The Design And Realization Of The Wide-band Antennas

With the further development of the wide-band wireless communication and software radio technology, a variety of wide-band systems emerged rapidly, so that the study of the wide-band antennas has been paid much more attention by many scholars. After discussion on the development and means of the wide-band antenna, the main task of this thesis is focus on the study of the three type wide-band antennas: conical antennas, planar monopole antennas as well as self-complementary symmetric antennas. These antennas are designed and analyzed in detail. And some antenna samples are fabricated and measured. The test results show that these antennas have the characteristic of wide-band and the different features of gain and radiation pattern. These establish a good foundation for the application to the wide-band systems.This thesis is divided into four parts. First of all, the significance and research trends of the wide-band antennas are introduced briefly and the electrical properties and possible realization means of wide-band antennas are also discussed. These give the theoretical basis for studying the specific wide-band antennas.Secondly, the broadband conical antenna is analyzed and discussed. By using the 3D numerical simulation software, the ordinary broadband conical antenna is analyzed, optimized, especially the affection on the antenna performance from structure parameters are studied in details. Then a new type of the conical antenna is proposed with half ball loading, which can make the antenna work at a lower frequency band. The antenna is fabricated and measured. The measured results indicate that the VSWR of the antenna is less than 2 in the working frequency band, which proves that the methods such as terminal loading, dielectric overlay can reduce the low working frequency of the antenna. And this antenna is suitable for UHF communications with good radiation performance and stable gain.Thirdly, the wideband planar monopole antennas are focused on study. Two microstrip-fed wideband planar monopole antennas are presented according to the theory of the planar monopole antennas. The structure parameters of the two antennas are designed and analyzed. The samples of two antennas are produced and measured respectively. The test results show that the relative bandwidth of the taper microstrip planar monopole antenna is about 136% from 434.5MHz to 2280.5MHz while the crescent-shaped microstrip planar monopole antenna is 118% from 3.079GHz to 11.989 GHz. The two antennas have the same advantages, such as simple prototype, easy manufacture, wideband.Next, a novel wide-band printed antenna based on the self-complementary structure with decrescent symmetrical dipoles and impedance matching network is proposed. The choices of the structure parameters are studied in details. The measurement results show that the relative bandwidth of the proposed antenna is 84.2% with good radiation performance. And the proposed antenna also has the advantages of simple structure, wideband, convenience machining and compact in size. This provides a new solution to realize the wideband antennas.Finally, the entire work and the future prospect of the relevant research work are summarized.