A microstrip-fed ultra-wideband antenna with dual band-rejection characteristics is investigated. The antenna has the same shape between radiation patch and ground plane, and is fabricated on a Rogers RT/duroid 5880 substrate with an overall size of 22×31.85×0.508 mm 3 . To generate two notched frequency bands, a U-shaped parasitic element on the back of the patch is utilized. The two notched bands can be controlled by adjusting the size of the parasitic element. The measured results show that the proposed antenna has an impedance bandwidth of 3.0 to 11.7 GHz for S 11 <−10 dB, expects two eliminated frequency bands 5.08~5.96 GHz for wireless local area network and 8.71~10.25 GHz for X-band.

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Abstract-This paper presents an efficient hybrid method consisting of finite-difference time-domain (FDTD) method, transmission line (TL) equations, and a fast calculation method for excitation fields, which can be applied to the coupling analysis of the shielded cable on the ground excited by plane wave rapidly. It can avoid modeling the infinite ground and the structure of the shielded cable directly. In this hybrid method, the shielded cable is decomposed into external and internal transmission line models, and the corresponding TL equations for the external and internal TL models are established necessarily. Then the FDTD method is utilized to solve the TL equations to obtain the transient responses on the shielding layer and core wires of the cable. A numerous examination of the coupling of coaxial cable exhibits that this hybrid method has very high accuracy and efficiency compared with the SPICE method. Finally, the methods of effective shielding protection of the cable have been proposed by analyzing the influences of the grounding states of the shielding layer, the electromagnetic parameters of the ground and the heights of the cable on the transient responses of the cable.

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