Investigation On Filtering Anteena Based On Coupling Matrix

Filter and antenna are essential microwave devices in communication equipment,and their performance decides whether the equipment could work well.In the past,filter and antenna are designed separately and connected through a matching network,which is not conducive to the miniaturization of equipment.In recent years,the co-design of the filter and the single-resonant antenna has been proposed.By establishing the equivalent circuit model,the module consisting of filter and antenna can be miniaturized.However,single-resonant antenna is generally difficult to meet the needs of broadband applications.And in the meantime,there is no co-design method of the multi-resonant antenna and filter at present.By introducing the transmission zero,the filter can be miniaturized and have a high frequency selectivity on low-order response.In this paper,the filtering antenna is studied in terms of miniaturization,broadband and high frequency selectivity.The detail is depicted as follow:(1)Diagnosis and tuning of filtering antenna based on coupling matrix.In this method,the antenna is considered as the resonator of the filter and the far-field radiation from the phase center of the filtering antenna is regarded as its second port.The coupling matrix is extracted according to the reflection and the realized radiation efficiency of the filtering antenna,and then it will be diagnosed and tuned by space mapping.For example,a stacked patch antenna(similar to a second-order filtering antenna)with poor initial response is tuned to basically meet our requirements by seven iterations of sensitivity matrix,which validates the feasibility of the method.(2)Design of quasi-elliptic filtering antenna.The traditional methods to obtain zero transmission are cross-coupling(coupled with non-adjacent),mixed coupling(introducing electronic coupling and magnetic coupling simultaneously),multi-mode resonators(different modes in a resonator),external tap coupling and so on.The stacked patch antenna and the dual-mode resonator adopt the method of the cross coupling and multi-mode resonator respectively.Here,the stacked patch antenna and the dual-mode resonator are integrated to form the fourth-order filtering antenna,which could make pass-band containing a transmission zero on both sides separately,and thus the harmonics can be suppressed when a low-pass structure is added to the feeding line.