Study And Design Of A Miniature Wide Band Antenna

Due to good performances, sinuous antennas are widely used in Direction Finding Systems.However, when Direction Finding Systems are applied in small vehicles, such as automobilesand airplanes, smaller sizes are required. The topic of this thesis is to do miniaturization ofsinuous antenna to meet these specific requirements.This thesis first introduces the theory of wideband antennas miniaturization as well as per-formance parameters that are used to evaluate the performances for small antennas. A varietyof antenna miniaturization technologies are also explored, including: dielectrically loaded andreactively loaded antennas, increasing current paths, inspiring more radiation modes simultane-ously, using metamaterials, as well as antenna optimization with smart algorithms.Then, we made an investigation on the basic sinuous antennas, which took the sinuousantennas’ characteristics, simulations and measurements into consideration. The investigationlaid the foundations for further research work. The dimension of the sinuous antenna is largelyreduced with an introduction of a coupling ring. The diameter of the Sinuous antenna loadedwith a coupling ring is 44 mm, which indicates that the reduction coefficient of the Sinuousantenna is 1.36. The antenna achieves a 154% bandwidth for return loss > 10 d B, covering2.45~18.7GHz. Due to the coupling ring, the impedance matching at lower frequency bandis improved, which enable the Sinuous antenna to realized miniaturization.This thesis also researched other methods for sinuous antenna miniaturization. One methodis reactive loading by changing the antenna structure. Such as change the Sinuous antenna to agradient structure. A second method is loading more coupling ring in the horizontal and verticaldirections, respectively. In addition, other methods such as inductive loading also can be appliedfor sinuous antenna miniaturization.Through the above research, we systematically investigated the operating principles anddesign methods of miniaturized sinuous antennas. Finally, the thesis has summarized the minia-turization technologies of sinuous antennas.