An AMC-Based Circularly Polarized Antenna for 5G sub-6 GHz Communications

This paper presents an AMC(artificial magnetic conductor)-based wideband circularly polarized printed monopole antenna for unidirectional radiation.The antenna includes an AMC reflector,a coplanar waveguide(CPW)feed structure to excite the antenna,a ground plane with a rectangular slot on the left side of feedline,and an asymmetrical ground plane on its right side.The induced surface currents on CWP feedline,rectangularly slotted,and asymmetrical ground planes cause circularly polarized radiations.The AMC reflector consisting periodic metallic square patches is used instead of the conventional PEC(perfect electric conductor)reflector,the distance between the antenna and reflector is reduced from 0.25λ0 to 0.18λ0 with performance improvement.By incorporating AMC layer with the monopole antenna,the gain of antenna is increased from 3.3 dBic to 8.7 dBic while the axial ratio bandwidth(ARBW)of antenna is increased from 27.27%to 51.67%.The simulated and measured results show that the proposed antenna has an overlapping 10-dB|S_(11)|and 3-dB ARBW of 51.67%(3.0–5.09 GHz).The overall dimensions of monopole antenna backed by AMC reflector is 1.20_(λ0)×1.20_(λ0)×0.21_(λ0) and covers 5G sub-6 GHz new radio bands(n77/n78/n79)for wireless communication systems.

Syntheses and Structures of Two Metal-organic Frameworks Constructed from Zn/Ni and 3-Formyl-4-(pyridin-4-yl)Benzoic Acid Ligand

Two metal-organic frameworks [（Zn0.5L）·（H2O）]n （1） and [（Ni0.5L）？（H2O）]n （2） constructed by the 3-formyl-4-（pyridin-4-yl） benzoic acid ligand （HL） were synthesized and characterized by single-crystal X-ray diffraction. 1 crystallizes in orthorhombic space group Pnna with a = 16.6152（8）, b = 12.6825（6）, c = 15.3908（8） A, V = 3243.2（3） ？3, Z = 4, Mr = 511.12, Dc = 1.047 g/cm3, F（000） = 1048, μ = 1.144 mm-1, GOOF = 1.061, the final R = 0.0471 and wR = 0.1262 for 12168 observed reflections with I 〉 2σ（I）. 2 is isostructural to 1, which also crystallizes in orthorhombic space group Pnna with a = 16.6152（8）, b = 12.6825（6）, c = 15.3908（8） ？, V = 3243.2（3） ？3, Z = 4, Mr = 511.12, Dc = 1.047 g/cm3, F（000） = 1048, μ = 1.144 mm-1, GOOF = 1.061, the final R = 0.0471 and wR = 0.1262 for 12168 observed reflections with I 〉 2σ（I）. Additionally, thermogravimetric analysis, FT-IR spectroscopy and powder X-ray diffraction were discussed.

A Compact Tri-Band Antenna Based on Inverted-L Stubs for Smart Devices

We designed and constructed a novel,compact tri-band monopole antenna for intelligent devices.Multiband behavior was achieved by placing inverted-L shaped stubs of various lengths in a triangular monopole antenna fed by a coplanar waveguide.The resonance frequency of each band can be controlled by varying the length of the corresponding stub.Three bands,at 2.4(2.37-2.51),3.5(3.34-3.71),and 5.5(4.6-6.4)GHz,were easily obtained using three stubs of different lengths.For miniaturization,a portion of the longest stub(at 2.4 GHz)was printed on the opposite side of the substrate,and connected to the main stub via a shorting pin.To validate the concept,the antenna was fabricated on a low-cost 1.6-mm-thick FR-4 substrate with dimensions of 20×15×1.6 mm^(3).The antenna exhibited a moderate average gain of 2.9 dBi with an omnidirectional radiations over the bandwidths required for RFID,Bluetooth,ISM,WiMAX,andWLAN-band applications.These features make the antenna suitable for compact smart devices.

Synthesis,Structure and Characterization of a 3D Chiral Barium Carboxylate Metal-organic Framework Based on TADDOL Ligand

A novel alkaline earth-based chiral metal-organic framework 1 {[Ba（1.5）L（μ-OH2）2（DMF）2（H2O）]·DMF·1.5 H2O}n was synthesized from C2-symmetric TADDOL-based ligand H4L and structurally characterized by single-crystal and powder X-ray diffraction, Fourier-transform infrared spectra（FTIR）, solid-state circular dichroism（CD） and thermal gravimetric analysis（TGA）. 1 crystallizes in monoclinic space group C2 with a = 43.5105（12）, b = 9.4781（3）, c = 15.5620（4） A°, β = 99.7770（10）o, V = 6324.5（3） A°^3, Z = 2, Mr = 1434.18 g/mol, Dc = 1.506 g/cm^3, F（000） = 2904, GOOF = 1.026, the final R = 0.0358 and w R = 0.0952 for 21747 observed reflections with I 〉 2σ（I）. Each Ba3 cluster in 1 is linked by eight ligands and each ligand with one coordination-free carboxyl oxygen, O（5）, is coordinated to four Ba3 clusters to generate a 3D network. In addition, the photoluminescence of 1 and H4L was also investigated.