Wideband Behavior Research Articles

A 60 GHz phased array with measurement and de-embedding techniques

We present a 60 GHz phased array system that combines several key technologies to realize 10 GHz bandwidth coverage. Particularly, a tightly coupled dipole array centered at 60 GHz is designed and tested for its wideband performance. The tightly coupled dipole elements offer excellent wideband behavior of 10 GHz with voltage standing wave ratio < 3 with scanning to 45°, as well as low cost printed circuit board fabrication. Additionally, we demonstrate a measurement setup with de-embedding procedure to measure gain at the antenna feed point. A feeding structure was designed and fabricated for de-embedding gain pattern measurements. Recovered measurements are shown to be in agreement with simulation.

Design of Wideband Button Antenna Based on Characteristic Mode Theory.

A wideband wearable button antenna working around 2.4GHz is proposed in this paper. The function of the textile antenna ground is analyzed based on characteristic mode theory. By properly locating the button on the ground, the latter can be efficiently excited and operates as a radiator. This is shown to greatly increase the impedance bandwidth. The antenna is analyzed both in free space and on the human body. A prototype is fabricated, and the measured results agree satisfactorily with the simulations. In free space, the bandwidth, the realized gain, and radiation efficiency are 658MHz, 1.8dBi, and 97%, respectively. While on the human body, the values can reach 788MHz, 5.1dBi, and 71%, respectively. This wide band behavior provides robustness across different environments and to relatively large fabrication tolerances. The specific absorption rate is below 0.45W/kg for an equivalent isotropically radiated power of 20dBm.

Wideband or Dual-Band Low-Profile Circular Patch Antenna With High-Gain and Sidelobe Suppression

This communication presents a wideband or dual-band circular disk antenna with high-gain and sidelobe suppression (SLS). The antenna has a single layer and single-fed configuration. The antenna can operate with the radiation field superposition of TM12 and TM14 modes at one frequency, which provides high-gain and SLS. A circle of 10 shorting vias with nonidentical diameters are loaded inside the antenna cavity in order to excite the field superposition of TM11 and TM13 modes at another frequency. By modifying the radius of the vias, the resonant frequency with the TM11 and TM13 superposition can be tuned closer to or further away from the one with the TM12 and TM14 superposition. In this way, a wideband or dual-band behavior can be obtained with high-gain and SLS. The proposed antenna achieves the impedance bandwidth of 6.46% for the wideband case, which is over 6 times wider than the previous literature. In the dual-band case, the bandwidth is 1.48% and 1.61% at each band. For both cases, the gain and the SLS are higher than 15 dBi and 10 dB within the operating bands, respectively. Measurements are carried out with prototypes and agree well with simulations.

An internal resonance based frequency up-converting energy harvester

Frequency up-converting vibration energy harvester can bridge the gap between high-frequency response and low-frequency input, greatly increasing the efficiency of energy conversion. This article proposed a novel frequency up-converting energy harvester based on 1:3 internal resonance in 2 degree-of-freedom cubic nonlinear systems. The harvester consists of two asymmetric cantilevers corresponding to two vibration degrees-of-freedom. The ratio of cantilevers’ first-order resonances is (or close to) 1:3. When excited frequency matches the resonant frequency of the first assisting cantilever, 1:3 internal resonance of the harvester system occurs, leading to drastic vibration of the second generating cantilever at its resonance. The generated voltage frequency is then three times increased. Finally, simulated and experimental results clearly proved this frequency up-converting principle. In addition, the resonant frequency tuning and wideband behaviors of the harvester were also investigated, which increased the viability of the proposed harvester under the practical environment vibrations.

Novel Broadband Antennas for Future Mobile Communications

Compact planar antipodal endfire broadband antennas based on novel windmilllike shape are proposed in this paper for future mobile applications. Asymmetric structure of the proposed antennas makes these antennas to radiate in boresight direction, while antipodal structure provides wideband behavior. In the first phase, an ultrawideband antenna is designed using an FR4 substrate with a size of 34 mm $\times$ 30 mm, for the frequency range from 4 to 10 GHz and a peak gain of 5 dBi. This antenna is then upgraded to Antenna-II, to shift its frequency band to more than 10 GHz and up to >150 GHz. To improve the performance of Antenna-II, a low-loss substrate Rogers RO4232 is used. The final optimized antenna achieves at least 175% fractional bandwidth in the frequency range from 10 to >150 GHz and exhibits a peak gain of 8.7 dBi while maintaining an overall average gain of 6.4 dBi in the entire frequency range. Design as well as the performance analysis of this antenna is also investigated for low earth orbit-to-low earth orbit intersatellite link applications with its power analysis.

Offset fed slot antenna for broadband operation

In this paper, a microstrip fed rectangular slot antenna with wideband characteristics is proposed. Both the impedance and radiation characteristics of the proposed antenna are presented. It is shown that a properly offset feed can give a dual resonance nature, which can be optimized to enable wideband behavior. From HFSS simulation, an impedance bandwidth (-10 dB) of 49.92 % (2.51 GHz to 4.18 GHz) about the center frequency of the band is obtained. Prototype measurement demonstrates a bandwidth of 45.30 % (2.51 GHz to 3.98 GHz). Simulated radiation patterns show bidirectional behavior, which is stable in the band with a peak gain of 5.7 dBi and a gain variation of 2 dBi.

CRLH-based compact wideband antenna for mobile applications using U-shaped feed

ABSTRACTIn this article, a compact composite right/left-handed wideband antenna has been proposed and analysed using finite-difference time-domain for cellular applications. The proposed antenna operates at different wireless standards such as GSM1800, WCDMA, WiMAX, Bluetooth and Wi-Fi. It exhibits wideband behaviour with a bandwidth of 55% (at 2.46 GHz). The proposed antenna is compact and has a radiating element size of 0.14 λo × 0.22 λo × 0.01 λo. In addition, commercial Ansys HFSS software has been used to verify the results and a prototype has also been fabricated to test the antenna experimentally. The proposed metamaterial antenna offers good radiation characteristics and is omni-directional in xz-plane with an average gain of 1.3 dBi in the operating bandwidth.

Design and Characterization of a Flexible Wideband Antenna Using Polydimethylsiloxane Composite Substrate

The design and characterization of a simple, flexible wideband antenna using polydimethylsiloxane (PDMS) composite are presented. Conductive fibers are used to construct the metallic parts on a PDMS composite. To characterize the performance, two identical antennas are designed, one using the PDMS composite while the other on conventional dielectric materials. It was observed that both antennas behave well in terms of the matched bandwidth; however, the radiation towards the broadside direction is reduced when using the PDMS composite as substrate, particularly at higher frequencies. The antenna exhibits a matched bandwidth of 59.9%, ranging from 3.43 to 11.1 GHz. Moreover, the bending analysis carried out for different scenarios show that the wideband behavior of the antenna is well preserved and the variation reaches a maximum of 1% variation.

Evaluation of the impact of different frequency dependent soil models on lightning overvoltages

This work assesses the influence of including the wideband behaviour of grounding systems in EMT-type programs on evaluation of transients resulting from direct lightning strikes to transmission lines. The grounding frequency behaviour is determined by using an accurate electromagnetic model and included in EMTP/ATP by means of an equivalent circuit derived from Vector Fitting technique. Furthermore, the impact of the frequency dependence of soil parameters on the lightning performance of transmission lines is addressed. It was found that representing the tower-footing grounding by a simple resistance can lead to significant errors in terms of grounding potential rise. However, for the overvoltages that appear across the insulator strings, the representation of the grounding system by a simple resistance leads to results whose accuracy is similar to those obtained using more complex representations which consider the wideband behaviour. Also, it was shown that the frequency dependence of soil parameters leads to a reduction of the grounding impulse impedance and causes a decrease of the backflashover rates, improving the lightning performance of transmission lines. In addition, the effect of considering the variation of soil parameters with frequency is more intense in the ground potential rise than in the overvoltages in the insulator strings.

Analysis of wideband circularly polarized ring slot antenna using characteristics mode for bandwidth enhancement

In this article, a coplanar waveguide fed ring slot antenna is proposed for the generation of circular polarization. It is shown that the bandwidth can be improved by adding a stub. Characteristics mode analysis is used to understand the wideband behavior and generation of circular polarization in different antenna configurations. Parametric analysis is used to optimize the performance of the antenna. The proposed antenna is fabricated and the measured results are compared with the simulated performance. The measured impedance bandwidth (|S11| ≤ －10 dB) is 64.6% (2.25 GHz–4.4 GHz) and a 3 dB axial ratio bandwidth is 64.6% (2.25 GHz–4.4 GHz).

Radiative Wireless Power-Transfer System Using Wideband, Wide-Angle Slot Arrays

This paper analyzes the benefits of using wideband, wide-angle arrays in radiative wireless power-transfer systems. A physical optics (PO) code is used to investigate the focusing capabilities and operating range of two 2-D antennas: Van Atta arrays and phase-conjugate/time-reversal arrays. In the PO analysis, the antennas are assumed to be ideal mirrors, which do not backscatter the impinging energy but rather completely absorb and reemit it. Sources located in both the near and far field of the antennas are considered. It is shown that for distances larger than the mirror size, the two antennas have similar focusing capabilities. In such scenarios, a Van Atta approach is preferred over a phase-conjugate approach due to its ease of implementation. Antenna elements used to realize these arrays/mirrors are typically resonant and exhibit strong backscatter, a limited field of view, and small bandwidth. To overcome these limitations, we propose an array/mirror consisting of long slots fed by parallel plate waveguides. A spectral Green’s function approach is used to derive the scattering performance of the infinite array in reception. It is shown that the array can collect the total power impinging from a remote source over a large field of view and bandwidth. The conclusions arrived at for the infinite case are extended to the finite case through full-wave simulations. It is shown that the array can refocus the energy impinging from a close source over a large bandwidth. An infinite magnetic line source is considered as an example. An accurate expression is provided for the voltage distribution across the feed lines of the array. The proposed solution paves the way toward the practical implementation of ideal Van Atta and time-reversal/phase-conjugate mirrors. The wideband behavior of the array may enable high-power, pulsed retrodirective arrays.

Influence of Zn2+ and Ni2+ cations on the structural and optical properties of Ba2Zn1−xNixWO6 (0 ≤ x ≤ 1) tungsten double perovskites

We studied the structural and optical properties of Ba2Zn1-xNixWO6 (0 ≤ x ≤ 1) double perovskites prepared by a solid-state reaction route using various tools, such as X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray (SEM/EDX), ultraviolet (UV)-visible diffuse reflectance, and photoluminescence. Rietveld refinement of the powder XRD data revealed that the compounds were highly crystalline and had a cubic crystal structure within the space group Fm-3m. The XRD results were consistent with EDX spectra results. SEM images exhibited large variation in the particle size with increasing zinc (Zn2+) and nickel (Ni2+) cations. The band gap of Ba2Zn1-xNixWO6 oxides calculated from the diffuse reflection spectra using Tauc plot was found between 3.18 and 3.53 eV, which indicated a wide-band gap semiconductor behavior in all samples. Finally, the photoluminescence study was performed at room temperature. Due to the high reflectance of the prepared double perovskite, we suggest that the material can be used for sunglass fabrication or photovoltaic energy conservation.

A Wideband Bandpass Filter With Frequency Selectivity Controlled by SAW Resonators

A wideband bandpass filter (BPF) with two cascaded sections, each consisting of a surface acoustic wave (SAW) resonator and one or two transmission lines in parallel, is proposed. The lower and upper rolloffs of the passband are separately controlled by the narrowband characteristics of the SAW resonators to realize high frequency selectivity. The filter principle is analyzed for the two sections using the modified Butterworth-Van Dyke model for SAW resonators. The effects of cascading the two sections using a transmission line are also discussed. To demonstrate the proposed filter topology, two types of resonators are chosen from a limited set of available SAW resonator chips. The filter is designed and simulated based on the data of on-wafer measurements of the chip resonators. It is shown that the wideband behavior of the SAW resonators has impact on the filter. A prototype BPF centered at 2.02 GHz is implemented on PCB combining the discrete chip SAW resonators and microstrip lines. The chips are assembled using 1-mil wire bond technique. The measured filter has a 3-dB fractional bandwidth of 28.8% with high frequency selectivity.

Curved Ring-Bar Slow-Wave Structure for Wideband MW-Power Traveling Wave Tubes

A coupled transmission line (TL)-based slow-wave structure is presented and characterized. This TL is a modified ring-loop structure referred to as curved ring bar. It inherits the features of the ring-loop structure, but includes elliptic loops to enhance the axial electric field for TM01 mode. The structure demonstrates wideband behavior and is especially designed for high-power traveling wave tube amplifiers. It is characterized using a pair of uniform and identical coupled TLs utilized to achieve desired dispersion characteristics. This characterization explains the dispersion curves and interaction impedance. A simple way to derive dispersion behavior in terms of circuit parameters is also provided. A traveling wave tube (TWT) model is also presented that gives an output power of 1 MW across 1.8–2.4 GHz. It is noted that the designed TWT provides a bandwidth of 20% and delivers an output power of 1 MW, larger than previously reported in S-band.

A stacked sierpinski gasket fractal antenna with a defected ground structure for UWB/WLAN/RADIO astronomy/STM Link applications

ABSTRACTAn aperture coupled stacked Sierpinski gasket fractal antenna with a defected ground structure is proposed in the current article for ultra wide band (UWB) and wireless local area network (WLAN) applications. The radiating structure is formed of two Sierpinski gasket fractal patch antenna layers on two layers of FR4 substrate stacked one over the other. This stacked structure is fed by a third (bottom) layer also of FR4 substrate, with ground layer at its top and the feed line with a stub, at the bottom. The top ground layer has a ‘†’ shaped slot cut in it to provide a wideband behavior to the antenna, and the feed line is designed with a stub to provide circular polarization to the EM fields radiated by the proposed antenna. The antenna is designed using CST Microwave Studio version 2010 assuming perfect boundary conditions. The proposed antenna shows a dual band wideband behavior with an impedance bandwidth of 630 MHz (4.75–5.38 GHz) and 400 MHz (6.8–7.2 GHz) with a gain of 5.85 dB and 9.5 dB at the center frequencies of the two bands, respectively. The antenna is capable of covering two UWB bands from (4.75–5.28) GHz and (6.8–7.2) GHz, a radio astronomy band from (5.01–5.03) GHz and IEEE 802.11a band from (5.15–5.35) GHz. The prototype of the proposed antenna is tested using a VNA and an anechoic chamber to validate against the simulated results. The proposed antenna has volumetric dimensions of 6 × 6 × 0.483 cm3 which makes it a suitable choice for RF front end circuits. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2786–2792, 2015

Wideband compact directive metasurface enabled pair of slot antennas

A simple novel compact wideband directive metasurface (MS) enabled antenna is proposed. Two same dimensions of edge fed slots are used to excite the MS layer which is made of a periodic arrangement of a rectangular loop-based unit cell. An optimised resonant slot fed at the edge with a simple micro-strip line together with the epsilon very large MS layer exhibits wideband behaviour. The antenna yields a bandwidth from 5.89 to 6.6 GHz for a voltage standing wave ratio < 2 (12%) compared with a measured fractional bandwidth of 14%. A maximum broadside directivity of 10.5 dBi has been achieved. Simulated efficiency is more than 87%. The measurements characteristics of this antenna are in agreement with simulated results.

E-shaped wideband plasmonic nantennas with linear and dual-linear polarizations

In this paper we present a novel nanoantenna (nantenna) design for energy harvesting. The nantenna has an “E” shape and is placed on a SiO2 substrate. Its operation is based on the excitation of surface plasmon polaritons through the gold arms of the E shape. By varying the lengths and widths of the arms, two overlapping working bandwidths can be achieved. This results in a wideband behavior characterized by a full width at half-maximum of about 2.2 μm centered around 3.6 μm. Two orthogonal E nantennas are placed perpendicular to each other to realize a dual-polarized nantenna. This nantenna can receive the two incident polarizations at two separate gap locations with very high isolation. The proposed structure can be used in several energy harvesting applications, such as scavenging the infrared heat from the Earth and other hot objects, in addition to optical communications.

Extremely wideband in‐phase power divider using modified Wilkinson design

ABSTRACTA planar in‐phase power divider with extreme wideband behavior using modified Wilkinson design is presented. Instead of using T‐junction at the input port of the traditional design, the proposed divider uses broadside coupled microstrip to slotline configuration. Moreover, the impedance matching of the output ports is significantly improved across several octaves bandwidth using three binomial sections, whereas the isolation between those ports is enhanced across that band using three isolation resistors. The utilized structure is suitable for single layer integration as both the input and output ports are located at the same layer. A prototype of the presented device is designed using a proper theoretical approach, built, and tested. The developed device has a compact size with an overall dimension of 40 × 55 mm2 using the substrate Rogers RO4003 (dielectric constant = 3.38, thickness = 0.406 mm). While the device can be used for any wideband application, the developed prototype is designed to operate within the band 1–7 GHz, which is used in most microwave‐based medical imaging applications. The achieved simulated and measured results show that the proposed device has equal power division between the two output ports with less than 0.2‐dB amplitude imbalance, more than 10‐dB return loss and 15‐dB isolation, and less than 2° phase difference between the two output signals across the extremely wide frequency band 1.2–7 GHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1799–1802, 2015

A Novel CMOS 24-GHz In-Phase Power Divider Using Synthetic Coupled Lines

A novel in-phase power divider using two synthetic coupled lines (CLs) and one isolation resistor is presented. The synthetic transmission lines (TLs) so-called the complementary-conducting-strip CL consists of periodical structures. By adopting the meandered and edge-coupled TLs the design reveals a two-way power divider and features a wideband behavior with a compact chip size. Moreover, the power divider also provides a 0° phase difference between input and output ports at 24 GHz. The chip is fabricated in a standard 0.18- $\mu \text{m}$ CMOS technology with a core area of 30 $\mu \textrm {m} \times 30\mu \text{m}$ . Measurements show that the minimum insertion losses ( $\vert S_{21}\vert $ and $\vert S_{31}\vert $ ) of the power divider are 5.38 and 5.43 dB at 23.5 GHz, respectively. Moreover, the power divider can operate from 15 to 28 GHz with superior RF performances on return losses and isolation.

An UWB dual polarized microstrip fed L-shape slot antenna

In this paper, a microstrip fed, L-shape slot antenna for dual polarization is proposed. The two arms of the slot generate electric fields of orthogonal polarizations. By properly sectioning the slot and the feed line, ultra wideband (UWB) behavior is obtained. The measured impedance bandwidth (S11&lt; −10 dB) is more than 8.6 GHz (112%) and 8.2 GHz (104%) for Port 1 and Port 2, respectively. The measured isolation is better than 25 dB over most of the band. The aperture field distribution justifies the dual polarized nature. A modified version which implements a band-notch over 5.1–5.85 GHz wireless local area network (WLAN) band is also presented. With a compact, single substrate design, the antenna can be useful in MIMO transmission systems, polarimetric UWB radar, high performance microwave imaging, and other future wireless communications devices.