| Cavity-backed Slot Antenna (CBSA) has been studied since1960s, which owns many advantages, such as solid, co-planarity and easy processing. However, CBSA has never formed a complete theory model, and the limit of poor operation ability of computer at that time makes it difficult for the practical design of CBSA. Now, with the improvement of the simulation ability, CBSA is paid more and more attention in some fields where coplanarity needs high quality. On the basis of theoretical analysis and numerical simulation, the2.4GHz and dual-frequency WIFI CBSA are designed, which are suitable for outdoor communication. This thesis focuses on the effect of the cavity-backed depth to the radiation characteristic of slot antenna, the building of the antenna input impedance circuit model, the practicability and dual-frequency of the CBSA. The main work and achievements are as follows:1. About the academic debate of the cavity-backed depth which should be half or one quarter, waveguide wavelength or air wavelength. This thesis clears that when the cavity-backed depth equals one quarter waveguide wavelength, the CBSA will have the maximum radiation. The conclusion is based on the analysis of the electromagnetic wave reflection model in the waveguide.2. This thesis puts forward a new input impedance circuit model of the CBSA based on the simulation results of the cavity-backed depth to the slot antenna input impedance.3. According to the simulation analysis results of the slot length, cavity-backed depth, feed place and antenna loads (rainproof membrane and PCB circuit are included) which will affect the antenna, the empirical conclusions of the CBSA design are got. The conclusions are that the antenna resonance frequency is up to the slot length and cavity-backed depth, the antenna impedance matching is up to the feed place. The test results show that the2.4GHz CBSA can completely replace the common monopole whip antenna.4. It designs dual-frequency CBSA working at WIFI band with two methods. The first method can get dual-frequency by changing the slot length and feed place. The advantage of this method is simple processing, moderate antenna bandwidth and gain. The other method combines the cavity-backed structure and microstrip antenna, forming cavity-backed microstrip slot antenna. With the problem of the impedance matching worsen by the cavity-backed, this thesis takes the methods of the metal sheet in the slot and the cross metal stripline in the cavity-backed, so that the impedance matching status can be improved. The test and simulation results show that the two kinds of antenna designed can work at2.4GHz and5.2GHz. |
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