In this study, a sandwiched titanium-on-glass (TOG) substrate was used to fabricate laterally driven microelectromechanical systems devices with bulk titanium as the structural material. 4'' TOG wafers with a titanium device layer of 25 µm were fabricated by low temperature SU-8 wafer bonding and chemical mechanical polishing. By using inductively coupled plasma for titanium deep etching as well as dry release, suspended high-aspect-ratio bulk titanium structures were realized with only one mask. A laterally driven electrostatic comb-driven bulk titanium resonator was manufactured as a preliminary demonstration. The resonator achieves a quality factor of 110 at 34 kHz, and survived 10 000 g shock without damage. Due to the high mechanical endurance and excellent corrosion resistance of titanium, TOG technology may open up many new applications in harsh environments.
In this paper, we proposed a broadband circularly polarized antenna with wide beamwidth. The main structure of the proposed antenna is a combined cross-polarized dipole antenna with four metal arms feeding by a single coaxial cable and two 90° phase delay lines. In order to attain a wide beamwidth antenna performance that can be used in a warehouse environment, we innovatively bent the metal arms and added a metal plane at a specific location to gain maximum beamwidth and the highest achievable gain. Especially, the application of folded metal arms not only reduce the space size of antenna, but also possess good axial ratio characteristic. The measurement illustrates that the antenna prototype achieves S 11 < -10 dB impedance bandwidth (IBW) of 40% (820 - 1230 MHz), a 3-dB axial ratio bandwidth (ARBW) of 7.3% (895 - 970 MHz), and a maximum half-power beamwidth (HPBW) of 104° (@915 MHz). In addition, the good radiation characteristics of a gain of 6.33 dBic and an average radiation efficiency of 76.3% were measured in the operating bandwidth, in which make the antenna a good candidate for the hasty logistics radio frequency identification (RFID) system.
Thin-film lithium niobate (TFLN) modulators are expected to play a key role in next-generation optical communication systems. In this work, we present the design, fabrication, and characterization of a TFLN Mach-Zehnder modulator (TFLN-MZM) with high extinction ratio (ER). The fabricated modulator has achieved the ER of 41 dB by integrating a waveguide polarizer, an intentional input-output waveguide misalignment, and a Mach-Zehnder interferometer (MZI) structure composed of 1 × 2 multimode interferometers (MMIs). The polarization extinction ratio (PER) of this integrated waveguide polarizer is 38 dB, effectively filtering out all polarizations except the transverse electric (TE) mode. The measured half-wave voltage ( V π ) for the fabricated modulator with a modulation arm length of 3.3 mm is 7.9 V, corresponding to a voltage-length product of 2.6 V·cm. The proposed modulator improves the extinction ratio without the need for additional control circuits, and thus it has wide applications in optical communication, quantum key distribution, lidar, fiber-optic distributed acoustic sensing (DAS), etc.
This review systematically outlines the development of photocatalytic lignin conversion, critically reviews the advantages and limitations of photocatalytic systems from the key studies, highlights key challenges and future perspectives.
In this paper, we analyze the microstrip phase delay (PD) lines of different lengths are applied between the unit-cells (UCs) of leaky-wave antenna (LWA). The employment of PD lines can offer the phase compensations (PCs) for each UC, the simulation experiments observed that the PD lines can significantly improve the realized gain of LWA and reduce the operating bandwidth due to longer PD lines exciting the higher order modes of phase constant. Therefore, the scanning rates (SRs), i.e., scanning range divided by operating bandwidth (%), can remarkably increase. Besides, in order to maintain the beam scanning ability of LWA in travelling-wave direction (or longitudinal direction), the PD lines are placed and varied in the lateral direction. The phase constants in the lateral direction component are also proven to be able to excite higher order modes. Benefit from this, the multi-beam LWAs in the lateral direction can be obtained by the PD lines with optimal lengths, and patterns of multi-beam are fixed with the operating frequency changing.
A compact circularly polarized (CP) planar spiral antenna with ultrawide bandwidth and directional radiation pattern is proposed for ultra‐wideband (UWB) positioning applications. The proposed antenna consists of a dual‐arm planar spiral with a tapered microstrip line, two L‐shaped metallic shorting stubs, and a square ground plane with four stepped slots. By connecting two L‐shaped metallic stubs to both the ends of the dual‐arm spiral through metal posts, the traveling wave current path is effectively extended, resulting in a significant improvement of the CP bandwidth. Additionally, both impedance bandwidth and circular polarization performance of the proposed antenna can be enhanced by adopting four stepped slots on the square ground plane. Measured results show that the planar spiral antenna features an impedance bandwidth from 3.23 GHz to 7.0 GHz (more than 73.7%), a 3‐dB axial ratio (AR) bandwidth of 62.1% (3.05 GHz–5.8 GHz), and finally achieves an overlapping bandwidth of 56.9% (3.23 GHz–5.8 GHz). On the overlapping bandwidth, this antenna maintains a gain consistently above 6 dBic while the peak gain reaches about 7.4 dBic. The overall size of the antenna is 0.59 λ g × 0.59 λ g × 0.17 λ g ( λ g is the free‐space wavelength at the lowest frequency, 3.23 GHz). Thanks to the ultrawide CP bandwidth and compact size, the proposed antenna can be a promising candidate for UWB positioning applications.
A slow-wave half-mode substrate integrated waveguide with a spoof surface plasmon polariton (SW-HMSIW-SSPP) transmission line structure is proposed, analyzed, and demonstrated. Results show longitudinal and lateral size reductions of more than 80% and 7 3 %, respectively, as compared with an equivalent SIW at the same cutoff frequency while maintaining a low attenuation constant of 0.02 dB/mm. By altering the geometric parameters of the SW-HMSIW-SSPP the dispersion curve can be tailored. The dispersion and electromagnetic (EM) field distribution characteristics of the proposed SW-HMSIW-SSPP unit cell and overall structure are analyzed by HFSS simulations and an equivalent circuit, and pertinent performance parameters are compared to those of SW-HMSIW and HMSIW-SSPP structures. A proof-of-concept PCB SW-HMSIW-SSPP sample was fabricated, and measurement results showing a band-pass of 4.8-11.5 GHz are found consistent with simulation results. The SW-HMSIW-SSPP structure has applications in the design of miniaturized microwave circuits.
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