Design Of Broadband Research Articles

A new bandwidth-extended harmonic-tuned Class-E/F3 power amplifier based on continuous mode design philosophy

For Class-E/F3 power amplifiers (PAs) working in the radio frequency (RF) band, the freedom of broadband design is limited because the original design space is a single point. In this paper, a new bandwidth-extended Class-E/F3 PA is proposed, which is based on finite harmonic tuning and continuous mode design philosophy. In the theoretical derivation, the high-efficiency frequency domain equations are solved in conjunction with the inherent conditions of the transistor, resulting in a waveform cluster that can expand the design space while keeping the efficiency constant. This approach eliminates the need for tedious circuit derivation and is able to allow greater design freedom. With the extended Class-E/F3 design space, a broadband PA using GaN HEMT CGH40010F operating in the bandwidth of 1.9–3.3 GHz is designed and tested. The experimental results show that the designed PA demonstrates 65% to 74.8% drain efficiency (DE) and 40.1 to 41.7dBm output power over the target bandwidth.

A continuous Class‐EF power amplifier based on the general continuous mode design theory

SummaryContinuous mode provides better bandwidth performance and constant efficiency by offering greater design flexibility in fundamental and harmonics. However, this mode is mainly applicable to limited classes of power amplifiers (PAs) (such as Class‐F, Class‐J, and their derived types). In view of this problem, this paper proposes a general design theory for high‐efficiency broadband continuous PAs, which can easily extend any waveform of PAs to obtain the continuous impedance space. In theoretical analysis, first, the high‐efficiency equations are analyzed from the perspective of frequency domain. Furthermore, combining time domain constraints, a general continuous mode analysis and solution theory is presented. The theory is applied to the bandwidth expansion of Class‐EF PAs, resulting in a new continuous Class‐EF (C‐EF) mode that maintains constant efficiency while offering greater broadband design freedom. The proposed theory is verified by fabricating a C‐EF PA using GaN HEMT CGH40010F, which demonstrated output power (Pout) ranging from 39.5 to 41.2 dBm and drain efficiency (DE) of 69.5% to 79.2% in the frequency range of 2.5–3.6 GHz.

Impact of truncation on absorption spectra in a graphene-based random photonic crystal

The present study investigates the influence of randomness on achieving multimode broadband and narrowband absorption of graphene-embedded photonic structures. In the first proposed photonic configuration, with a change in randomness parameter, it is possible to achieve single-mode and multimode broadband absorption up to 0.8. This value is further enhanced up to 0.99 by varying the Fermi level to −0.9 eV. The position of absorption peaks can be tuned by varying the thickness of the silicon carbide layer. Further, an investigation is carried out on the influence of adding a defective periodic photonic crystal to the first photonic configuration, which provides a multimode narrowband absorption with a value of up to 0.99, and the strength and location of absorption peaks can be altered to the desired value by changing the graphene Fermi level and the thickness of the silicon carbide layer. Finally, the authors also survey the influence of a magnetic field B on the absorption behaviour of left-handed circularly polarised (LCP) and right-handed circularly polarised (RCP) waves. The results indicate that the full width at half-maximum of absorption peaks expands with the application of a positive magnetic field for LCP waves, whereas it shrinks for RCP waves. This has applications in the design of tunable broadband and narrowband absorbers and sensors.

Broadband polarizer using single-layer grating with ultra-high extinction ratio

Polarizers are an essential optical element for tailoring the polarization state of electromagnetic waves in a wide range of optical devices. Such polarizers, which exhibit a wide operating bandwidth and high performance, are attracting increasing attention, due to their extensive prospects for use in applications ranging from polarization imaging, to optical communications and detection, among others. However, achieving both broadband performance and ultra-high extinction ratio (ER), and that simultaneously, is still challenging in the design of effective polarizers. To tackle that demand, in this work, an Au-on-silica grating structure has been proposed as the basis of the design of a miniaturized high-efficiency polarizer that practically can cover the entire visible and near-infrared spectral ranges. The single-layer polarizer thus designed can show an ER of 60 dB in this spectral domain, and it has been shown that the geometrical parameters selected have a significant effect on the performance characteristics of the polarizer. Furthermore, an ER of ∼150 dB could be achieved merely by regulating the thickness of the grating to achieve the optimum performance. By integrating the high-performance polarizer proposed in this work with an optical fiber “meta-tip,” a refractive polarizer with a value of the ER of >45 dB, and that over the entire spectral domain considered, has been demonstrated. Such an approach offers an alternative route to achieving a broadband, powerful, and flexible processing polarizer design.

Axion haloscope signal power from reciprocity

Axion haloscopes search for dark matter axions from the galactic halo, most commonly by measuring a power excess sourced by the axion effective current density. Constraining axion parameters from detection or lack thereof requires estimating the expected signal power. Often, this is done by studying the response of the haloscope to a known, but different, source current density, for example via a reflection measurement. However, only in the special case when both sources induce the same electromagnetic fields, do the quantities derived from a reflection measurement adequately describe the setup during an axion measurement. While this might be valid for the traditional resonant cavity haloscope, new broadband or open designs like dish antennas or dielectric haloscopes cannot make this assumption. A more general relation between axion- and reflection-induced fields is needed. In this article, we use the Lorentz reciprocity theorem to derive an expression for the axion signal power which instead of the unmeasurable axion-induced fields depends on the measurable reflection-induced fields. This entirely circumvents the need to know the response of the haloscope to the unknown axion source. It applies to a wide variety of haloscopes including resonant cavities, dielectric haloscopes, and broadband dish antennas.

A Ka - to G-Band Detector With 5.5-GHz Video Bandwidth Using a Modified Traveling-Wave Structure in 65-nm CMOS Technology

A broadband envelope detector implemented in 65-nm CMOS process is proposed in this brief. The travelling-wave topology is used for broadband design. A novel structure is presented to achieve wide RF bandwidth and video bandwidth (VBW) of this detector. A 1490-mV/mW maximum responsivity is measured at 300 GHz. The measured VBW of the proposed detector is 5.5 GHz. This circuit exhibits a very wide RF fractional bandwidth (164%) among the detectors covering up to 300 GHz.

Regulation of Impedance Matching and Dielectric Loss Properties of N-Doped Carbon Hollow Nanospheres Modified With Atomically Dispersed Cobalt Sites for Microwave Energy Attenuation.

The rational design of lightweight, broad-band, and high-performance microwave absorbers is urgently required for addressing electromagnetic pollution issue. Metal single atoms (M-SAs) absorbers receive considerable interest in the field of microwave absorption due to the unique electronic structures of M-SAs. However, the simultaneous engineering of the morphology and electronic structure of M-SAs based absorbers remains challenging. Herein, a template-assisted method is utilized to fabricate isolated Co-SAs on N-doped hollow carbon spheres (NHCS@Co-SAs) for high-performance microwave absorption. The combination of atomically dispersed Co sites and hollow supports endows NHCS@Co-SAs with excellent microwave absorption properties. Typically, at an ultralow filler content of 8wt%, the minimum reflection loss and effective absorption bandwidth of the NHCS@Co-SAs are up to -44.96dB and 5.25GHz, respectively, while the absorbing thickness is only 2mm. Theoretical calculations and experimental results indicate that the impedance matching characteristic and dielectric loss of the NHCSs can be tuned via the introduction of M-SAs, which are responsible for the excellent microwave absorption properties of NHCS@Co-SAs. This work provides an atomic-level insight into the relationship between the electronic states of absorbers and their microwave absorption properties for developing advanced microwave absorbers.

Design of broadband dual‐polarised reconfigurable frequency selective surface based on dual‐branch parallel circuit model

AbstractA broadband dual‐polarised reconfigurable frequency selective surface (RFSS) based on general dual‐branch parallel circuit model is proposed by the authors. The specific circuit model is constructed to feature the switchable functions of transmission and reflection characteristics by introducing a parallel branch. It is beneficial to clarify the operating mechanism and provide an effective guidance to satisfy the switching bandwidth requirements of the desired RFSS. In order to validate the proposed concept of the dual‐branch parallel circuit model, a broadband dual‐polarised RFSS prototype has been designed, fabricated and measured. A satisfactory agreement can be reached between the synthesis, simulation and measurement. The experimental results exhibit the merits of low insertion loss, broad switching bandwidth and good angular stability for different polarisation and different incident angles.

A Power-Efficient 20–35-GHz MZM Driver With Programmable Linearizer for Analog Photonic Links in 28-nm CMOS

Analog photonic links require linear drive of electrooptic modulators at high frequency to support emerging millimeter wave (mm-wave) communication standards. However, this is challenging due to the nonlinear distortion of commonly used Mach–Zehnder modulators (MZMs). This article presents the first CMOS MZM driver capable of operating over a wide 20–35-GHz frequency range with a programmable linearizer. A broadband design is achieved with a magnetically coupled resonator (MCR) technique that provides wideband impedance matching for the interstage and output-stage matching networks. Linearization is achieved with a topology consisting of inverter-based amplifier segments that provide programmable predistortion gains over the input signal regions. Fabricated in 28-nm CMOS, the driver delivers 2.5-Vpp swing to an external MZM. Operating the majority of the circuitry at 0.9 V, except for the 1.6-V output stage, allows for a power consumption of only 180 mW. The proposed programmable linearizer is able to compensate the amplitude-to-amplitude modulation (AM–AM) compression of the amplifier stages and the external MZM, extending output power 1-dB compression point ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {OP}_{1~\text {dB}}$ </tex-math></inline-formula> ) of the whole radio-over-fiber (RoF) link by 3 dB and achieving 4.8-dBm third-order input intercept point (IIP3) at 25 GHz.

Broadband circularly polarized folded transmitarray antenna based on polarization conversion metasurfaces

In this communication, a novel design of compact and low-profile broadband circularly polarized folded transmitarray antenna (CPFTA) is reported. A broadband linear-to-circular polarization conversion metasurface (PCM) with multi-mode operation is initially developed as the sub-reflector, to reflect the y-polarized waves and transmit x-polarized waves into right-handed circularly polarized waves. Additionally, by rotating the circularly polarized transmitters, geometric phase can be exploited for phase compensation. Then, a linear-to-linear PCM with high efficiency is designed as the main reflector. As verification, a CPFTA integrated with a broadband planar feed source and the proposed high-efficiency PCMs at X band is designed, fabricated, and experimentally characterized. The measured results are in good accordance with the simulated ones, revealing a −10 dB impedance bandwidth of 28.7%, a 3 dB gain bandwidth of 22.9%, and a 3 dB axial ratio bandwidth of 31.9%. Meanwhile, the achieved peak gain is 25.2 dBi at 10.35 GHz with a maximum aperture efficiency of 28.3%. Combining the advantages of broadband operation, flat gain, and ease of integration, the proposed CPFTA is an attractive candidate for modern wireless communications.

Symmetrical Z-Complementary code sets for optimal training in generalized spatial modulation

This paper considers the optimal training design for broadband generalized spatial modulation systems over frequency-selective channels using a novel class of code sets introduced, called “symmetrical Z-complementary code sets”, whose aperiodic auto- and cross- correlation sums exhibit zero-correlation zones at both the front-end and tail-end of the entire correlation window. Two constructions of (optimal) symmetrical Z-complementary code sets based on generalized Boolean functions are presented. Numerical evaluations indicate that the proposed training sequences for generalized spatial modulation can achieve optimal channel estimation performance and outperform other classes of sequences.

Design of broadband microstrip three‐way directional coupler for multibeam antenna application

AbstractIn this letter, a design of broadband microstrip three‐way directional coupler (TWDC) is presented. The broadband performance of the microstrip TWDC is realized by the method of cascading multi‐section. The broadband TWDC is designed to achieve equal power division and −120°, 0°, and +120° phase differences between output signals. To verify the broadband design, a prototype of three‐section microstrip TWDC operating at C‐band is designed, fabricated and measured. The measured results show that the power division error of the designed broadband TWDC is less than ±0.7 dB and phase error is less than ±12° at a relative bandwidth of 16%. To verify its performance in multibeam application, the designed TWDC is used as a beamforming network for multibeam antenna array to generate three orthogonal beams.

Multi-Objective Topology Optimization of a Broadband Piezoelectric Energy Harvester.

In recent years, topology optimization has proved itself to be state of the art in the design of mechanical structures. At the same time, energy harvesting has gained a lot of attention in research and industry. In this work, we present a novel topology optimization of a multi-resonant piezoelectric energy-harvester device. The goal is to develop a broadband design that can generate constant power output over a range of frequencies, thus enabling reliable operation under changing environmental conditions. To achieve this goal, topology optimization is implemented with a combined-objective function, which tackles both the frequency requirement and the power-output characteristic. The optimization suggests a promising design, with satisfactory frequency characteristics.

A review of Doherty power amplifier and load modulated balanced amplifier for 5G technology

SummaryIn this paper, functionality of the Doherty power amplifiers (DPAs) along with their design constraints such as DPA combining techniques are reviewed. This is because power amplifier (PA) is a key building block in the design of fifth generation (5G) communication systems. A significant trend is the DPA bandwidth enhancement technique, which is the subject of numerous papers in the literature. So, we will review some papers with different solutions to address DPA's bandwidth limitations. There are also different works in the literature that have focused on high‐efficiency PA structure designs, which are also discussed in this paper. An excellent option for effective power combining in broadband designs is using balanced amplifiers. We have discussed load modulated balanced amplifiers (LMBA) in this paper because designing an effective PA with a wide bandwidth is crucial. We also covered some papers that have proposed techniques based on the linearization method to bring the efficiency and linearity of DPAs to a fair level.

Design and Preparation of Broadband 3 dB Power Splitter with Compact Size and Low Loss

Design and Preparation of Broadband 3 dB Power Splitter with Compact Size and Low Loss

Design of an Inkjet-Printed Broadband Pixelated FSS Based Absorber Towards Unity Absorption

Design of an Inkjet-Printed Broadband Pixelated FSS Based Absorber Towards Unity Absorption

Expanding the color palette of bicolor-emitting nanocrystals.

Owing to their bright and tunable luminescence spectra, nanocrystals appear as a unique playground for light source design. Displays and lighting require white light sources that combine several narrow lines. As Kasha's rule prevents the emission of hot carriers, blends of multiple nanocrystal populations are currently the obvious strategy for broad-band source design. However, a few reports suggest that bicolor emission can also be obtained from a single particle even under weak excitation if a careful design of the exciton scattering mechanism sufficiently slows down its relaxation pathways. A key challenge remains to maintain quantum confinement for color tunability in the same structure, while simultaneously achieving a large size to leverage the critical, slower exciton diffusion or relaxation down to the ground state. Herein, we demonstrate that 2D nanoplatelets offer an original opportunity for the design of confined and large heterostructures. We demonstrate that bicolor emission is not limited to green-red pair and show that blue-yellow and purple-green emissions can be obtained from CdSe/CdTe/CdSe core/crown/crown and CdSe/CdS core/crown heterostructures, respectively.

Optimization of electromagnetic wave absorption properties of CoNi/MoSe2 composites with 3D flower-like by controlling the Co/Ni molar ratio

Developing composite materials with a rational composition structure has been a critical strategy to obtain superior electromagnetic (EM) wave absorption materials. CoNi/MoSe2 composites were synthesized by a two-step method in this work. Firstly, the flower-like MoSe2 was synthesized by hydrothermal method, and then the CoNi alloy was loaded on the MoSe2 surface by an electroless plating method. It is worth noting that in this paper, PdCl2 was not used for activation during the electroless plating process, and the flower-like structure of MoSe2 was not destroyed. In order to investigate the effect of different Co/Ni molar ratios on the absorption performance of the CoNi/MoSe2 composites, three samples with Co to Ni molar ratios of 1:3, 1:1, 3:1 and two other samples with only one metal (Ni or Co) were prepared. The analysis results show that the minimum reflection loss(RL) value of Ni/MoSe2 is −18.01 dB and the maximum effective absorption bandwidth(EAB) of Co/MoSe2 is 2.16 GHz. In comparison, the CoNi/MoSe2 composite exhibits the best EM wave absorption performance when the Co/Ni ratio is 1:3, and the minimum RL can reach −48.6 dB at a matching thickness of only 1.8 mm. And when the matching thickness is 1.4 mm, the broadest EAB is 3.76 GHz. Therefore, this work provides a new research idea for the design of broadband and efficient EM wave absorbers.

Customizable Acoustic Metamaterial Barrier with Intelligent Sound Insulation

Conventional acoustic metamaterial barriers are usually used to realize sound insulation for a continuous broad bandwidth. In some practical scenes, however, the noise signal from complex noise sources, such as gearboxes and motors, are usually complicated spectra with discrete peaks or valleys, instead of perfect continuous ones. In this case, the broadband design is unnecessary and may increase the thickness of metamaterials if too many frequency components are included. We need only a customized spectrum to achieve sound insulation at desired discrete frequencies, while, at other ones, insulation can be unwanted to preserve an effective signal other than noise. Here, we propose a customizable acoustic metamaterial barrier (CAMB) with intelligent and selective sound insulation. The CAMB is a composite structure consisting of a Helmholtz resonator (HR) and a microperforated panel (MPP) destined to control sound insulation at low frequencies, within 200--1000 Hz, and high-frequencies, within 1000--3000 Hz, respectively. An inverse process is proposed for customizable design. We use analytical and numerical methods to obtain the design libraries for the parameters of the HRs and MPPs. We numerically and experimentally demonstrate an example of a CAMB customized for a practical complex noise source. The sample has a thickness of 48 mm, approximately \ensuremath{\lambda}/11 for the lowest targeted frequency. The proposed customizable concept may pave the way for acoustic insulating metamaterials for complex sound sources with different frequency components.

Design of low profile, compact, high gain and broadband metasurface-based MIMO antenna for 5G/WiMAX/WLAN applications

ABSTRACT We have presented two-port MIMO antenna designs with low-profile material. Two different MIMO antenna designs are prepared and investigated to observe their effect on the gain, bandwidth, etc. The designs are prepared based on metasurface concepts with one design having a circular ring metasurface design and second having circular disk metasurface design. The designs are showing broadband response covering frequency range of 1.85 GHz to 4.27 GHz. The bandwidth of 2.320 GHz is achieved for this metasurface MIMO antenna design. The gain and directivity results show that highest gain of 5.88 dB and directivity of 6.39 dB are achieved with circular ring metasurface MIMO antenna design. Both metasurface MIMO antenna designs are fabricated, and measured results are also provided to verify the simulation results. The broadband and high gain design are applicable for 5G communication, WiMAX and WLAN applications.