Characterization Of Ultra-Wideband Pulse Networks And Antennas, And Their Applications In Design

Along with the rapid development of ultra-wideband communications technology and the in-depth study of transient electromagnetic theory, the ultra-wideband electromagnetic pulses gradually become a new research hotspot, which has important significance and value on improving the electromagnetic theory and enriching the applications of ultra-wideband technology. However, the amplitude variation and waveform distortion of ultra-wideband pulse signals cannot be described in a simply and intuitively by the conventional frequency domain characterization methods and parameters, which is not conducive to the understanding of the characteristics of ultra-wideband pulse networks and antennas. In addition, the traditional maximum power transmission design criteria cannot fully reflect the design requirements of ultra-wideband pulse networks, and thus it is not suitable for ultra-wideband pulse applications. For ultra-wideband pulse antenna, traditional frequency-domain characterization methods, design methods and optimization method are not devised specifically for the pulse applications. This not only is deleterious to the understanding of the antenna radiation mechanism and characteristics but also will lead to the relatively low design efficiency. Taking the problems listed above into consideration, the research pertaining to the characterization, design methods, and the devices for the ultra-wideband pulse networks and antennas is carried out in this dissertation. The main results are given as follows.1. In terms of the ultra-wideband pulse networks and antennas characterization:(1) Through the study of the UWB pulses in the quadratically integrable signal space, the normalized Euclidean distance parameter is proposed to comprehensively characterize the waveform distortion and pulse energy variation of ultra-wideband pulse signals and its natural relatedness with the fidelity and pulse amplitude ratio is also obtained. The time domain and frequency domain measuring methods of the normalized Euclidean distance parameter are studied and provided in this dissertation. Therefore, the proposed normalized Euclidean distance is featured by strict definition, clear physical meanings, and measurability. The normalized Euclidean distance parameter is extensively applicable since the practical ultra-wideband pulse signals are all belong to the quadratically integrable signal space.(2) A numerical characterization matrix is proposed to characterize the N-port ultra-wideband pulse network. The normalized Euclidean distance numerical characterization matrix is presented based on the analysis of ultra-wideband pulses, which not only can reflect the loss characteristics and dispersion effect of the network but also can easily compare the performance of the networks. Therefore, The normalized Euclidean distance numerical characterization matrix is in favor of the design and optimization of the ultra-wideband pulse networks.(3) A multi-ports network model for antennas is proposed by regarding different radiation directions as different network ports. On this basis, the normalized Euclidean distance characterization parameter and normalized Euclidean distance pattern are presented for a comprehensive description of waveform distortion and amplitude changes of the ultra-wideband pulse antenna radiation fields.2. In terms of the design methods:(1) According to the normalized Euclidean distance parameters, the optimal pulse transmission criteria for the design of ultra-wideband pulse networks is proposed in this dissertation. The optimal pulse transmission criteria comprehensively takes the waveform distortion and amplitude changes into account and can fully reflect the transmission characteristics and design requirements of ultra-wideband pulse networks. The optimal pulse transmission criteria is a generalization of the maximum power transfer criteria and thus has broad applicability.(2) A method for constructing of the optimization objective function based on the numerical characterization matrix is proposed. The constructed objective function can fully describe the difference between ultra-wideband pulse networks and the ideal target network, and thus avoids the determination of the weighted factor, frequency range and frequency points. The constructed objective function can guide the optimization process evolve toward the target network.(3) The radiation process and characteristics of ultra-wideband pulse antenna is explained through the study of the bremsstrahlung radiation of moving charge, which has important significance on understanding radiation mechanism of the ultra-wideband pulse antennas. On this basis, the time domain partial wave based Euclidean distance method is proposed to design and optimize the ultra-wideband pulse antennas, which makes the design and optimization process more purposeful and helps to improve design efficiency.3. In terms of the device implementation:(1) According to the proposed optimal pulse transmission criteria, the microstrip-coaxial transition structure, anisotropic substrate microstrip lines and ultra-wideband pulse matching network are designed and they are more suitable for the transmission of the ultra-wideband pulse signals.(2) A ultra-wideband pulse stripline power divider is designed and optimized by the objective function which is constructed using the normalized Euclidean distance numerical characterization matrix.(3) A low impedance slotline is proposed and its characteristic impedance is obtained by a semi-empirical and semi-analytical method. The ultra-wideband pulse transmission characteristics of the low impedance slotline is studied in this dissertation; Two antennas with exponential and Gaussian structures are fabricated. The designed antennas are featured by ultra-wide operating frequency band and low cross-polarization, which are suitable for the ultra-wideband pulse systems.Since the practical signals are all belong to the quadratically integrable signal space, the normalized Euclidean distance parameter, the optimal pulse transmission criteria, the normalized Euclidean distance numerical characterization matrix, and the normalized Euclidean distance pattern are not only suitable for the ultra-wideband pulse signals, networks, and antennas, but also are applicable for the common signals, networks and antennas.