Study And Application Of Left-handed Material And Periodical Electromagnetic Material

In recent years, the left-handed materials and periodical electromagnetic materials have been extensively investigated which are more and more important in the microwave field. Reasearchers can design many new devices by these new structures. Besides, the new materials can improve the performance of the traditional devices by means of the especial structures. This thesis studies the microstrip antenna which used the left-handed materials and the photonic band gap(PBG) holes, and designs some novel ultral wide band(UWB) filter using uniplanar compact photonic band gap(UC-PBG) structures and interdigital coupling.Firstly, this thesis introduces the especial phenomenon of the left-handed materials, such as negative refraction phenomenon, inverse Doppler effect, and perfect lens effect. By the double split rectangular ring resonators on the surface of the substrate, the directivity and gain of the microstrip antenna can be improved a lot. At the same time, the etching circular holes on the ground can effectively suppress the propagation of the surface wave, therefore improve the performance of the antenna. Compared with the traditional microstrip antenna, there is a 3.4dB increment in the gain of the antenna. And the half power angle of the new antenna decrease 24 deg. The measured results are in good agreement with the simulated results, which verified the proposed patch antenna.It is well known that the periodic structures can suppress the propagation of the electromagnetic waves in some frequency range due to PBG phenomenon. A novel filter can be realized by the UC-PBG structure. This thesis proposed a novel UWB filter based on interdigital coupling and UC-PBG structure and the bandwidth of 5.6GHz and the fractional bandwidth of 140% are achieved. Compared with the traditional filter, the pass band of this novel filter is wider and the performance is improved a lot. When the etching circular holes on the ground are used on the substrate, the performance of the novel filter will be improved further. The measured results are in good agreement with the simulated results, which verified the proposed filter. Besides, a new low pass filter is also investigated in this thesis. By means of UC-PBG structure the performance of this low pass filter is also improved obviously.This thesis also proposed a novel periodic structure UWB filter by the periodic fishbone structure and the etching periodic square holes on the ground. The bandwhidth of this filter is 5.4GHz and fractional badwidth is 106%, which verifies the effectiveness of the periodic structures again. By the periodic square holes on the ground and the periodic fishbone structure, the surface wave of the filter has been suppressed obviously and the strength of the coupling of the interdigital structure has been tightened a lot. Therefore the performance of the novel filter has been improved a lot. The measured results are in good agreement with the simulated results, which verified the proposed filter.