Wide Operating Bandwidth Research Articles

Wide-Angle Coverage Deployable Bunker Antenna for Ground Applications

Compact and lightweight antennas are required for future ground communication systems to provide wide-angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> steradians coverage for man-pack radio communication units carried by soldiers on the ground. Two innovative “Bunker” antennas at K-band are described in this article. The novelty includes antenna deployment from folded to unfolded configurations, compact size, low mass, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\pi $ </tex-math></inline-formula> steradians coverage, low cost, wide bandwidth performance, and built-in radome for protection from severe environmental conditions. Design of these antennas, trades, RF simulations, mechanical design, antenna deployment, and material selection leading to product development are described for the first time in this article. A prototype antenna has been fabricated and measured results are presented. An excellent correlation between measured and simulated patterns has been achieved. The Bunker antenna has very wide frequency bandwidth of 86% covering Ku and Ka secondary frequency bands in addition to its primary K-band and thus could in the future replace three antennas on a dedicated man-pack with a single tri-band antenna solution.

A Compact Wideband Pattern Diversity Antenna for 5G-NR Applications

In this letter, a novel compact wideband antenna with broadside and conical diversity patterns is presented for fifth-generation (5G)-NR applications. The capacitive loading is implemented to enhance the port isolation and for size reduction (0.35 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.29 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.047 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ). With an extra slot mode introduced by the coupled feeding scheme, a wide impedance bandwidth is obtained. A miniaturized broadband 180° hybrid coupler is designed to provide in-phase and out-of-phase excitations. It is composed of a quarter-wavelength parallel coupled-line and lumped <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> components. As a result, conical and broadside diversity radiation patterns are achieved. The proposed antenna is analyzed, fabricated, and measured. Good agreement is achieved between the simulated and measured results. The measured overlapped −10 dB impedance bandwidth is 20.5% (3.16–3.81 GHz). The measured in-band isolation is better than 22.7 dB and the peak value achieves 34.7 dB. The proposed pattern diversity antenna exhibits good overall performance, including compact size, wide bandwidth, high isolation, and good radiation performance. Therefore, it is suitable for space-limited 5G-NR applications.

Wideband Beam-Forming Networks Utilizing Planar Hybrid Couplers and Phase Shifters

In this article, a new approach to designing 6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 6 beamforming networks (BFNs) for producing five or six beams is presented. The configuration of the 6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 6 BFNs is designed utilizing planar wideband hybrid couplers and phase shifters. A new type of wideband hybrid coupler is built based on a slotline resonator and microstrip-to-slotline transitions. The proposed coupler design can achieve high level of isolation between the sum and difference ports. Two different formats of wideband 6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 6 BFNs are then developed, to generate five and six beams, respectively. A prototype is fabricated and tested, and the experimental results agree with the simulation ones very well, achieving a wide operating bandwidth of more than 30%. Finally, the BFN is verified by feeding a six-element array, and the realized patterns match the predicted ones very well, demonstrating the function of the BFN. The topology of an extended 12 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times12$ </tex-math></inline-formula> BFN is also given to demonstrate the possibility of creating higher-order BFNs using the presented approach.

A Wideband 2-Bit Transmitarray Antenna for Millimeter-Wave Vehicular Communication

A wideband transmitarray antenna based on the magnetoelectric (ME) dipole element and 2-bit phase compensation scheme is presented for vehicular communications in this paper. A wideband 90° phase shifter is proposed and combined with the rotating method to achieve four discrete phase states. Thanks to the polarization-twisting technique and the simple structure of the phase shifter, the proposed element can be easily designed. For the transmitarray design, a multi-frequency phase compensation strategy is applied to guarantee stable performance over the operating band. To validate the design, a 12 × 12 transmitarray antenna simultaneously covering vehicle-to-satellite band (20 GHz), and 5G millimeter-wave (mmWave) bands (24 GHz/28 GHz) is designed, fabricated and measured. The experimental results show that the prototype can achieve high aperture efficiencies (>40%) within a wide bandwidth (34%). The measured peak aperture efficiency is up to 53% at 23 GHz. These results demonstrate that the proposed 2-bit transmitarray antenna enjoys the advantages of wide operating bandwidth, high aperture efficiency and comparatively low design complexity. With these characteristics, the proposed transmitarray antenna can be a promising candidate for vehicular communications that require reliable satellite links and 5G millimeter-wave connections simultaneously.

Broadband dual-channel channelizer based on a microwave photonic power tunable image rejection down-conversion.

Radiofrequency (RF) channelization has potential high frequency and wideband advantages in frequency-domain channel segmentation and down-conversion reception. In this paper, we propose a compact dual-channel channelizer that can process high-frequency wideband signals. It uses double-polarization double-sideband electro-optic modulation and Hartley structure photoelectric conversion to realize down-conversion channelization of the high-frequency wideband signal. The power matching between two polarization signals can be realized by controlling the modulator bias, so the crosstalk between the two output signals can be suppressed. The proposed channelizer has a compact structure since the electro-optic modulation is based on one single laser and one single integrated modulator. No filters are used in the structure, contributing to a very wide RF operation bandwidth and low constraints of laser wavelength. In the experiment, the single frequency signal pairs from 9 GHz to 15 GHz can achieve an inter-channel image rejection ratio of 53 dB. Furthermore, the channelizer slices multi-octave bandwidth quadrature phase shift keying (QPSK) signals up to 16 GHz with the wideband isolation higher than 10 dB and outputs them to two channels in parallel. The error vector magnitudes (EVM) of 9-17 GHz and 18-26 GHz band QPSK signals are guaranteed to be under 23.58% after channelized separation. To the best of our knowledge, the proposed channelizer provides high inter-channel interference suppression at dual-band adjacent signals with 8 GHz bandwidth for the first time. Therefore, the proposed channelizer has great application value for the reception and processing of millimeter signals in the future.

High‐gain tapered slot antenna with spoof surface plasmon polaritons director

In this letter, the authors propose a high-gain and low-profile tapered slot antenna (TSA) with a composite patch made of ellipse and spoof surface plasmon polaritons (sSPPs) structures. The authors first demonstrate the construction details and associated dimensions of the antenna fabrication. Then the authors discuss the role of the patch, which is placed at the antenna's radiating opening to improve the directivity of the antenna. Measurements of the fabricated antenna show a wide operating bandwidth of 82.3% (5–12 GHz) is achieved. The gain of the antenna varies from 5.2 to 13.4 dBi, in which radiation patterns show good directivity and end-fire radiation performance. The measured results are in good agreement with the simulation results, indicating that the antenna performance has been improved as expected by adopting this design.

A Compact Dual-Polarized Filtering Antenna With Steep Cut-Off for Base-Station Applications

A dual-polarized filtering antenna with steep cut-off and compact size is developed for base-station applications. In this design, four controllable radiation nulls are obtained by utilizing split rings, slotted T-shaped branches, a single-stub tuner, and a parasitic loop. Split rings are first used as the dipole arms to obtain the first radiation null at upper out-of-band. Four T-shaped branches working as DGS are printed under the crossed dipoles to achieve the second radiation null. The connected outer conductors of the differential feed structure acting as a single-stub tuner can provide the third radiation null to further enhance the upper band rejection. Finally, a parasitic loop is incorporated around the split rings, and the out-of-band rejection of the lower band is further enhanced by the fourth radiation null. More importantly, the impedance bandwidth of the antenna can be expended with two newly introduced resonant modes. As a result, a compact filtering antenna with a wide operational bandwidth of 1.7–3.01 GHz (56%) is realized for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vert \text{S}_{dd11}\vert &lt; -15$ </tex-math></inline-formula> dB with the isolation higher than 38 dB. The out-of-band suppression is higher than 18.4 dB in 3.1–4.5 GHz and more than 47 dB in 0.8–1.1 GHz.

Design of Wideband Base Station Antenna by Involving Fragment-Type Structures on Dipole Arms

Base station antenna usually requires dual-polarization operation with satisfactory input return loss, adequate dual-polarization isolation, stable gain, and half-power beamwidth (HPBW) in a wide bandwidth covering the entire or part of the mobile communication bands. Such comprehensive requirements provoke great challenges in antenna design. A novel design scheme is proposed by involving fragment-type structures (FTSs) in antenna and seeking for the optimal FTS by multiobjective optimization searching. The technique is demonstrated by improving crossed dipoles for operation in band ranging from 1.7 to 3.8 GHz. Part of the dipole arms can be gridded into cells and reconfigured by using FTS elements. For automatic optimization searching, a binary coding scheme for both the FTS distributions and canonical dipole structure dimensions is proposed. Simulation and measurement show that the optimal crossed dipole antenna may acquire a wide operation bandwidth of 76.3%, with the return loss higher than 15 dB, isolation higher than 30 dB, HPBW of 65° ± 5°, and gain of 9 dBi ± 0.65 dBi for ±45° polarizations.

Piezoelectric Micromachined Ultrasonic Transducer Array-Based Electronic Stethoscope for Internet of Medical Things

A piezoelectric micromachined ultrasonic transducer (PMUT) array-based smart electronic stethoscope is presented for Internet of Medical Things (IoMT). For the first time, an electronic stethoscope based on a high-performance PMUT array is demonstrated to record mechanoacoustic cardiopulmonary signals from the body. This electronic stethoscope can continuously capture the cardiopulmonary signals and enable the telemedicine as well as the digital smart medical becoming a reality. The measured cardiopulmonary signals are collected using the PMUT array and transmitted to a mobile terminal via Bluetooth. Then, primary diagnosis can be implemented in real time using a customized APP in the terminal. The PMUT array was designed with high acoustic pressure sensitivity, high noise resolution, and wide operation bandwidth. These crucial parameters enabled simultaneous monitoring of multiple health parameters associated with the cardiopulmonary system, namely, respiratory rate, heart rate, lung sounds, and heart sounds. A feasibility test was implemented on patients with preexisting medical condition, in order to detect weak mechanoacoustic signals related to tachyarrhythmia and asthma. This article demonstrates the potential use of smart electronic stethoscope in healthcare applications, such as the assessment of heart and lung diseases, which provides an innovative auscultation technology and brings great benefits to IoMT.

Gain and isolation enhancement of a wideband MIMO antenna using metasurface for 5G sub-6 GHz communication systems

This work proposes a compact metasurface (MS)-integrated wideband multiple-input multiple-output (MIMO) antenna for fifth generation (5G) sub-6 GHz wireless communication systems. The perceptible novelty of the proposed MIMO system is its wide operating bandwidth, high gain, lower interelement gap, and excellent isolation within the MIMO components. The radiating patch of the antenna is truncated diagonally with a partially ground plane, and a metasurface has been employed for enhancing the antenna performance. The suggested MS integrated single antenna prototype has a miniature dimension of 0.58λ × 0.58λ × 0.02λ. The simulated and measured findings demonstrate a wideband characteristic starting from 3.11 to 7.67 GHz including a high realized gain of 8 dBi. The four-element MIMO system has been designed by rendering each single antenna orthogonally to one another while retaining compact size and wideband properties between 3.2 and 7.6 GHz. The suggested MIMO prototype has been designed and fabricated on a low loss Rogers RT5880 substrate with a miniature dimension of 1.05λ × 1.05λ × 0.02λ and its performance is evaluated using a suggested 10 × 10 array of a square enclosed circular split ring resonators within the same substrate material. The inclusion of the proposed metasurface with a backplane significantly reduces antenna backward radiation and manipulates the electromagnetic field, thus improving the bandwidth, gain and isolation of MIMO components. The suggested 4-port MIMO antenna offers a high realized gain of 8.3 dBi compared to existing MIMO antennas with an excellent average total efficiency of 82% in the 5G sub-6 GHz spectrum and is in good accordance with measured results. Furthermore, the developed MIMO antenna exhibits outstanding diversity characteristics in respect of envelope correlation coefficient (ECC) less than 0.004, diversity gain (DG) close to 10 dB (> 9.98 dB) and high isolation between MIMO components (> 15.5 dB). Therefore, the proposed MS-inspired MIMO antenna substantiates its applicability for 5G sub-6 GHz communication networks.

A Novel Wideband 90° Filtering Phase Shifter Using Broadside-Coupled MSLs

This brief presents a novel wideband 90° phase shifter using broadside-coupled microstrip lines (MSLs). Firstly, compared with its traditional counterpart, the proposed one can significantly increase the coupling degree as inquired in the traditional design so as to realize a much wide operating bandwidth in a simple topology. Secondly, for facilitating the design process, this brief introduces a synthesis method to efficiently design the proposed broadband phase shifter with prescribed parameters. Finally, to verify the proposed design, a prototype of the proposed phase shifter is designed, fabricated, and measured. The measured results show that the wideband phase shifter proposed in this brief can achieve 90°±3°, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> <−22 dB, and fractional bandwidth (FBW) of 80%.

Planar Two-Dimensional Scanning Multibeam Array Antenna Based on a 3 × 3 Butler Matrix Network

In this letter, a wideband two-dimensional (2-D) scanning multibeam array antenna is proposed using a novel beamforming network (BFN). First, a novel three-beam Butler matrix (BM) network, as the core of the BFN, is proposed and described. The BM network comprises a directional coupler, T-shaped power dividers, and coupling baluns, which avoids using crossovers and lossy lumped elements as in a conventional BM network. In addition, a dual-stripline structure is employed to combine multiple components, which considerably reduces the BM network aperture. Then, six three-beam BMs are stacked and interconnected to form a complete 2-D BFN, whose scanning features of two orthogonal planes are controlled by two sets of BMs. Finally, to verify the working principle of the BFN, a 3 × 3 all-metal antenna array is designed and combined with the BFN. Notably, the low-profile antenna element achieves a wide operating bandwidth of 34.5%. Furthermore, a prototype is fabricated and tested, which shows that the antenna realizes switched beams in nine directions, indicating that an excellent 2-D scanning function is realized.

Wideband Isotropic Antenna With Miniaturized Ground for Enhanced 3 dB Coverage Ratio

In this letter, a wideband three-dimensional (3-D) isotropic antenna is proposed with improved 3 dB coverage ratio. Based on the investigation about the effect of the metallic ground size on isotropic radiation, a compact sequential-phase feeding network made of lumped components with miniaturized ground is elaborately designed for wide operating bandwidth and enhanced 3 dB coverage ratio in 3-D space. In the measurement, the antenna prototype is with the size of 70 × 70 × 0.5 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> (0.23 × 0.23 × 0.0017 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ). The measured result shows that the proposed antenna provides the 6 dB gain variation fractional bandwidth of 4% and the 3 dB coverage ratio of more than 80%, leading to promising usage for wideband isotropic radiation applications.

High-Efficiency Mitigation of Nonlinear Distortion in Microwave Photonics Link Assisted by Artificial Neural Network

A microwave photonics radio over fiber link can deliver the radio frequency (RF) signal to realize the antenna remote. When the signal is a broadband and multicarrier RF signal, there are some linear distortions in the link, such as the crossmodulation distortion (XMD) and third-order intermodulation distortion (IMD3). It will destroy the wide-bandwidth performance of the link. Traditional postdigital compensation methods for XMD and IMD3 mitigation extract the baseband signal and reconstruct the compensation signal with calculated compensation factor. Here, a kind of artificial neural network genetic algorithm (ANN-GA) distortion compensation technique is proposed to seek the compensation factor instead of calculations. The neural network algorithm is used to fit the mapping function between the compensation factor and the distortion and give a set of predicted data as the original individual fitness value for the genetic algorithm. Based on the original value, the minimal distortion, the corresponding optimal compensation factors γ and α are found with optimization iterations. Taking advantage of the optimal compensation factors, based on the traditional postdigital compensation method, the distortion is mitigated with a suppression ratio of -84.4 dB. In our paper, the mitigation technology of the XMD and IMD3 can be applied for any kinds of link instead of mathematically modelling the link and calculating the compensation factor. The technology can improve the intelligence and flexibility of microwave photonic link linearization design.

Fully integrated hybrid microwave photonic receiver

Microwave photonic receivers are a promising candidate in breaking the bandwidth limitation of traditional radio-frequency (RF) receivers. To further balance the performance superiority with the requirements regarding size, weight, and power consumption (SWaP), the implementation of integrated microwave photonic microsystems has been considered an upgrade path. However, up to now, to the best of our knowledge, chip-scale fully integrated microwave photonic receivers have not been reported due to the limitation of material platforms. In this paper, we report a fully integrated hybrid microwave photonic receiver (FIH-MWPR) obtained by comprising the indium phosphide (InP) laser chip and the monolithic silicon-on-insulator (SOI) photonic circuit into the same substrate based on the low-coupling-loss micro-optics method. Benefiting from the integration of all optoelectronic components, the packaged FIH-MWPR exhibits a compact volume of 6 cm 3 and low power consumption of 1.2 W. The FIH-MWPR supports a wide operation bandwidth from 2 to 18 GHz. Furthermore, its RF-link performance to down-convert the RF signals to the intermediate frequency is experimentally characterized by measuring the link gain, the noise figure, and the spurious-free dynamic range metrics across the whole operation frequency band. Moreover, we have utilized it as a de-chirp receiver to process the broadband linear frequency-modulated (LFM) radar echo signals at different frequency bands (S-, C-, X-, and Ku-bands) and successfully demonstrated its high-resolution-ranging capability. To the best of our knowledge, this is the first realization of a chip-scale broadband fully integrated microwave photonic receiver, which is expected to be an important step in demonstrating the feasibility of all-integrated microwave photonic microsystems oriented to miniaturized application scenarios.

Characteristics of a 2-2 Piezoelectric Composite Transducer Made by Magnetic Force Assembly

A wider operational bandwidth, a higher electromechanical coupling factor, and lower acoustic impedance are important requirements for ultrasound transducers for use across many applications. Conventional 2-2 piezoelectric composite transducers have been widely researched because of their wider bandwidth and higher sensitivity over their piezoelectric ceramic counterparts. In this paper, the fabrication of a novel 2-2 piezoelectric composite using magnetic force assembly is proposed to explore the potential of the transducer and to minimize mode coupling effect compared to 1–3 composites. To determine the desired transducer performance, such as the electromechanical coupling factor, the operational bandwidth, and the acoustic impedance, the design of a 2-2 composite should be considered using the mode-coupling theory and an effective medium model. The experimental results indicate that the electromechanical coupling factor and the −6 dB fractional bandwidth of the composite achieve values of 0.58 and 65.2%, respectively, which are comparable to those of traditional 1-3 piezoceramic/epoxy composites.

Wideband and compact filtering power divider based on vertically installed planar structures

In this article, a wideband filtering power divider using vertically installed planar (VIP) circuit is proposed, where three-line coupled structures are introduced to realize filtering responses. The even-odd mode analysis method is applied to assess the electrical performance of the whole structure. The simulated and measured results demonstrate that the proposed design has a wide operation bandwidth (>103%), low insertion loss (<0.6 dB) and good isolation (>15.2 dB). Moreover, the amplitude imbalance and phase imbalance are less than 0.2 dB and 0.5°, respectively.

Design and performance analysis of a compact, wideband dual polarized antenna for WLAN &amp; WiMAX applications

Abstract Dual polarization is achieved by putting a rectangular or circular patch in between two orthogonal gaps. At the beginning a single-polarized patch is considered. Then by using anequivalent circuit, the impedance matching property of the gap is being configured. After optimization of the length of the patch and width of the gap, a dual polarized antenna is being considered. Here in this article we projected a new technique to design dual polarized microstrip antenna for WLAN, WiMAX, wireless applications using circular patch. By combining all resonant modes we have finally achieved a wide operating bandwidth. Experimental result of the projected antenna shows the operating bandwidth of 21.56% (5.24–6.37 GHz) for (differential mode S-parameter) S dd11 ≤ −10 dB with a high port isolation of 40 dB and a relative gain of 13.5 dBi is achieved. From the result analysis this antenna finds its applications for various WLAN and Wi-MAX frequency band.

Soliton picosecond pulse generation with a spin-coated PEDOT: PSS thin film

Organic materials have been widely explored in various of electronic and photonic applications. poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) is one of the organic materials that exhibits excellent optical properties including wide operating bandwidth and fast relaxation time. These properties are important for fiber laser applications to induce ultrafast phenomenon. In this experiment, PEDOT: PSS thin film was successfully fabricated based on spin coating technology for use as a saturable absorber (SA) and it featured saturation intensity of 0.21 MW/cm2 and modulation depth of 22%. The incorporation of PEDOT: PSS SA into erbium-doped fiber laser cavity successfully induced a 1.74 ps mode-locked laser at wavelength of 1567.6 nm. The pulse energy and output power were achieved at about 2.79 nJ and 6.89 mW respectively. This is the first time that PEDOT: PSS is applied as a SA to generate a soliton mode-locked laser at wavelength of 1.55 μm.

A Novel Double U-Slot Microstrip Patch Antenna Design for Low-Profile and Broad Bandwidth Applications

A low-profile double U-slot microstrip patch antenna with a wide operating bandwidth has been developed in this article. This design produces the dual radiative resonant modes adjacent to each even at the thickness of the antenna of <inline-formula> <tex-math notation="LaTeX">$0.02 {\lambda _{0}}$ </tex-math></inline-formula>. An extremely stable radiation gain that varied from 6.2 to 6.8 dBi is achieved within the whole operating band. In addition, detailed parametric studies in this article provide antenna engineers with simple approximate rules that result in an excellent first-pass design with prescribed characteristics requiring only minimal tuning. Finally, the proposed antenna with the thickness of <inline-formula> <tex-math notation="LaTeX">$0.04 {\lambda _{0}}$ </tex-math></inline-formula> is fabricated and measured. Simulated and measured results are found in good agreement with each other. They have evidently illustrated that the bandwidth is increased by 50&#x0025; compared to the traditional U-slot antenna. With the help of these simple design procedures and examples in this article, antenna designers could easily develop a low-profile broadband antenna.