| In recent years, short-range wireless communication has developed into a more potential industry. Ultra Wide-Band (UWB) has become one of the competitive technologies to realize high-speed digital communication because of its good performance, low power consumption and low cost. As pulse based technology, the UWB system needs a very wide bandwidth of several GHz for signal transmission.Antenna is one of the important parts in UWB system. However, some classic broadband antennas don't suit UWB system because of their some deficiencies. The infinite bi-conical antenna has a perfect performance of broadband. But a practical bi-conical antenna is made by ending the two cones of the infinite bicone. The ends of the cones cause reflections that narrow the bandwidth of the antenna. In this paper, first we briefly introduce the infinite bi-conical antenna. Then we compare the performance of the finite bi-conical antennas of different angels. We will mend the structure of the biconical antenna to weaken the reflection current on its surface. By these work, the bandwidth of the antenna will be widen to satisfy the request of UWB system. And the size of the antenna will also be optimized. The FDTD (Finite Difference Time Domain) method is used to achieve the time-domain characteristic of the antennas. The special PML (Perfectly Matched Layer) for cylindrical coordinate is applied to the absorbing boundary conditions... |
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