Search

A new set of measurement system on the Experimental Advanced Superconducting Tokamak (EAST), based on voltage and current probes, is installed on transmission line between matching system and ion cyclotron range of frequencies antenna to measure the antenna input impedance. The data can be used for impedance-matching points optimizing, as well as coupling coefficient assessment by deducing the antenna coupling resistance from antenna input impedance. The measurement error of amplitude and phase difference show distinct impact on the coupling resistance. Generally, the amplitude measurement error has a small impact on coupling resistance, while the phase measurement error significantly affects the coupling resistance. Instead of using phase detectors, phases can be extract from the power measurements. Thus, the antenna input impedance and coupling resistance can be deduced from the amplitude of voltage probe, amplitude of current probe, as well as the antenna feeding power. on previous experiments, the impedance measurement technique based on voltage probes array is utilized to evaluate coupling resistances. In EAST 2016 campaign, the load coupling resistance calculated by using such two techniques were detected and the results showed agreement.

In this paper, a 94 GHz substrate integrated waveguide (SIW) parallel-plate long-slot array antenna is presented, which is able to generate dual-circular-polarization (CP) low sidelobe level (SLL) beams from a single radiating aperture. This antenna consists of two layers of substrates. One is used to construct the unequal feeding network and the other is used to construct a $15 \times 15$ shared-aperture parallel-plate long-slot array antenna. This multilayer topology has a smaller size compared with the single-layer design. A simple and feasible method is applied to control the radiation pattern, which is able to realize dual-CP low SLL beams without a complicated feeding network. Two 1-D sixteen-way unequal dividers are employed to suppress the SLL in two planes of a CP array. Then, a 90° coupler is employed in the feeding network to switch the polarization modes between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). Finally, a prototype of SIW parallel-plate long-slot array antenna is fabricated. Simulation and measured results show that SLLs of the fabricated antenna are under −18.5 dB in two planes.

A mechanism for driving current off-axis in high beta tokamaks using fast electromagnetic waves, called Helicons, will be experimentally tested in the DIII-D tokamak. This method is calculated to be more efficient than current drive using electron cyclotron waves or neutral beam injection, and it may be well suited to reactor-like configurations [1] , [2] . A low power (100 W) 476 MHz “combline” antenna, consisting of 12 inductively coupled, electrostatically shielded, modular resonators [3] , was recently installed in DIII-D. Initial operation showed that the plasma operating conditions were achieved under which helicon waves can be launched. Plasma operations also showed that the location of the antenna has not reduced the performance of, or introduced excessive impurities into, the discharges produced in DIII-D. The development of a high power (1 MW) Helicon system is underway. This antenna consists of 30 modules mounted on the inside of the outer wall of the vacuum vessel slightly above the midplane. Carbon tiles around the antenna protect the antenna from thermal plasma streaming along field lines. A 1.2 MW, 476 MHz klystron system will be transferred from the Stanford Linear Accelerator to DIII-D to provide the RF input power to the antenna. A description of the design and fabrication of high power antenna and the RF feeds, the klystron and RF distribution systems, and their installation will be presented.

In this communication, a circularly polarized (CP) substrate-integrated waveguide horn antenna is proposed and studied. The CP horn antenna is implemented on a single-layer substrate with a thickness of $0.12\lambda _{\mathrm {\mathbf {0}}}$ at the center frequency (1.524 mm) for 24 GHz system applications. It comprises of an integrated phase controlling and power dividing structure, two waveguide antennas, and an antipodal linearly tapered slot antenna. With such a phase controlling and power dividing structure fully integrated inside the horn antenna, two orthogonal electric fields of the equal amplitude with 90° phase difference are achieved at the aperture plane of the horn antenna, thus, yielding an even effective circular polarization in a compact single-layered geometry. The measured results of the prototyped horn antenna exhibit a 5% bandwidth (23.7–24.9 GHz) with an axial ratio below 3 dB and a VSWR below 2. The gain of the antenna is around 8.5 dBi.

In this article, an Ultra Wide Band (UWB) monopole antenna based on Metamaterial (MTM) unit cell with reconfigurable feature has been developed. The proposed antenna covers 3.1–10.6 GHz for UWB applications and it has a reconfigurable narrow-band for L-band (1.27 GHz) and wireless applications. The gaps in Split Rings Resonator (SRR) element are made for the Left-hand capacitance and Ω-shape strip layer by four via junctions are used for Left-hand inductance. The antenna is printed on FR-4 low cost substrate with relative permittivity of 4.4 and thickness of 1.6 mm. The total size of the antenna is 40 mm × 40 mm. The simulation is carried out using HFSS commercial full-wave software. In addition, the experimental results are presented and compared with simulated results. The antenna gives a maximum peak gain of 6 dBi with Omni-Directional radiation pattern and high efficiency of more than 70%. By embedding four switches in Ω-shape strip layer, a reconfigurable antenna has been successfully designed for wireless applications with sufficient qualification. The monopole part covers the UWB spectrum and the CRLH is responsible for the controllable narrowband resonance. The simulation and experimental results are confirmed by the numerical results.

Two element UWB diversity antenna with defected ground structure and parasitic elements with high gain is proposed. Total antenna size of designed two elements multiple input multiple output system is reduced by sharing radiator between two circular antenna elements. The shape of ground plane is optimised to achieve ultra wide band characteristics (2.43---12 GHz). With the utility of defected ground structure effective area of antenna is reduced as well as there is suppression of cross polar fields. Reduction in mutual coupling is studied by using parasitic element. Simulated and measured results shows that, ultra wide bandwidth can be achieved with good isolation (S12 < ź 15 dB), maximum simulated gain of 6 dBi and maximum efficiency 83%. Correlation coefficient between two antennas elements is near to zero proves antenna is suitable for diversity performance. The compact size of antenna with dimensions 50 mm × 40 mm exhibit nearly omnidirectional pattern in H plane.

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 new design of circularly polarized (CP) integrated filtering antennas with reconfigurable polarization is proposed in this paper. Two phase-reconfigurable coupled λ/2-resonator pairs have been used to feed the antenna and generate the 2nd-order filtering response and the circular polarization simultaneously. By switching the PIN diodes inserted in the feeding network, a phase difference of +90° or - 90° can be realized at the outputs of the feeding network. This renders the antenna’s capability of switching its polarization from right hand circular polarization (RHCP) to left hand circular polarization (LHCP) or vice versa. The use of the coupled-resonator pairs significantly improves the frequency selectivity and out-of-band rejection of the CP antenna. To the best of the authors’ knowledge, this is the first report of a multifunctional antenna which has integrated filtering performance, circular polarization and polarization reconfigurability. To verify the design concept, a reconfigurable CP antenna operating at 2.45 GHz is implemented. The simulated and measured results agree well with each other and show that the antenna has an impedance bandwidth of 4.5 %, an average in-band gain of 6.0 dBic (LHCP)/6.1 dBic (RHCP), out-of-band rejections of greater than 10.8 dB, and 3-dB AR bandwidth of 9.4 %/10.5 %.

In order to achieve higher gains and lower side lobe in antenna design, array antenna is conventionally adopted. Besides, Chebyshev polynomial amplitude ratio is widely employed in the design, and it optimizes the main and side lobes under specific main lobe width and side lobe level. However, the actual product can be easily affected by machining error and the antenna material property, which change along with the frequency. The influence is evident at millimeter waves level owing to the short wave length. In micro-strip antenna applications, the test frequency for key parameters of high-frequency base material is limited by 10 GHz, while the parameters have no explicit definition at higher frequency. Therefore, a large mismatch between the design and actual product may exist when the frequency reaches 77 GHz or higher. In this paper, a weighting method is proposed to compensate parameters of the base material and machining error. Based on this method, simulation result of the design is revised to match tested result of actual product.

This study presents an antenna with dual-band and high-gain for a wireless local area network and Worldwide Interoperability for Microwave Access applications operating over 3.4-3.6 and 5-6 GHz bands. The proposed antenna is composed of three double-sided bowtie radiators loaded by a 2 × 6 array of double split rectangular (DSR) unit cells, which leads to a considerable gain enhancement. The DSR unit cell acts as an equivalent medium with a high refractive index operating at 3.5 and 5.5 GHz. By loading 2 × 6 arrays of proposed unit cells in the off-axis of the bowtie antenna in the H-plane, the main beam direction is tilted by 17° and 20° at the 3.5 and 5.5 GHz bands, respectively. A prototype of the bowtie antenna loaded with asymmetric unit cells in the H-plane is fabricated and measured. The measured results confirm the deflection of the main beam direction by 17° at 3.5 and 20° at 5.5 GHz with a peak gain of 10 and 10.5 dBi, respectively.

In this paper, a novel bandwidth-enhanced ultra-wideband (UWB) tapered slot antenna with Y-shaped corrugated edges, is proposed. In the double-slot structure, the two slots are separated by a V-shaped metal surface with straight edges, which is beneficial to improve the directivity of the antenna. Meanwhile, an exponential Y-shaped corrugated edge is designed. This novel corrugated edge can not only improve the impedance bandwidth, but also enhance the gain of the antenna. Additionally, according to the theory of microwave network, this paper analyzes the reason of bandwidth enhancement realized by double-slot structure. The proposed antenna provides 167% fractional bandwidth from 2.5 GHz to 28 GHz. The gain of the proposed antenna is more than 10 dB from 3.5 GHz to 25 GHz, and more than 8 dB at the whole operating band.

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 shows the terahertz planar antenna integration module structure using a fan out wafer level package (FOWLP), and the important parameters when that structure is designed. A FOWLP enabled a low-loss connection. Embedding an insulator and reflector into the mold resin improved flexibility of the module design. In this paper, the patch antenna was employed as a planar antenna in a proposed structure, and that antenna was operated at 300 GHz. For the design of this structure, two parameters were noted as the most important factors. One was the thickness of the insulator of the patch antenna. The optimal thickness of between 40 μm and 80 μm allowed the radiation efficiency to remain high. The other factor was the gaps of the vias between the ground of the microstrip line and the reflector. The gaps of a quarter-wavelength or less made the antenna characteristics excellent.

A broadbeam cross-dipole antenna with improved low-elevation gain for global positioning system (GPS) applications is reported. The cross-dipole consists of two perpendicular dipoles, which are printed on two separate substrates that are vertically placed inside a cylindrical back cavity. Circularly polarized fields are generated by applying two quadrature signals with equal amplitude to the dipoles. To enhance the low-elevation gain, circular dipoles, curved ground planes, and corrugated back cavity are deployed in our design. A prototype operating in GPS L1 band (1.575 GHz) was designed with ANSYS HFSS, and measurement was done to verify the simulations. The reflection coefficient, axial ratio (AR), radiation pattern, antenna gain, and antenna efficiency are studied. It is found that the antenna has a wide 3 dB AR beamwidth of over 230° and a 3 dB gain beamwidth of 150°. The measured and simulated antenna gains at $\theta = 85^{\circ }$ are 0.11 and 0.68 dBic, respectively, which are higher than those of existing designs.

This communication reports a novel planar array antenna having a cosecant squared pattern for millimeter-wave communication systems. The substrate integrated waveguide, which has high quality factor, low transmission loss, and no parasitic radiation, has been adopted to develop the proposed antenna. To improve the design efficiency, the aggressive space mapping (ASM) algorithm is used for synthesizing the desired excitations with low computation cost and high accuracy. A radiation model that considers mutual couplings among element antennas is developed based on the active element pattern for the coarse model of the ASM. And the genetic algorithm is adopted for the parameter mapping and extraction of the ASM process. As a demonstration, a prototype has been designed with a center frequency of 42.6 GHz, and experiments are carried out to verify the design. The measured results show that the measured antenna has a cosecant squared region up to 40°, a gain of 17.7 dBi at 42.6 GHz, and the maximum sidelobe is lower than −16.5 dB. The proposed antenna can be used for the base station of the long-range Qlink-Pan communication system.

A compact dielectric resonator antenna for ultrawideband vehicular communication applications is proposed. Two cylindrical dielectric resonators are asymmetrically located with respect to the center of an offset rectangular coupling aperture, through which they are fed. Optimizing the design parameters results in an impedance bandwidth of 21%, covering the range from 5.9 to 7.32 GHz in the lower-band and a 53% relative bandwidth from 8.72 to 15 GHz in the upper-band. The maximum achieved gain is 12 dBi. Design details of the proposed antenna and the results of both simulations and experiment are presented and discussed. &nbsp

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 monostatic dual-polarized simultaneous transmit and receive (STAR) antenna system with high isolation is introduced. A beamforming network (BFN) producing 0°, ±90°, ±180°, and ±270° phase progression is used to feed TX and RX ports of four dual-polarized antenna elements arranged in a sequential rotation array (SRA). Due to the phase progression and geometrical symmetry of SRA, the coupling from TX to RX ports is canceled at the RX port of the BFN; therefore, infinite system isolation is theoretically obtained. Full-wave simulations are used to verify the theory and study effects of element spacing and BFN imbalances. An additional cancelation layer is designed and used to compensate for the imbalances by the BFN and nearby scatterers. The proposed STAR antenna system is prototyped and tested in the 2.4–2.5 GHz industrial, scientific, and medical band where the measured isolation and return loss are above 47 and 22 dB, respectively. A dual circularly polarized antenna performance with realized gains above 7 dBic, broadside axial ratio

The paper presents a low profile dual polarized dipole antenna topology backed by a novel broadband multilayer Artificial Magnetic Conductor (AMC) based reflecting surface. The antenna consists of a pair of square loop shaped dipoles with T-shaped feed structures arranged orthogonally to provide dual slant polarizations at ±45°. The antenna structure is backed by a novel multilayered AMC structure consisting of stacked square patches with via connected at middle and an air filled ground plane at the bottom. Experimental results show that the proposed antenna operates from 700 to 1000 MHz with bandwidth of 35% and an average gain of 8.5 dBi over the bandwidth. The Simulated and measured results of the antenna structure indicate the antenna to be suitable for interoperable Long Term Evolution (LTE), Code Division Multiple Access (CDMA) and Global System for mobile communications (GSM) applications.

In this paper, the design and implementation of a quadrifilar helix antenna are presented where the four arms are 3-D printed. The antenna structure is miniaturized by resorting to a combination of two approaches. The first approach is based on loading the tips of the four helical arms with circular conductive disks. The size and location of these elements directly affect the antenna’s operating frequency. The second miniaturization approach is based on incorporating an FR-4 dielectric material into the vacant space between the four arms of the quadrifilar helix. As a result, the length of the antenna is reduced by a ratio of 43%. The quadrifilar helix antenna is also designed on top of a ground plane with an optimized conical shape and topology. The antenna is partially fabricated using 3-D printing additive technology, where measurements show great agreement with simulated results.

An antipodal Vivaldi antenna (AVA) with novel symmetric two-layer double-slot structure is proposed. When excited with equiamplitude and opposite phase, the two slots will have the sum vector of their E-field vectors parallel to the antenna’s plane, which is uniform to the E-field vector in the slot of a balanced AVA with three-layer structure. Compared with a typical AVA with the same size, the proposed antenna has better impedance characteristics because of the amelioration introduced by the coupling between the two slots, as well as the more symmetric radiation patterns and the remarkably lowered cross-polarization level at the endfire direction. For validating the analysis, an UWB balun based on the double-sided parallel stripline is designed for realizing the excitation, and a sample of the proposed antenna is fabricated. The measured results reveal that the proposed has an operating frequency range from 2.8 to 15 GHz, in which the cross-polarization level is less than −24.8 dB. Besides, the group delay of two face-to-face samples has a variation less than 0.62 ns, which exhibits the ability of the novel structure for transferring pulse signal with high fidelity. The simple two-layer structure, together with the improvement both in impedance and radiation characteristics, makes the proposed antenna much desirable for the UWB applications.

A wideband phase shift surface (PSS) antenna is proposed in this paper, which launches quasi-nondiffraction beam with accurately controllable inclination angle and depth-of-field. First, a novel method to generate the off-axis quasi-nondiffraction beam in an arbitrary direction is proposed. It modifies and further combines the design methods of the off-axis focusing antenna and the zero-order Bessel beam antenna. This method is helpful to improve the design precision of the depth-of-field of the beam. Then, one kind of hexagonal patch is employed as the element of the PSS. Its phase shift compensation capability can increase the bandwidth and improve the stability of the performance of the antenna over a wideband from 27 to 31 GHz. The results of numerical simulation, full-wave simulation, and experiment show that the proposed antenna can effectively generate the expected beam.

A linearly polarized, dual-port, and dual-band radio frequency identification reader antenna is designed to simultaneously operate at ultrahigh frequency (UHF) and ultra-wideband bands for positioning systems. A hybrid design using patch and slot structures within a shared radiating aperture is proposed and demonstrated to achieve a high gain and wideband operation with a limited profile. The size of the total antenna is 200 mm $\times200$ mm $\times10$ mm. The measured impedance bandwidth of the UHF antenna ranges from 0.890 to 0.907 GHz with a minimum antenna gain of 9 dBi. The measured impedance bandwidth of the ultra-wideband antenna can cover the frequency band from 3 to 4.99 GHz with a minimum antenna gain of 9 dBi. The antenna gains near two WLAN bands are less than −15 dBi at 2.45 GHz and −5 dBi at 5.8 GHz, respectively. The mutual coupling between the two ports is less than −30 dB over the two bands.

A novel wideband and high-gain millimeter-wave antenna is presented. The wide 3 dB gain bandwidth is achieved by using Fabry–Perot cavity (FPC) and printed ridge-gap waveguide technologies. The FPC is formed by placing a dual-layer partially reflective surface (PRS) above a slot antenna operating at 60 GHz and fed by a printed ridge-gap waveguide for surface-wave suppression. The PRS is based on a 2-D printed unit cell, the unit cell composed of two different frequency-selective surfaces (FSS) provides a positive phase gradient over the desired frequency range. The impedance bandwidth of the proposed antenna is 18.4%, from 55.4 to 66.6 GHz. Moreover, the 3 dB gain bandwidth is 12.5%, from 58.6 to 66.4 GHz. A maximum gain of 16.8 dB is achieved; this is about 12.2 dB over the gain of the slot antenna only. Consistent radiation patterns are achieved over the operating bandwidth. Experimental and numerical results are presented to justify the improved antenna performance. This communication, to the best of our knowledge, is the first one to utilize a dual-layer printed FSS-based superstrate at 60 GHz to enhance the radiation characteristics of a printed ridge-gap waveguide-fed slot antenna.

In this contribution, an algorithm based on the space-alternating generalized expectation–maximization principle is proposed for estimating the locations of scatterers involved in the last-hops of propagation paths when a large-scale antenna array is used in a receiver for channel measurement. The underlying generic parametric model is constructed under the spherical wave-front assumption, which allows characterizing a path with a new parameter, i.e., the distance between the scatterer at the last-hop of the path and a specific receiving antenna, additional to the conventional parameters characterizing a specular path under the plane wave-front assumption. Cramer–Rao lower bounds of mean squared errors are derived for the parameter estimators in a single-path scenario, and their accuracy is evaluated through Monte Carlo simulations. The performance of the algorithm when being applied in reality is also evaluated through experiments conducted in an office with a carrier frequency of 9.5 GHz, a bandwidth of 500 MHz, and the receiver equipped with a 121-element virtual array. The proposed signal model and algorithm can be extended to the case of localizing the scatterers in the first- and last-hops of paths when large-scale antenna arrays are used in both the transmitter and the receiver.

In this paper, a millimeter-wave air-filled slot antenna is presented based on bulk silicon microelectromechanical systems micromachining technology. The antenna is suitable for system-in-package application by utilizing this silicon micromachining technique. To achieve high radiation efficiency in millimeter-wave band, three gold-plated silicon layers are bonded together to realize an air-filled slot antenna. The air-filled structure has the advantages of reducing transmission loss and enhancing the radiation gain. To mitigate the discontinuity between silicon and air, the proposed antenna employs a patch to feed the air-filled structure that also broadens the impedance bandwidth. Owing to the micromachining technique and the air-filled structure, the antenna can be easily integrated with integrated circuit without suffering from dielectric loss. The measured impedance bandwidth of the proposed antenna is 56.3–63.4 GHz, and the measured peak gain is 7.8 dBi at 60 GHz.

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.

A broadband dipole antenna with a very simple low-cost mechanical structure is proposed. This dipole of the height of 173 cm with inductor/resistor ( LR ) loading circuits is designed to operate in the frequency range of 30–512 MHz—hence a 17:1 bandwidth (178%). By choosing the optimized location of LR loads, the radiation pattern is controlled. Meanwhile, the VSWR 1:3.5 is adjusted by an input matching circuit, tuning a number of LR loads, and using a transmission line transformer. The impedance matching is better than −6.5 dB in whole frequency bandwidth. The antenna gain is gradually increased from −20 dBi at 30 MHz to −2 dBi at 512 MHz. The manufactured prototype is presented along with its measured characteristics which map well onto software simulated counterparts. The antenna is considered to be used in portable applications. Therefore, the simulations and the measurements are conducted near the human body. A simple model of the adult human body at the frequency band of the proposed antenna is used, which helps to study the effects of the human on the antenna performance. Moreover, the electromagnetic exposure on the human body is investigated. Experimental evidence is presented to verify the conclusion.

Mode-transducing antenna transforms TEM mode into circular TE11 mode and then radiates it from an open-ended waveguide. Mode conversion is carried out by changing the phase velocity of each mode-transducing section. The maximum achieved gain of this antenna is 8.8 dB in 1.48 GHz frequency. An optimized dual dielectric window at the end of the waveguide improves the antenna matching. The measured results are in good agreement with simulation results.

A broadband helical liquid antenna made of saline water is proposed. A transparent hollow support is employed to fabricate the antenna. The rotation structure is fabricated with a thin flexible tub...

In this paper single band antenna is converted to dual band reconfigurable antenna. The converted antenna is reconfigurable in both dual band frequency agility (with central frequencies 912 MHz and 1102 MHz) and radiation pattern. The direction of the main lobe is being varied in both E and H planes with the change in the switches’ states. The Antenna’s re-configurability in frequency is obtained with the use of two copper tapes acting as switches between the four copper annealed patches which are embedded on FR4 substrate. There is no need to change the material or dimension of the antenna to turn it into reconfigurable but the antenna is showing the reconfigurable properties only by changing the internal structure of the antenna using the switches. The antenna is fed by coaxial cable which is connected with SMA connector. The dimension of the designed antenna is 100 mm × 100 mm × 33.4 mm. The reconfigured antenna is optimized to get maximum directivity 1.687 dBi in H Plane at angel 0owhen the area of substrate is 90 mm ×90mm and the area of patch is 43.2 mm × 43.2 mm. The CST MW studio is used for design of antenna and simulating the results. The structure and dimensions of the antenna’s components paly important role in antenna design and improving the antennas’ parameters the future work is recommended to use diode switches in place of copper tapes to make an antenna reconfigurable.

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.

In this paper, we propose an ultrawide band design for the double ridged horn (DRH) antenna to be used behind the obstacle radar (BOR) applications such as ground penetrating radar (GPR) and through the wall radar (TWR) imaging. The design is developed and optimized by the help of full electromagnetic simulator code; CST. The design parameters such as frequencies of operation and the half power beam width (HPBW) are taken into account by considering the BOR application requirements. The design double ridged horn antenna provides a frequency bandwidth between 1.5 GHz and 7 GHz and HPBW around 30° around the center frequency that are very suitable for GPR and TWR applications. The final optimized design that is formed by CST is physically manufactured and measured. The prototyped DRH antenna’s measurement antenna parameter results are in good agreement with the simulated ones.

This article presents the design and performance analysis of a high gain dual-polarized two-element cylindrical dielectric resonator antenna (DRA) array excited by two orthogonally placed H-shaped apertures. The antenna is operated in dual linear polarized mode by exciting TM110 (HEM11) mode in two DRAs using aperture coupling. The proposed antenna has a −10 dB impedance bandwidth of 9.52% (6.0–6.6 GHz) with isolation more than 40 dB among the two ports. Realization of gain enhancement and high isolation are accomplished by simultaneously exciting two DR elements using a pair of wideband Wilkinson's power divider placed on the bottom side of the substrate. The measured gain of the proposed antenna for both the ports is found to be 12.5 dB with a front to back ratio of 16 dB. The antenna has an overall radiation efficiency of 94% and symmetrical radiation patterns with co-polarization levels 40 dB higher than the cross-polarization in both the principal planes (XY and XZ) of bore-sight direction.

A compact ultra-wideband (UWB) planar printed bow-tie quasi-Yagi antenna is proposed and experimentally studied in this paper. It is composed of three wideband configurations: micro-strip-line to slot-line transition structure with a shorting vias (balun), a pair of bow-tie driver, and rhombus director, which aims at breaking the bandwidth limitation of the conventional micro-strip (MS) quasi-Yagi antenna. To further improve the impedance matching, the tapered co-planar strip-line is adopted between the bow-tie driver and the balun as bridge. The overall size of the proposed antenna is only 30 mm × 27 mm. A prototype UWB quasi-Yagi antenna is fabricated and measured to verify the validity of this design. The measured impedance bandwidth, defined by −10 dB reflection coefficient, can reach an operating bandwidth of 101% from 3.62 to 11 GHz, over which the antenna exhibits excellent end-fire radiation with a front-to-back ratio of greater than 19 dB and a moderate gain of better than 3.81 dBi. In co...

In this paper, a modified L-strip fed patch antenna is theoretically analyzed for wideband applications. Dual U-shaped slots are incorporated in the radiating patch and a maximum bandwidth of 16.93% (2.65 GHz to 3.14 GHz) is achieved. Further, when two parasitic elements are used, antenna bandwidth improves up to 25.89% (2.90 GHz to 3.77 GHz). The maximum gain of dual U-slotted patch and with parasitic elements is 8.23 dBi and 8.46 dBi respectively. Antenna parameters are calculated by CST Microwave studio and equivalent circuit model theory is presented. The proposed antenna is fabricated and the measured results compare well with the theoretical as well as simulated results.

A novel polarization-reconfigurable planar antenna is presented. The antenna consists of an electronically reconfigurable polarizer integrated with a printed slot. By changing the states of the PIN diodes on the polarizer, the linearly polarized (LP) waves radiated by the slot can be converted to either right-hand circularly polarized (RHCP) or left-hand circularly polarized (LHCP) waves. The polarizer contains 16 unit cells arranged as a 4 × 4 array. The antenna radiates RHCP waves if the PIN diodes on the top side of the polarizer are switched ON, while LHCP waves are radiated if the PIN diodes of the bottom side of the polarizer are switched ON instead. The physical mechanisms of the antenna are discussed and the parametric study is carried out by full-wave simulations. To verify the concept, one prototype at 2.5 GHz is designed, fabricated and measured. Good agreement between the measured and simulated results is obtained. The antenna achieves a gain ? 8.5 dBic in both RHCP and LHCP with aperture efficiency of 70%. Advantages of the proposed design include electronicallyreconfigurable polarizations for RHCP or LHCP, low profile, low cost, high isolation between the DC bias circuit and RF signals, high power handling capability and easy extension to large-scale arrays without increasing the complexity of the DC bias circuit. To the best knowledge of the authors, this is the first report of an electronically polarization-reconfigurable circularly polarized antenna with a single-substrate polarizer.

We present a terahertz (THz) wave detector based on antenna-coupled single-metal nanoscale thermocouples. The dipole antenna is tuned to receive 600-GHz electromagnetic waves, and the nanoscale thermoelectric converter (NTEC) converts the heat, generated by the dissipated antenna currents to electrical signals. The measured polarization- and thermopile-length-dependent responses of these THz detectors, configured in thermopiles with various lengths, confirms that the measured signal is the result of the heating caused by the radiation-induced antenna currents and detected by the NTEC.

Detection of moving targets in cluttered environments is important in numerous applications, such as disaster search-and-rescue, law enforcement, urban warfare and so on. One of the popular techniques employed for this purpose is the use of stepped-frequency continuous-wave radar due to its low cost and reduced complexity. However, the stepped-frequency radar suffers from long data acquisition time. This study focuses on the detection of moving targets in cluttered medium; such as behind walls, using stepped-frequency radar enhanced by compressive sensing (CS). The application of CS enables the reconstruction of the target space using fewer frequencies, which decreases the acquisition time. This study presents simulation results that demonstrate the applicability of CS to stepped-frequency radar measurements in accurately locating and tracking targets behind walls. The plane-wave spectrum approach is employed in conjunction with through-wall transmission coefficients for calculating the scattered fields of targets behind the wall. The received voltage at the antenna terminals is then computed by adopting the concept of complex antenna factor frequently used in Electromagnetic Compatibility (EMC) community, which fully takes into account the antenna effects, enabling an accurate simulation.

This paper demonstrates the design of a triple band notched ultrawideband circular microstrip patch antenna loaded with Complementary Split RingResonator (CSRR) and S-shaped slot in microstrip feed line. Complementary Split Ring Resonator slot and S-shaped slot are used to produce band notched characteristics for WiMAX band (3.30–3.60 GHz) and WLAN band (5.10–5.80 GHz) respectively. The downlink frequency band (7.25–7.75 GHz) of X-band for satellite communication is notched using Symmetrical Split Ring Resonator Pair (SSRRP) as electromagnetic coupling element near microstrip feed line which produces band stop characteristics. Measured results of fabricated antenna prototype are compared with simulated results and found in correspondence. The VSWR and vector current plots show evidence of the significant suppression in the desired frequency bands.

A non-Foster matching network has been designed for a small cylindrical slot antenna, and its broadband matching capability has been examined at varying signal power levels. It has been observed that the non-Foster circuit (NFC) impedance changes considerably as the signal power increases, thus reducing its matching capability as well as introducing stability problems. To analyze its true advantage in transmit applications, the third-order intermodulation output intercept point (OIP3) and the gain-bandwidth product of the non-Foster matched antenna have been compared with the unmatched antenna, when both are attached to the same power amplifier. Simulations show that the unmatched antenna has a higher OIP3 and gain-bandwidth product, despite being more poorly matched. Although the OIP3 can be slightly improved by increasing the bias current of the NFC, improved linearization techniques should be studied to offset distortion effects in NFCs.

A $1 \times 4$ antenna array with wideband and high gain is proposed for 60-GHz applications. The operating bandwidth is from 57 to 66 GHz. A superstrate above and an electromagnetic bandgap reflector below the array structure increase peak gain and decrease backward radiation, respectively. This paper elaborates the design guidelines. The slot stubs are designed appropriately to increase the bandwidth of square-slot antenna and maintain the radiation pattern. The simulated and measured impedance bandwidth ( $\vert S_{11}\vert \le -10$ dB) are 28.8% (52.6–69.9 GHz) and 23.2% (52.6–66.5 GHz), respectively. The peak antenna gain ranging from 57 to 66 GHz is simulated to be 14.2–12.4 dBi, while the measured peak gain at 57, 60, 63, and 66 GHz are 13.6, 13.4, 12.6, and 11.3 dBi, respectively. The above results can satisfy requirement of many commercial applications.

A broadband magnetic coupling antenna with low far-field gain for ultrahigh frequency radio frequency identification near-field applications is presented in this communication. The proposed antenna is consisted of a number of loop units and each unit has in-phase current along the loop. It generates a strong uniformly distributed magnetic field over a large interrogation. To meet different scenarios, the interrogated area can be adjusted by changing the number of units. The proposed antenna has low far-field gain and broadband characteristics. Mechanism analysis is carried out to provide the guidelines for the antenna design. As an example, a 10-unit antenna has been fabricated and measured. The experimental results show that the antenna achieves the impedance matching over the frequency range from 740 to 4600 MHz. And the proposed antenna achieves 100% reading rate with 140 button tags in the region of 100 mm $\times750$ mm $\times12$ mm.

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.

Though a microstrip patch antenna has advantages of low profile and structural planarity, but a single microstrip patch antenna has limitation of low gain and narrow bandwidth. To overcome these problems, multi-layer structures are used. The antenna performance can further be enhanced, if multi-layer structures are designed for array of patch antennas. Moreover, the simultaneous improvement of gain and bandwidth, which are two conflicting parameters, is another challenge. To meet these challenges, this article proposes a microstrip patch antenna array, inspired with a superstrate – comprising of Split Ring Resonators (SRR) and wire strips. Gain and bandwidth of 4.3 dBi and 425 MHz, respectively, is achieved by an unloaded array at IEEE 802.16a 5.8 GHz Wi-MAX band. However, by covering this array with the proposed superstrate, gain and bandwidth of 12.1 dBi and 780 MHz, respectively, is obtained, thus providing the gain improvement of 7.8 dBi and bandwidth enhancement of 355 MHz. Fabrication and testing of the proposed antenna is done for comparing simulated and measured results. Equivalent circuit of this newly devised array has been designed and discussed.

This paper demonstrates a polyimide based optical rectangular patch antenna capable of operating at THz frequencies. The proposed antenna’s performance has been analysed in terms of various antenna characteristics such as impedance bandwidth (GHz), directivity (dBi), gain (dB), return loss (dB) and VSWR. The Polyimide substrate having thickness of 20 μm and lower dielectric constant, er of 3.5 has been employed in the antenna design. The feedline, radiating patch and ground deployed in the proposed THz antenna design are of copper (Cu) having conductivity and resistivity of 5.8 × 107 S/m and 1.68 × 10−8 Ω− m, respectively. The proposed antenna has been fed by means of microstrip feedline having impedance of 49.78 Ω. The proffered antenna has a gain of 5.22 dB and directivity of 5.08 dBi at corresponding resonant frequency of 0.67 THz. The propounded antenna has an impedance bandwidth of 40.16 GHz with operating frequency range of 0.65 THz to 0.69 THz with corresponding resonant frequency of 0.67 THz. The proposed antenna can be suitably employed for video rate imaging system (0.6 THz) and homeland defence applications (0.6–0.8 THz). The designing and simulation of the proposed antenna has been performed using CST Microwave Studio 2014 based on the method of FDTD technique.

In this paper, we discuss the design scheme of a waveguide feeder for a wideband rectangular parallel plate slot-array antenna for a high resolution synthetic aperture radar sensor on-board a 100kg micro-satellite, scheduled to be launched in 2020. We analyze the performance of the edge-feed system with two waveguide feeders for each antenna panel. HFSS simulation results show that the edge-feed system reduces the undesired Poynting vector tilt in the parallel plate and achieves good antenna gain and efficiency with larger bandwidth, thereby giving it an edge over the conventional end-feed system However, the two-feeder antenna system increases the weight and active reflection and due to asymmetric design, phase opposition is difficult to achieve, thereby leading to structural complexity.

This communication presents a wideband aperture-coupled patch antenna array based on ridge gap waveguide feed layer for 60-GHz applications. The novelty of this antenna lies in the combination of relatively new gap waveguide technology along with conventional patch antenna arrays allowing to achieve a wideband patch antenna array with high gain and high radiation efficiency. An $8 \times 8$ -element array antenna is designed, fabricated, and tested. Experimental results show that the bandwidth of VSWR < 2 is up to 15.5% (57.5–67.2 GHz). More than 75% efficiency and higher than 21.5-dBi gain are achieved over the operational bandwidth. The results are valuable for the design and evaluation of wideband planar antenna arrays at millimeter-wave frequencies.

In this paper, we present a new horn antenna that can mechanically reconfigure the beam direction and polarization by combining a traditional linearly polarized horn antenna with an anisotropic Huygens metasurface. Three layers of Jerusalem-cross structures are integrated in a dielectric substrate to form the anisotropic Huygens metasurface; the entire structure has a thickness of about one fifteenth the working wavelength. By placing the metasurface in front of a traditional linearly polarized horn antenna, the main beam of the horn antenna is steered to a predetermined direction. Furthermore, the direction and polarization of the main beam are reconfigurable by rotating the anisotropic Huygens metasurface. The measured results of the antenna confirm the simulated results. Possible applications of the presented antenna include radar detection, base-station communications, and satellite communications.