In this paper, spoof surface plasmon polariton (SPP) is integrated in the closed substrate integrated waveguide (SIW) structure and a novel hybrid SIW-SPP guided-wave transmission line (TL) is ...proposed. In this design, the surface wave mode of SPP can be excited and transmitted inside the closed structure of SIW. The dispersion property of the proposed SIW-SPP hybrid structure indicates that it has both slow wave feature of SPP and fast-wave feature of SIW. With the low-pass feature of SSP and the high-pass feature of SIW, the proposed hybrid SIW-SPP TL becomes a bandpass filter (BPF) naturally. The concept of integrating SPP and SIW opens a new way to develop novel wideband BPFs. A broadband filter is fabricated to verify the theory and the measured passband is from 16.1 to 25.4 GHz with a relative bandwidth of 43.8%. The filter bandwidth can be easily controlled by tuning parameters, thus the proposed structure is attractive and useful for the design of various BPFs.
A low-profile wideband circularly polarized (CP) crossed-dipole antenna that has both wide axial-ratio beamwidth (ARBW) and half-power beamwidth (HPBW) is presented in this paper. The crossed dipoles ...are composed of four trapezoidal patch arms, and they are fed by a pair of vacant-quarter printed rings to generate CP radiation. Four identical parasitic elements that consist of a horizontal triangle patch and a vertical metallic plate are symmetrically intervened between the crossed dipoles and the ground plane. It has been found that the parasitic elements can effectively decrease the antenna profile, increase the operating bandwidth, and simultaneously enhance the ARBW as well as the HPBW. A prototype was fabricated and measured to verify the design. The measured results show that the prototype has a low profile of <inline-formula> <tex-math notation="LaTeX">0.1\lambda _{0} </tex-math></inline-formula>, a −10 dB impedance bandwidth of 78.3% and a 3 dB AR bandwidth of 63.4%. Moreover, a 3 dB ARBW of more than 120° and an HPBW of more than 110° are achieved simultaneously within a wide passband of 50.7%.
The existing tunable circuits mainly concentrate on the control of frequency and amplitude. The control of phase characteristics becomes more and more important in the modern system for further ...performance enhancement. But none of existing coupler configurations can achieve this tunability. A novel hybrid coupler with simultaneous phase- and frequency-tunable characteristics is presented for the first time. Varying the difference between the capacitances for two rows of tunable capacitors loaded on the branch lines can provide different phase differences between two output ports with equal magnitude. Based on the same circuit, a tunable operating frequency can be realized while maintaining the equal power division and desired phase characteristics. This is achieved by simply changing the capacitances for two rows of tunable capacitors in unison. The high flexibility to achieve tunability in phase and frequency simultaneously is implemented. For demonstration purposes, a hybrid coupler operating at 1 GHz is designed and measured to validate the concept. It exhibits a variable phase difference from 45° to 135° while maintaining equal power division. Meanwhile, the same circuit gives a tunable operating frequency extending from 0.8 to 1.1 GHz while maintaining good performance for a 3 dB coupler with a tunable phase difference from 50° to 130°.
In this communication, we propose a high scanning rate leaky-wave antenna (LWA) based on a slow-wave substrate integrated waveguide (SIW) structure. The slow-wave effect is introduced by etching ...periodical slots on the top surface of SIW. The LWA radiation is subsequently realized by introducing sinusoidal modulation to the slots profile. Such a structure significantly improves the scanning rate of LWA due to the small group velocity at the slow-wave region. Simulation and measured results indicate that the proposed LWA scans a wide angle in a narrow bandwidth near the cutoff frequency of surface plasmon polariton. Within the frequency band 13.5-13.9 GHz (3% relative bandwidth), the measured scanning angle is from 2° to 37° with the measured gain all above 9.2 dBi.
A novel decoupling method is investigated for the multi-input multi-output (MIMO) microstrip patch antenna (MPA) array. This method makes use of the TM 10 and TM 02 modes, which are simultaneously ...excited in the rectangular MPA. It is found that by adjusting the frequencies of the two modes, their <inline-formula> <tex-math notation="LaTeX">E </tex-math></inline-formula>-fields coupled to the adjacent passive MPA can counteract each other to generate a specific null-field region. When the feeding position of the passive MPA is located in the null-field region, the MPA cannot be excited effectively, and hence an extremely low mutual coupling is obtained without requiring any extra decoupling structure. To validate the feasibility of this decoupling method, an E- and an H-plane-coupled <inline-formula> <tex-math notation="LaTeX">1\times 2 </tex-math></inline-formula> MIMO MPA arrays are respectively simulated, fabricated, and measured. The isolation of the E-plane-coupled array is enhanced from ~11 to 57 dB, while that of the H-plane-coupled array is improved from ~18 to 51 dB.
Although an extensive continental arc magmatism was recorded in the northern North China Craton (NCC) during the Carboniferous, a general geodynamic model has not been constructed, and associated ...crust–mantle processes are not fully understood. Here, we carried out systematic geochronological and geochemical investigations on the alkali‐feldspar granite pluton in the Zhaojinggou area, northern NCC. U–Pb dating of high‐U–Th zircons failed to obtain concordant ages due to severe metamictization, while apatite U–Pb dating yielded a perfect age of 327.6 ± 4.1 Ma, indicating the emplacement of granites in the Early Carboniferous. The granites have high SiO2 (74.99–76.88 wt%) and K2O (5.73–6.43 wt%) contents and exhibit enriched LREEs, K, Rb, Th, U, and Pb, and depleted Nb, Ta, P, and Ti contents, which are typical of highly fractionated, I‐type high‐K granites formed under a continental arc setting. Moreover, the high‐K granites show highly enriched Nd isotopic compositions (with whole‐rock and apatite εNd(t) of −33.6 to −16.3) that are distinctly lower than other Carboniferous continental arc rocks in the northern NCC (εNd(t) from −18.5 to −9.9). These geochemical characteristics indicate that the high‐K granites possibly originated by partial melting of the Archean TTG gneisses and mafic rocks in the lower crust. Involvement of mantle‐derived fluids is crucial to induce the low‐temperature melting, and sufficient fractional crystallization was reached during subsequent magmatic evolution. Previous studies suggest that the Carboniferous continental arc rocks in the northern NCC have mantle‐derived or crust–mantle mixed sources. Our study, however, indicates that there also exist coeval crust‐derived magmatic rocks in this area. In combination with previous work and this study, we support the hypothesis that the widespread Carboniferous continental arc magmatism in the northern NCC is related to the southward subduction of the Palaeo‐Asian Ocean (PAO), and the different magma sources and extensive crust–mantle interactions are responsible for the formation of diverse types of magmatic rocks with contrasting isotopic compositions. We also draw attention to the fact that phosphate minerals such as apatite may be a preferable chronometer relative to high‐U–Th zircon in a highly fractionated igneous system.
Early Carboniferous high‐K granites are reported with enriched isotopic signatures in the Zhaojinggou area of the northern North China Craton, which possibly originated by partial melting of the Archean TTG gneisses and mafic rocks in the lower crust with involvement of mantle‐derived fluids during extensive crust‐mantle processes.
A simple decoupling method of using specific higher-order modes to improve the isolation of dielectric resonator antenna (DRA) elements is investigated. The higher-order modes have the feature that ...they can be excited by the active (source) DRA while unexcitable by means of the feeding network. As a result, the coupled fields in the passive (coupled) DRA are unable to reach the feeding port, leading to a very low mutual coupling level. When the coupled modes in the passive DRA have the same radiation characteristics with the mode that excited in the active DRA, the distortion of radiation patterns can also be avoided. This method is found effective for reducing both the E-plane and H-plane coupling. As no extra decoupling element is needed, the entire antenna system is very simple. For verification, an E-plane-coupled <inline-formula> <tex-math notation="LaTeX">1\times 2 </tex-math></inline-formula> multiple-input-multiple-output (MIMO) DRA array has been fabricated and measured. The results show that using a proper mode, the isolation can be enhanced from about 15 to 45 dB at 5.25 GHz.
In this paper, we propose a novel slow-wave half-mode substrate integrated waveguide (HMSIW) combined with spoof surface plasmon polariton (SPP) structure. In this design, subwavelength corrugated ...grooves are etched on the up metal layer of HMSIW to support an SPP mode. The dispersion and transmission characteristics of the proposed hybrid HMSIW-SPP structure are analyzed and compared with the classic HMSIW. To experimentally validate this design, a prototype is fabricated and measured. A slow-wave effect is clearly observed in the proposed hybrid transmission line, and its wavelength is reduced by over 50% without sacrificing its transmission performance. This structure features a simple architecture and excellent slow-wave effect.
A simple decoupling method of using metallic vias to improve the isolation of millimeter-wave multiple-input-multiple-output (MIMO) dielectric resonator antenna (DRA) elements is investigated. The ...vias are vertically added to the DRA elements, at appropriate positions. By means of the interaction with the electromagnetic fields, the vias can potentially affect the filed distributions and further reduce the coupled fields effectively. The isolation between the MIMO DRA elements can, therefore, be enhanced substantially. As the vias are placed inside the DRA elements, no extra footprint is needed, making the entire antenna system very simple and compact. Two typical examples, including an H-plane and an E-plane, coupled 1\times2 MIMO DRA arrays, have been designed, fabricated, and measured to demonstrate the feasibility and universality of this method. The results show that by using the vias appropriately, the isolation of the H-plane coupled MIMO DRA array can be enhanced from ~15.2 to 34.2 dB, while that of the E-plane array can be improved from ~13.1 to 43 dB at 26 GHz.
In this study, we aimed to explore the molecular mechanisms underlying the development of osteoporosis in post‐menopausal females. Real‐time PCR was conducted to measure the expression of potential ...lncRNAs involved in the osteoporosis of post‐menopausal females. In addition, Western blot and IHC assays were used to study the possible correlation among HOTAIR, miR‐138 and TIMP1, while a computational analysis was carried out to predict the ‘seed sequence’ responsible for the binding between miR‐138 and HOTAIR/TIMP1. Furthermore, luciferase reporter assays were conducted to validate the negative regulatory relationship between miR‐138 and TIMP1/HOTAIR. To evaluate the effect of oestrogen on the function of HOATIR and its downstream effectors, luciferase activity was measured in cells cotransfected with different vectors or treated with different doses of oestrogen. The results of the luciferase assay were further validated by real‐time PCR, Western blot, MTT assay and flow cytometry. Among the candidate lncRNAs, HOTAIR was the only lncRNA down‐regulated in post‐menopausal females. HOTAIR bound to miR‐138 and negatively regulated its expression. Meanwhile, miR‐138 could also bind to TIMP1 mRNA and reduce its expression. Furthermore, a dose‐dependent up‐regulation of HOTAIR was observed in cells treated with oestrogen, and the elevated HOTAIR increased the level of TIMP1 by targeting miR‐138. In addition, oestrogen promoted cell viability and suppressed cell apoptosis, and effects of oestrogen were blocked by the silencing of HOTAIR. Therefore, it can be concluded that oestrogen deficiency could induce the apoptosis of osteoblasts and lead to osteoporosis in post‐menopausal females via modulation of the HOTAIR/miR‐138/TIMP1 signalling axis.
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