Modeling Of Probe Fed Patch Antenna And Design Of Filtering Antenna

Microstrip antenna has been widely used in the field of wireless communication, due to its outstanding properties of easily fabricated, low profile and easily integrated with radio frequency and microwave circuit. In order to design convenient and reduce the error of antenna design, it is required to combine the antenna design and its theoretical analysis. Lumped element equivalent circuit method is not only simple in calculation, fast and accurate, but also provides a clear physical idea of work mechanism for antenna. With the growing demand of the wireless communication, antenna needs to be integrated with other circuits in a single device, which has become the mainstream design method of RF front end. The antenna and filter are integrated into a single device with the functions of radiating and filtering at the same time, and the device is called filtering antenna.In the first part of this thesis, the research status of microstrip antenna is presented, a brief introduces of basic theory of the microstrip antenna is introduced, including microstrip antenna feed means, theoretical analysis method and some electrical parameters. Then the principle theory of filter and some performance parameters involved in the design are summarized.In the next, classical lumped equivalent circuit element method is used to model the probe fed rectangular microstrip antenna operating at 2.4GHz. Through theoretical analysis and simulation, electromagnetic simulation and circuit simulation results can agree with each other in a relatively wide frequency band. For the narrow-band characteristic of the studied microstrip antenna, a Γ type matching network is adopted to broaden its bandwidth. After taking the Γ type matching network, the antenna impedance bandwidth increases from 36.5 MHz to 92.8 MHz, this can prove the validity of the proposed method.Finally, in order to realize the validity of the equivalent circuit in a broadband, this paper puts forward a new kind of lumped element equivalent circuit method, which uses partial access method to model the probe fed patch antenna, this method can make the equivalent circuit of the components and physical model has more reasonable. The reflection coefficient and input impedance of both antenna structure and its equivalent circuit model can keep consistent in a wide frequency range. In order to verify the feasibility of the equivalent circuit modeling, based on the filter synthesis theory and the proposed equivalent circuit, design of a 2.4GHz filtering antenna with characteristics of second-order Butterworth bandpass filter is demonstrated. In the design, the second port and the last resonant circuit of the prototype filter are replaced by the proposed equivalent circuit of a 2.4 GHz probe fed patch antenna. Comparisons between results of electromagnetic simulation and equivalent circuit modeling show good agreement. The measured results, including the reflection coefficient, radiation pattern, and radiation gain versus frequency, agree well with the simulated ones.