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In this paper a novel compact microstrip feed square patch antenna with right angled isosceles Koch fractal geometry on its edges is designed for ultra wideband applications. The radiating patch is modified in several steps to achieve a multiband circularly polarized antenna. The fractal antenna is simulated using CST Microwave Studio Simulator. Antenna’s performance is then compared with equilateral Koch, Minkowski and Sierpinski fractal geometries. The suggested antenna is assembled on FR4-epoxy (εr = 4.4) substrate with dimensions 60 × 55 × 1.59 mm3. The developed antenna efficiently operates at 4.3 GHz, 5.0 GHz, 6.1 GHz, 7.4 GHz, 8.9 GHz and 9.2 GHz. Circular polarizations are achieved near four resonant frequencies, which are realized by adding a circle in the middle of the patch. The presented antenna has a good gain, bandwidth, VSWR and axial ratio bandwidth. In this paper, an approach for multiband antennas is proposed. The novelty of the paper lies in the fact that a right angled triangular Koch curve is formed on the edges of the square patch. Keywords: Microstrip patch, Koch fractal, Circular polarization, Ultra wideband (UWB)

A multi-polarised quad-band planar circular disc monopole antenna consisting of a parasitic double T-stub and parasitic long and short inverted L-stubs is presented. By loading parasitic multistubs along the y-axis behind a circular patch, the antenna can yield four resonance modes at 2.5, 4.5, 5.7, and 7.7 GHz frequencies while keeping the size of 30 × 40 mm2. The proposed antenna has been fabricated and experimentally studied. The measured impedance bandwidths of 290 MHz (2.36–2.65 GHz), 540 MHz (4.28–4.82 GHz), 530 MHz (5.47–6.0 GHz), and 780 MHz (7.28–8.06 GHz), for Bluetooth, 2.4/5.8 GHz wireless local area network, 2.5/5.5 GHz worldwide interoperability for microwave access, 5.9 GHz intelligent transportation systems (ITS), downlink of Indian National Satellite System and X-band satellite applications. The 3 dB axial ratio bandwidth is 280 MHz (5.79–6.07 GHz) for the 5.9 GHz ITS band. The antenna E-field radiation has y-directed (vertical linear) polarisation at first, second, third resonance bands and slant + 45° linear polarisation at the fourth resonance band. At the ITS band, the E-field radiation has right-handed circular polarisation. In addition, the design procedure, electrical model and effects of parasitic stub dimensions on the antenna characteristics are discussed.

Due to the increasing demand for wireless communications, millimeter-wave band has gained a great attention recently. Also, achieving secure wireless communications is of high importance. Antenna subset modulation is a low complexity single beam directional modulation technique suitable for millimeter-wave wireless communications, whereas multi-beam antenna subset modulation is a multi-directional, generalized form of antenna subset modulation. In this paper, interference mitigation for multi-beam antenna subset modulation via side lobe level reduction is introduced. A method for designing thinned arrays with minimum side lobe levels for antenna subset modulation is introduced and generalized for multi-beam antenna subset modulation. A new variable constraint is applied to the optimization problem to control the localization of optimum solution within the antenna array. Two solutions are introduced, convex optimization combined with local search and local search assisted genetic algorithm. Simulation results show the superiority of the proposed algorithms compared to simulated annealing algorithm and traditional genetic algorithm.

The direction-of-arrival (DOA) estimation of a conformal antenna array with directive elements is studied in this communication. The two-dimension Cramer–Rao lower bound (CRLB) is derived for a conformal antenna array by using the active directive radiation patterns of the array elements and compared with the isotropic ones. Moreover, the MUSIC method is used to confirm the CRLB results. Without loss of generality, the CRLB of a truncated hexagonal pyramid conformal array with seven patches is investigated which verify the significant effect of the directive elements in the DOA estimation accuracy rather than that of the isotropic ones. The simulation results prove that this conformal array achieves better DOA estimation performance rather than that of the planar array antenna especially at the horizon angles. Moreover, the conformal antenna array tilt angle is studied to achieve the optimum conformal array structure which depicts a tradeoff between the DOA estimation accuracy at low and high $\theta $ incident angles.

This paper presents a compact active integrated antenna (AIA) comprising of class-A power amplifier (PA) and stepped impedance planar inverted-F antenna (PIFA). In the proposed design, a common ground is used for both PA and PIFA, resulting a compact antenna of size 0.14λ 0 × 0.11λ 0 × 0.01λ 0 (λ 0 is free space wavelength at 0.85 GHz). Moreover, it is demonstrated that by using the stepped impedance radiator the operating frequency of the active PIFA is shifted down from its natural resonant frequency of 1.36 GHz to 0.85 GHz, offering an extensive size reduction of 80%. This active integration increases the passive antenna gain through the effective loading of the antenna to the power amplifier. The measured result indicates that the active and passive antennas achieved the gain of 15.7 dB and 3.81 dBi, respectively after the integration. In addition, the maximum SAR value of antenna is found to be 0.64 W/kg.

This communication presents a high-order-mode microstrip patch antenna driven by substrate integrated waveguide (SIW) for millimeter-wave polarization-adjustable applications. Different polarization status can be yielded from variable excited signals, including vertical and horizontal linear, right-handed and left-handed circular polarizations. In the patch antenna configuration, an enlarged aperture coming from high-order mode makes it easy to be fed by orthogonal SIWs for dual polarizations. Loaded slots on the patch significantly improve the radiation patterns. The impedance bandwidth with dual resonances is originated from the SIW slot and patch modes. A Ka-band $2\times 2$ antenna array integrated with single-layer SIW feeding network is designed and tested to illustrate this technique. The results manifest that the planar integrated $2 \times 2$ antenna array features adjustable polarization with considerable gain. Furthermore, a two-layer scheme of orthogonal SIW feeding is developed, which would provide a more flexible topology for the scale-expandable array antenna with adjustable polarizations.

Passive implantable sensors have received considerable attention for wireless in vivo measurement of physiological parameters in challenging locations of the human body. They are considered promising alternatives to the existing catheter-based biomedical transducers and battery powered implants. In this paper, we report a novel planar reader antenna for wireless interrogation of $LC$ -based passive implantable sensors. The antenna utilizes two planar, electromagnetically isolated loops for wireless detection of the resonance frequency of the $LC$ sensors. 2-D and 3-D versions of the antenna with the identical geometry were developed for a comparative study. A comprehensive analysis of the antenna together with in vitro evaluation of the antenna performance is presented. With the proposed antenna topology, the isolation level of 58 dB within the frequency range of 1–50 MHz, and at least 37 dB up to 100 MHz was achieved. The 3-D version of the antenna demonstrated improved performance by the T/R isolation of at least 64 and 44 dB within the frequency bands of 1–50 and 50–100 MHz, respectively.

A miniaturized UWB antenna with multiple notch bands is proposed for modern wireless applications. The proposed microstrip-line-fed antenna consists a Y-shaped strip supported by defected ground structure. Procedure of bandwidth enhancement with multiple notch bands is presented. 163.6% of impedance bandwidth ranging from 1.5 to 15 GHz with three notch bands at 3–3.6, 6–6.8 and 9.2–9.8 GHz is achieved with gain of 2–6 dBi within the band. Accurate equivalent circuit model is presented for proposed antenna structure. Proposed antenna shows good radiation characteristics with very large bandwidth including three notch bands and suppressed cross-polarization level up to − 35 dB. The designed antenna is tested experimentally and measured results are verified with the simulated and theoretical results.

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.

This paper presents a novel and simple ultrawideband (UWB) printed rectangular monopole antenna (PRMA) for body-centric wireless communications. The design is based on etching a Q-slot on a rectangular radiator, and is optimized to produce the largest bandwidth in free space and close to the human body. We analyze the design of the proposed antenna and assess its performance in terms of bandwidth, gain, efficiency, and radiation patterns. We also characterize the antenna in the time-domain by calculating its fidelity factor. Our results show that the Q-slot antenna maintains its bandwidth when placed in close contact with the human body, or in contact with breast-mimicking tissue phantoms. The very good agreement between calculated and measured antenna performance in free space and on body suggests that the antenna is immune to variations in the human tissue, and is also robust to fabrication tolerances.

A major challenge for a combined reconfigurable antenna is to realize both polarization switching and beam steering independently in a compact antenna structure. A cavity-backed proximity-coupled reconfigurable microstrip antenna proposed in this communication provides an efficient solution. Beam lead p-i-n diodes DSM8100–000 are employed as switching elements to achieve reconfiguration. Three different linear polarizations (0°, 45°, and 90°) are realized by switching the diodes on a proximity-coupled feed network. For each polarization state, the main beam can be steered to three directions by using a reconfigurable parasitic-element network. The parasitic-element network is printed on the same plane of the radiating patch, thereby making the antenna compact. This antenna has nine different working modes, and for all the working modes, the reflection coefficients are below −10 dB with the measured realized gains ranging from 7.2 to 8.1 dBi.

A novel carbon nanotube (CNT)-based rectangular microstrip antenna for wide impedance bandwidth applications has been designed and developed. The copper patch commonly placed on the substrate in a conventional rectangular microstrip antenna is replaced with a CNT patch prepared using spin coating. The MWCNT patch antenna was fabricated by spin coating method and it exhibits an increased impedance bandwidth of 20%. The enhancement of the impedance bandwidth does not affect the broadside radiation characteristics. The carbon nanotubes are highly conductive nanomaterial. Due to this unique property, each nanotube present on the surface resonates electromagnetic waves individually and influences the enhancement in the bandwidth. The simple design and fabrication of the proposed antenna can be employed for synthetic aperture radar applications.

In this paper, a compact microstrip antenna with radiation pattern reconfigurable characteristic employing MEMS switches is proposed and investigated. This novel antenna mainly includes four parts: a circular-shaped patch, six MEMS switches, six fan-shaped coupling cells and six fan-shaped radiation cells. Through controlling the states of MEMS switches, radiation pattern selectivity of the proposed antenna can be achieved. When switching operation states of the antenna from state 1 to state 12 sequentially, the main radiation beam direction in azimuth planes could rotate 30˚ from 0˚ to 330˚ with each switch. Meanwhile, the radiation beam directions in elevation plane and the operation frequencies of proposed antenna for different operation states are stable at about 35˚ and 4GHz, respectively. With the consideration of MEMS switches actual size, the antenna structure and dimensions were optimized and adjusted. The simulated and measured results were analyzed and compared, indicating this compact antenna can be widely used for multifunctional applications and modern wireless communication systems.

A low-profile dual-polarized planar antenna with compact structure for 2.4GHz Wireless local area network (WLAN) and 2.5GHz Long term evaluation (LTE2500) base stations is proposed. A combination of a planar radiator and compact Artificial magnetic conductor (AMC) reflector is utilized to achieve a full planar structure without adding extra matching circuit, an extremely low-profile of 0.127 wavelength, as well as a high front to back ratio (F/B) of 25dB. The antenna is fabricated to test the performance such as S-parameters, radiation patterns and peak gain. Reasonable results show the suitability of the proposed antenna for 2.4GHz WLAN and LTE2500 applications.

We propose a wideband circularly polarized antenna that consists of a metallic patch and some parasitically coupled elements mounted on a grounded dielectric-ferrite substrate. The metallic patch is fed by a proximity-coupled feed line placed between the ferrite and the dielectric layers. The parasitically coupled elements are included to improve the impedance bandwidth of antenna and are excited through the metallic patch. The antenna utilizes the resonant modes of the structure, which rotate only in the clockwise or counter-clockwise direction. A semi-analytical solution based on the magnetic wall approximation shows that the resonance frequencies of the clock- and counter-clockwise resonant modes differ significantly when operating in the frequency range where the effective permeability of the ferrite layer is negative. Moreover, there is a good agreement between the model presented and full-wave numerical simulations. For the proposed antenna, the results show that the radiation bandwidth is more than 15.5% and the 3 dB axial ratio bandwidth is more than 50%. The proposed antenna is easy to design and fabricate, does not require a complicated feeding network, and has a wideband and wide-angle circular polarization.

The upcoming standards of wireless communications result in additional and more stringent requirements for antennas in mobile phones. In this paper, we present a frequency-reconfigurable antenna that could potentially be suited for future mobile devices. Frequency reconfigurability is achieved through a cluster of mutually coupled antenna elements that is excited with frequency-dependent weights using a multichannel transceiver. We report a mobile handset antenna cluster measuring 15 $\times $ 15 $\times $ 1.6 mm3 that covers the frequency bands of 1.7–2.7, 3.3–4.5, and 5.475–6.425 GHz with an antenna efficiency better than 90%. The operation of the antenna cluster is experimentally verified by feeding all the antenna elements with proper weights using tailor-made power splitters that represent a multichannel transceiver with adjustable amplitude and phase in each branch. The results obtained with the feed networks suggest the feasibility of the reconfigurability concept and pave way for codesign of the antenna and the transceiver.

As technology is moving towards miniature structures, demand for designing efficient compact antennas is increasing simultaneously. So it would be valuable to improve the features of small antennas, such as bandwidth and gain. A compact chip-resistor loaded microstrip antenna at 2.48 GHz frequency for industrial scientific and medical (ISM) band, with dimensions of 10 × 10 mm2 is presented in this paper. With a novel geometry design, antenna is promoted to an active integrated antenna (AIA) on a two-layer printed circuit board (PCB), which contains passive antenna and active circuitry with a common ground plane. A monolithic amplifier is used to have an improvement around 10 dB in antenna gain. The impedance bandwidth has been increased during chip-resistor loading and adding active circuitry processes. For chip-resistor loaded antenna, that is 5.7 and 9.48% in simulation and measurement respectively. Moreover, the active integrated antenna has the measured impedance bandwidth of 58.7%. Since the low gain and narrow bandwidth of compact microstrip antennas might be a challenge for their operation, by compensating these drawbacks, proposed antenna would become more practical for special medical diagnostic applications, where doctors need stronger signals for monitoring.

The analysis and design of a millimeter-wave conical conformal shaped-beam substrate-integrated waveguide (SIW) array antenna is demonstrated in this paper. After investigating the influence of the conical surface on the propagation characteristics of a conformal SIW, a modification for the width of a conical conformal SIW is proposed to obtain the same propagation characteristic along the longitudinal direction. This feature is indispensable to employ the classic equivalent circuit of a planar slot array antenna in the design of a conical conformal antenna. In this case, the design process of the conformal antenna can be simplified. An efficient and accurate model method of the conical conformal SIW antenna is presented as well. Then, a design process of the conical conformal SIW slot array antenna is introduced. Furthermore, to implement the transition between a conical surface and a cylindrical surface, a flexible SIWtransition is designed with a good impedance matching. Finally, two low sidelobe level (SLL) SIW conical conformal antennas with and without the flexible transitions are designed. Both of them have −28 dB SLLs in H-plane at the center frequency of 35 GHz.

A graphene microstrip patch antenna is designed to operate in the three bands of the atmospheric windows promising for the future wireless communications. The graphene has a reconfigurable surface conductivity that can be tuned to operate at the desired frequencies. This paper studies the role of chemical potential ( μ c ) of the graphene to tune the resonant frequency of a microstrip antenna. The results show that the resonant frequency of a microstrip antenna increases as the chemical potential grows that can be employed to realize a reconfigurable antenna. The proposed resonances for the low-loss 300 GHz, 350 GHz and 410 GHz atmospheric windows can be achieved for μ c = 0.21 eV, μ c = 0.4 eV and μ c = 1.5 eV respectively. Finally, a design process for a multi-band graphene-based antenna has been presented.

Ultra-wideband (UWB) planar antennas with single or multiple notched frequency bands properties have recently been considered for various communications between wireless devices. In this study, a low profile microstrip monopole antenna with double band-filtering function is designed and investigated. FR-4 dielectric with properties of e = 4.4 and δ = 0.02 has been employed as the antenna substrate. The configuration of the proposed design is composed of a modified fork-shaped radiating patch with inverted Ω-shaped slot and a pair of coupled Γ-shaped parasitic structures, a feed-line and a ground plane. The proposed dual band-notched UWB antenna provides good impedance bandwidth characteristic from 2.89 to 12.43 GHz for VSWR

In this study, a compact multiband antenna employing a wideband dual zeroth-order resonator (ZOR) is proposed for mobile handset applications. The theory of wideband zeroth-order mode and multimode is used to design the proposed antenna covering LTE850/900 (824–960 MHz), LTE1700/1800/1900/2100 (1710–2170 MHz), LTE2300 (2300–2400 MHz), LTE2600 (2500–2690 MHz), and Wi-Fi (2400–2500 MHz) bands. In order to achieve wideband operations, the proposed antenna consists of a low-band ZOR and a high-band ZOR that can generate and merge resonance frequencies of zeroth-order, negative-order, and positive-order modes. The performance of the antenna is verified by both full-wave simulations and experiments. The overall size of the antenna is 40 mm × 6 mm × 3 mm . The antenna provides omnidirectional radiation patterns and measured radiation efficiencies exceeding 43% and 47% for low and high bands, respectively.

A novel design concept of enhancing the impedance bandwidth of a single-layer shorted microstrip patch antenna (MPA) is proposed under simultaneous radiation of the one- and three-quarter wavelength resonant modes (TM0,1/2 and TM0,3/2 modes). Initially, a conventional MPA with the shorting wall is studied to demonstrate that none of the redundant modes can be excited between the dual-resonant modes. Then, a pair of shorting pins are appropriately installed underneath the patch to progressively turn up the resonant frequency of TM0,1/2 mode without significant influence on that of TM0,3/2 mode. After that, a V-shaped slot is etched out on the patch to dramatically reduce the resonant frequency of TM0,3/2 mode with little effect on that of TM0,1/2 mode. With the use of these arrangements, the dual-desired radiative resonant modes are gradually moved in proximity to each other, thus widening the impedance bandwidth under emergence of dual resonant poles. In order to validate the principle and design method, the proposed antenna is designed, fabricated, and measured. The measured results demonstrate that the impedance bandwidth of the proposed shorted patch antenna has been extended to about 11.8%, and it is about 1.82 times of 6.5% of the traditional shorted MPA. Meanwhile, the fabricated antenna exhibits other attractive performances including stable radiation pattern, same polarization, and a low-profile property with the height of 0.042 free-space wavelength.

Objectives: The aim is to design a Microstrip Patch Antenna (MSA) for enhancement of bandwidth and improved outcome for return loss. The approach for dimension decrease is also a parameter for designing of this antenna. Method: A shorted pin, coaxial feed, Microstrip Patch Antenna (MSA) is used for wireless communication. The patch with U type slot, cut at corner and also shorted by shorting pin is the design of an antenna. For good efficiency proposed antenna’s design parameters are optimized by HFSS’s Optometric. Findings: The proposed antenna has a wide band frequency ranged from 1.4 GHz to 4 GHz with Bandwidth of 210 MHz and 250 MHz return loss of-11.45db and -20.50dB respectively. In this design HFSS (High Frequency Structure Simulator) software is used which is a FEM based electromagnetic solver. The parameteric analysis of return loss, gain and bandwidth is done in an extended form in the proposed antenna design. Application: This design is suitable for the function in wireless communication system and also for fabrication proposes design is very simple.

Microstrip antenna with electrically large property (ELP) is discussed and designed in this paper. The modal wave equation for the microstrip resonant cavity is analyzed and the fundamental resonant mode (TM100 mode) of the cavity is discussed by considering the boundary conditions. As an example, effective media parameters of one I-shaped resonant metamaterial is extracted from the S-parameters and the ELP is achieved for the antenna in the band of $\varepsilon > 0$ and $\mu . The results show that the resonant frequency of the planar microtrip-line-slot feed antenna is increased about 4.6 times by loading with metamaterial in-between the feeding part and radiating part of the planar antenna without deteriorating the directional radiation pattern. One prototype is fabricated and the measured result shows that the resonant frequency for the ELP antenna is centered at about 30 GHz which confirm the theory analysis. The proposed method is a good option to design millimeter wave and terahertz wave antennas and devices in the future.

In this paper, a conformal wideband circularly polarized (CP) antenna is presented for endoscopic capsule application over the 915-MHz Industrial, Scientific, and Medical (902–928 MHz) band. The thickness of the antenna is only 0.2 mm, which can be wrapped inside a capsule’s inner wall. By cutting meandered slots on the patch, using open-end slots on the ground, and utilizing two long arms, the proposed antenna obtains a significant size reduction. In the conformal form, the antenna volume measures only 66.7 mm3. A single-layer homogeneous muscle phantom box is used for the initial design and optimization with parametric studies. The effect of the internal components inside a capsule is discussed in analyzing the antenna’s performance and to realize a more practical scenario. In addition, a realistic human body model in a Remcom XFdtd simulation environment is considered to evaluate the antenna characteristics and CP purity, and to specify the specific absorption rate limit in different organs along the gastrointestinal tract. The performance of the proposed antenna is experimentally validated by using a minced pork muscle phantom and by using an American Society for Testing and Materials phantom immersed in a liquid solution. For measurements, a new technique applying a printed 3-D capsule is devised. From simulations and measurements, we found that the impedance bandwidth of the proposed antenna is more than 20% and with a maximum simulated axial ratio bandwidth of around 29.2% in homogeneous tissue. Finally, a wireless communication link at a data rate of 78 Mb/s is calculated by employing link-budget analysis.

A single patch antenna suitable for integration and operation in 24 GHz band for wireless inter vehicular communication is designed and developed. The requirements on the design are the large bandwidth, simple configuration, light weight and low profile. The antenna is fed by using inset feed line to provide impedance matching. Antenna gain values of ∼5.9 dBi are obtained in addition to a very less return loss of ~39 dB. The developed antenna provides a bandwidth of 120 MHz and an input impedance of ~50Ω. The antenna was tested in a real time environment and the received power levels are noted. A simple Rician channel is simulated for the measured values and the BER is tabulated.

This paper presents the design of a tri-band flower-shaped planar monopole antenna operating at three frequencies i.e. 1.576 (GPS), 2.668, and 3.636 GHz (Mobile WiMAX). The radiating element of the antenna is backed by a 1.6 mm thicker FR-4 substrate having a dielectric constant of 4.3. The substrate is backed by a truncated ground plane. The antenna is fed through a 50 Ω microstrip line. The flower shape of the radiating element is derived from the basic circular shape by introducing in it rounded slots of various radii. The upper part of the antenna is flower shaped while the lower part comprises a microstrip feed line and two branches, each having two “leaves” at the end. The leaves and branches contribute in the impedance matching of the lower (1.576 GHz) and middle (2.668 GHz) frequency bands. The antenna gives an acceptable simulated efficiency >70% in the three frequency bands. Suitable gains of 1.63, 2.59, and 3.23 dB are obtained at 1.576, 2.668, and 3.636 GHz, respectively. The antenna m...

A simple and novel approach of size reduction of a slot antenna loaded with spiral ring resonator (SRR) on the patch surface is highlighted. The antenna resonates at 4.5 GHz when a half wavelength slot section is fed by the coplanar waveguide line. The fundamental resonant frequency is lowered by 2.05 GHz when the slot antenna is loaded with a pair of SRR at the end of the half wavelength slot section. The additional inductive and capacitive reactance of the resonator enables the patch to resonate at lower frequency (2.45 GHz). The proposed antenna structure reduces the resonant frequency with respect to the reference antenna (slot antenna without SRR) by 45.5%, causing the patch to almost reach an electrically small size. Finally, asymmetrical slot has been used and a wide band antenna of band width 900 MHz has been achieved. Despite the loaded patch touching the electrically small limit, the antenna needs no matching networks, offers high efficiency and exhibits a bandwidth better than the unperturbed patch. The radiation pattern is also seen to be unaffected by the presence of the SRR.

In this article, a wideband substrate integrated waveguide (SIW) cavity-backed antenna with multi-resonance slots for Ku−band application is presented and experimentally investigated in terms of antenna performances including S-parameter, optimized parameter values, gain, and radiation pattern. With the proper placement of multi-resonant slots on the backside of the cavity, the hybrid modes are generate in the frequency band of interest. These modes can be tuned by varying the slot parameters which result the merging of different resonant frequencies, therefore the simulated impedance bandwidth is substantially enhanced to 1.46 GHz, ranging from 12.7 to 14.16 GHz with a gain of 6.0 to 8.0 dBi. The measured result showing the fractional bandwidth of the proposed antenna is 11.8% and 11% achieved at the resonant frequencies of 13 and 14 GHz, respectively. Moreover, the antenna has the features of simple-single layer structure, resonant frequency flexibility with multi-resonance characteristics over a wide impedance bandwidth.

A compact rectangular microstrip antenna embedded with open-ended ground slots is presented in this paper. Three equal open-ended ground slots have been incorporated inside the ground plane in order to excite the antenna with a lower order resonant mode. On variation of the length parameter of the middle slot of the antenna, a resonant mode of lower order has been obtained near 1.52 GHz. The maximum size reduction of the designed structure is obtained, considering the lower band resonant frequency obtained is about 85.83% with a fractional bandwidth of 6.97%. The simple configuration has been fabricated on low-cost FR-4 substrate material. The proposed low-profile triple band microstrip patch obeys all the necessary standards prescribed for wireless communication and, therefore, finds its applicability in multiband wireless communication systems.

This paper focuses on a new dual turn spiral resonator (DTSR) loaded electrically small microstrip patch antenna. The proposed DTSR loaded antenna is mounted on Rogers RT/Duroid 5880 tm substrate and numerically analyzed with electromagnetic solver. The resonant frequency of the antenna gets lowered with improved magnetic permeability of dielectric materials through metamaterial loading. The DTSR loaded antenna resonates at 14.76 GHz compared to unloaded simple microstrip patch antenna resonating at 27.44 GHz. The proposed antenna also satisfies the condition of Chu limit for being electrically small antenna with appreciable return loss and gain of 7.17 dB and fractional bandwidth is 7.96%. This antenna can be used for satellite communications. The full wave simulated resonant frequency of DTSR is compared with frequency derived from equivalent circuit of model. It is observed that the analytically calculated resonant frequency is in close agreement with full wave numerically analyzed frequency. The negative permeability of the DTSR is also plotted to depict the metamaterial behavior.

Methods to improve the performance and survivability of state-of-the-art military aircrafts have been widely researched as their missions are complex and diverse. The load-bearing antenna approach ...

A miniaturized multiband slotted Microstrip antenna for wireless applications is designed and its characteristics have been investigated. The proposed antenna consists of a substrate, one side of substrate is having rectangular radiating patch containing C-shaped slots and other side is having a partial ground plane. The dimensions for proposed antenna are kept small to 25 × 25 × 1.6 mm. The number, length/width, and positions of the C-shaped slots have been selected suitably so as to achieve results for return loss, VSWR in frequency bands of interest. The proposed antenna characterizes four bands at resonant frequencies of 3.39, 4.29, 5.46, and 5.77 GHz with return loss values of −16.45, −19.24, −11.85, and −12.35 dB and VSWR values of 1.37, 1.24, 1.69, and 1.64 respectively. The designed antenna can serve IEEE 802.11a radio WLAN applications in frequency band 5.180–5.825 GHz, IEEE 802.16-2004 fixed WiMAX applications in frequency band 2–11 GHz, and IEEE 802.16e mobile WiMAX applications in frequency band 2–6 GHz. The proposed antenna has nearly omnidirectional radiation pattern exhibiting reasonable gains across the desired frequency bands.

In this paper, the concept of perturbation theory is applied to derive a general electric field (E-field) expression for any arbitrary-shaped microstrip patch antenna. The arbitrary shape is created by adding small perturbation in a regular patch shape, which is used to find perturbed and unperturbed electromagnetic wave solutions for resultant E-field of patch antenna. Ansoft HFSS simulator is used to validate the derived field expression in curvilinear coordinates for a regular circular-shaped patch. Then the proposed field analysis is applied to develop two new arbitrary-shaped patches in C-band for desired E-field patterns.

This communication deals with the design of a $16\times 16$ slot array antenna fed by inverted microstrip gap waveguide (IMGW). The whole structure designed in this communication consists of radiating slots, a groove gap cavity layer, a distribution feeding network, and a transition from standard WR-15 waveguide to the IMGW. First, a $2\times 2$ cavity-backed slot subarray is designed with periodic boundary condition to achieve good performances of radiation pattern and directivity. Then, a complete IMGW feeding network with a transition from WR-15 rectangular waveguide to the IMGW has been realized to excite the radiating slots. The complete antenna array is designed at 60-GHz frequency band and fabricated using Electrical Discharging Machining Technology. The measurements show that the antenna has a 16.95% bandwidth covering 54–64-GHz frequency range. The measured gain of the antenna is more than 28 dBi with the efficiency higher than 40% covering 54–64-GHz frequency range.

A novel broadband circularly polarized (CP) antenna with wide axial ratio (AR) beamwidth is proposed. It is composed of two curved arms shaped like an inverted “S.” The mechanisms of wideband CP operation and wide AR beamwidth are explained. To validate the concept, a prototype at C-band is manufactured and measured. Experimental results confirm that the antenna achieves an impedance bandwidth of 63% and a CP bandwidth of 42%. Furthermore, maximum AR beamwidth of 140° is achieved and wide AR beamwidth can be maintained in a frequency bandwidth of 35% in nearly all elevation planes. In addition, the antenna has the advantage of being easily extended to arrays. A four-element array using the proposed antenna is investigated through both simulations and experiments, and achieves 60% CP bandwidth and wide AR beamwidth. The proposed inverted-S antenna can realize wide CP bandwidth and wide AR beamwidth, and can easily form wideband CP arrays.

Objectives: Dual-Band, reduced size, coaxial fed probe, Inverted C-slot patch antenna for wireless communication is designed in this paper. The excellent dual-band performance is attained by using inverted C-slots on the patch. Methods/Statistical Analysis: The slots provide two notched bands covering 2.7 GHz to 4.04 GHz for WiMAX and 5.32 GHz to 6 GHz for WLAN with excellent return loss and satisfactory VSWR. Findings: Two resonant peaks obtained are at 3.2 GHz and at 5.4 GHz. The proposed antenna size is 29 mm × 29 mm. The antenna has been effectively simulated on HFSS and tested on VNA tool. The peak gain of 4.65 dB and efficiency of 95% is obtained. The antenna presentation is analyzed on the basis of size of antenna, VSWR, bandwidth, return loss and efficiency. The presented antenna is an excellent choice for WLAN and WiMAX. Improvements: As compared to conventional Microstrip Patch Antenna return loss is improved with 67% and area minimization of 63% has been attained.

A differential-fed microstrip patch antenna (MPA) with bandwidth enhancement is proposed under the operation of TM10 and TM30 resonant modes in a single patch resonator. Initially, a rectangular differential-fed MPA is theoretically investigated so as to demonstrate that all of the undesired modes between the TM10 and TM30 modes are suppressed or removed out effectively. Then, by symmetrically introducing two pairs of shorting pins, the resonant frequency of TM10 mode is progressively turned up. After that, with the help of two long slots, the resonant frequency of TM30 mode is decreased with slight effect on that of TM10 mode. Furthermore, a short slot is inserted at the center of the patch to cancel the parasitic inductances of the shorting pins and probe feeds. With this arrangement, these two radiative resonant modes are moved in proximity to each other for wideband antenna. Finally, the proposed differential-fed MPA is fabricated and measured. Experimental results illustrate that the impedance bandwidth ( $\vert S_{{{\text {dd}11}}}\vert dB) of the antenna has gained a tremendous increment up to about 13% (1.88–2.14 GHz), while keeping a low profile property with the height of 0.029 free-space wavelength. Additionally, the antenna has achieved a stable gain varied from 5.8 to 7 dBi over the operating band.

A planar broadband antenna with a center frequency of 81.75 GHz is proposed in this communication, which is composed by an open-ended pentagonal slot etched on the broad surface of a substrate-integrated waveguide (SIW) and a short circuited metallic via inserted inside the ring slot. The broadband SIW 180° phase-shifter and the SIW power-divider are deployed in the design to implement the beam-forming network. As a demonstration, a $2 \times 8$ array is designed on a 0.5 mm thick Rogers5880 substrate, and fabricated by using the low-cost printed circuit board process. Experiments are carried out to verify the design, which show that the measured antenna has a 10 dB return loss bandwidth from 77 to 86. 5 GHz, that is, the fractional bandwidth of 11.6%. The proposed antenna is a promising candidate for the E -band high-speed wireless communication system.

A low-profile, beam tilted microstrip patch antenna (MPA) with broad-useful bandwidth and improved gain is presented. The proposed design comprises of a rectangular MPA and a square-loop unit-cell-based metasurface superstrate with different effective refractive index regions. The beam tilting is achieved by the phenomenon of phase difference produced by the superstrate having different refractive index regions. The experimental results display a maximum beam tilt of 27° in the E-plane at 5 GHz with a slight frequency dependability of 0.013°/MHz. The proposed design also offers a broad-useful bandwidth of 11% centred at 4.82 GHz, while maintaining relatively low antenna height of 0.06λ. Moreover, uniform field distribution due to superstrate provides a maximum gain of 8.4 dBi with a variation ≤1.3 dB.

A folded-patch tag antenna (30 mm x 30 mm x 3 mm or 0.0912λ x 0.0912λ x 0.009λ) is designed for mounting on metallic objects. It consists of a serrated patch radiator, ground patch, and loopshaped stub, which are made on a flexible inlay wrapping around soft foam. Digital serration is used for fine-tuning the resonant frequency. The proposed tag antenna is able to achieve a read range beyond 7 m on metal. It can also be read from at least 3.5 m when used on dielectrics with permittivity in the range from 1 to 12.

For the requirements of efficient integration and simple fabrication, a new codesign approach for a microstrip filter with an antenna array with reduced sidelobe level is introduced in this communication. The microstrip patch antennas and the stub-loaded resonators are used to illustrate the synthesis of a bandpass filtering antenna array. By controlling the coupling strength between the resonators, a uniform or nonuniform power divider network can be obtained. A nonuniform power division is used to reduce the sidelobe level. The equivalent lumped circuit model is developed and analyzed in detail. Two types of eight-element filtering antenna array with uniform and tapered power-distribution among the elements have been designed. Simulated and measured results provide a good verification for the theoretical concepts.