An ISGW Filtering Antenna with Spurious Modes and Surface Wave Suppression for Millimeter Wave Communications

In this paper,an integrated substrate gap waveguide(ISGW)filtering antenna is proposed at millimeter wave band,whose surface wave and spurious modes are simultaneously suppressed.A secondorder filtering response is obtained through a coupling feeding scheme using one uniform impedance resonator(UIR)and two stepped-impedance resonators(SIRs).To increase the stopband width of the antenna,the spurious modes are suppressed by selecting the appropriate sizes of the ISGW unit cell.Furthermore,the ISGW is implemented to improve the radiation performance of the antenna by alleviating the propagation of surface wave.And an equivalent circuit is investigated to reveal the working principle of ISGW.To demonstrate this methodology,an ISGW filtering antenna operating at a center frequency of 25 GHz is designed,fabricated,and measured.The results show that the antenna achieves a stopband width of 1.6f0(center frequency),an out-of-band suppression level of 21 dB,and a peak realized gain of 8.5 dBi.

Spurious-mode vibrations caused by alternating current poling and their solution process for Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3) single crystals

The effects of alternating current poling(ACP)at 80℃on electrical properties of[001]-oriented 0.72 Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.28PbTiO_(3)(PMN-28PT)single crystals(SCs)have been investigated.The square-wave ACP SCs poled at high voltage(HV,5 kV_(rms)/cm)occasionally showed large fluctuations and low opposite values of piezoelectric coefficient(d_(33)=±1370 pC/N)in one plate.This revealed spuriousmode vibrations(SMV)of impedance spectrum.However,after depolarizing and repolarizing the sample with a sine-wave ACP at low voltage(LV,3.5 kV_(rms)/cm),the d_(33) enhanced to be 1720 pC/N(+26%)and did not exhibit large fluctuation or opposite values in one plate any more.The impedance spectrum became clean and the abnormal SMV disappeared.We proposed four possible mechanisms of the SMV,and speculate that the main cause maybe by macro-scale sub-domain structure and/or phase change in the main domain structure and/or phase in the SC plate due to the specific poling conditions not eternal mechanical damage of PMN-PT SCs.This study will be useful to realize a high d_(33) and improve other properties of PMN-PT ACP SC ultrasonic transducers without any SMV for high-frequency medical imaging equipment.

Force-Based Quadrilateral Plate Bending Element for Plate Using Large Increment Method

A force-based quadrilateral plate element( 4NQP13) for the analysis of the plate bending problems using large increment method( LIM) was proposed. The LIM, a force-based finite element method( FEM),has been successfully developed for the analysis of truss,beam,frame,and 2D continua problems. In these analyses,LIMcan provide more precise stress results and less computational time consumption compared with displacement-based FEM. The plate element was based on the Mindlin-Reissner plate theory which took into account the transverse shear effects.Numerical examples were presented to study its performance including accuracy and convergence behavior,and the results were compared with the results have been obtained from the displacementbased quadrilateral plate elements and the analytical solutions. The4NQP13 element can analyze the moderately thick plates and the thin plates using LIMand is free from spurious zero energy modes and free from shear locking for thin plate analysis.

Development of the Large Increment Method in Analysis for Thin and Moderately Thick Plates

Many displacement-based quadrilateral plate elements based on Mindlin-Reissner plate theory have been proposed to analyze the thin and moderately thick plate problems. However, numerical inaccuracies of some elements appear since the presence of shear locking and spurious zero energy modes for thin plate problems. To overcome these shortcomings, we employ the large increment method(LIM) for the analyses of the plate bending problems, and propose a force-based 8-node quadrilateral plate(8NQP) element which is based on MindlinReissner plate theory and has no extra spurious zero energy mode. Several benchmark plate bending problems are presented to illustrate the accuracy and convergence of the plate element by comparing with the analytical solutions and displacement-based plate elements. The results show that the 8-node plate element produces fast convergence and accurate stress distributions in both the moderately thick and thin plate bending problems. The plate element is insensitive to mesh distortion and it can avoid the shear locking for thin plate analysis.