tailieunhanh - Microstrip Antennas Part 5

Tham khảo tài liệu 'microstrip antennas part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 6 Mathematical Modeling of Spherical Microstrip Antennas and Applications Nikolaos L. Tsitsas and Constantinos A. Valagiannopoulos National Technical University of Athens Greece 1. Introduction Microstrip antennas offer many attractive features and hence it is very challenging to model efficiently their resonance and radiation characteristics Pozar Schaubert 1995 . In particular microstrip antennas composed of perfectly electric conducting PEC patches mounted on spherical surfaces possess two basic advantages against the planar ones. First their curved shape makes them more applicable to real-world moving configurations such as missiles satellites and aircrafts where large plane boundaries are usually absent. Second the frequency scanning problem encountered in case of planar microstrips at low elevations may be overcome due to the conformability of spherical antennas. Apart from these two advantages spherical microstrip antennas offer due to their relatively simple geometry additional attractive features like low cost light weight easy fabrication as well as integrability with microwave and millimeter-wave circuits. As far as the metallic patch is concerned circular or annular-ring ones are preferable for mounting on a spherical body. Interesting design characteristics of microstrip antennas are mainly the complex resonant frequencies the radiation pattern and the input impedance. An extensive literature survey concerning the analysis of non-planar radiating microstrip structures as well as the investigations of the aforementioned design characteristics is included in the classic book Wong 1999 . The mathematical methods developed for analyzing the behavior of a spherical microstrip may be categorized as follows i the full-wave approach implements the method of moments MoM to approximate the surface current on the PEC patch by means of suitable basis functions Uwaro Itoh 1989 Tam Luk 1991 Wong 1999 Sipus et al. 2003 Giang et al. 2005 ii the cavity model analysis .