This article initially proposes a directly‐fed circular patch antenna with L‐shaped ground plane for Radio Frequency Identification (RFID) applications in the 900 MHz (902−928 MHz) ultrahigh frequency (UHF) band. To achieve circularly polarized (CP) radiation, two arc‐shaped notches are loaded into the main patch. To enhance the CP bandwidth so that the proposed antenna can also cover the UHF RFID band for Europe (866−869 MHz), a parasitic element is printed besides the main patch. Experimental measurements show that the 10‐dB return loss bandwidth of the proposed antenna was 30.95% (833−1138 MHz) and its corresponding 3‐dB axial ratio bandwidth was 8.95% (865−946 MHz). Good gain and radiation efficiency of more than 7 dBic and 90%, respectively, were also exhibited across the two desired UHF RFID bands. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:681–687, 2015.
This paper reports a novel method for fabricating a monolithic inkjet chip by combination of thick resist photolithography and electroforming technologies. It integrates two-step photolithography process by two kinds of thick photoresists, SU-8 and JSR, and one-step nickel electroplating process to form the channels, chambers and nozzles of monolithic inkjet chip. The nickel nozzle plate can be replaced by SU8 material as second thick SU8 resist is used. The first thick resist of SU8 for both kinds of nozzle plates, nickel and SU8, is used for the structure formation of ink channel and chamber. Followed the nickel or SU8 nozzle plates are fabricated on SU8 chambers. The nickel nozzle plate is performed by second thick resist JSR and electroforming process while the SU8 nozzle plate is only by second thick SU8 resist process. A lightabsorbing polymer layer is coated between two thick resist layers for protecting the first SU8 layer from overheating during the metal seed layer deposition or over-exposure during the second thick resist lithography process. A prototype of monolithic inkjet chip with a 300 dpi resolution has been successfully demonstrated. IntroductionInkjet technology has been widely used in the fields of printing, packaging, bio microarray, optoelectronics and so on. The conventional inkjet chip needs complex alignment and bonding process to stick the nozzle plate and heating chip together [1]. It takes long time, high cost and much lower alignment resolution. Some monolithic inkjet chips [2-7] fabricated by the MEMS technology can improve the above drawbacks but suffer in the high temperature sealing process or back-shooting nozzle membrane broken during processes. Chen et al.[2] used the method of anisotropic wet etching and chemical vapor deposition (CVD) sealing process to form the side-shooting nozzle plate. It requires the CVD high temperature process and the strength of sealed Si-based nozzle plate is a challenge. Westberg and Andersson [3] used CMOS process in combination with bulk etching and aluminum sacrificial etching to fabricate a monolithic CMOS compatible inkjet chip. However, the device was rather fragile and hard to handle during the process. Lee et al. developed two fabrication methods for the top-shooting nozzle plate: first, two-step electroplating process [5] and secondly, multiexposure and single development (MESD) and nickel electroplating process [6]. The latter method could improve the morphology and yield of the former. MESD process utilized single photoresist and two-mask exposure with different UV light dosage to control the thickness of channel and nozzle plate. But the problem is light dosage to control the thickness of channel and nozzle plate by one photoresist generally suffering the relationship of thickness and dosage with abrupt variation at some thickness range [8] or with less accuracy than that controlled by spin speed of two photoresists for the thickness of channel and nozzle plate respectively. In this paper, we combine the thick resist and electroforming t...
The choices of substrates for lithium microbatteries or thin-film batteries have been limited by the high annealing temperatures, which are generally required in the fabrication of polycrystalline thin-film cathodes. In this paper, a plasma-assisted technique was developed for the low temperature fabrication of polycrystalline lithium transition-metal oxides as thin-film cathodes. The thin films were deposited by magnetron sputtering, followed by thermal annealing, and plasma treatments. By applying the plasma treatments, polycrystalline films of LiCoO 2 , LiMn 2 O 4 , and LiFePO 4 were obtained under relatively lower annealing temperatures ͑Ͻ400°C͒. The low temperature prepared films with/without plasma treatments were compared in terms of morphologies, crystal structures, and electrochemical performances. The plasma treatments lifted the discharge voltages and increased the capacity of the low temperature prepared films. The results demonstrated the feasibility of fabricating thin-film batteries on polymers or glass substrates, which generally can only endure temperatures lower than 400°C.Minimization is the ultimate target of the next generation of batteries. Batteries of low weight, small volume, and high energy density have always been pursued by both industries and academia. The concepts of thin-film batteries or all-solid-state microbatteries are therefore of great interest. Although the choices of cathode materials strongly depend on the electrolyte nature and stability, the conventional cathode materials, such as LiCoO 2 , LiMn 2 O 4 , and LiFePO 4 , of lithium/lithium-ion batteries have been candidates for the cathodes of microbatteries. The minimization of lithium batteries is best achieved by thin-film technologies, such as sol-gel 1-3 and sputtering 4-6 techniques. The thin-film cathode materials are characterized by three main categories: 7-10 ͑i͒ layered oxides composed of hexagonal close-packed oxygen atom networks with lithium and transition-metal ions on alternating ͑111͒ planes, such as LiCoO 2 , LiNiO 2 , and LiCo x Ni 1−x O 2 ; ͑ii͒ spinels composed of threedimensional octahedral and tetrahedral frameworks, such as LiMn 2 O 4 ; and ͑iii͒ polyanion compounds composed of tetrahedral anion mainframes, such as LiFePO 4 . There have been many papers regarding the preparation of these thin-film cathodes. However, most of them showed that post or in situ high temperature annealing is inevitable to fabricate well-crystallized thin-film cathodes. 1-8 Although amorphous or nanocrystalline thin films were also used as cathode materials, 11 they generally exhibit a low specific capacity and sloppy discharge plateau compared with their polycrystalline counterparts. Reducing the processing temperatures of the thin-film cathodes is therefore a great manufacturing challenge.In the present work, a plasma treatment technique is developed. The plasma treatment improves the performance of the low temperature deposited lithium transition-metal oxide thin films. ExperimentalThe thin films of LiCoO 2 , LiMn 2 O 4 ,...
FeSiCr alloy (Fe: 90%, Si: 7.9%, and Cr: 2.1%) with pre-milled flaky shape was re-milled in a planetary ball-mill for 30 h. The complex permittivity (ε′−jε″) and permeability (μ′−jμ″) are measured by using the transmission/reflection method for two different aspect ratios of flake-shaped FeSiCr/epoxy composites for 30%, 40%, and 50% weight ratios. Dielectric loss tangent and magnetic loss tangent of re-milled FeSiCr powder show larger electromagnetic wave energy dissipation than those of the raw flaky FeSiCr powder. For 30 wt. % of FeSiCr/epoxy absorbers with 2 mm thickness, the calculated reflection loss reaches −25 dB at 13.0 GHz for raw flaky powder, −40 dB at 11.4 GHz for the re-milled FeSiCr powder with higher aspect ratios.
A wide-stopband Wilkinson power divider (WPD) is proposed, which can be realised by using open dual-transmission line (TL) stub and L-type artificial lowpass TL structures. To further achieve miniaturisation, synthetic TLs are also employed. The simulated and measured results are consistent, and the measured |S 21 | and |S 31 | (insertion losses) have shown stop-bandwidth of larger than 18.33 GHz (1.67-20 GHz) and 18.28 GHz (1.72-20 GHz), respectively, under the condition of 30 dB harmonic suppression level. The wide-stopband of the WPD can cover 2f o-22.2f o (f o = 0.9 GHz), and the occupied area of the WPD (not include the feeding network) is only 0.11λ g × 0.06λ g (λ g : guided wavelength at f o).
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