Research On Filtering Antennas And Their Frequency Reconfigurable Technology

Antenna and filter are two necessary components in wireless communication system.Antenna is a radiator which convet the microwave energy in transmission line located in the RF terminal into the space energy.Conversely,it can also be used as a receiver.Filter is a two port device which outputs the input signal from its input port through the output port after a certain selection.In many cases,the antenna and filter can be used independently,and the filter connecting the back end of antenna in series can realize filtering when the antenna needs filtering.However,the overall size of system will become bigger through the way of connecting two devices,and the mismatch of the junction will increase the loss,and the separate processing of antenna and filter will increase the cost.In order to resolve the question,the antenna and filter can be integrated together,which is equivalent to the combination of two devices into one device.This can also increase the stability of the system,and realize the miniaturization,low loss,high matching and low cost of the whole RF terminal system on the basis of ensuring the system performance.In order to achieve more and more functions in a limited space,reconfigurable antenna emerges.It can realize many functions through the electrical adjustment of components,so that complex functions can be realized in a limited space.In this dissertation,single polarization filtering antenna,dual polarization filtering antenna,filtering antenna near and far passband and reconfigurable filtering antenna are studied.The main contents of this dissertation are as follows:1.The mono-polarized filtering antenna is studied.Four antennas are designed.The first antenna is a multi-layer filtering antenna.By loading coupling branches,shorting stub on the feed line and slot on the radiation patch,the radiation zero of the filtering antenna near passband is introduced,and the filtering function is realized.Based on the traditional dipole antenna,the second antenna is designed by loading shorting stub,slot,open stub,and three radiation zeros near passband are generated and the omni-directional filtering radiation is achieved.The introduction of two radiation zeros distributed on both sides of the passband and the enhanced bandwidth is obtained by loading branches and shorting pins on the feed line in the third antenna.Finally,filtering function near passband is realized.The fourth antenna is a dual frequency filter antenna based on a short-circuit resonator.2.The dual polarized filtering antenna is studied.A single-layer dual polarized filtering antenna is designed.On the basis of a single layer substrate,the antenna loading trapezoidal shorting patch,slender shorting branch,parasitic shorting patch and L-shaped branch is adopted to introduce transmission zeros on both sides of the passband.So filtering function near passband is realized.3.Antenna with filtering function near and far passband is studied.Firstly,the dipole antenna which has filtering effect on the far passband is designed.The antenna can suppress the signal in the far passband by loading shorting pins,slots and coupling stubs on the radiation patch.Secondly,the antenna with the function of filtering function near and far passband is studied.The designed antenna is a unidirectional radiation antenna which can filter signals both the near passband and the far passband,simultaneously.The antenna can filter signals at both the near and far passband by loading slot at the radiation patch,loading shorting pins and coupling stub.Finally,a patch antenna with the function of filtering at near and far passband is designed.The signals at near and far passband are filtered by loading shorting pins on the feed line and two shorting pins on the radiation patch.4.A filtering antenna with adjustable passband is designed.The filtering network is loaded on the basis of the traditional monopole antenna to realize the filtering function.Adjustable bandwidth modes of the antenna are realized by adjusting the on-off of the diode on the filter network.