| Antennas are the essential components in wireless communication system, the performance of which will be related to the success or failure of the system. Because of low cost and low profile and so on, microstrip antennas are widely used in wireless communication systems. With the development of wireless communication system technologies, the demand for the broadband technologies of micrsostrip antennas is increasing day by day. It is more commonly way to adopt dielectric substrates with low dielectric constant and thick thickness in the broadband technologies of micrsostrip antennas. However, when the dielectric substrate thickness ranges from 0.1λd to 0.2λd (λd is the medium wavelength), the existing analysis formulae of the resonant frequency and quality factor for circular and rectangular patch antennas will be no longer applicable. Electromagnetic numerical simulation software can be used to optimize microstrip antennas, but it has low efficiency and poor versatility, and it can not establish a precise mapping relationship between the physical dimensions and electrical parameters of antennas. So it is necessary to study the analysis formulae of microstrip antennas.Under the supports of the National Naturel Science Foundation of China (Foundation number:61401056), this thesis is devoted to the researches on the analysis formulae of microstrip patch antennas. The main achievements obtained are as follow:(1) A novel analysis formula of the resonant frequency for the circular patch antenna is proposed. The formula is obtained through curve fitting techniques and Taguchi optimization method based on 3449 sets of simulated datum, the validity of which is proved by electromagnetic simulation experiments. The simulation results show that the average relative deviation is less than 2% and maximum relative deviation is less than 3% between formula calculation and simulation.(2) A new analysis formula of the resonant frequency for the rectangular patch antenna is presented. When the length, width, dielectric constant and thickness of the antennas are given, the resonant frequency of rectangular patch antennas with the single or double dielectric substrate can be directly calculated by using this formula. The validity of the formula is verified by the electromagnetic simulation and actual test. There is a better agreement between simulation results and measurements, and the average relative deviation is less than 3% and maximum relative deviation is less than 5% between formula calculation and simulation. In addition, simulation results and measurements indicate that increase of the substrate electrical thickness can upgrade impedance bandwidth of the antennas, but the substrate electrical thickness should be less than 0.13.(3) An improved analysis formula of the quality factor for the rectangular patch antenna is put forward. The existing formula is improved by using curve fitting techniques and Taguchi optimization method, and the validity of the improved formula is verified through electromagnetic simulation. The simulation results of HFSS and ADS software show that the improved formula has higher accuracy than the existing formula for rectangular patch antennas with varying in dielectric substrate thickness from 0.06Aλd to 0.14λd. |
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