Research on synthetic aperture radar imaging technology of one-dimensional layered rough surfaces

A quick and exact imaging method for one-dimensional layered rough surfaces is proposed in this paper to study the scattering characteristics of a layered medium that exists widely in nature.The boundary integral equations of layered rough surfaces are solved by using the propagation-inside-layer expansion combined with the forward and backward spectral acceleration method（PILE＋FB-SA）,and the back scattering data are obtained.Then,a conventional synthetic aperture radar（SAR） imaging procedure called back projection method is used to generate a two-dimensional（2D） image of the layered rough surfaces.Combined with the relative dielectric permittivity of realistic soil,the random rough surfaces with Gauss spectrum are used to simulate the layered medium with rough interfaces.Since the back scattering data are computed by using the fast numerical method,this method can be used to study layered rough surfaces with any parameter,which has a great application value in the detection and remote sensing areas.

Nonlinear differential geometric guidance for maneuvering target

Based on the idea of zeroing the line of sight rate（LOSR）,a novel nonlinear differential geometric（DG） law for intercepting the agile target is proposed.In the first part,the DG formulations are utilized to describe the relatively kinematics model of missile and target,and the nonlinear DG guidance（DGG） law is proposed based on the nonlinear control theory to eliminate the influence brought by target.Further,the missile guidance commands are derived to overcome the information loss caused by decoupling condition,the new necessary initial condition is developed to guarantee capture the agile target.Then,the designed nonlinear DGG commands are transformed from an arc-length system to the time domain.A desirable aspect of the designed guidance law is that it does not require rigorous information about target acceleration.Representative numerical results show that the designed guidance law obtain a better performance than the traditional DGG law for agile target.

Compact Dual-Band Zeroth-Order Resonance Antenna

A novel microstrip zeroth-order resonator (ZOR) antenna and its equivalent circuit model are exploited with two zeroth-order resonances.It is constructed based on a resonant-type composite right/left handed transmission line (CRLH TL) using a Wunderlich-shaped extended complementary single split ring resonator pair (W-ECSSRRP) and a series capacitive gap.The gap either can be utilized for double negative (DNG) ZOR antenna or be removed to engineer a simplified elision-negative ZOR (ENG) antenna.For verification,a DNG ZOR antenna sample is fabricated and measured.Numerical and experimental results agree well with each other,indicating that the omnidirectional radiations occur at two frequency bands which are accounted for by two shunt branches in the circuit model.The size of the antenna is 49% more compact than its previous counterpart.The superiority of WECSSRRP over CSSRRP lies in the lower fundamental resonance of the antenna by 38.2% and the introduction of a higher zeroth-order resonance.