substrate resistivity and antenna pair separation on transmission gain have been studied.The results indicate that thinner diamond layer along with high resistivity substrate is preferred.Our method makes integrated dipole antennas well suitable for intra-chip wireless interconnection which is known as a future solution to replace critical wiring interconnection.

Optimization of Linear Antenna Arrays Based on Genetic Algorithms

The methods of moment and genetic algorithm (GA) are combined to optimize the Yagi Uda antenna array and Log periodic dipole antenna (LPDA) array. The element lengths and spacing are optimized for the Yagi Uda array; while the ratio factor of spacing to length as well as the ratio of length to diameter of the elements are optimized for LPDA array. The results show that the main parameters, such as gain and pattern, have been improved apparently; and the high back lobe level of LPDA can be reduced greatly, therefore, GA is a very competent method for optimizing the linear array as well as in other fields.

Stretchable electromagnetic interference shielding and antenna for wireless strain sensing by anisotropic micron-steel-wire based conductive elastomers

We prepare stretchable elastic electromagnetic interference(EMI) shielding and stretchable antenna for wireless strain sensing using an elastic composite comprising commercial steel wool as a conducting element. The prepared elastic conductor shows anisotropic electrical properties in response to the external force. In the stretchable range, the electrical resistance abnormally decreases with the increase of tensile deformation. The EMI shielding effectiveness of the elastic conductor can reach above-30 d B under 80% tensile strain. The resonance frequency of the dipole antenna prepared by the elastic conductor is linearly correlated with the tensile strain, which can be used as a wireless strain sensor. The transmission efficiency is stable at about-15 d B when stretched to 50% strain, with attenuation less than 5%. The current research provides an effective solution for stretchable EMI shielding and wireless strain sensing integrated with signal transmission by an antenna.

PCB Base Log-periodic Antenna for Mobile Communications

A log-periodic antenna can provide directivity and gain when operating in a wide band.The log-periodic antenna is used in many applications where wide bandwidth is required along with direct and medium gain.This research implements a sequential approach to the design and simulation of the performance of a printed log-periodic dipole antenna(LPDA)capable of operating in the 1800 MHz frequency range.The advantage of this antenna is the compactness and easy integration into planar circuits suitable for applications requiring wide bandwidth and high gain.The dimension of the designed antenna was originally calculated taking high frequency as 1885 MHz and low frequency as 1805 MHz,then modeled using HFSS-13 electromagnetic simulation to determine the effect of substrate dielectric properties on dipole width and length for element optimization.The design was verified by creating and measuring S11 and radiation diagrams.The designed antenna has a total gain of 7.9 dB and a wide bandwidth.

Superdirective Circular Arrays of Electric and Huygens Dipole Elements

Uniform circular arrays(UCAs)provide both omnidirectional(360°)and directive(sector)coverage of the azimuthal plane.Superdirective versions with unidirectional,high front-to-back ratio(FTBR)properties could provide the radiated field char-acteristics being pursued for NextG wireless networks and their perceived applications.Typical UCA configurations–full,semi-circular,and sector–that radiate vertically-polarized(VP)fields and are composed of either omnidirectional electric dipole ele-ments or unidirectional Huygens dipole elements are analyzed first with conventional methods as reference cases.These omni-and uni-directional element configurations are then treated with several optimization techniques:the classic Rayleigh-quotient(RQ)method and its unidirectional-constrained version;the eigenbeam decomposition and synthesis(EBDS)technique used to design su-perdirective acoustic receiving arrays;and the Bessel-azimuthal multipole(BEAM)approach developed herein.Several arrays are identified as being superdirective with extremely high FTBR values.The performance characteristics of the arrays of unidirectional elements are demonstrated to be superior in general.Moreover,it is shown that larger radius arrays with RQ-specified excitation amplitudes are robust to changes in them whereas the outcomes of the corresponding small radius versions are not.On the other hand,the BEAM-optimized densely-packed small-radius superdirective arrays are quite tolerant to those variations while generating unidirectional pseudo-needle beams.

Frequency-Diversified Space-Efficient Radiating Surface Using Convolved Electric and Magnetic Currents for Highly Dense Multiband Antenna-Frontend Integration

We propose and investigate a methodology based on convolved electric and magnetic currents for the generation of multi-band responses over a space-shared radiating surface.First,a single wideband antenna operation principle based on inter-leaved dipole and slot modes is studied and analyzed using full-wave simulations followed by a qualitative time domain analysis.Subsequently,a 2×2 dual-band radiating unit is conceived and developed by closely arranging single wideband antennas.In this case,multimode resonances are generated in a lower frequency band by a proper convolving and coupling of the magnetic and electric currents realized in the gaps between the antennas and on the surface of the antennas,respectively.This methodology can be deployed repeatedly to build up a self-scalable topology by reusing the electromagnetically(EM)connected radiating surfaces and gaps be-tween the radiating units.Due to the efficient reuse of the electromagnetic region for the development of multiband radiation,a high aperture-reuse efficiency is achieved.Finally,as a proof of concept,a 2×4 dual-band array operating in Ku-and Ka-bands is devel-oped and fabricated by a linear arrangement of the two developed radiating units.Our measurement results show that the proposed antenna array provides impedance and gain bandwidths of 30%and 25.4%in the Ku-band and 10.65%and 8.52%in the Ka-band,respectively.

High Performance Electrically Small Huygens Rectennas Enable Wirelessly Powered Internet of Things Sensing Applications:A Review

Far-field wireless power transfer(WPT)is a major breakthrough technology that will enable the many anticipated ubiquitous Internet of Things(IoT)applications associated with fifth generation(5G),sixth generation(6G),and beyond wireless ecosystems.Rectennas,which are the combination of rectifying circuits and antennas,are the most critical components in far-field WPT systems.However,compact application devices require even smaller integrated rectennas that simultaneously have large electromagnetic wave capture capabilities,high alternating current(AC)-to-direct current(DC)(AC-to-DC)conversion efficiencies,and facilitate a multifunctional wireless performance.This paper reviews various rectenna miniaturization techniques such as meandered planar inverted-F antenna(PIFA)rectennas;miniaturized monopole-and dipole-based rectennas;fractal loop and patch rectennas;dielectric-loaded rectennas;and electrically small near-field resonant parasitic rectennas.Their performance characteristics are summarized and then compared with our previously developed electrically small Huygens rectennas that are proven to be more suitable for IoT applications.They have been tailored,for example,to achieve batteryfree IoT sensors as is demonstrated in this paper.Battery-free,wirelessly powered devices are smaller and lighter in weight in comparison to battery-powered devices.Moreover,they are environmentally friendly and,hence,have a significant societal benefit.A series of high-performance electrically small Huygens rectennas are presented including Huygens linearly-polarized(HLP)and circularly-polarized(HCP)rectennas;wirelessly powered IoT sensors based on these designs;and a dual-functional HLP rectenna and antenna system.Finally,two linear uniform HLP rectenna array systems are considered for significantly larger wireless power capture.Example arrays illustrate how they can be integrated advantageously with DC or radio frequency(RF)power-combining schemes for practical IoT applications.

Characterization of the radiation from single-walled zig-zag carbon nanotubes at terahertz range

This paper investigates the radiation characteristics of metal single-walled zig-zag carbon nanotubes as a dipole antenna at terahertz wave range. The current distribution, input impedance and mutual impedance are calculated for various geometrical parameters of vertically-aligned carbon nanotubes. The numerical results demonstrate the properties of the antenna depending strongly on the geometrical parameters such as the radius, the lengths of carbon nantobues, and the spacing between nanotubes. It is found that the zig-zag carbon nanotubes exhibit very high input impedance and the mutual impedances for antenna array applications. These unique high impedance properties are different from the conventional metal thin wire antenna. The far-field patterns and gain of antenna array are also calculated. The maximum gain of array of 100-element array is up to 20.0 dB, which is larger than the gain of 0.598 dB of single dipole antenna at distance d = 0.5λ.

Polarization Projection for 3D Geometry-Based Stochastic Channel Model

Comprehensive radiation characteristics of polarized antenna are crucial in creating practical channel coefficients for next generation wireless communication system designs.Being currently supported within3 D geometry-based stochastic channel models(GSCM),field patterns are technically obtained by chamber measurement(or by its best fitting).However,in some channel related performance analysis scenarios,design insight can be crystallized better by starting the derivations with theoretical co-polarization and cross-polarization components.Specifically,these two components are mathematically linked with field patterns through the proposed polarization projection algorithm.In this manuscript,we focus on revealing the transformation criterion of polarization states between the antenna plane and the propagation plane.In practice,it makes retrieving the field patterns by electromagnetic computation possible.Meanwhile,the impact imposed by distinct antenna orientations is geometrically illustrated and consequently incorporated into the proposed algorithm.This will further facilitate flexible performance evaluation of related radio transmission technologies.Our conclusions are verified by the closed-form expression of the dipole field pattern(via an analytical approach) and by chamber measurement results.Moreover,we find that its 2D degenerative case is aligned with the definitions in 3^(rd) generation partnership project(3GPP)technical report 25.996.The most obvious benefit of the proposed algorithm is to significantly reduce the cost on generating channel coefficients in GSCM simulation.

Metamaterial inspired terahertz devices: from ultra-sensitive sensing to near field manipulation

We present a review of terahertz plasmonic metamaterial devices that have functionalities and applications ranging from sensing, enhanced electromagnetic fields, and near field manipulation. Metamaterials allow the properties of light propagation to be manipulated at will by using a combination of appropriately designed geometry and suitable materials at the unit cell level. In this review, we first discuss the sensing aspect of a planar plasmonic metamaterial and how to overcome its limitations. Conventional symmetric metamaterials are limited by their low Q factor, thus we probed the symmetry broken plasmonic metama- terial structures in which the interference between a broad continuum mode and a narrow localized mode leads to the excitation of the sharp Fano resonances. We also discuss the near field mediated excitation of dark plasmonic modes in metamaterials that is caused by a strong coupling from the bright mode res- onator. The near field coupling between the dark and bright mode resonances leads to classical analogue of electromagnetically induced transparency in plasmonic systems. Finally, we discuss active switching in terahertz metamateriMs based on high temperature superconductors that holds the promise of reducing the resistive losses in these systems, though it fails to suppress the radiation loss in plasmonic metamaterial at terahertz frequencies.