Bandwidth Radiation Research Articles

Bandwidth of a Compton radiation source with an electron beam of asymmetric emittance

Compton scattered radiation sources have been utilized in a broad range of experiments from fundamental science to industrial applications for their unique features, the generation of energy-tunable, nearly mono-energetic polarized photon beams. In the Compton radiation sources, the radiation bandwidth can be controlled by a collimator to restrict the scattering angle, but the bandwidth is also affected by the emittance and energy spread of the electron beam. In this study, we discuss collimator optimization to obtain narrow-band radiation from a Compton source with an electron beam having asymmetric emittance in the horizontal and vertical planes. A Monte Carlo simulation code based on Geant4 has been developed and used to compare circular and rectangular collimators for shaping the radiation spectrum of Compton sources.

An analytical approach of designing compact microstrip patch antenna using metal-ring superstrate for wideband and broadside radiations

A compact design of microstrip patch antenna is presented to realize wideband characteristics. An annular metal-ring has been used as a superstrate as well as an inductive load to the rectangular patch. Robust analytical technique is applied to choose the dimensions of the ring and the patch where they resonate very close to each other. This strategic approach ensures a wide matching bandwidth with a broadside radiation pattern. An additional enhancement of bandwidth has been achieved by employing a unique design strategy. A set of antenna prototype has been fabricated for experimental validation. As much as 34% matching bandwidth has been revealed experimentally using a compact antenna (~λ × λ). The boresight gain is maintained about 10 dBi over the operating frequency band. The cross-polarized isolation in E- and H-planes are maintained above 40 dB and 30 dB respectively over the operating bandwidth. The back-radiation of the antenna is also maintained below −20 dB over the wide matching bandwidth.

Design of a side-feed rectangular waveguide helical array antenna with fan-beam radiation characteristics

In the millimeter wave train-ground communication system of high-speed maglev train, train-mounted antennas are required to have the characteristics of miniaturization, wide band, circular polarization, and fan-beam radiation. A side-feed rectangular waveguide helical array antenna is designed to meet these requirements in this paper. Short axial-mode helical antenna which has compact structure and circularly polarized radiation characteristics is used as the unit antenna. To realize fan-beam radiation characteristics, this array is composed of 2×15 unit antennas. All elements are fed by a rectangular waveguide which is divided into two rectangular waveguides from the side direction of the antenna. By properly designing the length of the coupling probe in the feed system, an equal excitation amplitude distribution can be realized for all unit antennas. The radiation phase of the unit antenna can be adjusted by rotating the helix arounding its axis to realize in-phase radiation of all elements. An array antenna with a center frequency of 38.0 GHz was designed through simulation. Simulation results show that the antenna has a gain of 22.1dB, an axial ratio of 2.09dB, an elevation plane beam width of 4.4°, an azimuth plane beam width of 30.1° at 38.0GHz. In the band of 37.0-39.0GHz, the reflection coefficient of this antenna is less than -15dB, the antenna gain is greater than 21.5dB and the axial ratio is less than 2.0dB which meet the design requirements of train-mounted antenna in the millimeter wave train-ground communication system.

Enhanced bandwidth, low sidelobe resonant cavity antenna using tapered complementary FSS layers

A novel resonant cavity antenna (RCA) with low sidelobe levels over an enhanced bandwidth is presented. Radiation bandwidth of the antenna is increased by using a pair of complementary FSS layers, giving a positive reflection phase over a wide frequency range, as the proposed PRS. Low sidelobes are achieved by lowering the reflection amplitude of the PRS along its length while keeping reflection phase almost the same throughout the operating band. The performance of the proposed PRS is validated by creating a circular aperture RCA and measuring its radiation characteristics. The cavity is excited by an aperture coupled patch antenna having a broad impedance bandwidth. Prototype RCA gives a peak realized gain of 16.1 dBi and a 3-dB gain bandwidth of 8.6% ranging from 14.5 to 15.8 GHz. Measured sidelobe levels are reduced, respectively, to less than −17 dB and −23 dB in the E- and H-plane of the prototype antenna.

Design of a miniaturized dipole RFID tag antenna

Objectives: This study introduces a new design strategy for an RFID Tag.Methodology/Findings: A low-profile meander line dipole antenna has been fabricated as a proof of concept due to its electrically small size and simple structure. Good agreement is achieved between the results obtained by this method and those calculated by simulations using CST. The antenna is designed to operate at a frequency of 915 MHz, allocated for UHF RFID. In order to ensure that the design has good performance, all of the antenna parameters are optimized. The results of antenna parameters such as radiation pattern,bandwidth, gain and return loss are also considered. This made it possible to achieve a reduction in size of the order of 40%. Applications: Meander line dipole antennas are useful as radio frequency identification (RFID) tag antennas because of their relatively high radiation efficiency and small size. Keywords: UHF; RFID; tag; meander; dipole

60 GHz Compact Larger Beam Scanning Range PCB Leaky-Wave Antenna Using HMSIW for Millimeter-Wave Applications

A half-mode substrate integrated waveguide (HMSIW), based on printed circuit board (PCB) technology, is employed to construct a novel V-band leaky-wave antenna incorporating composite right-/left-handed (CRLH) media. Including modified half-sinusoidally varied interdigital capacitive slots on the radiating edge of the HMSIW enables the feature of effective CRLH media to produce adequate radiation coverage and bandwidth with improved sidelobe level (SLL) and higher gain. Unit cell characteristics and space harmonic analysis were thoroughly investigated through dispersion and Bloch impedance analysis. By appropriately tuning the physical parameters of the design, the balanced condition was obtained at a broadside frequency of 60 GHz. The highly directed radiated fan beam covered a scanning range of 120° with beam steering from -72° to 48° of the visible space. The proposed antenna operated over 55-65 GHz with a maximum realized gain of 14.5 dBi, maximum beamwidth of 9.15°, better than 15 dB SLL and 20 dB cross-polar radiation. All simulated responses showed reasonably good accordance with experimental data thereby validating the novel design of the proposed leaky-wave structure for millimeter-wave wireless applications.

Wideband Wide Beamwidth Full-Wavelength Sectorial Dipole Antenna Under Dual-Mode Resonance

In this article, a novel design approach to wide beamwidth dual-resonant, wideband sectorial dipole antennas is advanced. At first, a 1-D, full-wavelength dipole is evolved into a 2-D, sectorial dipole, so as to determine its two usable resonant modes. Then, both wideband and wide beamwidth characteristics are simultaneously attained under dual-mode resonance. Next, dual-resonant sectorial dipole antennas with flared angle of 270° and 240° are designed and studied. As experimentally validated, the proposed antenna exhibits an omnidirectional pattern with its impedance bandwidth over 70.4%. A few prototypes mounted above a ground plane are further investigated, so as to achieve a broad H-plane half-power beamwidth (HPBW) to over 120°. In addition, the antennas exhibit stable gain frequency response with fluctuation less than 2.2 dB within the entire impedance bandwidth. Thus, the advanced design approach based on 2-D dual-resonant, full- wavelength dipole leads to the formulation of novel wide beamwidth antennas with low frequency dispersion and simple configuration within a wide radiation bandwidth over 53.3%. Finally, a dual-polarized dipole antenna with port-to-port isolation higher than 34.5 dB and available radiation bandwidth of over 49% is implemented to further validate its potential for practical applications.

A Six-Port Dual-Function RF Device With Four-Element MIMO Antenna Array and Bandpass Filter Operations

This article presents a dual-function RF device, with four antenna ports and two filter ports, which behaves either as a multiple-input multiple-output (MIMO) antenna array or a bandpass filter. It consists of four parallel-coupled microstrip lines as the dual-function part and two feed parts for the two channels. The former part simultaneously performs wideband array radiator and fourth-order filter resonator characteristics. For MIMO antenna array operation, the parallel-coupled microstrip line structure is equivalent to a traditional patch, which is divided into four strips with three slots. Based on such a configuration, wide antenna impedance bandwidth is achieved. With regard to the filter operation, it features a conventional fourth-order microstrip parallel-coupled filter typology. As a result, high circuit integration is achieved, and although the two channels share the common part, the bandwidth improvement for both the channels is realized. For demonstration, the proposed dual-function device is implemented and fabricated. As an MIMO antenna array, the center frequency and the measured impedance bandwidth is 4.5 GHz and 27.3%, respectively. The isolation between the two channels in this band is more than 23.6 dB. In addition, it features ±45° continuous beam scanning capacity with less than 3 dB gain reduction. With respect to the bandpass filter operation, the center frequency and measured impedance bandwidth is 0.55 GHz and 15.6%, respectively. The measured in-band insertion loss is 2.12 dB and channel isolation is more than 58 dB.

Nongray models for radiative absorption and anisotropic scattering by water droplets in fire CFD simulations

An efficient wide band radiation model is developed for absorption and scattering by water droplets in fires. The model applies eight spectral bands that enable coupling with radiating gas and soot media. Optical properties from the Mie theory are averaged within each band and tabulated for six droplet diameters within 10–1000 μm. The table is interpolated/extrapolated as needed during CFD simulations. An energy-conserving, finite-volume angular discretization is also described for efficiently computing anisotropic scattering. These approaches have been implemented in FireFOAM and are demonstrated using the standard emitting-receiving configuration, where a hot and a cold surface are separated by water droplets in transparent gases. The results show that the method conserves energy and predicts centerline incident fluxes within 1% of a previously published, high-fidelity benchmark. The typical normalization approach for energy conservation yields up to 100% error in the fluxes. Validation is performed against a detailed model that combines the Mie theory with a Monte Carlo Ray Tracing (MCRT) solver. Centerline fluxes are predicted within 10% of the detailed model. Gray model predictions are off by up to a factor of two. Finally, the scattering model is shown to introduce minimal overhead (only 15% of radiation solver time).

120 GHz on-chip multi-mode wideband dielectric resonator antennas for THz applications

This work discusses the design methods of 120 GHz on-chip dual-mode and three-mode dielectric resonator antennas (DRAs) based on a standard CMOS technology. The bandwidths of the DRAs are expanded by merging adjacent modes with similar radiation patterns. The impedance bandwidth of 18.6% with the peak gain of 6 dBi is achieved for the proposed on-chip dual-mode DRA. In addition, the impedance bandwidth of 20.1% with the peak gain of 6.9 dBi is achieved for the proposed three-mode DRA. To the best of authors’ knowledge, the on-chip multi-mode DRAs are first proposed. The impedance bandwidth of the proposed three-mode on-chip DRA is wider than the other on-chip DRAs using planar feeding with on-chip ground. The proposed antennas are promising for terahertz applications due to the merits of wide band, high gain and high radiation efficiency.

A rectangular slot antenna with perfectly conducting superstrate and reflector sheets for superior radiation in the 6–9 GHz band

AbstractThis paper presents the design and analysis of a rectangular slot antenna for producing a directional radiation pattern over a wide bandwidth of 6–9 GHz. A basic wideband slot antenna is designed for the desired frequency band by microstrip offset feed technique. This antenna is then loaded with a superstrate and a reflector, both made of conducting sheets. Analogous to a three-element Yagi antenna, the superstrate enhances the boresight gain, while the reflector improves the front-to-back ratio (FBR) of the basic slot antenna. The antenna is optimized for superior wideband performance with boresight gain ≥5 dBi, peak cross-pol level ≤−10 dB and FBR ≥10 dB, over the −10 dB impedance band of 6–9 GHz, which in this paper is termed as the radiation bandwidth. Prototype measurement demonstrates a radiation bandwidth of 6.05–8.22 GHz (or 30.41%), which is in decent agreement with the simulation.

Design of Multiband Frequency Reconfigurable Antenna with Defected Ground Structure for Wireless Applications

A novel printed rectangular shape, multi-band frequency reconfigurable antenna with defected ground structure (FRDGS) for multi standard wireless communication systems is designed in this article. The ground plane is modified by embedding U shaped slots with open ends and I shaped slot in short ends to realize the multi band frequency of the antenna and to improve the parameters of the antenna design. The two U shape slots are etched symmetrical to each other to reduce the cross polarization of the antenna. The DGS in the ground plane altered the modeling characteristics of transmission lines with the equivalent values of inductance, capacitance and resistance. Three PIN diodes are inserted in the ground plane to acquire the switching characteristics of multi-resonance frequency. Simulated and measured output clearly depict that the antenna proposed is efficient to change between twelve dissimilar resonant frequency bands centered at 1.36, 1.8, 3.0, 3.9, 5.0, 6.2, 6.4, 7.4, 7.9, 8.2, 8.4, 8.6 GHz through different states of modes over the frequency spectrum from 1.33 to 8.7 GHz. The parameters such as reflection coefficient, VSWR, 2D and 3D radiation pattern, bandwidth, peak gain, peak directivity, gain and directivity are simulated using Ansoft HFSS 17.0v. The proposed antenna finds application in various wireless communication system such as Wi-Fi (5 GHz), WLAN (5 GHz), WI-MAX, UWB (3.1–10.6 GHz) system, fixed mobile and satellite communication systems.

Designing and Analysis of Wideband Antenna for 4G and 5G Applications

A wideband antenna design for 4G and 5G applications has been analyzed and evaluated in this research. The advanced technology equipment’s are getting smaller, which require compact and miniaturized antennas. The antenna designed in this research work is investigated for wideband operations for time division duplex long term evolution bands from band number 33 to 43 and for 5G New Radio n78 band. The design is ruled out for size miniaturization and wide bandwidth so that it can be used in any compact radio device. The antenna design is simulated using CST Microwave Studio and is fabricated on low cost easily available FR-4 substrate. The results are simulated and measured for 4G/5G bands for sufficient radiation characteristics, bandwidth, gain and minimum reflected power.

Probe-fed wideband AMC-integrated hexagonal antenna with uniform gain characteristics for WLAN applications

Demand of antennas those possess wide radiation bandwidth while operating in S-band for wireless communication systems is increasing day by day. Thick substrates are popular solution to achieve wideband but they lead to frequency shift and suffer from limited gain. A potential technique to overcome the issue is to integrate an artificial magnetic conductor (AMC) between dielectric layers of a probe-fed thick substrate antenna as proposed in the paper. A parallel plate capacitor is incorporated to compensate impedance mismatch due to inductive probe. An operating band of 340 MHz is observed between 2.24 and 2.58 GHz for a gain greater than 0 dB while antenna exhibits a peak gain of 6.7 dBi. The proposed low profile AMC integrated hexagonal antenna is easy and economical to fabricate using multilayer printed circuit boards. The square loop AMC is analyzed with different inner widths to estimate the band stop frequency in both TE and TM modes. The phenomenon observed in presence of AMC during design and simulations of S-band antenna are validated with experimental results.

Analysis and design of novel wideband and high efficiency millimeter-wave antenna arrays for 60-GHz applications

A type of millimeter-wave antenna array with flexible design is proposed for a variety of applications at 60 GHz. The antenna array can be adjusted to be linearly or circularly polarized by simply changing the radiation part of the antenna array. High gain, wideband, and high radiation efficiency characteristics can be achieved by adopting a low insertion loss feeding network and broadband antenna elements. For the linearly polarized antenna array, simulation results show that the impedance bandwidth of the 2×2 antenna subarray reaches 21.6%, while the maximum gain achieves 15.1 dBi and has a fluctuation of less than 0.4 dBi within the working bandwidth. Simulation results of the 8×8 linearly polarized antenna array show a bandwidth of 21.6% and a gain of (26.1±1) dBi with an antenna efficiency of more than 80%. For the 8×8 circularly polarized antenna array, simulation results show that an impedance bandwidth of 18.2% and an axial ratio (AR) bandwidth of 13.3% are obtained. Gain and efficiency of up to 27.6 dBi and 80% are achieved, respectively. A prototype of antenna array is fabricated, and results are compared and analyzed.

Theoretical Analysis of Parameter Optimization for Lower-Ionosphere Excitation ELF/VLF Waves Based on Chirp-BOK Modulated Heating

To improve the anti-interference for ELF/VLF communication based on modulated heating lower-ionosphere, chirp spread spectrum technology with strong anti-interference is combined with square wave amplitude modulation, a novel method of chirp-BOK modulated heating lower-ionosphere is proposed in this paper. On this basis, to improve the radiation efficiency of ELF/VLF, the effects of heating parameters (effective radiation power, pump frequency, polarization mode, modulation frequency, duty cycle, and bandwidth) on the radiation efficiency of ELF/VLF were analyzed. The results show that the radiation amplitude of ELF/VLF increases with the increase of effective radiation power, while the radiation efficiency increases first and then decreases; the X-mode is better than the O-mode; the radiation intensity of ELF/VLF decreases with the increase of pump wave frequency from 4MHz to 10MHz; the ELF/VLF equivalent dipole moments increase with the rise of modulation frequency from 500Hz to 5kHz; with the change of duty cycle from 10% to 90%, the dipole moments first increase and then decrease, and the optimal range of duty cycle is 40% to 70%; with the increase of bandwidth, the dipole moments are unchanged. Furthermore, the ELF/VLF dipole moments of square wave amplitude modulated heating ionosphere is unchanged before and after the chirp spread spectrum.

A 3-D Printed Spherical Antenna With Bandwidth Enhancement Under Operation of Dual Resonance

In this paper, a three-dimensional (3-D) printed spherical antenna with bandwidth enhancement under the operation of TM101 and TM211 modes is presented. The antenna is started from a metallized spherical cavity with a rectangular feed waveguide. Then, some slots are suitably introduced on its sidewall. With the help of these introduced slots, two resonant modes (TM101 and TM211) can be excited simultaneously and merged with each other, resulting in a wideband radiation characteristic with two resonances. An antenna prototype operating at X and Ku bands is designed and implemented as proof of concept. The antenna is additively manufactured by incorporating polymer-based stereolithography and electroless copper plating techniques. Measured results show that the antenna not only owns a wide impedance bandwidth of 40.9% from 9.77 to 14.81 GHz, but also maintains stable radiation patterns over the operating band. Besides, the measured average gain is as high as 10.1 dBi. As the measured results are in good agreement with the simulated ones, a simple and effective design of 3-D printed wideband spherical antenna with high radiation performances is verified.

Reply to Comments on “Wideband Radiation Reconfigurable Microstrip Patch Antenna Loaded With Two Inverted U-Slots”

We appreciate the comments given in [1] on active scattering parameters and realized gain of the antenna in [2] . In this correspondence, we would like to address the aforementioned parameters, which were simply overlooked in [2] , by slightly modifying the antenna structure in [2] . The resultant antenna is now capable of radiating both the broadside and conical patterns over a 45% active impedance bandwidth, which is still much greater than that of the microstrip patch antennas with reconfigurable radiation patterns reported in [3] – [13] . The modifications to [2] to improve the isolation between the two ports include incorporating an H-shaped stub, inspired by the one in [14] , at the center of the patch, as shown in Fig. 1(a) , and placing shorting vias at appropriate positions on the antenna, which extends from the top layer of the patch to the ground plane. These vias, along with the narrow slits at the center of the patch, considerably aided in reducing the mutual coupling between the probes. The H-shaped stub and the shorting vias on it facilitated in improving the impedance matching. In the interest of maximizing the overall active reflection coefficients of both the modes of operation, i.e., SUM and DIFFERENCE modes, L-shaped probes are used to excite the antenna structure in lieu of the SMA probes. To integrate the L-probes, the profile of the antenna is now increased from $\sim 0.02\lambda _{\mathrm {d}}$ to $\sim 0.08\lambda _{\mathrm {d}}$ , where $\lambda _{\mathrm {d}}$ is the dielectric wavelength at the center frequency of operation.

A Compact High Efficient Wideband Electromagnetic Pulse Radiator

A wideband electromagnetic pulse oscillation and radiation method is studied. A compact high efficient wideband electromagnetic pulse radiator is developed based on this method. Simulation analysis and experimental results show that the radiation device can obtain more than 40% equivalent voltage radiation efficiency.

A Central Symmetrical and Low-Profile Omnidirectional Circularly Polarized Antenna

In this paper, a compact circularly polarized (CP) antenna with omnidirectional radiation is presented, which has a central symmetric configuration (CSC) and planar structure. It consists of three identical end-fire CP antenna units. Based on the combination of two parallel complementary current sources, each unit cell can be realized by a scalloped cavity and a couple of curved strip lines. Due to a single-layer circular structure with low profile, this configuration can be excited by a coaxial probe in the centre of the whole frame simultaneously. In addition, this prototype was miniaturized with a diameter of 32 mm (0.266λr, the wavelength of the centre frequency in free space is represented by λr) and a height of 1.5 mm (0.012λr). Centre resonance frequency 2.492 GHz is selected, resulting in an omnidirectional radiation and impedance bandwidth (VSWR ≤ 2) of 25 MHz (2481–2506 MHz).