Research And Design On Omnidirectional Filtering Patch Antenna

Miniaturization and integration are the trend of modern wireless communication systems.High integrated RF frond-end with high performance can reduce the system size and enhance the overall performance.Antennas and filters are two of the most important components in RF front-end.They are cascaded together to eliminate the out-of-band noises in traditional designs.Matching circuits are usually used between the two components,which not only increase the circuit footprint but also bring about extra loss.If the two components can be integrated into a single module,named as filtering antennas,the antenna would be able to simultaneously play the roles of radiating and filtering.In this case,the system size can be effectively reduced and a higher integration level would be obtained in RF front-end,leading to a higher overall performance of the systems.Therefore,filtering antennas are becoming a topic of concern in the antenna field.In this paper,three omnidirectional filtering antennas are designed based on the fusion design method with the thorough theory of filters and antennas.The main work of this article is as follows:(1)An omnidirectional circular ring patch antenna is proposed.Based on traditional omnidirectional annular slot filtering antenna,we effectively improve the frequency selectivity and out-of-band suppression by using a circular annular slot and a circular ring patch.This antenna has better gain performance and impedance bandwidth without introducing extra filtering circuits and special feed structures.(2)A wideband omnidirectional slotted patch antenna with filtering response is proposed.A circular slot is skillfully introduced on the circular ground plane,this design not only broadens the passband bandwidth of the antenna,but also can effectively increase the frequency selectivity and the stopband suppression level,comparing with the traditional patch slots.At the same time,the addition of the circular ground plane slot can combine the three modes of the antenna,so that the bandwidth of the passband can be further broadened.(3)A low-profile omnidirectional filtering antenna is proposed.The use of equilateral triangular patch can produce a radiation null at the upper band-edge,ensuring that the upper stopband with good filtering.At the same time,the equilateral triangular patch has the effect of reducing the patch size,comparing with the circular patch.The combination of a shorting vias and a ring slot leads to an LC resonance,generating a radiation null at the lower frequency to improve the lower band-edge filtering characteristics and increasing the bandwidth of the passband.