Decoupling technique of patch antenna arrays with shared substrate by suppressing near-field magnetic coupling using magnetic metamaterials

In this paper,we propose the decoupling technique of patch antenna array by suppressing near-field magnetic coupling（NFMC） using magnetic metamaterials.To this end,a highly-integrated magnetic metamaterials,the substrate-integrated split-ring resonator（SI-SRR）,is firstly proposed to achieve negative permeability at the antenna operating frequency.By integrating SI-SRR in between two closely spaced antennas,magnetic fields are blocked in the shared substrate due to negative permeability of SI-SRR,reducing NFMC between the two antennas.To verify the technique,a prototype was fabricated and measured.The measured results demonstrated that the isolation can be enhanced by more than 17 dB even when the gap between the two patch antennas is only about 0.067 A.Due to high integration,this technique provides an effective alternative to high-isolation antenna array.

Effect of sintering temperature and composition on microstructure and properties of PMS-PZT ceramics

The piezoelectric ceramics xPb(Mn1/3Sb2/3)O3-(1-x)Pb(Zr1/2Ti1/2)O3 (abbreviated as PMS-PZT) were synthesized by traditional ceramics process. The effect of sintering temperature and the amount of Pb(Mn1/3Sb2/3)O3 (abbreviated as PMS) on phase structure, microstructure, piezoelectric and dielectric properties of PMS-PZT ceramics was investigated. The results show that the pure perovskite phase is in all ceramics specimens, the phase structure of PMS-PZT ceramics changes from tetragonal phase to single rhombohedral phase with the increasing amount of PMS. The dielectric constant εr, Curie temperature TC, electromechanical coupling factor kp and piezoelectric constant d33 decrease, whereas the mechanical quality factor Qm and dielectric loss tanδ increase with the increasing amount of PMS in system. The optimum sintering temperature is 1 200?1 250 ℃. It is concluded that the PMS-PZT (x=0.07) ceramics sintered at 1 250 ℃ is suitable for high-power piezoelectric transformer. These properties include εr= 674.8, tanδ=0.005 25, kp=0.658, Qm=1 520, d33=230 pC/N, Tc=275 ℃.

A reduction approach to prepare ZnSe nanocrystallites

ZnSe nanocrystallites powders were successfully prepared by reduction method with H2SeO4 or H2SeO3 as selenium source and Zn(Ac)2·H2O as zinc source. The reaction mechanism was also discussed through XRD and DTA/TG analysis. In the process, ZnSeO4·H2O or ZnSeO3·H2O crystallites precipitated in organic solvent was prepared at first. Then the crystallites were reduced with carbon monoxide atmosphere. The XRD analysis reveals that the structure of ZnSe phase is sphalerite (cubic ZnS). The XPS results show that the atomic ratio of Se to Zn is 1?1 approximately. The TEM shows that the size of ZnSe crystallite is 30?50 nm. This method of synthesis of ZnSe nanocrystallites has the potential application in the preparation of optical composite thin films from sol-gel process.

A Wide-Band Metamaterial Absorber Based on Loaded Magnetic Resonators

A wide-band polarization-insensitive and wide-angle metamaterial absorber based on loaded magnetic resonators is presented.The unit cell of this absorber consists of a magnetic resonator loaded with lumped resistances,a dielectric substrate and a back metal film.Theoretical and simulated results show that this absorber has a wide-band strong absorption for the incident wave from 3.87 GHz to 21.09 GHz.Simulated absorbance values under loading and unloading conditions indicate that electrocircuit's resonances are more stable than electromagnetic resonances and thus can be used to realize wide-band absorption.Simulated absorbance values under different polarization angles and different angles of incidence indicate that this absorber is polarization-insensitive and wide-angle.It may have potential applications in military fields.

Synthesis and electromagnetic absorption properties of micro-nano nickel powders prepared with liquid phase reduction method

Monodisperse micro-nano nickel powders have been prepared by chemical reduction of aqueous solution NiSO_(4),NaOH and NaH_(2)PO_(2),and the influence of pH value and initial concentration of NiSO_(4) on the size,structure,morphology and microwave absorption properties of nickel powders were investigated.The crystal structure of nickel powders was characterized by X-ray diffraction(XRD).And the morphology of the as-synthesized products was characterized by scanning electron microscopy(SEM)and transmission electron microscopy(TEM).The microwave absorption properties of the composite materials were characterized by network analyzer.The result indicates that the growth of nickel powders produced by NiSO_(4) and NaH_(2)PO_(2) at alkaline condition deeply relies on pH value and initial concentration of NiSO_(4) in reaction system.Different sizes of nickel powders with the diameter of 1.5μm and 180 nm were produced at the pH value of 10 and initial concentration of NiSO_(4) at 0.5 mol/L.The network analyzer showed definite microwave absorption properties of nickel powders with different sizes in the range of 0.5-18.0 GHz.