Research On Time-domain Pulsed Ultra-wideband Antennas

The tremendous development of wireless communication has led to more and more scholars researching on ultra-wideband technology.Because UWB technology uses sub-nanosecond pulse signals for communication(frequency domain exhibits ultra-wideband characteristics)and therefore has the advantages of high-speed data rate,resistance to multi-path fading,and low power spectral density,so it is widely used in military,satellite applications,detection,medical imaging and precise positioning.In 2002,the Federal Communications Commission(FCC)approved the opening of 3.1-10.6 GHz band to the business,which has greatly promoted the development of UWB technology.The miniaturization of antenna size,broadband frequency band,simple design,high gain,and high fidelity of time domain performance are undoubtedly the key development directions of UWB antennas,and the distortion-free transmission pulse signal is a research difficulty and key point of UWB antenna.Based on this,this paper designs three different types of time-domain UWB antennas based on different application scenarios to meet the double requirements of the actual communication requirements for the time-domain performance of the time domain UWB antenna.In order to meet the urgent requirement of miniaturization of wireless communication system,the third chapter of this paper designed a miniaturized UWB Vivaldi antenna.Compared with a conventional Vivaldi antenna of the same size,the proposed tapered slot edge with stepped structure(TSESS)can significantly extend the low-end bandwidth limitation and make the surface current converge near the opening radiating slot to improves the antenna gain and radiation characteristics.The measured group delay curve is relatively flat over the entire operating frequency band,indicating that the antenna has good time domain performance that can better meet the requirements of a UWB system.Although ultra-wideband systems have low power spectral density,narrowband communications such as WiMAX(3.3-3.5 GHz)and WLAN(5.15-5.35 GHz;5.725-5.825 GHz)are also within the UWB band.In the fourth chapter,a planar quasi-Yagi antenna with double notch characteristics is designed in order to achieve electromagnetic compatibility.The notch structure is designed by adjusting the spacing and length of the adjacent radiation dipoles.Not only the design method is simple but also the antenna can keep good frequency domain response and time domain response in the passband.In order to realize the bi-directional wireless communication under the long straight distance,the fifth chapter designs a high-gain bi-directional UWB array antenna.On the basis of full study of wide slot antenna,uesd the array method to avhieve the high antenna gain and bi-directional characteristic,and then by rotating the radiation patch and connecting small rectangular structure at the bottom of the slot floor to improve the impedance matching of the array antenna in low frequency and high frequency.The group delay test and time domain pattern experiments show that the antenna can work well in UWB systems.