Working Bandwidth Research Articles

High-performance chiral all-optical OR logic gate based on topological edge states of valley photonic crystal

For all-optical communication and information processing, it is necessary to develop all-optical logic gates based on photonic structures that can directly perform logic operations. All-optical logic gates have been demonstrated based on conventional waveguides and interferometry, as well as photonic crystal structures. Nonetheless, any defects in those structures will introduce high scattering loss, which compromises the fidelity and contrast ratio of the information process. Based on the spin-valley locking effect that can achieve defect-immune unidirectional transmission of topological edge states in valley photonic crystals (VPCs), we propose a high-performance all-optical logic OR gate based on a VPC structure. By tuning the working bandwidth of the two input channels, we prevent interference between the two channels to achieve a stable and high-fidelity output. The transmittance of both channels is higher than 0.8, and a high contrast ratio of 28.8 dB is achieved. Moreover, the chirality of the logic gate originated from the spin-valley locking effect allows using different circularly polarized light as inputs, representing “1” or “0”, which is highly desired in quantum computing. The device’s footprint is 18 μm × 12 μm, allowing high-density on-chip integration. In addition, this design can be experimentally fabricated using current nanofabrication techniques and will have potential applications in optical communication, information processing, and quantum computing.

Design, performance evaluation and calibration of an indirectly-excited piezoelectric wind energy harvester via a double-bluffbody exciter

Using piezoelectric wind energy harvester to harvest energy from fluids has been an effective way to power wireless sensing systems in the last decade. In order to solve the problems of low reliability, poor environmental adaptability and narrow operating bandwidth of existing piezoelectric wind energy harvesters, a piezoelectric wind energy harvester with a double-bluffbody exciter (DE-PWEH) is proposed in this research. By summarizing the disadvantages of traditional piezoelectric wind energy harvester with upwind structure, a downwind structure was adopted to improve the ability of PWEH to adapt to high wind speed environment. In order to further improve the reliability of the DE-PWEH, a wind isolation structure and an indirect excitation structure was adopted, which means the piezoelectric element was installed inside a cylindrical shell. Therefore, this 2-DOF indirectly excited DE-PWEH could possess both high reliability and broad working bandwidth. To verify the principle feasibility and design regarding the proposed DE-PWEH, a prototype of the DE-PWEH was fabricated and tested in terms of output and operating bandwidth. The results showed that the relative size and position of the adjustable plate and cylindrical shell brought significant effects on the output and operating bandwidth. When the distance-diameter ratio was 0.6, the width-diameter ratio was 1 and the height ratio was 1, the maximum output voltage was 90.35 V and the critical wind speed was 0.96 m/s. The maximum increase of the critical wind speed was 550%, and the minimum was −85.67%. With a wind speed of 15 m/s and the optimal load resistance of 2000 kΩ, a maximum power of 2.57 mW was attained. In order to quantitatively study the performance of DE-PWEH, a data fitting method based on polynomial was proposed for the first time to calibrate PWEH performance. The sixth order polynomial fitting equation can be used to characterize the output characteristics of DE-PWEH. And in practice, 80 LEDs in series were successfully driven by the DE-PWEH. The DE-PWEH could charge the 470 μF, 1000 μF, 2200 μF and 3000 μF commercial capacitors to 2 V in 60 s, 128 s, 340 s, and 400 s, respectively.

A broadband zigzag-shaped energy harvester for both wind energy and vibration energy: modeling and experimental verification

In this work, a novel zigzag-shaped energy harvester is proposed to harvest wind energy and vibration energy simultaneously in a practical environment. The harvester is constituted of an inclined beam and a horizontal beam with a bluff body fixed at the free end. The inclined beam is covered by a piezoelectric patch. The vibration induced by the wind flow and base excitation produces electric energy through the piezoelectric material and realizes energy harvesting. In particular, the softening characteristic created by the magnetic interaction can extend the working bandwidth. Dynamical coupling equations are derived, and the corresponding simulations are carried out. The results show that the cubic bluff body can help increase the wind-induced energy harvesting. The responses obtained under base excitation combined with wind flow demonstrate that the hybrid excitation can provide a significant enhancement to the non-resonance region. Related validation experiments are carried out. The experimental results are in good agreement with the numerical results. Compared with the conventional base excitation or wind flow excitation, the output power obtained under hybrid excitation increases by 106% and 206%, respectively.

Generation of a Fundamental/Doubled Frequency Phase-Coded Microwave Signal Based on Polarization Multiplexed Technology

Microwave photonic phase-shifting technology can be used to generate high-frequency, broadband, and tunable phase-coded microwave signals, which are helpful in solving the contradiction between the detection range and the range resolution in radar systems. A method for generating a reconfigurable carrier phase-coded signal of a fundamental or doubled carrier frequency, based on polarization multiplexed technology, is proposed and verified by the experiments in this paper. A dual-parallel dual-polarization Mach–Zehnder modulator (DP-DPMZM) and a polarization-dependent phase modulator (PD-PM) were used to load the carrier and the phase-shifting signal, respectively. By reasonably configuring the state of the RF switch and the bias voltages of the sub-DPMZM, the fundamental or doubled carrier frequency can be obtained through photoelectric conversion. The reconfigurable carrier frequency gives the system a wider work bandwidth range and can effectively reduce the frequency requirement for local oscillator (LO) signals. By adjusting the driving voltage, the broadband microwave signal can be phase-shifted within the range of 360°, and when the phase-shifted control signal is a multilevel amplitude signal, it can generate binary, quaternary, or other high-order phase-coded signals, which have high reconfigurable performance and potential application value in multifunctional radar systems. In addition, the scheme has wideband tunability, since no optical filter is involved. The proposed scheme was theoretically analyzed and experimentally verified. Binary, quaternary, and octal phase-coded signals, with fundamental and doubled frequencies centered at 8 GHz and 16 GHz, were successfully generated.

Experimental demonstration of a flexible and high-performance mode-order converter using subwavelength grating metamaterials.

Mode-order converters, transforming a given mode into the desired mode, have an important implication for the multimode division multiplexing technology. Considerable mode-order conversion schemes have been reported on the silicon-on-insulator platform. However, most of them can only convert the fundamental mode to one or two specific higher-order modes with low scalability and flexibility, and the mode conversion between higher-order modes cannot be achieved unless a total redesign or a cascade is carried out. Here, a universal and scalable mode-order converting scheme is proposed by using subwavelength grating metamaterials (SWGMs) sandwiched by tapered-down input and tapered-up output tapers. In this scheme, the SWGMs region can convert, TEp mode guided from a tapered-down taper, into a TE0-like-mode-field (TLMF) and vice versa. Thereupon, a TEp-to-TEq mode conversion can be realized by a two-step process of TEp-to-TLMF and then TLMF-to-TEq, where input tapers, output tapers, and SWGMs are carefully engineered. As examples, the TE0-to-TE1, TE0-to-TE2, TE0-to-TE3, TE1-to-TE2, and TE1-to-TE3 converters, with ultracompact lengths of 3.436-7.71 µm, are reported and experimentally demonstrated. Measurements exhibit low insertion losses of < 1.8 dB and reasonable crosstalks of < -15 dB over 100-nm, 38-nm, 25-nm, 45-nm, and 24-nm working bandwidths. The proposed mode-order converting scheme shows great universality/scalability for on-chip flexible mode-order conversions, which holds great promise for optical multimode based technologies.

Topologically optimized concentric-nanoring metalens with 1 mm diameter, 0.8 NA and 600 nm imaging resolution in the visible.

Metalenses can achieve diffraction-limited focusing via localized phase modification of the incoming light beam. However, the current metalenses face to the restrictions on simultaneously achieving large diameter, large numerical aperture, broad working bandwidth and the structure manufacturability. Herein, we present a kind of metalenses composed of concentric nanorings that can address these restrictions using topology optimization approach. Compared to existing inverse design approaches, the computational cost of our optimization method is greatly reduced for large-size metalenses. With its design flexibility, the achieved metalens can work in the whole visible range with millimeter size and a numerical aperture of 0.8 without involving high-aspect ratio structures and large refractive index materials. Electron-beam resist PMMA with a low refractive index is directly used as the material of the metalens, enabling a much more simplified manufacturing process. Experimental results show that the imaging performance of the fabricated metalens has a resolution better than 600 nm corresponding to the measured FWHM of 745 nm.

Field programmable topological edge array

Valley Hall topological photonic crystals, inspired by topological insulators in condensed matter physics, have provided a promising solution to control the flow of light. Recently, the dynamic manipulation property of topological photonic crystals has been widely studied. Here, we propose a novel solution for programmable valley photonic crystals, called field programmable topological edge array (FPTEA), based on the field reorientation property of nematic liquid crystals and robust valley-protected edge modes. FPTEA is composed of an array of graphene-like lattices with C3 symmetry, in which the birefringence of liquid crystal is larger than 0.5105. Due to the dielectric anisotropy of liquid crystals being sensitive to external fields such as light, heat, electric, and magnetic fields, each lattice is tunable, and the topological propagation routes and even the lattice parameters can be dynamically changed while changing the distribution of external fields. We numerically demonstrate three methods of composing an FPTEA device to design arbitrary passive optical devices by electric driving, thermal inducing, or UV writing. These results show the great application potential of liquid crystals in topological photonic crystals, and enrich the design of programmable integrated topological devices with broad working bandwidth ranging from microwave to visible light.

Design of compact two‐port dual‐band dual‐polarized MIMO antenna for CBRS and WLAN sub‐6‐GHz applications

SummaryThis communication presents a compact field de‐correlation lines integrated dual band with dual‐polarized (LP &amp; CP) multiple‐input multiple‐output (MIMO) antenna for the fifth generation (5G) sub‐6‐GHz wireless communication systems. Dual working bandwidths, smaller interelement gaps, and superior isolation within the MIMO components are the distinguishing characteristics that give the proposed MIMO system an aspect of novelty. The modeled MIMO antenna has compact configurations of 20 × 21 × 0.8 mm3. The unit cell consists of a microstrip feed line with optimized rectangular slots branches etched from the radiated patch. The MIMO module is generated by the antiparallel replication of a single unit cell. To enhance the isolation, two rectangular slots are incorporated on the patch between the unit elements, which act as field de‐correlation lines. The MIMO identity is supported by diversity performance calculations in terms of ECC, DG, and TARC. Simulated and measured counterparts are found in the agreement.

Spherical Magnetoelastic Generator for Multidirectional Vibration Energy Harvesting.

Vibration is a common, usually wasted energy, and an attractive target for sustainable electricity generation. In this work, we introduce a new working mechanism to the vibration energy harvesting community by contributing a spherical magnetoelastic generator (S-MEG), which permits multidirectional vibration and is highly adaptable to many natural oscillation frequencies, exhibiting a resonant frequency of 24 Hz and a relatively wide working bandwidth of 15 Hz in the low-frequency range. It also features a low internal impedance of 70 Ω, which can respectively deliver a maximum short-circuit current density of 7.962 A·m-2 and a power density of 15.1 mW·m-2. To demonstrate the capability of S-MEG for ambient vibration energy harvesting, a 220 μF commercial capacitor was successfully charged to 2 V within 25 s, sustainably driving wearable bioelectronics for multiple physiological information monitoring. It could also harvest multidirectional vibration energy from both hand-shaking and bicycle-riding, generating approximately 2.5 mA and 6 mA alternating current from the motions, respectively, even with heavy perspiration or on a rainy day without the need for encapsulation. In summary, this work brings forth an appealing platform technology to the community of vibration energy harvesting, holding a collection of compelling features, including high current density, low inner impedance, intrinsic waterproofness, and scalability for large-scale vibration energy harvesting.

Bandwidth Enhancement of Slot Antenna Using Fractal Shaped Isosceles for UWB Applications

In this paper, a coplanar waveguide (CPW) fed slot antenna using fractal-shaped isosceles trapezoidal corrugations is designed and presented for Ultra-Wideband (UWB) applications. The proposed antenna is formed by a regular hexagonal patch fed through a CPW feed line and radiates amidst a notched wide hexagonal slot. The edge of the wide slot is shaped by a fractal structure that is formed by five trapezoidal notches. The antenna is printed on RO4350B substrate having a compact size of 0.305λ0 × 0.313λ0 × 0.012λ0 at 2.35 GHz. . Good agreement is registered between the experimental results of the fabricated prototype and the calculated ones. By using an Agilent 8722ES vector network analyzer, the fabricated prototype confirms that the antenna has an excellent matching impedance over the bandwidth 2.35-10.65 GHz (127%) which covers the entire UWB band. Furthermore, good radiation performances are measured in an anechoic chamber. Consistent radiation patterns with a reasonable peak gain are measured over the entire working bandwidth. Therefore, the designed structure may be worthily considered for different wireless communications systems.

1 × 5 broadband photonic crystal power splitter designed by the Powell algorithm.

We propose a novel, to the best of our knowledge, 1×5 broadband power splitter based on the photonic crystal. The Powell algorithm is used to reverse-design the proposed broadband power splitter. The results show that the transmittance of each output port of the broadband photonic crystal power splitter can be adjusted by changing the radii and offsets of the dielectric rods at the junction area of each waveguide. According to the target splitting ratio, the reverse design of the structural parameters using the Powell algorithm significantly improves the optimization efficiency and splitting performance of the broadband power splitter. The designed power splitters have a wide working bandwidth of 1525-1565 nm, a flexible and designable power splitting ratio, excellent splitting performance, and a compact size, which have great application prospects in all-optical communication networks, high-density photon integration, and other fields.

A 2.5D low-profile wideband frequency selective structure with high-selectivity performance

In this paper, a low-profile high-selectivity 2.5D FSS based on the dislocation patch structure is proposed and discussed. The dislocation patch structure is used to construct the low-profile transmission line, and a second-order band- pass FSS with a controllable transmission zero is realized by introducing a series LC structure to the dislocation patch structure. The effects of the geometrical parameters on the frequency response of the proposed second-order bandpass FSS are analyzed based on the transmission matrix method and the equivalent circuit simulation. Then, two proposed second-order bandpass FSSs with different transmission zeros are combined and placed crossly to construct two propagation paths, and a high-selectivity third-order FSS is obtained. Finally, the prototype is fabricated and measured to prove the effectiveness of the proposed FSS. The measured results show that the proposed high-selectivity FSS has a wide working bandwidth, proper selective performance, and a thinner profile than other high-selectivity 2D/3D FSSs.

A bistable energy harvester with low base-acceleration and high root mean square output for train bogies: theoretical modeling and experimental validation

Energy harvesting provides potential power solutions for distributed sensors in rail transportation condition monitoring. However, reported harvesters have low efficiency and a narrow working bandwidth for rail transportation condition monitoring scenarios. An energy harvester is developed in this paper that has a higher energy output efficiency and a wider working bandwidth. The harvester is suitable for train monitoring scenarios. The key novelty lies in the combination of a spherical moving magnet and a cylindrical moving magnet to give a spherical–cylindrical coupled moving magnet, which not only maintains the advantage of low friction but also improves energy conversion efficiency. Furthermore, analytical models are established to describe the dynamics of the harvester with different moving magnets (spherical, cylindrical, spherical–cylindrical coupled), and a theoretical framework is established to guide the design. The theoretical model is validated by developed prototypes and experimental results. The working bandwidth of the energy harvester with a spherical–cylindrical coupled moving magnet is 9.5–45.1 Hz at 2g and the output power reaches 18.2 mW at 40 Hz and 1200 Ω load. Compared with traditional energy harvesters with cylindrical and spherical moving magnets, the base excitation is lower and the normalized output power is higher. Thus, this energy harvester is more suitable for train monitoring scenarios.

Optical Transparent Broadband Antenna Array Integrated With Polycrystalline Silicon Solar Cells

This letter presents a 4 × 4 transparent broadband single-arm spiral antenna array integrated with polycrystalline silicon solar cells (PSSCs). For the sake of appraising the antenna, a kind of multilayer structure is established, enabling the PSSCs and single-arm spiral antenna array to combine perfectly, which has little influence on antenna performance and solar cell efficiency. The employment of the transparent substrate and meshed antenna increases the optical transparency to 92%. By adopting this kind of structure, the antenna array can achieve a working bandwidth of 1.26–3.2 GHz (2.54:1) and the highest gain of 19.4 dBi. This circularly polarized antenna array can realize wide working bandwidth, high gain, and high optical transparency while being well integrated with solar cells.

Experimental research of a dual-beam compressive-mode piezoelectric energy harvester

In this article, we present a dual-beam compressive-mode piezoelectric energy harvester (DC-PEH). The DC-PEH is made up of a force amplifier, a piezoelectric stack, and a pair of symmetrically arranged cantilever-mass systems, supported by a base that is fixed on a rod. A two-stage force amplification mechanism of the DC-PEH is realized by coupling the elastic beams with the force amplifier. We first established a force analysis to describe the two-stage force amplification effect of the DC-PEH. Furthermore, a prototype has been fabricated and we carried out a series of experiments. We examined the open-circuit voltage and working bandwidth of the DC-PEH to verify the two-stage force amplification effect under different accelerations. Moreover, a parametric study was performed to investigate the influence of structure parameters on the output performance of the DC-PEH. We conducted the frequency sweep response and power output comparisons with different lengths of beams and different masses.

A Metal Solar-Cell Phased Array Antenna

This study proposes a metal solar-cell phased array antenna of 36 units with a rectangular grid, which is composed of leaf-shaped metal radiators, feeding and ground probes, a solar cell, and a metal ground. The metal leaf-shaped radiators are vertically welded on the metal ground through feeding and ground probes. The solar cell is located on the metal ground of the antenna, and 36 holes are dug to ensure that the feeding probes and the ground probes can pass through the solar cell without connection. The radiators are hollowed out to reduce the shadow area on the solar cell from sunlight. We have fabricated a sample of the solar-cell antenna and further measured the electromagnetic characteristics and its power output performance. The measured results agree with the simulated results well. The proposed solar-cell phased array antenna has a wide working bandwidth of 3–5 GHz, a wide 2-D phase scanning angle of ±45°, a high aperture efficiency of 74.1%–86.9%, and a high average relative maximum output power ratio of 96.2% compared with the same pure solar cell. This metal solar-cell phased array antenna is scalable and can be used for CubeSats.

High quality of LiMg0.9Zn0.06Ni0.04PO4-TiO2 microwave ceramic and its application for 5G dielectric waveguide bandpass filter

A new microwave dielectric composite ceramic (1-x) wt%LiMg0.9Zn0.06Ni0.04PO4-x wt%TiO2 (0 ≤ x ≤ 18 wt%) was synthesized in the low sintering temperature range of 850 °C − 975 °C by the solid-state reaction method. The XRD diffractogram confirmed the coexistence of LiMg0.9Zn0.06Ni0.04PO4 and TiO2, and no second phase was detected. Due to their opposite τf values, the τf values of LiMg0.9Zn0.06Ni0.04PO4 solid solution ceramics were adjusted by adding different volume fractions of TiO2. The composite ceramic with x = 15 wt% sintered at 975 °C shows desirable microwave dielectric properties of εr∼10.30, Q×f ∼ 58,400 GHz (tan δ = 2.093 ×10−4), and τf ∼ + 4.04 ppm/ °C (at ∼12 GHz). Based on the 85 wt% LiMg0.9Zn0.06Ni0.04PO4-15 wt% TiO2 ceramics, a fourth order dielectric waveguide filter filled with composite ceramics is designed and packaged for the RF front-end of the China Mobile 5 G base station. The test results show that the center frequency of the filter is 4.65 GHz, the working bandwidth is 300 MHz, the filter has a good out of band rejection capability, and the insertion loss in band is 0.18 dB. Combined with the filter test data and material performance, the designed dielectric waveguide filter meets the communication requirements of the base station, and the higher Q×f microwave dielectric ceramic material can achieve low insertion loss and excellent frequency selection performance of the filter.

Enhanced performance of piezoelectric energy harvester by two asymmetrical splitter plates

This paper proposes a novel vortex-induced vibration piezoelectric energy harvester attached to two asymmetrical splitter plates (VIVPEH-S), which aims at converting the vibration mode from vortex-induced vibration (VIV) to galloping and improving the energy harvesting efficiency. The conceptual designing of VIVPEH-S with two asymmetrical splitter plates under various installation angles is first conducted, the experimental prototypes are then fabricated and the wind tunnel experimental system is constructed, and the simulation model of the harvester system is finally established. The effects of the installation angles of two asymmetrical splitter plates on the vibration characteristics and harvesting performance of VIVPEH-S are experimentally investigated, and the vortex shedding characteristic and mode conversion mechanism are revealed by CFD simulation. The results demonstrate that the installation of the asymmetrical splitter plates changes the vortex shedding characteristics and transforms the vibration mode from VIV to galloping, which can significantly broaden the working bandwidth, and improve the energy harvesting performance. A maximum enhancement ratio of the output power of VIVPEH-S with α = 60° and β = 90° is up to 471.2% over the conventional VIVPEH. This work provides an important foundation for designing a more efficient piezoelectric energy harvester by using asymmetrical splitter plates.

Ultra-wideband circularly polarized millimeter wave antenna based on adjacent coupled feed

ABSTRACT In order to improve the performance of 5 G Millimeter wave, a new gap-coupled fed ultra-wideband circularly polarized antenna is proposed. Firstly, by fabricating the top structure of the slot antenna ，a C-shaped patch structure can adjust the surface transverse current as well as the longitudinal current to generate circularly polarized waves; then the feed structure at the bottom layer of the antenna is designed and resonance is generated with the top layer of the antenna to expand bandwidth. From the simulation and the measurement results can know that the −10 dB impedance bandwidth of the antenna is 19.21 GHz−45.50 GHz (81.25%); the 3 dB circularly polarized axial ratio (AR) bandwidth is 20.59 GHz−38.33 GHz (60.2%), with ultra-broadband circular polarization performance. The designed antenna has a simple structure, small size, low profile and wide working bandwidth, which can fully include N257, N258 and N261 bands, and has a good application prospect in 5 G communication.

DOUBLE-LAYER METAMATERIAL PATCH ANTENNA WITH ENHANCED GAIN AND DIRECTIVITY

A double-layer metamaterial with epsilon-near-zero (ENZ) properties is proposed loading on the patch antenna. The double-layer metamaterial that has two layers of the same material and structure is produced on FR4 substrate. The gain and radiation directivity of the patch antenna can be greatly improved covering with the proposed ENZ metamaterial. Simulation results show that by coating the ENZ superstrate, the gain of the patch antenna is increased from 5.99 dBi to 10 dBi, corresponding to 66.9&amp;#37; gain enhancement and greatly improved radiation directivity. While the performance of the patch antenna is improved, the working frequency and bandwidth of the patch antenna are not affected.