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Broadband Circularly Polarized Filtering Antennas
摘要： This paper consists of two parts. The first part presents a review of the recent development in broadband circularly polarized filtering antennas. The second part presents a novel design of broadband integrated filtering antenna based on eighth-mode SIW (EMSIW) resonators for rectenna applications. This work has three main novel contributions: (i) By adjusting the external quality factors and coupling coefficients of the resonators in this filtering antenna, optimum input impedance with a complex value can be realized within the filtering antenna. Thus there is no need for an external impedance matching network, which is usually required between the antenna and the rectifying circuits; (ii) Compared with traditional microstrip resonators, high-Q EMSIW cavities are used to increase antenna gain; (iii) The coupling gap between the EMSIW resonators also acts as the feeding structure of the radiator. So the feeding structures are all on the middle layer. The ground plane on the back side is a complete structure without any defects. This novel structure design improves front-to-back ratio to enhance the antenna receiving efficiency. To validate this method, two C-band circularly polarized integrated filtering antennas with an input impedance of 50 Ω and complex impedance are designed, simulated and fabricated. The measured results show that the operating frequency bandwidth of the proposed antennas is more than 14.5% at C band with the gain above 8 dBi. The 3 dB Axial Ratio (AR) bandwidth is larger than 8.5% and the front-to-back ratio is higher than 18 dB. Moreover, the proposed antenna with complex impedance is conjugate matched with the input impedance of a specific rectifying circuit at 5.8 GHz and harmonics suppression at the 2nd harmonic frequency is achieved.
关键词： filtering antenna,Broadband antenna,circularly polarized antenna,impedance match,rectenna
更新于2025-09-09 09:28:46
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Theoretical Analysis of Moving Reference Planes Associated with Unit Cells of Nonreciprocal Lossy Periodic Transmission-Line Structures
摘要： This paper presents a theoretical analysis of moving reference planes associated with unit cells of non-reciprocal lossy periodic transmission-line structures (NRLSPTLSs) by the equivalent bi-characteristic-impedance transmission line (BCITL) model. Applying the BCITL theory, only the equivalent BCITL parameters (characteristic impedances for waves propagating in forward and reverse directions and associated complex propagation constants) are of interest. An infinite NRLSPTLS is considered first by shifting a reference position of unit cells along TLs of interest. Then, a semi-infinite terminated NRLSPTLS is investigated in terms of associated load reflection coefficients. It is found that the equivalent BCITL characteristic impedances of the original and shifted unit cells are mathematically related by the bilinear transformation. In addition, the associated load reflection coefficients of both unit cells are mathematically related by the bilinear transformation. However, the equivalent BCITL complex propagation constants remain unchanged. Numerical results are provided to show the validity of the proposed theoretical analysis.
关键词： bilinear transformation,Unit cell,periodic transmission-line structure,bi-characteristic-impedance transmission line (BCITL)
更新于2025-09-09 09:28:46
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COMPACT TRI-BAND BANDPASS FILTER BASED ON HYBRID RESONATOR WITH IMPROVED SELECTIVITY PERFORMANCES
摘要： A novel microstrip tri-band bandpass ?lter is proposed and implemented using hybrid resonator with independently controllable center frequencies and good in-between isolation. This hybrid resonator is constructed by a stepped-impedance stub resonator and a single end shorted resonator. The stepped-impedance stub resonators are applied to achieve the ?rst and second passband, while the third passband is implemented by single end shorted resonators. By applying the even-odd mode approach, the resonance frequency ratio between even mode and odd mode inside the stepped-impedance stub resonators is attained. Furthermore, the ?lter with multi-path coupling structure can generate the transmission zeros at the edge of the passband, which can e?ectively improve the ?lter passband selectivity. Finally, a tri-band ?lter operating at 1.91, 2.73, and 3.45 GHz is designed and fabricated. The measurement results accord well with the full-wave electromagnetic designed responses.
关键词： single end shorted resonator,multi-path coupling structure,hybrid resonator,tri-band bandpass ?lter,stepped-impedance stub resonator
更新于2025-09-09 09:28:46
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SYNTHESIS AND CHARACTERIZATION OF CERIUM FLUORITES BASED ON Ce1-xLn xO2-δ SYSTEM (Ln: Nd3+, Sm3+, Eu3+, Gd3+, Dy3+ AND Ho3+)
摘要： This paper describes the synthesis of 18 oxides of Ce1-xLnxO2 (Ln: Nd3+, Sm3+, Eu3+, Gd3+, Dy3+ and Ho3+), with x = 0.05, 0.10 and 0.15 mol% by use of a wet chemical route that involving the obtention of coordination compounds type citrate, which allow the generation of a number of chemical and surface properties with potential catalytic applications in solid oxide fuel cells technologies. The materials obtained by this route, has a high purity and homogeneity, enabling calcination temperatures and residence times considerably brief, in comparison with conventional synthetic routes. All oxides, were calcined at 300 °C under flow oxygen and were characterized by X-ray diffraction (XRD), from obtained results, we confirmed the presence of a pure fluorite structure of CeO2 consistent with the ICSD pattern reference of 072155 with space group Fm-3m (225). Subsequent physicochemical characterization by TPR and electron microscopy (SEM-TEM), confirm that cerium oxides could be reduced in two single steps at different temperatures, kinetically detectable and clearly prolonged as well as the obtention of nanostructured solids with a crystallite size between 32-47 nm. According with obtained results, the solids show a high surface area as result of the low calcination temperature. The electrical characterization by impedance spectroscopy (IS), revealed an important concentration of charge carriers in fluorite oxides, mainly in the sample of GDC5, which is a crucial characteristic in advanced materials for SOFC applications. The catalytic studies, conducted on materials at 700 °C under stable reaction conditions, confirm that the methane conversion levels change throughout the series GDC5 → NDC5 → HDC5 → EDC5 → DDC5 → SDC5, which established that the GDC5 solid, exhibits the most promising results. Finally, a stability test was achieved with the GDC5 catalyst under the same reaction conditions established in previous form, for a period of 240 hours of continuous flux, establishing the effectiveness of the proposed method to choice the most promissory material. The results confirmed as the methane conversion vary as function of time and the obtained syngas levels change for potential technological applications.
关键词： TPB,Impedance,Polymerization,Fluorite
更新于2025-09-09 09:28:46
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[IEEE 2018 International Conference on Advances in Computing, Communications and Informatics (ICACCI) - Bangalore, India (2018.9.19-2018.9.22)] 2018 International Conference on Advances in Computing, Communications and Informatics (ICACCI) - Design and Analysis of Circularly Polarized Defected Ground Elliptical Patch Antenna for Long Term Evolution (LTE) and 4G Wireless Applications
摘要： In this article the strategy and analysis of a defected ground stacked elliptical patch microstrip antenna (EPMA) is presented for circular polarization (CP). This antenna gives an impedance bandwidth of 44.0% with respect to resonant frequency 1.98GHz, which is eight times greater in comparision to conventional elliptical patch microstrip antenna (EPMA) along with axial ratio bandwidth of 5.5% with reverence to frequency 1.98GHz. The antenna is studied on a Flame Retardant (FR-4) substrate having substrate permittivity 4.4 and thickness 1.59mm. The CP behaviour is observed by truncating the conventional elliptical patch and inserting slots. A square slot is also etched in ground plane at an angle of 45 degrees with respect to horizontal axis. This antenna design having a dimension of ground plane 35.0×32.0 mm2. To achieve the higher impedance bandwidth, the technique of multilayer stacked of patch is used. The over all height of antenna is 9.18mm. This antenna can be used in Long Term Evolution (LTE) and 4G Wireless Applications.
关键词： circularly polarized (CP) antenna,Elliptical microstrip antenna (EPMA),impedance bandwidth (IBW),defected ground (DG) technique,multi-layered stacked structure,axial ratio bandwidth (ARBW)
更新于2025-09-09 09:28:46
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[IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Quality Analysis of Antenna Reflection Coefficient in Massive MIMO Antenna Array Module
摘要： Number of antennas per an antenna module will increase in upcoming 5G millimeter wave (mmW) radio products. The usage of antenna arrays compensates the increased propagation loss of a radio signal at mmW frequencies. The worst performing antenna defines the quality level MIMO antenna module. This paper presents an analysis and a relationship between the variation of the antenna resonance frequency and the reflection coefficient. A probability density function (PDF) of the antenna reflection coefficient at the specification limit is a non- linearly scaled mirrored version of the PDF of the variation of the antenna resonance. We measured the PDF of antenna reflection coefficient from manufactured prototypes and there is a good correlation between the measured and the simulated PDFs.
关键词： 5G,Antenna,Impedance matching,Process capability index,Probability density function,mmW
更新于2025-09-09 09:28:46
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HIGH IMPEDANCE PROPERTIES OF TWO-DIMENSIONAL COMPOSITE RIGHT/LEFT-HANDED TRANSMISSION LINES
摘要： The electromagnetic characteristics of two-dimensional composite right/left-handed transmission lines (2D CRLH TLs) were investigated for the normal incidence of plane waves. The measured characteristic impedance and re?ection phases exhibited resonant high impedance properties (equivalent to zero re?ection phase) at a frequency within the left-handed mode for one-dimensional CRLH TL. An equivalent circuit was proposed to explain the measured characteristics. The relationship between the resonant frequency and the circuit parameters for 2D CRLH TLs was clari?ed by deriving an approximate equation for the resonant frequency.
关键词： equivalent circuit,plane waves,resonant frequency,two-dimensional composite right/left-handed transmission lines,high impedance properties
更新于2025-09-09 09:28:46
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Dielectric, electrical and impedance study of single perovskite Pb(Ni1/3Mn1/3W1/3)O3
摘要： A multiferroic material Pb(Ni1/3Mn1/3W1/3)O3 with ferroelectric and ferromagnetic properties at room temperature is designed for multifunctional applications. A orthorhombic perovskite crystal structure has been assigned for the present perovskite according to the X-ray diffraction patterns. At 1 kHz, dielectric constant (er) increases from 1655 at 298 K to its ?rst maximum 3514 at 457 K referred as magnetic transition. The high values of er in the low frequency range show better dispersion, and with the increase in frequency, a gradual decrease in the er values was observed. The contribution of grain and/or electrode/interface effects in the resistive/capacitive properties was ascertained by the Nyquist plots. An equivalent circuit has been suggested consisting of resistive and capacitive components (R, C, Q) estimates the bulk (grain) and grain boundary resistance and capacitance. The activation energy was found to be greater than 0.2 eV, supporting the conduction mechanism due to hopping of charge carriers.
关键词： Solid-state reaction,Multiferroic material,Dielectric response,Electrochemical impedance spectroscopy,Ceramics
更新于2025-09-09 09:28:46
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Improvement of dielectric breakdown strength and energy storage performance in Er2O3–modified 0.95Sr0.7Ba0.3Nb2O6-0.05CaTiO3 lead-free ceramics
摘要： In this study, 0.95Sr0.7Ba0.3Nb2O6-0.05CaTiO3-x wt. % Er2O3 ceramics (SBNCTEx; x = 0-5) were synthesized using traditional solid-state method, and we investigated the microstructure, energy storage properties as well as the relationship between dielectric breakdown strength and interfacial polarization. As compared with pure 0.95Sr0.7Ba0.3Nb2O6-0.05CaTiO3 ceramics, the Er2O3 dopants suppressed the grain growth of SBNCTEx, and the doped ones showed the dense microstructure. The secondary phase was found for x ≥ 1 according to the EDS results, and the influence of the secondary phase on relative dielectric breakdown strength has also been studied. The dielectric breakdown strength increased from 18.1kV/mm to 34.4 kV/mm, which is good for energy storage. The energy storage density of 0.28J/cm3 and the energy storage efficiency of 91.4% were obtained in the SBNCTE5 ceramics. The results indicate that SBNCTE ceramics can be used as energy storage capacitors.
关键词： Impedance,Er2O3 addition,Dielectric breakdown strength,Energy storage
更新于2025-09-09 09:28:46
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Effect of Environmental Humidity in the Electrical Properties of Lead Halide Perovskites
摘要： In large quantities, water is detrimental to lead halide perovskite solar cells, mainly because of the decomposition of the perovskite layer. On the contrary, the presence of small quantities of water has been observed to play a key role in the crystallization of the perovskite and in the performance of the corresponding devices. However, it is still under debate the exact role of water during the operation of perovskite solar cells. In this paper, impedance spectroscopy is used to analyze the changes produced by environmental humidity in the electronic properties of methylammonium lead triiodide perovskite. Our results show that water absorbed from environmental humidity induces a huge increase in the capacitance of this material. This capacitance can reach values as large as the accumulation capacitance found in devices based in perovskite, which is the responsible of the characteristic large hysteresis observed between forward and reverse J-V curves. In parallel to this outstanding rise of the capacitance, water absorption produces a significant rise of the conductivity, in agreement with previous reports in the literature. Activation energy of 0.52 eV is found for electronic transport, a value in line with activation energy of ionic transport found in literature, what suggests ambipolar diffusion as the transport mechanism that links these two phenomena.
关键词： impedance spectroscopy,environmental humidity,electrical properties,lead halide perovskites,capacitance,conductivity
更新于2025-09-09 09:28:46