Investigation Of Planar Ultra-Wideband Antennas And Arrays

Since the Federal Communications Commission (FCC) declaration of the frequency band 3.1 to 10.6 GHz for commercial application in 2002, inexpensive realization of ultra-wideband (UWB) systems have become one of the key topics in the industry worldwide. Challenges of the feasible UWB antenna design include the Ultra-wideband performances of the impedance matching, stable gain and omni-directional radiation character, Furthermore, as a key component of the UWB communication system for short-range high-speed and low power application, it is important to maintain the fidelity of pulse signal, more compact size, low manufacturing cost, and easily integrated with monolithic microwave integrated circuits (MMIC). Moreover, the report of FCC 02-48 provides for the operation of vehicular radar in the 22-29 GHz band using directional antennas on terrestrial transportation vehicles.In this thesis, two novel CPW-fed disc antennas etched with C-like slots are proposed with the impedance bandwidths ratio more than 10 : 1, the surface current distributes of the radiator was adjusted by C-like slots, thus, the impedance bandwidths characteristics were improved both in high end and low end frequency, the results shown that the advantages of super wide band (SWB), stable gain and omni-directional radiation patterns. The impedance bandwidths not only cover the bandwidth of 3.1 to 10.6 GHz, moreover, they cover the whole centimeter wave band which including the vehicular radar systems application.For more compact size, to half cut the CPW-fed UWB antenna was an effective method. 2 tapered micro-coplanar strip (MCS) fed UWB antenna were presented. The edge-fed tapered MCS structure including tapered strip and gradient slot is applied to reduce the dimensions and improve the impedance matching in the whole UWB band. The return loss is greater than 10 dB within UWB bandwidth. The results shown that return loss were greater than 10 dB within UWB bandwidth. On the other hand, the width dimension is only 11 mm, so that it can be easily integrated with the wireless USB equipments and suitable for various wideband applications.In order to improve the UWB antenna gain character, 2 units and 4 units UWB antenna array with gradient parallel CPW splitter were designed and study, which obtain the high gain and Flexible orientation.For short-range high-speed low power UWB communication, The time domain characteristics are significant criteria to estimate the performance of UWB antenna as well as traditional frequency domain parameters. The time domain characteristics were studied both the UWB antennas and array proposed in this thesis with correlation factor and the pulse width stretch ratio (SR).