Wide Operating Bandwidth Research Articles

Wideband Omnidirectional Circularly Polarized Antenna for Millimeter-Wave Applications Using Conformal Artificial Anisotropic Polarizer

A wideband omnidirectional circularly polarized (CP) antenna using a conformal artificial anisotropic polarizer is proposed for millimeter-wave applications. The antenna consists of three parts: an omnidirectional linearly polarized (LP) radiator, an annular hyperbolic lens, and a conformal anisotropic polarizer. The annular hyperbolic lens regulates the spherical wavefront from the LP radiator into a cylindrical shape prior to propagating into the conformal artificial anisotropic polarizer. Each curved slab of the polarizer is conformally tilted 45° to the incident electric field. Therefore, the conformal polarizer is the three-dimensionalization of the 2-D planar artificial anisotropic polarizer. The polarizer designing methodology is the first of its kind to generate wideband CP wave omnidirectionally. The hyperbolic lens and the conformal polarizer are fabricated together using stereolithography (SLA) 3-D printing technology. The measurement results show that the antenna has a wide operating bandwidth of 45% (from 24 to 38 GHz), which completely covers potential 5G 28 GHz spectra. The proposed design has a low fabrication complexity and brings possibilities for high-speed wireless communications using circular polarization.

A Conformal Frequency Reconfigurable Antenna with Multiband and Wideband Characteristics.

A compact flexible multi-frequency antenna for smart portable and flexible devices is presented. The antenna consists of a coplanar waveguide-fed slotted circular patch connected to a rectangular secondary resonator (stub). A thin low-loss substrate is used for flexibility, and a rectangular stub in the feedline is deployed to attain wide operational bandwidth. A rectangular slot is etched in the middle of the circular patch, and a p-i-n diode is placed at its center. The frequency reconfigurability is achieved through switching the diode that distributes the current by changing the antenna’s electrical length. For the ON state, the antenna operates in the UWB region for −10 dB impedance bandwidth from 2.76 to 8.21 GHz. For the OFF state of the diode, the antenna operates at the ISM band (2.45/5.8 GHz), WLAN band (5.2 GHz), and lower X-band (8 GHz) with a minimum gain of 2.49 dBi and a maximum gain of 5.8 dBi at the 8 GHz band. Moreover, the antenna retains its performance in various bending conditions. The proposed antenna is suitable for modern miniaturized wireless electronic devices such as wearables, health monitoring sensors, mobile Internet devices, and laptops that operate at multiple frequency bands.

UWB Fastly–Tunable 0.5–50 GHz RF Transmitter Based on Integrated Photonics

Currently, due to the 6G revolution, applications ranging from communication to sensing are experiencing an increasing and urgent need of software-defined ultra-wideband (UWB) and tunable radio frequency (RF) apparatuses with low size, weight, and power consumption (SWaP). Unfortunately, the coexistence of ultra-wideband and software-defined operation, tunability and low SWaP represents a big issue in the current RF technologies. Recently, photonic techniques have been demonstrated to support achieving the desired features when applied in RF UWB transmitters, introducing extremely wide operation and instantaneous bandwidth, tunable filtering, tunable photonics-based microwave mixing with very high port-to-port isolation, and intrinsic immunity to electromagnetic interferences. Moreover, the recent advances in photonics integration also allow to obtain very compact devices. In this article, to the best of our knowledge, the first example of a complete tunable software-defined RF transmitter with low footprint (i.e., on photonic chip) is presented exceeding the state-of-the-art for the extremely large tunability range of 0.5–50 GHz without any parallelization of narrower-band components and with fast tuning (<200 μs). This first implementation represents a breakthrough in microwave photonics.

0D/1D/2D architectural Co@C/MXene composite for boosting microwave attenuation performance in 2–18 GHz

Ti3C2Tx is considered a candidate for high-efficiency microwave absorption materials due to its adjustable electrical conductivity, low density and high specific surface area in recent years. However, the single absorption mechanism could not meet the practical requirements as the functional microwave absorbers. Herein, 0D/1D/2D architectures of Co@C/MXene with 0D Co nanoparticles, 1D carbon nanotubes (CNTs) and 2D Ti3C2Tx MXene nanosheets were rationally fabricated to enhance the microwave attenuation performance, in which Co@CNTs were in situ grown on Ti3C2Tx MXene nanosheets. By changing the amount of Ti3C2Tx MXene to optimize the impedance matching properties, the Co@C/M − 10 absorber exhibits excellent microwave attenuation performance with a minimum reflection loss of −50.5 dB at 5.9 GHz under a thickness of 4.0 mm. Meanwhile, the maximum effective absorption bandwidth (<−10 dB) of Co@C/M − 10 absorber can reach 5.8 GHz under 2.0 mm. The remarkable absorption performance can be ascribed to the synergistic effects of interface polarizations and magnetic loss. Moreover, the radar cross section (RCS) simulation was also performed via CST. Under the incident angle of 0°, the RCS reduction value of Co@C/M − 10 can reach 33.5 dBm2. This work provides a strategy for synthesizing MXene-based composite materials with tunable electromagnetic attenuation and wide absorption bandwidth performance.

A thin shared radiator based ACS‐fed orthogonal pattern diversity antenna with physical tilt for mmWave 5G access points

A low profile and compact two-port antenna is proposed for mmWave 5G access point applications. Since the overall space inside a typical mmWave 5G access point is limited, a small form factor based antenna module is proposed. The two-port antenna shares a common radiator that miniaturizes the overall antenna module. The proposed antenna comprises of single-layered asymmetric coplanar strip (ACS)-fed shared radiator with wide operating bandwidth ranging from 25 to 31 GHz that accounts for fractional bandwidth of 21.4%. The two-port antenna elements are oriented at right angles to each other for obtaining orthogonal pattern diversity (OPD) thereby obtaining wide angular coverage in the E-plane. Vertical linear corrugations with varying lengths are incorporated for decreasing mutual coupling between these two antenna elements and producing a uniform high gain end-fire radiation pattern. Isolation of around 4 dB is enhanced by insertion of these vertical corrugations. The proposed antenna attains peak gain of 7.2 dBi with high pattern integrity over the entire operational frequency band. The presented OPD antenna occupies overall area of 74.75 mm2 which is minimal. Moreover, implementation of the proposed antenna inside a typical mmWave 5G access point is also demonstrated. Simulation and measured results are presented with adequate technical explanation.

Compact wideband Wilkinson power divider on gallium arsenide integrated passive device technology

In this article, a novel topology of wideband on-chip Wilkinson power divider (WPD) with good insertion loss (IL) performance is proposed and demonstrated on gallium arsenide (GaAs)-based integrated passive device (IPD) technology. The proposed WPD is further analyzed by the even and odd method. To verify the advantage of the proposed WPD against the conventional one, two examples are numerically investigated, showing that the proposed one achieves better performance in terms of IL and isolation. In addition, the proposed design achieves a miniature area and small amplitude and phase imbalance (AI) performance. The fractional bandwidth (FBW) of the proposed WPD is 100% (6–18 GHz), where the magnitude imbalance is less than 0.08 dB and phase imbalance is better than 0.4°. Furthermore, the minimum IL is better than 0.96 dB and return loss is better than 13.7 dB within the core passband. Meanwhile, the isolation of the WPD is better than 17.6 dB. Finally, to further demonstrate our design conception, the proposed WPD has been fabricated on GaAs IPD technology with size of 1.5 × 0.9 mm2, and measured by on-wafer probing. All the simulated and measured results of the proposed WPD are matched reasonably well with each other, thus firmly validating the claimed superior performance of the proposed WPD in the wide operating bandwidth, low IL and high isolation.

A 56-Gb/s Reconfigurable Silicon-Photonics Transmitter Using High-Swing Distributed Driver and 2-Tap In-Segment Feed-Forward Equalizer in 65-nm CMOS

This article presents a reconfigurable silicon- photonics transmitter (TX) for short-reach optical interconnects. The proposed hybrid-integrated TX combines a 65-nm CMOS driver with a 180-nm SOI-CMOS silicon-photonic Mach-Zehnder Modulator (MZM). The driver integrated with in- segment fractional-UI spaced feed-forward equalizer (FFE) is proposed to support the non-return-zero (NRZ) signaling, electrical- and optical-domain 4-level pulse-amplitude modulation (PAM-4) signaling. The driver employs a reconfigurable distributed topology to achieve high swing, wide bandwidth and flexible operation. The MZM is driven differentially in a push-pull configuration for high modulation efficiency. Measurement results show that the proposed TX operates up to 50-Gb/s NRZ data rate with 4-Vppd swing and 1.92-ps RMS jitter. In the optical PAM-4 mode, it reaches 56-Gb/s data rate and achieves &#x003E;5-dB extinction ratio (ER) at the cost of 10.9-pJ/bit power efficiency.

D-Band MUTC Photodiodes With Flat Frequency Response

Novel back-illuminated modified uni-traveling- carrier photodiodes (MUTC-PDs) are reported to demonstrate wide bandwidth and high output power performance at D-band (110–170 GHz) regime. A comprehensive design model is employed to predict and tune the frequency response by incorporating coplanar waveguides (CPWs) with different inductive peaking effects. As a demonstration, 4.5-μm-diameter photodiodes with two types of CPWs are fabricated to exhibit different frequency response profiles. Both PDs exhibit a 3-dB bandwidth over 150 GHz and the measured frequency responses are in excellent agreement with simulations. Thanks to the proper design of the CPW electrodes, the two PDs exhibit an output power roll-off of only 4.3 dB and 4.8 dB from dc to 170 GHz, respectively, and high saturation performance is maintained over the broadband frequency range of 130–170 GHz.

A Low-Profile Broadband Metasurface Antenna With Polarization Conversion Based on Characteristic Mode Analysis

In this paper, a low-profile, broadband metasurface antenna for polarization conversion is proposed based on characteristic mode analysis (CMA). A new type of metasurface unit with a partially chamfered symmetrical triangular structure is designed. The inherent physical characteristics of the antenna are analyzed based on CMA, and the expected characteristic modes are selected for excitation at a suitable position. Slot-coupled feeding via microstrip line realizes the performance of wide impedance bandwidth and axial ratio bandwidth (ARBW). The measured -10 dB impedance bandwidth of 36.3% (4.38–6.32 GHz) and the 3 dB ARBW of 20.1% (5.41–6.62 GHz) are achieved. The left-hand circular polarization (LHCP) is realized, and the measured highest gain in the working frequency band is 6.05 dBic. The overall size of the designed and fabricated metasurface antenna is 0.58 λ0 × 0.58 λ0 × 0.07 λ0at 5 GHz. The proposed metasurface antenna can be well used in C-band satellite communications due to its low profile, broadband, and circular polarization.

Broadband Directional Coupler with High Isolation

A novel wideband microstrip directional coupler operating at 1 to 5 GHz with high isolation is presented in this paper. Parallel coupling lines replace the traditional coupling transmission lines, providing broadband characteristics. The rectangular defected ground structure (DGS) on the RF ground on the back increases the isolation. The coupler was designed using 3D electromagnetic simulations. FR4-type dielectric substrate has been used due to its low cost. Simulation results prove that the proposed directional coupler provides an isolation of at least 20 dB on the full frequency band from 1 to 5 GHz, and reaches 66 dB at 2.89 GHz. The coupling degree is about 12 dB. Moreover, the proposed design can also achieve wide operating bandwidth (approximately 139% fractional bandwidth).

Dual-Conversion Microwave Down Converter for Nanosatellite Electronic Warfare Systems

In this work, a microwave down converter is proposed for nanosatellite electronic warfare applications. It provides high spurious suppression by exploiting a dual-conversion architecture and premium performance in terms of noise figure and linear dynamic range. The system design takes advantage of commercial off-the-shelf components, thus allowing for both fast and cost-effective prototyping, which are key requirements particularly concerning CubeSat systems. Since different military, commercial, radar and communication systems operate in the 2–18 GHz frequency band, the capability to integrate such kinds of receivers in CubeSats represents the new frontier of the electronic warfare systems. Moreover, due to the wide operating bandwidth, it can be successfully exploited as the receiver for different applications, e.g., satellite communication, radars, etc.

A dual wideband high gain 2 × 2 multiple‐input‐multiple‐output monopole antenna with an end‐launch connector model for 5G millimeter‐wave mobile applications

This article presents the design, analysis, and realization of a new printed multiple-input-multiple-output (MIMO) antenna with a very high gain and wide bandwidth for the millimeter-wave (mm-wave) 28/38 GHz fifth generation (5G) new radio (NR) applications. The proposed MIMO antenna consists of four identical patch elements in a 2 × 2 configuration to achieve high gain with wide operating bandwidth. The proposed antenna holds an attractive compact size of 31.891 × 37.528 mm2. The proposed MIMO configuration is designed on a 0.508 mm thick Rogers-5870 substrate material with a loss tangent of 0.0009 and a relative dielectric constant of 2.33. An effective technique for folding the feed line and applying a new protruding ground is introduced to obtain good mutual coupling. The fabricated prototype of the proposed antenna is tested to verify the simulation results for the validation of the suggested design approach. The suggested MIMO antenna exhibits −10 dB impedance bandwidth of 2.6 GHz (27.4–30.0 GHz) and 3.3 GHz (36.7–40.0 GHz) to cover the intended frequency range for 5G applications with isolation less than −22 band peak gains of 18 and 14.5 dBi at 27.5 and 38.8 GHz, respectively. To validate the MIMO performance of the proposed antenna several MIMO diversity parameters such as mean effective gain (MEG), envelope correlation coefficient (ECC), and diversity gain (DG) are evaluated. Determined results indicate ECC < 0.001, DG > 9.995, and an average MEG of −3 dB at the operating bands. The proposed antenna exhibits good agreement between the simulated and measured results, which confirm its suitability for forthcoming mm-wave 5G MIMO systems and services.

Morphology‐controlled preparation and tunable electromagnetic wave absorption performance of manganese dioxide nanostructures

AbstractThe development of electromagnetic wave (EMW) absorption materials with lightweight, wide absorption bandwidth, thin thickness, and strong EMW absorption performance has become a hotspot. Herein, the morphology‐controlled preparation of α‐manganese dioxide (α‐MnO2) was successfully obtained via a facile hydrothermal method, and the EMW absorption performance of α‐MnO2 was investigated in detail. The results indicated the as‐obtained Mn‐1.0‐120 possessed the best EMW absorption performance with minimum reflection loss of −53.43 dB at about 5.2 GHz with a thickness of 4.1 mm originated from the synergistic effects of multiply scattering, dielectric loss, and magnetic loss. This contribution demonstrates that the MnO2 has promising candidates with a tunable EMW absorption performance for applications in the electromagnetic field in the future.

A Low-Profile Wideband Metasurface Antenna With Fan-Beam Radiation

This work presents a design of a fan-beam metasurface with a low profile and a wide operating bandwidth. We introduce a new meta unit of four-loop structure which produces high refractive index over the wide operating bandwidth. The metasurface composes of impedance matching layers and core layers to contribute to the fan-beam radiation. A prototype working at X-band is designed, fabricated, and measured. The measured results agree well with simulated ones. The measured results exhibit a wide bandwidth of 51&#x0025;. The measured fan-beam radiation performances show that the 3-dB beamwidths on E and H-plane are 17. and 45., respectively. The realized metasurface is with the height of about 0.24 <inline-formula> <tex-math notation="LaTeX">$\lambda_{0}$ </tex-math></inline-formula>, where <inline-formula> <tex-math notation="LaTeX">$\lambda_{0}$ </tex-math></inline-formula> is the wavelength at center frequency in free space. Measured realized gain is about 15.6 dBi at center frequency. In addition, the measured cross polarization discrimination is better than 25 dB across the entire bandwidth.

Wideband Bidirectional Same Sense Endfire Circularly Polarized Antenna

In this paper, a wideband bidirectional endfire circularly polarized (CP) antenna is proposed by combining two endfire CP antennas with a single coaxial probe feed. The wideband characteristics are achieved with the help of a two-layered substrate separated by an air gap, and the excitation of CP waves in the endfire directions is yielded by the wideband magnetic dipoles and tapered electric dipoles. The proposed CP antenna has shown wide 10-dB impedance bandwidth (IBW) and 3-dB axial ratio bandwidth (ARBW) of 20.76% (5.05 - 6.22 GHz) and 16.10% (5.14 - 6.04 GHz), respectively. Besides showing an overall size of 0.733&#x03BB;_L &#x00D7; 0.863&#x03BB;_L&#x00D7; 0.058&#x03BB;_L (&#x03BB;_L is the wavelength corresponding to the lowest operating frequency) with wide operational bandwidth, the proposed CP antenna has also demonstrated a desirable peak gain of 4.45 dBic.

A Dual-Mode SIW Compact Monopulse Comparator for Sum and Difference Multibeam Radar Applications

In this letter, a compact wideband substrate integrated waveguide (SIW) monopulse comparator is proposed. The TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> modes of an SIW transmission line are used to generate in-phase and out-of-phase excitation fields for the sum and difference beams without complex phase shift network. The monopulse comparator can realize maximum 0.4-dB amplitude balance, 3.6° phase balance for both sum and difference ports, and −37.0-dB isolation coefficient within the operating bandwidth of 9.43–10.65 GHz. In addition, to integrate the monopulse comparator with a low-cost beam scanning capability, six monopulse comparators are used as the sources to excite a flat Luneburg lens. The experimental result demonstrates that ±58° beam coverage range with around −20.0-dB null depth and 15.0-dBi gain can be realized. The advantages of the proposed monopulse multibeam antenna, including low profile, low cost, wide beam scanning range, and wide operating bandwidth, make it a very promising solution for low-cost monopulse radar systems.

A Wideband Monofilar Helical Reflectarray Antenna With Large-Angle Beam-Scanning Performance

A circularly polarized wideband reflectarray is presented using a monofilar single-turn helical antenna as reflecting element. An <inline-formula> <tex-math notation="LaTeX">$11\times 11$ </tex-math></inline-formula> elements reflectarray is designed, simulated and measured in X-band which demonstrates a wide bandwidth and large-angle beam-scanning performance. Phase range of 360&#x00B0; is obtained by rotating off-centred reflecting elements. Full wave simulations show that 1-dB bandwidth of 29.1&#x0025; is achieved at the center frequency of 10 GHz with a maximum gain of 23.9 dB at normal angle of incidence (<inline-formula> <tex-math notation="LaTeX">$\boldsymbol {\phi }$ </tex-math></inline-formula> &#x003D; 0&#x00B0;, <inline-formula> <tex-math notation="LaTeX">$\boldsymbol {\theta }$ </tex-math></inline-formula> &#x003D; 0&#x00B0;) where the measured gain for the focused beam is 23.6 dB with an aperture efficiency of 51.7&#x0025;. Simulated and tested axial ratio is less than 3 dB from 8.9 GHz to 10.7 GHz. Moreover, large-angle beam scanning performance is verified by changing the angle of incidence from &#x002B;30&#x00B0; to &#x2212;30&#x00B0; in both orthogonal planes and maximum gain loss is tested to be less than 1.3 dB at all scanned angles. Feasibility of design is demonstrated by the measured radiation performance and the results are in good agreement with the simulations.

A Broadband Dual-Polarized Solar Cell Phased Array Antenna

This study proposes a broadband dual-polarized solar cell phased array antenna. It is constructed by using crisscross distributed metal-meshed tie-shaped dipoles, an optical transparent glass substrate, feeding probes and ground probes, a solar cell, and a metal ground. The meshed tie-shaped dipoles are sputtered on the top surface of the glass substrate. Circular metal-meshed patches located at the crisscrossing points of the dipoles on the back surface of the glass substrate are introduced to extend the operational bandwidth of the solar cell antenna. The solar cell was placed on the ground of the antenna. We fabricated a sample of the solar cell antenna and measured the electromagnetic characteristics and its power output. The results of the measurements agreed with those of simulations. The proposed solar cell antenna array had a wide operational bandwidth of 2.5–5 GHz, a wide 2-D range of the phase scanning angle of ±45°, a high aperture efficiency of 68.9%–84.1%, and a high relative maximum output power ratio of 87.1% compared with a pure solar cell. It is scalable and can be used in a self-sustained 5G wireless communication system for sub-6 GHz applications.

A Frequency Selective Surface Loaded UWB Antenna for High Gain Applications

This paper presents the design of wideband and high gain Frequency Selective Surface (FSS) loaded antenna for ultra-wideband (UWB) wireless applications requiring high-gain. The antenna consists of a monopole and an FSS reflector. Initially, a conventional rectangular monopole antenna is modified using slot and stub to achieve wide operational bandwidth and size reduction. This modified antenna shows 50% miniaturization compared to a primary rectangular monopole, having a wide impedance bandwidth of 3.6–11.8 GHz. Afterward, an FSS is constructed by the combination of circular and square ring structures. The FSS array consisting of 8 × 8-unit cells are integrated with the antenna as a reflector to enhance the performance of the proposed miniaturized UWB antenna. The loading of FSS results in an improvement of at least 4 dBi gain in the entire operational bandwidth. Moreover, the antenna's bandwidth is also increased at the lower frequency band due to the presence of the FSS. A prototype of the antenna is fabricated and tested to verify the simulation results. The simulation and measurement results show that the antenna offers a wideband –10 dB impedance bandwidth ranging from 2.55–13 GHz with a stable peak gain of 8.6 dBi and retains the radiation pattern stability.

A Design of Millimeter-Wave Dual-Polarized SIW Phased Array Antenna Using Characteristic Mode Analysis

A millimeter-wave dual-polarized beam-scanning substrate integrated waveguide (SIW) phased array is proposed for the 5G communications. The principle of the proposed antenna radiating element is first analyzed with the characteristic mode analysis to obtain a wide operating bandwidth. Then, the horizontally and vertically polarized radiations are excited by a differentially fed SIW cavity and a linearly tapered microstrip line through the coupled slots, respectively. To further validate the proposed design, a 1 × 4 phased array is fabricated and tested. The experiment results show that the 11.0% overlapped dual-polarization bandwidth is from 25.8 to 28.8 GHz with the return loss larger than 10 dB, and the isolation between the dual-polarization is higher than 31.5 dB. The measured far-field patterns demonstrate that the beam-scanning ranges can cover <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm 44^\circ $</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${{\bf and}}$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \pm 41^\circ \ $</tex-math></inline-formula> at 28 GHz for the horizontal and vertical polarization, respectively.