The design and numerically investigation of a silicon polarization splitter (PS) is proposed using triple-tapered directional couplers (DCs).The proposed device consists of a triple-tapered DC, a ...triple-bent DC at through port, and a tapered waveguide at cross port. The coupling length of the device is 20.5 µm. At the 1550 nm wavelength, the realized PS exhibits the extinction ratio (ER) values of 35.7 dB and 37.35 dB as well as the insertion loss values of < 0.58 dB and < 0.4 dB for the TE and TM polarization modes, respectively. Furthermore, the device’s bandwidth for ER > 20 dB and ER > 25 dB are 170 nm and 136 nm, respectively.
10¹²) for FeRAM Applications Walke, Amey M; Popovici, Mihaela I; Sharifi, Shamin H ...
IEEE electron device letters,
01/2024, Letnik:
45, Številka:
4
Journal Article
Recenzirano
70% of the initial polarization at the end of Formula Omitted and ~30% polarization is projected to remain at the end of 10 years. The retention was found to be limited by the imprint effect. Our ...demonstration brings HZO based FE capacitors one step closer to nonvolatile FeRAM applications.
A multifunctional reconfigurable metasurface based on liquid metal injection is presented. The reflective flexible material metasurface formed by two switchable microfluidic layers- the top layer ...comprising an array of meandered half-rings and the lower layer, straight meander lines-can be reconfigured into four states. The proposed metasurface becomes a reflector with emptied channels, whereas it exhibits linear-to-circular polarization conversion (or linear-to-cross-polarization conversion) properties when the top (or bottom) layer is filled with a liquid metal alloy. Upon normal excitation of linearly u/v-polarized waves and activation of the bottom layer, the metasurface reflects cross v/u-polarized waves in the frequencies from 9.83 to 17.42 GHz (53% bandwidth) with a polarization conversion ratio (PCR) of at least 90%. On the other hand, the metasurface operates as a linear-to-circular polarizer (for u/v-polarized waves) over 8.97-11.30 GHz (23% bandwidth), reflecting left- or right-hand circularly polarized waves. To verify the polarization conversion performance, a <inline-formula> <tex-math notation="LaTeX">25\times 25 </tex-math></inline-formula> element metasurface array is fabricated and measured. The experimental results confirm the simulation results over the 8-12 GHz test band. The compactness, structural flexibility, and multifunctionality of the proposed metasurface make it a suitable candidate for modern integrated antenna array systems.
Based on characteristic mode theory (CMT), a quad-polarization reconfigurable antenna with suppressed cross polarization is proposed in this article. The proposed antenna is composed of the radiator, ...excitation units, and feeding network. A square conductive slab (SCS) is used as the main radiator, which is designed elaborately by characteristic mode analysis (CMA). Different modes of the radiator are stimulated selectively by four groups of balanced inductive exciters (BIEs) to realize horizontal polarization (HP), vertical polarization (VP), left-hand circular polarization (LHCP), and right-hand circular polarization (RHCP). Two p-i-n diodes are embedded into the feeding network to switch the excitation states of the four groups of BIEs, thereby achieving quad-polarization reconfiguration. More importantly, a novel method exploiting the CMA is adopted for achieving low cross polarization. By means of introducing the orthogonal mode, the cross-polarization component of the fundamental mode can be canceled out by the co-polarization component of the orthogonal mode, which greatly reduces the cross polarization from −10 to −40 dB in the two principal planes. The measurement results demonstrate that the quad-polarization agility and a cross-polarization level around −30 dB under all polarization states are achieved simultaneously, verifying the functionality and reliability of the proposed method.
A novel metallo-dielectric Huygens' unit cell is proposed that can be designed to operate either as a quarter-wave plate (QWP) or as a half-wave plate (HWP). The unit cell is based on a single-layer ...perforated dielectric, with straight (non-metallized) and 45° (metallized) elliptical holes. The novelty of the unit cell is its suitability for millimeter-wave implementation in printed-circuit board (PCB) fabrication due to the absence of metallic patterns of small line widths and gaps. As an example of their applicability, the wave plates are demonstrated in the near-field of 60-GHz band diffusion-bonded slot array antennas. The unit cell operating as a QWP is demonstrated in full-wave simulations and experimentally for linear-to-circular polarization conversion, whereby the combination of a linearly-polarized (LP) antenna and the QWP produces a circularly-polarized (CP) wave. Measurement results of the antenna and the QWP show ≤ -10-dB reflection from 59 to 63 GHz (6.6%), ≤ 3-dB axial ratio from 59.5 to 61.5 GHz (3.3%), and an overall efficiency ≥ 77% from 59.5 to 61.5 GHz. The unit cell operating as a HWP is demonstrated in full-wave simulations for polarization rotation of the LP antenna, and for changing the sense of rotation of a right-hand CP antenna into left-hand circular polarization.
The so-called “negative difference effect” (NDE) exhibited by corroding magnesium (Mg) surfaces, where the rate of hydrogen evolution increases with the extent of anodic polarization, has been well ...documented. Recently this behaviour has been explained by a theory involving an increase in the cathodic exchange current density that occurs during anodic polarization, rather than the popular theory involving the formation of a univalent Mg+ ion and its subsequent chemical reaction with water to produce hydrogen. The present study reports on the results of transmission electron microscopy (TEM) conducted on focused ion beam (FIB) prepared cross-section lamellae of the dark film formed on a corroding area of a Mg surface from which hydrogen evolved. The film was found to consist of an outer columnar mixed magnesium oxide-hydroxide layer on top of a magnesium oxide-rich inner layer. X-ray energy dispersive spectroscopy (EDS) reveals iron (Fe)-rich particles embedded in the columnar outer layer. Subsequent cathodic polarization measurements showed that the corroded surface became cathodically activated relative to a non-corroded surface. These observations demonstrate that a surface film enriched in more noble metals can catalyze the cathodic process, provide physical evidence towards support of the enhanced catalytic surface theory explaining the NDE, and validate the chemistry and structure of the surface film that forms upon corroding regions during anodic polarization.
This paper introduces a novel polarization-mixing strategy to significantly widen the beamwidth of dual-linear-polarized antenna arrays without changing the array topology. Instead of using the two ...polarizations separately as usual, it blends the orthogonal linearly-polarized radiations to achieve wider beamwidth. The proposed method is implemented on a typical ±45°-polarized base station antenna array with its thought process and working mechanism elaborated. Much wider beamwidth is achieved compared to the traditional pattern synthesis methods based on amplitude and phase weighting or sparse arrays. The beamwidth can be controlled by simply tuning one phase shifter. Importantly, this method allows all the elements to be fully excited with the same amplitude, thus avoiding using additional amplifiers or attenuators. In the meantime, the polarization-mixing method leads to spatially-variable polarizations (SVP). To obtain polarization diversity required in cellular communication systems, two SVP arrays with the same pattern shapes are designed to have their polarizations orthogonal to each other in all directions of interest. The conditions of achieving orthogonal patterns using this method are theoretically derived and thoroughly validated in theory and in simulation. It is shown that the obtained spatially-variable-orthogonal-polarization (SVOP) arrays have a much broader beam pattern and better polarization orthogonality (PO) than that of the dual-polarized antenna element.
In this paper, a wideband stacked patch antenna array composed of four linearly polarized antenna elements is proposed for the implementation of four polarization reconfigurable states, i.e., ...vertical linear polarization (LP), horizontal LP, left-hand circular polarization, and right-hand circular polarization. A double-layer structure, including a driven substrate integrated waveguide (SIW) cavity and four parasitic radiation patches, is used to develop the wideband antenna element. The parasitic radiation patches are excited by etching a ring slot on the top surface of the SIW cavity, which has two diagonal ports fed by grounded coplanar waveguide lines. A 180° phase-shifting is achieved for polarization reconfigurable applications by individually feeding the antenna element with the two diagonal ports. A prototype operating at 5.7 GHz is fabricated and tested for the demonstration of the polarization reconfigurable capability. The measured results show that both the 10-dB impedance bandwidths and the 3-dB axial ratio bandwidths are wider than 5.19-6.1 GHz for the linear and circular polarization states. The measured maximum gains of the antenna array are 9.85 dBic and 10.1 dBi for the circular polarization states and the LP states, respectively. Experimental results show good agreement with simulated results, which indicate a good performance of the proposed patch antenna array.
PDF
