The Research And Design Of The High-fidelity Ultra-wideband Antennas

In the design of ultra-wideband communication systems, the impact on transmitting signals'quality by the producing of pulse waveforms and launch/receiving antennas should be considered comprehensively. Generally, standing wave ratio, gain and directional pattern are used to measure antenna's performance in narrow-band antennas'design, which are functions of frequency, and have micron-variation in a certain range of bandwidth. However, when the bandwidth is several octaves or a dozen octaves, e.g. ultra-wideband antennas, the electrical characteristics mentioned above are not enough to reflect ultra-wideband antennas'performance. Consequently, the fidelity of ultra-wideband antennas'pulse waveform in time-domain gradually becomes research hotspot in the research of ultra-wideband antennas'performance. Based on the study of relationship between fidelity and antenna parameters, a high-fidelity ultra-wideband antenna is designed.This thesis is divided into four parts. Firstly, the significance of developing ultra-wideband antennas is introduced. And then, the cause and process of distortion produced when pulse signals travels through ultra-wideband antennas and free space are explained. And then, the research method for this paper's subject is given.Secondly, this paper introduces the performance parameters of ultra-wideband antennas, and gives the ultra-wideband antenna system diagram and the calculation and measurement methods for the transmitting signals. Then, based on the frequency- and time-domain analysis of ultra-wideband half-PTMA antenna, relationship between phase-frequency Characteristics,gain-frequency characteristic of ultra-wideband antennas and fidelity of pulse signals is researched.Then, on the analysis of relationship between the structural parameters and the property of Vivaldi antenna, a ultra-wideband antipodal Vivaldi antenna is designed and fabricated with impedance bandwidth of 3GHz-11GHz. And then, relationship between fidelity of pulse signals and ultra-wideband antennas'phase-frequency Characteristics, gain-frequency characteristic is analyzed. Based on above two ultra-wideband antennas ,it is obtained that the relationship between fidelity of pulse signals and ultra-wideband antenna's phase-frequency Characteristics,gain-frequency characteristic providing a basis for the design of high-fidelity ultra-wideband antennas.Finally, a high-fidelity ultra-wideband half-planar monopole antenna is designed and fabricated. Firstly, as the reference antenna, the trapezoidal planar monopole antenna's parameters are analyzed on their roles. Then, terminal loading and impedance matching technologies are applied to the ultra-wideband planar monopole antenna with impedance wideband of 650MHz-11.5GHz , which is 0.86 fidelity for transmitting or receiving and 0.78 fidelity for transmitting and receiving. The half cut of above ultra-wideband planar monopole antenna is 0.98 fidelity for transmitting or receiving and 0.85 fidelity for transmitting and receiving.