| Ultra-wideband (UWB) technology has been widely used in various radar, positioning, electronic warfare and secure communication systems, hence it was considered to be one of the most critical military technologies and kept in secret for a long time. In the past decades, it was gradually disclosed to the commercial applications and immediately became a hot research topic. Some novel UWB systems with great prosperity appeared and got rapidly developed: 1) UWB wireless communication systems could operate effectively with extremely low power and wide bandwidth, which could be a decent solution of high-speed wireless communications among the very limited spectrum resources attributable to its merits of high data rate, large space capacity and low hardware cost. 2) The low-profile uni-directional UWB antennas could be easily deployed on various platforms and provide good electromagnetic compatibility, and hence have a great prosperity in commercial wireless systems. For military applications, it could simultaneously cover kinds of functions like communication, radar, navigation and electronic warfare, which could significantly improve the quality of various antenna loads and achieve the optimum deployments of airborne antenna systems. Furthermore, it also has the potential of significant RCS reduction, and undoubtedly should be considered as one of the most critical military technologies. 3) The wireless interconnect system, especially the UWB type, could potentially fulfill the functions of existed metal-wire interconnects by using on-chip circuits and antennas, and it has the merits of low delay, low power consumption, CMOS-compatibility and little interference on other on-chip components, which could effectively solve the"Crisis of Interconnect"of high-speed integrated circuits.However, the corresponding UWB antennas in above systems should also be high-performance, small size, light weight, low cost and highly reliable, which were undoubtedly out of the competence of current antenna technologies. The existing UWB antennas obviously lagged behind the fast development of UWB systems at the aspects of theory, technology and even concept, which have become the main bottlenecks of successful UWB applications: 1) Misunderstanding the concept of applicable bandwidth, only seek for the largest impedance bandwidth. 2) No systematic understanding of time-domain/frequency-domain radiation behaviors of the UWB monopole and dipole antennas. 3) The existed UWB antennas have obvious defects on size and applicable bandwidth. 4) Lack of effective design methodologies for low-profile uni-directional UWB antennas. 5) Lack of complete criterions for the characterization, design and test of on-chip antennas.In order to fulfill the requirements of high-performance UWB antennas in above systems and to solve the existing problems of UWB antennas at the aspects of theory, technology and concept, a great deal of research and experimental works were carried out and lots of original results were obtained and presented in this thesis including: The evaluation criterion of UWB antennas was summarized; The time-domain and frequency-domain radiation theories of printed UWB dipole and monopole antennas were developed; two design methodologies for low-profile uni-directional UWB antennas were introduced; and the evaluation, design and test of on-chip antennas were investigated. Some novel UWB antennas with great prosperity were proposed and introduced in detail. The original works and contributions of this thesis were detailed as follows:1. The frequency-domain radiation model of printed monopole antennas was presented, which shows that a printed monopole antenna could be equivalent to a single-fed unbalanced dipole antenna. Therefore, both of the monopole element and ground plane should be considered in the analysis and optimization of UWB printed monopole antennas. At the guidance of this model, quasi-circular monopole, stacked-circular monopole and notched ground were introduced for impedance bandwidth enhancement and size reduction of UWB printed monopole antennas, which also verified the proposed radiation model.2. The effects of monopole element and ground plane on the radiation patterns were analyzed. The equal-width ground and trapezoidal ground were firstly proposed for the pattern bandwidth enhancement of planar monopole antennas. An example monopole antenna based on the equal-width ground has a very compact size of 30×8 m m2and a measured impedance bandwidth of 2.75-16.2 GHz. In addition, within its impedance bandwidth, stable H-plane radiation patterns were obtained and the variations were less than 4 dB. A mirrored-ground methodology was introduced for the improvement of transmission characteristics of UWB printed monopole antennas.3. Complete time-domain radiation model of UWB printed monopole antennas, which includes the contributions of monopole element, ground plane and dielectric substrate, was summarized. The curved ground and hexagonal ground were developed, which improves the time-domain performance of printed monopole antennas via the structural optimizations without any increases of antenna size. The measured pulse preserving coefficients of the example antennas with the curved and hexagonal grounds were improved by over 14% for the line of sight transmission and reception process.4. Novel compensating stub and large scale factor for UWB log-periodic microstrip antennas (LPMA) were firstly proposed, the overall efficiency was improved by 6 % on average while over 40 % of size reduction was also obtained.5. The performance of UWB dipole antennas on H-type and E-type periodic reflectors was investigated, and a novel sliced periodic reflector was firstly proposed. Compared to typical Vivaldi antennas or corrugated horns with similar performance, overall profile of the proposed antenna was over 70 % lower; compared to the same source antenna with absorbing cavity, the gain of the proposed antenna was at least 2 dB higher.6. The methodology of using multi-interconnect-layers for bandwidth enhancement and size reduction of on-chip dipoles was proposed. The example antennas were also fabricated and tested through the HJTC 0.18μm CMOS process. A novel global interconnect using a SIW structure in the AlN layer was numerically investigated. Finally, some personal experiences on the design and test of on-chip antennas were summarized.
|
PDF Full Text Request