Research On Wide-Band Tapered EBG And Spiral EBG With Their Applications On Microstrip Antenna

In recent years,wireless communication technology developed rapidly,so the antenna which is working for receiving and transmitting electromagnetic wave require better performance.The electromagnetic band gap structure which is integrated into the antenna can effectively improve the capability of the antenna.The electromagnetic band gap structure also makes the research more practical.There are two important characteristics of the electromagnetic band gap structure as follow:the co-reflecting phase characteristic and the surface wave suppression characteristic.The EBG structure designed based on the above characteristics can be better applied to the antenna system.The main work of this paper is as follow:First of all,researching the properties of tapered EBG.An EBG structure which combines the tapered surface structure and the tapered defected ground structure is proposed,then a miniaturized method is studied through analyzing the relation between working frequency and the size of tapered periodic structure,the S parameters are simulated by using the HFSS,the actual size is 40×20×0.6mm3,the simulated stop-band is 1.88GHz-29.2GHz(the bandwidth is 27.3GHz),the measured stop-band is 2.20GHz-27.85GHz(except 16.56GHz-17.00GHz).It is fabricated by the PCB technology and the measured results are basically consistent with the simulated results which indicates that the EBG can be used for the band-stop filters and associated antennas.Secondly,a new spiral EBG is designed.The new structure has three main parts:(1)4 connected spiral slots and cross slot;(2)square patch in the middle;(3)a circular patch at the end of each spiral slot.According to refer research,it is necessary to use the metal via to realize the miniaturization.But the new structure is compact and easy to manufacture without the metal via,the size of each EBG unit is lO×10×1.8mm3.When the EBG placed on both sides of the feed line of the circular monopole antenna,the antenna obtains two wide frequency bands:1.8GHz-3.21GHz and 4.02GHz-6.12GHz,and the antenna with the EBG gets the largest gain at 2.53GHz.Finally,a new EBG based on the coplanar compact structure is designed.The structure includes a square patch with a cross slot,a folded line placed around the square patch and a small square patch in the folded line gap.The EBG designed in this paper has compact structure and better usability,the size of single cell is 9.2×9.2×2mm3,the stop-band is 0.78GHz to 1.83GHz.When the EBG is used for double layer proximity coupling antenna,the EBG is placed on the upper surface near the feed point can increase the available bandwidth of the antenna.The bandwidth of antenna is broadened of 240MHz and 230MHz in 1.0GHz and 2.3GHz respectively,and the gain in 1.0GHz is also improved by 1dB.The results in this paper provide a reference for the design of new EBG structure,and the research of the EBG structure applied to the antenna also can provide a new way to design antenna.