| Photonic Crystals or Photonic Band-gap (PBG) structures are periodic metal-dielectric material with a frequency band-gap. PBG structures have been extensively studied since the concept came into being in the end of 1980's. The research of work of PBG structures in microwave region progresses rapidly because of the advantage in fabrication and measurement. PBG microstrip antennas based on photonic band-gap structures is a relatively new area, and has attracted great attention these years.The paper firstly introduces the fundamental theory and method concerned with PBG and microstrip antenna, and then use the theoretical analysis together with the experimental method to design Microstrip Antenna Based on Crossed Idiosyncratic PBG Structure and PBG Structure in Novel Strip Microstrip Antenna by using the special features of photonic crystals structures. The results obtained show that the designed PBG structures in the paper can improve performances of the antennas, for example, enhance the radiation gain, broaden the frequency band, improve the return loss, gain and restrain the high harmonics.The paper mainly includes the following contents:(1) Microstrip antennas based on drilled and crossed idiosyncratic PBG are designed. The finite-difference time-domain (FDTD) method together with the perfectly matched layer (PML) boundary treatment has been used to study the performance of the antenna. Owing to the effect of drilled-PBG's forbidden band, the surface waves in the bottom substrate of the microstrip antenna would be suppressed, and such substrate will reflect the energy extensively, which would improve the antenna's frequency bandwidth and radiation gain. We find the return loss of antenna reduced about 10dB, the bandwidth increased 30M, and the gain improved 11dB.(2) Study a novel strip microstrip antenna and the application of PBG structures in it, the intrinsic mechanism how high impedance surface (HIS) PBG and heterostructure PBG structures influence the novel antenna are analyzed. The obtained results indicate that the antenna's surface waves would be restrained with the gain improved as a matter of high impedance characteristic of HIS PBG structure, because the HIS PBG would restrict the flow of surface electricity, and a forbidden frequency range would be formed. On the other hand, the heterogenetic PBG structure will lead to aberrance between the two heterogenetic structures, and the electromagnetic energy near a frequency range would get a higher gain due to the electromagnetic waves' highly localized effect caused by aberrance. In such forbidden frequency band, the PBG structures can reduce the back radiation, and increase the front radiation; therefore, the antenna's gain and performance would be improved accordingly.(3) Characteristics of the microstrip antenna based on drilling air holes and embedding a metal boundary in the substrate were studied. We find that the surface waves transmitted along embedded multiple PBG patch antenna's substrate(with rectangular metal border) can be restrained in the forbidden frequency band. It has a lower return loss compared to the conventional antenna and the PBG antenna without metal border. Also, it can radiate most of the energy in the antenna's substrate so that it has a high gain; thus, the radiation energy coupling into the free space is improved, and its Radiation efficiency improved. It provides a reference to the microstrip antennas further use, and a new idea to combine the PBG structure and microstrip antenna is put forward. |
PDF Full Text Request