Reseach On Planar Integrated Filter Antenna

With the development of integrated circuit technology,the active circuits have achieved the miniaturization or even micromation,so the whole wireless communication system began to require passive circuits to be more miniature and highly performed.So filter antenna characteristics takes an very important part in this.Microstrip filter antenna means a microstrip antenna which has a function of filtering at some certain frequency range.Since the microstrip filter antenna has the function of both antenna and filter,it has many advantages.In addition,due to the collaborative design of the microstrip filter and the antenna,the overall volume will be reduced and the performance will be improved.At the beginning of this paper,the traditional design method has been shown which takes the antenna and filter as two separate devices.Then we analyzes the deficiencies existing in this design method.Then,the research on the integrated design of antenna and filter in recent years are also been collected and studied.And based on the above theory,this paper proposes a new design method of microstrip filter antenna.The filter antenna is composed of a parallel coupled bandpass filter and a invers L-shaped antenna,in which invers L-shaped antenna acts as the third order parallel coupling level at the end of the resonator bandpass filter,so forms a third-order filtering microstrip antenna.The center frequency of the filtering microstrip antenna is 5 GHZ,and realizes a passband of 7.2% gain greater than 3 dB,and gain fluctuation index of less than 0.5 dB.And the simulation results go well with the test results.As an extension,we changed the feeding way of the parallel coupled bandpass filter,and the pseudo refers to the coupling structure is used to realize the strong coupling,which makes the line spacing increase,and more easy to processing.As the last part,the research work is summarized,and the possibility of further optimization of the filter antenna is discussed.