The Research And Realization For Loaded Wire Antenna Of VHF To UHF

It is well accepted that the anti-jamming performance of our electronic devices, e.g.wireless telephones and radars, shows significant contribution in ensuring the essentialcommunication and surviving capability in today’s digital battle field. Due to itspeculiar excellent anti-jamming ability, frequency hopping technique has been widelyapplied in the digital communication systems. Consequently, line-shapedomni-directional wire antennas with wide or ultra-wide band are preferred by thetransmitter and the receiver of modern frequency hopping communication system. Themajor work in this thesis is related to improving the bandwidth of the antenna specifiedabove, and has the following content:1. Introduction of the analysis and optimizing method in line-shaped wire antennadesign and wideband impedance matching methodology.2. According to the current line-shaped wideband wire antenna principle, by usingthe method of moments (MOM), the loaded line-shaped wire antenna has beenemphasized and studied. The operation properties of line-shaped wire antenna withdifferent feeding and/or different loading are shown and synthesized. By applyinggenetic algorithm, the loaded line-shaped wire antenna can be optimized. Theoptimizing principle is discussed, while the corresponding procedure with coding isexhibited together, which would offer the loaded line-shaped wire antenna design andoptimization theoretical basis and software support.3. In order to realize the matching of ultra-wide band antenna, a new model basedon the standing wave ratio (VSWR) method is proposed. Combining the geneticalgorithm, the application of SWR method has been extended. With the using of bothimpedance Smith Chart and circuit synthesizing, a generalized impedance matchingmethod with breaking the application restriction of real frequency method, which canrealize ultra-wide band impedance matching, is proposed. With the aid oftransmission-line-transformer theory, coupled circuits are applied in achieving theimpedance matching, benefiting a matching network with reduced dimensions.4. By using the genetic algorithm, the loaded line-shaped wire antenna is optimized. An omni-directional antenna working in a frequency band from VHF to UHF isfabricated and measured. This antenna, with voltage standing wave ration (VSWR)lower than2.5in the whole ultra-wide frequency band and horizontal gain greater than-3.5dBi covering90%frequency band, could be used in communication system basedon frequency hopping.