Showing papers on "Microstrip antenna published in 2019"

A Compact, Low-Profile Fractal Antenna for Wearable On-Body WBAN Applications

Abstract: A compact and low-profile wearable antenna is presented for on-body wireless body area network (WBAN) applications. The proposed triangular patch antenna is designed using low-cost widely available vinyl polymer-based flexible substrate. The final antenna topology is obtained by the combination of the Koch fractal geometry, meandering slits, and defected ground structure, to achieve a novel hybrid structure with compact footprint, good structural conformability, and enhanced impedance bandwidth (BW) to operate in the Industrial, Scientific, and Medical band with center frequency at 2.45 GHz. The fabricated prototype of the antenna has shown a good agreement between numerical and experimental results. In comparison to state-of-the-art prototypes, our design has more compact form factor of 0.318λo × 0.318λo × 0.004λo, along with 7.75% impedance BW, a peak gain of 2.06 dBi, and overall radiated efficiency of 75%. For the assessment of a specific absorption rate (SAR) performance of our design, it is tested on realistic heterogeneous HUGO voxel model. Both numerical and experimental investigations revealed extremely good robustness to both human body loading and structural deformation, making it an ideal candidate for flexible and body-worn devices.

Eight-Element Dual-Polarized MIMO Slot Antenna System for 5G Smartphone Applications

Abstract: In this paper, we propose an eight-port/four-resonator slot antenna array with a dual-polarized function for multiple-input-multiple-output (MIMO) 5G mobile terminals. The design is composed of four dual-polarized square-ring slot radiators fed by pairs of microstrip-line structures. The radiation elements are designed to operate at 3.6 GHz and are located on the corners of the smartphone PCB. The square-ring slot radiators provide good dual-polarization characteristic with similar performances in terms of fundamental radiation characteristics. In order to improve the isolation and also reduce the mutual coupling characteristic between the adjunct microstrip-line feeding ports of the dual-polarized radiators, a pair of circular-ring/open-ended parasitic structures is embedded across each square-ring slot radiator. The −10-dB impedance bandwidth of each antenna-element is 3.4–3.8 GHz. However, for −6-dB impedance bandwidth, this value is 600 MHz (3.3–3.9 GHz). The proposed MIMO antenna offers good S-parameters, high-gain radiation patterns, and sufficient total efficiencies, even though it is arranged on a high-loss FR-4 dielectric. The SAR function and the radiation characteristics of the proposed design in the vicinity of user-hand/user-head are studied. A prototype of the proposed smartphone antenna is fabricated, and good measurements are provided. The antenna provides good features with a potential application for use in the 5G mobile terminals.

Performance-Based Nested Surrogate Modeling of Antenna Input Characteristics

Abstract: Utilization of electromagnetic (EM) simulation tools is mandatory in the design of contemporary antenna structures. At the same time, conducting design procedures that require multiple evaluations of the antenna at hand, such as parametric optimization or yield-driven design, is hindered due to the high cost of accurate EM analysis. To a certain extent, this issue can be addressed using fast replacement models (also referred to as surrogates). Unfortunately, due to curse of dimensionality, traditional data-driven surrogate modeling methods are limited to antenna structures described by a few parameters with relatively narrow parameter ranges. This is by no means sufficient given the complexity of modern designs. In this paper, a novel technique for surrogate modeling of antenna structures is proposed. It involves a construction of two levels of surrogates, both realized as kriging interpolation models. The first model is based on a set of reference designs optimized for selected performance figures. It is used to establish a domain for the final (second level) surrogate. This formulation permits efficient modeling within wide ranges of antenna geometry parameters and wide ranges of performance figures (e.g., operating frequencies). At the same time, it allows uniform allocation of training data samples in a straightforward manner. Our approach is demonstrated using two microstrip antenna examples and is compared with conventional kriging and radial basis function modeling. Application examples for antenna optimization are also provided along with experimental validation.

A Simple Decoupling Method for 5G Millimeter-Wave MIMO Dielectric Resonator Antennas

Abstract: A simple decoupling method of using metallic vias to improve the isolation of millimeter-wave multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) elements is investigated. The vias are vertically added to the DRA elements, at appropriate positions. By means of the interaction with the electromagnetic fields, the vias can potentially affect the filed distributions and further reduce the coupled fields effectively. The isolation between the MIMO DRA elements can, therefore, be enhanced substantially. As the vias are placed inside the DRA elements, no extra footprint is needed, making the entire antenna system very simple and compact. Two typical examples, including an H-plane and an E-plane, coupled $1\times2$ MIMO DRA arrays, have been designed, fabricated, and measured to demonstrate the feasibility and universality of this method. The results show that by using the vias appropriately, the isolation of the H-plane coupled MIMO DRA array can be enhanced from ~15.2 to 34.2 dB, while that of the E-plane array can be improved from ~13.1 to 43 dB at 26 GHz.

A Miniaturized Microstrip Antenna Array at 5G Millimeter-Wave Band

Abstract: A miniaturized two-element microstrip antenna array is proposed for the millimeter-wave band of fifth generation (5G) wireless communication systems. A surface of electromagnetic bandgap structures (EBG) is applied as the ground for two closely packed patch antennas operating in 5G New Radio (26 500–29 500 MHz) frequency band. With the help of the proposed EBG ground, the two E-shaped microstrip antenna elements can be placed in close proximity to each other by 0.3 wavelength center to center distance in free space at the center frequency, yet the mutual coupling between them can still reach to more than 23 dB within the whole band of interest, which is about 10 dB larger than that on normal ground. All major radiation characteristics of the two-element array are well reserved with the EBG ground. The proposed design can be used in multiple-input-multiple-output applications or as the building subarray of larger phased arrays at millimeter-wave bands for mobile communication systems.

Broadband and High-Gain Microstrip Patch Antenna Loaded With Parasitic Mushroom-Type Structure

Abstract: This letter presents a novel broadband microstrip patch antenna with a simple geometry. Two parasitic mushroom-type arrays are incorporated along with the two radiating edges of a main radiating patch. First, thanks to the mushroom-type structure, a new resonant mode, characterized as quasi-TM $_{30}$ mode, is generated. Besides, the main radiating patch produces the original TM $_{10}$ mode. Thus, wideband performance is realized on the basis of the two combined modes. Second, the current distributions on those metal patches are nearly uniform so that high gains are achieved over the entire operating bandwidth. Measured results indicate that the enhanced impedance bandwidth is from 11.9 to 18.2 GHz, which covers the whole Ku-band. Meanwhile, a nearly constant peak-radiating gain between 10 and 10.5 dBi at broadside radiation is obtained. The proposed antenna maintains the advantages of wide bandwidth, ease of fabrication, flat and high gains, and a low profile less than ${\lambda _0}$ /13 thickness substrate.

Dual band omnidirectional millimeter wave antenna for 5G communications

Abstract: A planar dual band millimeter wave printed monopole antenna and a 2×2 MIMO antenna are presented for 28/38 GHz future 5G wireless communications. The shape of the radiating element of the p...

A Compact Quasi-Isotropic Dielectric Resonator Antenna With Filtering Response

Abstract: A compact quasi-isotropic dielectric resonator (DR) antenna (DRA) with filtering response is first investigated in this communication. The cylindrical DRA is fed by a microstrip-coupled slot, exciting in its ${\text {HEM}}_{11 \delta }$ mode which radiates like a magnetic dipole. A small ground plane is used for this DRA and it radiates like an electric dipole. The combination of the two orthogonal dipoles leads to a quasi-isotropic radiation pattern, with gain deviation as low as 5.8 dB in the 360° full space. To integrate the filtering function, the microstrip feed-line and the ground plane are turned upside down, and further two stubs with different lengths are used together to excite the DR. Due to the different loading effects of the feeding stubs, two resonances of the DR ${\text {HEM}}_{11 \delta }$ mode are excited in the passband, effectively enhancing the bandwidth of DRA ( $\varepsilon _{r} = 20$ ) to 7%. Furthermore, two controllable radiation nulls are generated by the DR loaded microstrip feed-line, bringing about high frequency selectivity at the edges of the passband and a quasi-elliptic bandpass response. For demonstration, a prototype operating at 2.4 GHz was fabricated and tested; reasonable agreement is obtained between the simulated and measured results.

Isolation enhancement of densely packed array antennas with periodic MTM-photonic bandgap for SAR and MIMO systems

Abstract: A metamaterial photonic bandgap (MTM-PBG) periodic structure is used as a decoupling frame to improve the isolation between transmit-receive (T/R) sections of the densely packed array antenna in synthetic aperture radar (SAR) and multiple-input-multiple-output (MIMO) systems. With this technique the MTM-PBG structure is shown to effectively suppress surface wave propagations between the T/R array antennas by an average of 12 dB. MTM-PBG layer comprises a periodic arrangement of dielectric circles etched in the cross-shaped microstrip frame that is inserted between the radiating elements. Unlike other recently reported methods, the advantages of the proposed technique are: (i) simplicity; (ii) cost effectiveness as there is no need for short-circuited via-holes or three-dimensional metal walls; and (iii) can be retrofitted in existing array antennas. The proposed T/R array antennas were designed to operate over an arbitrary frequency range (9.25-11 GHz) with a fractional bandwidth of 17.28%. With this technique (i) the side-lobes are reduced; (ii) there is minimal effect on the gain performance; and (iii) the minimum edge-to-edge gap between adjacent radiating elements can be reduced to 0.15 λ at 9.25 GHz.

Wideband Radiation Reconfigurable Microstrip Patch Antenna Loaded With Two Inverted U-Slots

Abstract: A wideband rectangular microstrip patch antenna with reconfigurable radiation patterns is proposed in this paper, which contains two symmetrically inverted U-slots, and incorporates two coaxial probes along the resonant length of the patch. By controlling the phase shift of applied currents through these probes, the antenna can be set to excite either the SUM or the Difference mode, in accord with the TM01 and TM02 modes, respectively. Unlike previous endeavors on U-slot microstrip antennas, a wide impedance bandwidth of 68% is realized, along with stable polarization and symmetrical radiation patterns. It is worth mentioning that the thickness of the substrate is very small, which is in the order of $0.02 \lambda _{d}$ , where $\lambda _{d}$ is the wavelength in the dielectric medium at the center frequency of 3 GHz. The slot and patch parameters are numerically analyzed to achieve wide bandwidth along with symmetric radiation patterns. The realized null depth in the Difference mode is well below −30 dB, which makes the proposed antenna well suited for monopulse radar applications. The antenna covers a frequency range of 1.98–4 GHz. A prototype is fabricated and tested. Good agreement between the measured and simulated results is observed.

Ultra-Wideband Antennas for Wireless Communication Applications

Abstract: A review paper concerning wide-band and ultra-wideband (UWB) antennas used for wireless communication purposes in terms of the materials as well as a numerical analysis is presented. These antennas which are taken into account are listed as wide-band microstrip antenna, wide-band monopole antenna over a plate, wide-slot UWB antenna, stacked patch UWB antenna, taper slot (TSA) UWB antenna, metamaterial (MTM) structure UWB antennas, elliptical printed monopole UWB antenna, and flexible wearable UWB antenna. The antennas’ performance is compared based on their size and how they can be applicable for portable communication device applications. This review paper furnishes a proper direction to select varieties of figures in terms of impedance bandwidth, gain, directivity, dimensions, time domain characteristics, and materials affecting these antenna’s characteristics.

Linearly and Circularly Polarized Filtering Dielectric Resonator Antennas

Abstract: In this paper, linearly polarized (LP) and circularly polarized (CP) filtering dielectric resonator antennas (DRAs) are presented. They have conducting loops inside them. Equivalent horizontal magnetic dipoles can be obtained from the HEM $_{11\delta }$ mode of the DRA and the loop structure. When they are equal in magnitude but opposite in phase, the radiated fields can be canceled out and a good filtering response can be obtained. To demonstrate the idea, both the LP and CP filtering DRAs operating at 2.4 GHz were designed, fabricated, and tested. The reflection coefficient, axial ratio, radiation pattern, antenna gain, and antenna efficiency are studied, and reasonable agreement between the measured and simulated results is found. The LP and CP designs have measured peak realized gains of 5.86 dBi and 5.1 dBic, and out-of-band suppression levels of over 19 and 18 dB, respectively.

A Compact Building Block With Two Shared-Aperture Antennas for Eight-Antenna MIMO Array in Metal-Rimmed Smartphone

Abstract: In this paper, a compact building block composed of a slot antenna and a loop antenna is proposed. The slot antenna and the loop antenna share a rectangular clearance, which improves the compactness of the building block effectively. Although the slot and the loop have overlapped completely, the proposed building block exhibits good isolation (better than 19 dB) without any external decoupling structure. Four such building blocks are used to implement a compact eight-port multiple-input multiple-output (MIMO) array operating at 3.5 GHz band (3.4–3.6 GHz) for fifth-generation (5G) metal-rimmed smartphone applications. The proposed eight-antenna MIMO array exhibits good isolation of better than 16 dB across the whole operating band. The measured efficiencies of the proposed MIMO array were between 59% and 73%, and its corresponding measured envelope correlation coefficients (ECCs) were better than 0.05. Furthermore, the calculated channel capacity of the proposed MIMO array with 20 dB signal-to-noise ratio (SNR) was about 38.2–39.8 bps/Hz across the desired bands (3.4–3.6 GHz). The measured results confirm that the proposed MIMO array is a good candidate for 5G terminals.

A Multistate Frequency Reconfigurable Monopole Antenna Using Fluidic Channels

Abstract: A reconfigurable microstrip monopole antenna that uses three closely spaced substrate milled channels filled with either air or dielectric fluid is presented. Based on the number of channels filled with fluid, four states—namely states 0, 1, 2, and 3—of operation are selected. Introduction of fluid (distilled water) in the channel modifies the effective permittivity of the dielectric medium and perturbs the E -field distribution in vicinity to the antenna arm. The position and size of channels are optimized to maximize the shift in operating frequency and $S_{11} $-$ 10 dB impedance bandwidth through full-wave electromagnetic (HFSS) simulations. A prototype of the antenna is fabricated and measured, exhibiting frequency shifts of 12.0%, 17.9%, and 23.7% with impedance bandwidth of 32.0%, 30.1%, and 29.9% in states 1, 2, and 3 of the antenna, respectively. The reference state, i.e., state 0, offers 34.7% impedance bandwidth. The measured peak gains achieved are 2.4, 1.6, 1.2, and 0.3 dBi for states 0, 1, 2, and 3, respectively. In all the states of operation, the radiation pattern remains stable and omnidirectional.

Structural Design for Stretchable Microstrip Antennas.

Abstract: Wireless technology plays a critical role in the development of flexible and stretchable electronics due to the increasing demand for compactness, portability, and level of comfort. As an important candidate in wireless technology, microstrip antennas have recently been explored for flexible and stretchable electronics. However, the stretchable characteristics of the microstrip antenna typically come at the cost of reduced electrical conductivity and radiation efficiency. By utilizing a soft silicone substrate and the structural design of the conventional metallic materials for both patch and ground plane in the microstrip antennas, we have demonstrated two designs of stretchable microstrip antennas: "meshed microstrip antenna" and "arched microstrip antenna". The former exploits initially wavy structures from patterning, and the latter also uses the deformed wavy structures created from the prestrain strategy. In comparison to their solid microstrip antenna counterpart, the radiation properties of the resulting stretchable microstrip antennas do not change much. Meanwhile, the resonance frequency decreases with the externally applied tensile strain along the feeding direction in the design of the meshed microstrip antenna but increases with the increasing strain in the design of the arched microstrip antenna. The change in the resonance frequency with the externally applied tensile strain in the latter design has a high sensitivity, manifesting a 3.35- and a 1.49-fold increase of sensitivity when compared to those in previous reports that used silver nanowire- or liquid-metal-based stretchable microstrip antennas. Considering the high sensitivity and compliant characteristic of the stretchable microstrip antenna, we have demonstrated an arched microstrip antenna-based strain sensor that is capable of detecting the motion of human wrists with high sensitivity, little hysteresis, and possible wireless communication.

Design and Analysis of a Wideband Multiple-Microstrip Dipole Antenna with High Isolation

Abstract: A wideband multiple-microstrip dipole antenna with dual polarization is proposed in this letter. The antenna consists of a radiator, a cross-shaped slot coupler, a pair of microstrip baluns, and a reflector. When baluns are excited, the cross-shaped slot coupler would work as a four-way equal-split power divider and generate four differential signals at four ends of the slotlines. Afterward, the signals would be coupled to four modified dipoles to radiate and synthesize slant ±45° linear polarizations. The proposed design is verified by the fabrication and testing of a prototype antenna. Measured results agree well with the simulated ones, giving a wide impedance bandwidth from 1.68 to 2.75 GHz, a high port-to-port isolation (better than 37 dB) within the operating frequency bandwidth, and a good radiation pattern. Besides, the proposed antenna maintains a compact structure measuring 0.78 λ 0 × 0.78 λ 0 × 0.18 λ 0.

Beam-scanning leaky-wave antenna based on CRLH-metamaterial for millimetre-wave applications

Abstract: This paper presents empirical results of an innovative beam-scanning leaky-wave antenna (LWA), which enables scanning over a wide angle from - 35° to + 34.5° between 57 and 62 GHz, with broadside radiation centred at 60 GHz. The proposed LWA design is based on composite right/left-handed transmission-line (CRLH-TL) concept. The single-layer antenna structure includes a matrix of 3 × 9 square slots that is printed on top of the dielectric substrate; and printed on the bottom ground-plane are Π- and T-shaped slots that enhance the impedance bandwidth and radiation properties of the antenna. The proposed antenna structure exhibits metamaterial property. The slot matrix provides beam scanning as a function of frequency. Physical and electrical size of the antenna is 18.7 × 6 × 1.6 mm 3 and 3.43λ 0 × 1.1λ 0 × 0.29λ 0 , respectively, where λ 0 is free space wavelength at 55 GHz. The antenna has a measured impedance bandwidth of 10 GHz (55-65 GHz) or fractional bandwidth of 16.7%. Its optimum gain and efficiency are 7.8 dBi and 84.2% at 62 GHz.

Novel UWB printed metamaterial microstrip antenna based organic substrates for RF-energy harvesting applications

Abstract: In this paper, an intensive study is proposed to recycle the organic materials use for microwave applications including RF-energy harvesting. Thus, the Iraqi Palme Tree Remnants (IPTR) is exemplified for this study to create dielectric substrates. The main texture of the fabricated substrates is IPTR mixed with Nickel Oxide Nanoparticles (NONP) hosted in Polyethylene (PE) to be called INP substrates. Nevertheless, a metamaterial (MTM) printed antenna on the proposed substrate is fabricated by material printer with Sliver Nanoparticles Conductive Ink (SNPCI). The antenna performance is tested numerically/experimentally in terms of S11 spectrum and radiation patterns. It is found excellent matching bandwidths at 2.45 GHz and 5.8 GHz frequencies with acceptable gains of 1.56 dBi and 2.48 dBi, respectively. The proposed antenna bandwidth is found to start from 2.4 GHz up to more than 10 GHz. The maximum achieved gain and efficiency are found about 3.456 dBi and 78% at 9 GHz. For this, the proposed antenna provides novel performance with ultimate antenna size reduction due to the introduction of the MTM based the proposed INP substrate. Finally, the harvested RF energy by the fabricated antenna is measured and found about 15 mV with a conversation efficiency of 85% at 2.45 GHz and 17.5 mV with a conversion efficiency of 91% at 5.8 GHz.

A Polarization-Reconfigurable High-Gain Microstrip Antenna

Abstract: A novel polarization-reconfigurable cut ring microstrip antenna with high gain is proposed. This simple structure microstrip antenna consists of a ring radiation patch, two switches (p-i-n diodes), and six nonmetallic columns. By controlling the switches, the antenna can be operated on three polarized states: one state for linear polarization (LP), one state for left-hand circular polarization (LHCP), and one state for right-hand circular polarization (RHCP). In addition, the antenna peak gain can reach 10.0 dB for LP, LHCP, and RHCP over the operating bandwidth and stable unidirectional radiation patterns. The proposed antenna is fabricated and verified. By analyzing simulated and measured results, the measured common operating bandwidth of the proposed antenna on three states is from 3.86 to 3.98 GHz with the relative bandwidth of 3.1%. The cross-polarization of the antenna on the whole states is very low. Good polarization-reconfigurable characteristics of the proposed antenna have been obtained from 3.86 to 3.98 GHz. The proposed antenna is also a good candidate for advanced wireless communication systems.

Novel approach for the design and analysis of a terahertz microstrip patch antenna based on photonic crystals

Abstract: In this study, we designed and analyzed five terahertz microstrip patch antennae based on a modified photonic band gap substrate in the frequency range from 0.5 to 0.8 THz. The objective was to achieve the best antenna characteristics around 0.65 THz, which has applications in sensing and communication technologies. Simulations were performed for rectangular patch antennae based on different substrates, including homogeneous, periodic photonic crystals and four new aperiodic photonic crystal substrates. Each of the modified photonic crystal substrates contained several sets of air holes perforated in the polyimide substrate, where each set had its own specific radius. The proposed antennae had high radiation characteristics around 0.65 THz compared with conventional antenna. The best characteristics were achieved with the second antenna structure, which obtained a minimal return loss of −83.73 dB and a wide bandwidth greater than 230 GHz. The gain achieved and radiation efficiency were 9.19 dB and 90.84%, respectively. The simulations were performed based on the finite integration technique with the commercially available CST Microwave Studio simulator.

A Dual-Band Dual-Polarized Stacked Microstrip Antenna With High-Isolation and Band-Notch Characteristics for 5G Microcell Communications

Abstract: A dual-band dual-polarized stacked microstrip antenna with high-isolation and band-notch characteristics is proposed. The proposed antenna is comprised of three layers of substrate. To obtain high isolation between two input ports, a pair of orthogonal differentially driven feeding lines are printed on the top side of the bottom layer. To yield the desired lower- and upper-frequency bandwidths for 5G microcell communications, two sets of $2\times 2$ radiating patch arrays are printed on the second and top layer substrates, respectively. Compared with the conventional microstrip antenna, besides demonstrating a smaller size of $0.48\times 0.48\times 0.085\,\,\lambda _{0}^{3}$ , the proposed antenna has also exhibited higher isolation of better than 40 dB and higher gain of >8 dBi. Finally, a novel technique of arranging four meander lines that connects the four array elements printed on the second layer substrate is proposed to achieve an adjustable band-notch characteristic.

A Low-Profile Circularly Polarized Metasurface Antenna With Wide Axial-Ratio Beamwidth

Abstract: This letter proposes a low-profile circularly polarized metasurface antenna with a wide axial-ratio beamwidth (ARBW). The proposed antenna consists of an array of square metallic metasurface cells that are excited by a microstrip line through four cross slots. The feeding structure can be seen as a symmetrical multiple-feed structure. Thus, ${E_\varphi }$ and ${E_\theta }$ can be nearly equal in amplitude with a phase difference of 90° over a wide angle range. A wide ARBW is obtained. With a size of 0.93 λL × 0.93 λL × 0.024 λL ( λL is the wavelength in free space at the lowest operating frequency), the proposed antenna achieves an impedance bandwidth of 17% and an AR bandwidth of 14.5%. Moreover, the ARBW is more than 205°.

Size reduction of MIM surface plasmon based optical bandpass filters by the introduction of arrays of silver nano-rods

Abstract: In this paper, first a square-shaped plasmonic cavity (SSPC), which is laterally coupled to two metal-insulator-metal (MIM) waveguides , is used to create a single-mode plasmonic bandpass filter . Thereafter, we try to modify the SSPC topology so that the resonance wavelength (λ r ) of the filter be transferred to higher wavelengths (without increasing the SSPC size). Such a technique is equivalent to less footprint for a fixed operational wavelength. Similar ideas are already being used to decrease the size of microstrip antennas, where defects and slots are introduced to the ground plate and the radiating microstrip patch to make the antenna wideband and compact. For this purpose, we discuss the effect of different possible types of defects on the filter's performance. It is shown that among the studied topologies, the best results are obtained for circular defects with square and triangular patterns in the original SSPC. The proposed topologies can provide an approximately 50% increase in the resonance wavelength. All results are obtained using finite difference time domain method . It is worth mentioning that the metals and insulators used in this paper are silver and air and the Drude model has been used for characterization of the silver.

Analysis and design of a terahertz microstrip antenna based on a synthesized photonic bandgap substrate using BPSO

Abstract: A microstrip patch antenna based on a synthesized photonic bandgap (PBG) substrate is designed and analyzed by using a technique based on the combination of an evolutionary heuristic optimization algorithm with the CST Microwave Studio simulator, which is based on the finite integral technique. The initial antenna is designed by analyzing air cylinders embedded in a thick silicon substrate, which has high relative permittivity. Then, to synthesize the PBG substrate, a binary particle swarm optimization (BPSO) algorithm is implemented in MATLAB to design a two-dimensional (2D) photonic crystal on a square lattice that improves the initially designed microstrip antenna. The unit cell is divided equally into many square pixels, each of which is filled with one of two dielectric materials, silicon or air, corresponding to a binary word consisting of the binary digits 0 and 1. Finally, the performance of the initial antenna is compared with the BPSO-optimized antenna using different merit functions. The results show remarkable improvements in terms of the return loss and fractional bandwidth. Both microstrip patch antennas based on the synthesized photonic crystal substrate achieve noticeable sidelobe suppression. Furthermore, the first design, which is a dual-band antenna, shows a return loss improvement of 5.39 %, while the fractional bandwidth of the second design is increased by 128 % (bandwidth of 128 GHz), compared with the initial antenna based on the air-hole PBG substrate. Both antennas maintain a gain close to 9.17 dB. Also, the results show that the obtained antennas have resonant frequencies around 0.65 THz, as required for next-generation wireless communication technology and other interesting applications.

3-D-Printed Tunable Circularly Polarized Microstrip Patch Antenna

Abstract: We present a tunable circularly polarized (CP) microstrip patch antenna developed using three-dimensional (3-D) printing. Circular polarization is achieved by a novel method of introducing an L-shaped slot in a square patch antenna. Moreover, by loading the four edges of the patch with shunt varactors, the frequency of the antenna can be tuned while maintaining CP radiation. The use of 3-D printing for manufacturing enables the vertical integration of varactors between the patch and the ground, which has not been shown before. Such integration minimizes the interaction of varactors with the radiating properties of the antenna and results in reduced parasitics. Measured results show that the antenna has a frequency tuning range of 27.2% for CP operation with the center of tuning range around 1.9 GHz. The 3 dB axial-ratio bandwidth remains above 3% for each fixed frequency band of operation.

Single-fed 4G/5G multiband 2.4/5.5/28 GHz antenna

Abstract: In this study, a single-fed printed multiband antenna for 4G/5G wireless communication systems is presented. The proposed multiband antenna consists of Franklin strip monopole antenna to cover 4G, and wireless applications (WLAN and WiMAX), and a rectangular patch antenna that is designed to cover 5G band. Furthermore, a modified compact microstrip resonant cell low-pass filter is printed between the antenna parts to allow feeding the Franklin antenna at low-frequency bands while isolating the Franklin antenna from the rectangular patch at the 5G band. The proposed antenna is designed on Rogers 5880 with compact size 45 × 40 × 0.508 mm 3 . The proposed antenna is utilised to operate at triple band: 2.4, 5.5 and 28 GHz with wide impedance bandwidth (15.8, 23.5 and 11.3%) and the gain reaches (1.95, 3.76 and 7.35 dBi).

Generating Circularly Polarized Vortex Electromagnetic Waves by the Conical Conformal Patch Antenna

Abstract: The generation of vortex electromagnetic (EM) waves carrying orbital angular momentum (OAM) has attracted more and more attention due to its special characteristics and potential applications. In this paper, the circularly polarized vortex EM waves with different OAMs have been generated at 2.4 GHz by a novel conical conformal patch antenna (CCPA) consisting of a conical substrate, a correspondingly conformed circular-ring metallic patch, and a single-feed point. First, we analyze the radiated field of a standard circular-ring patch, in which a circularly polarized TM $_{nm}$ mode excited by two coaxial feeds can generate the circularly polarized OAM wave with the topological charge of $l = (n - 1$ ). Then, a pair of the slot is added to the CCPA for obtaining a simpler structure with a single feed point. By adjusting the size of the slot and the angle between the slot and the single-feed point, two orthogonal modes with the same amplitude and a relative 90° phase shift can be obtained for generating the circularly polarized vortex wave. In addition, we have also tried to use an additional conical horn outside of the CCPA for enhancing the performance of the antenna. Finally, in order to validate the theoretical results, we have also fabricated and measured the CCPA, from which we can confirm that our design is efficient for generating the vortex waves.

Metasurface Loaded High Gain Antenna based Microwave Imaging using Iteratively Corrected Delay Multiply and Sum Algorithm

Abstract: In this paper, the design consideration is investigated for a cylindrical system with low-cost and low-loss dielectric materials for the detection of breast tumor using iteratively corrected delay multiply and sum (IC- DMAS) algorithm. Anomaly in breast tissue is one of the most crucial health issues for women all over the world today. Emergency medical imaging diagnosis can be harmlessly managed by microwave-based analysis technology. Microwave Imaging (MI) has been proved to be a reliable health monitoring approach that can play a fundamental role in diagnosing anomaly in breast tissue. An array of 16 high gain microstrip antennas loaded by Index Near-Zero (INZ) metasurfaces (MS), having the impedance bandwidth of 8.5 GHz (2.70–11.20 GHz) are used as transceivers for the system. The MS is used to increase the electrical length of the signal that results in the gain enhancements. The antennas are mounted in a cylindrical arrangement on a mechanical rotating table along with a phantom mounting podium. A non-reflective positive control switching matrix is used for transmitting and receiving microwave signals. A set of lab-made realistic heterogeneous breast phantoms containing skin, fat, glandular, and tumor tissue dielectric properties in individual layers are used to verify the performance of the proposed technique. The control of the mechanical unit, data collection, and post-processing is conducted via MATLAB. The system can detect multiple tumor objects. The imaging results and numerical Signal to Mean Ratio (SMR) values of the experiment validate the system efficiency and performance that can be a viable solution for tumor detections.

A Low-Profile Filtering Antenna Using Slotted Dense Dielectric Patch

Abstract: A low-profile filtering antenna using a thin dense dielectric patch (DDP) with a pair of silver-coated slots is investigated in this letter. The dominate TM101 mode of the DDP owning the similar characteristics of the traditional microstrip patch is directly excited by the microstrip line for antenna design. The silver-coated slots etched along the polarization direction, as a key technique in the proposed design, can not only generate a lower band radiation null directly, but also shift high-order TM111 mode down (close to the TM101 mode) to build an upper band null since the TM111 mode is nonexcitation and nonradiation. Accordingly, a good filtering performance of the proposed antenna without any additional circuits is obtained due to the two radiation nulls located on both sides of the antenna's operation band. For demonstration, a prototype is implemented and tested. The simulated and measured results are given, showing good agreement.