Research And Design Of Filtering Antennas Based On Cross-Dipole

Antennas and filters are key components of RF front-end circuits,and their size and performance can have a decisive impact on the design quality of the entire communication system.The traditional method is to independently design these two types of devices and then cascade them,which will inevitably introduce the loss caused by the connection.In addition,base station antennas are also difficult to miniaturize themselves in order to ensure radiation characteristics.In recent years,the proposal of a new design called filtering antenna has attracted much attention.It integrates the antenna and filter into one and realizes the dual functions of radiation and filtering at the same time,so as to meet the compact design goals and performance improvement requirements of the RF front-end.Based on the cross-dipole widely used in the design of base station antenna,the following researches are carried out on the optimization of radiation performance and the introduction of radiation nulls in the design of filtering antennas:1.Design of a low-profile cross-dipole antenna based on artificial magnetic conductor.After analyzing the structure and radiation principle of the cross-dipole in detail,the gradient structure and the artificial magnetic conductor are applied to solve the problem of high profile and realize the expansion of bandwidth.Finally,the working bandwidth of the antenna is significantly broadened,and its structure size is much smaller than that of a conventional dipole antenna.2.Design of a filtering dipole antenna based on improved radiator.To introduce radiation nulls through the radiator of the antenna,the antenna realizes band-pass filtering response by placing half-wavelength U-shaped parasitic patches in the vertical and parallel directions of the dipole arm.Through a pair of slits etched on the parasitic element,the roll-off rate at the upper edge of the passband is further optimized.3.Design of a filtering dipole antenna based on improved feed line.To introduce radiation nulls through the feed line of the antenna,the antenna achieves band-pass filtering response by loading two quarter-wavelength open-circuit microstrip lines corresponding to different frequencies on the feed lines of the dipole.Through adding a full-wavelength microstrip square ring below the main radiator,the out-of-band radiation in the lower stopband is further suppressed.4.Design of a filtering dipole antenna based on improved ground plate.To introduce a radiation null through the ground plate of the antenna,the antenna obtains low-pass filtering characteristics by the half-wavelength complementary split-ring resonator etched on the back ground plate.After the quarter-wavelength open-circuit microstrip line is loaded on the front feed line,the antenna finally realizes band-pass filtering response.Further,the out-of-band suppression level of the lower stop band is improved through the parasitic full-wavelength microstrip square ring under the main radiator.In this paper,a low-profile cross-dipole antenna and three filtering dipole antennas are designed.The design process of the low-profile antenna focuses on the optimization of the crossdipole itself,while the design process of filtering antennas focuses on the resonator theory that can introduce radiation nulls.From the design results of filtering antennas,it can be known that the three designed antennas have realized the band-pass filtering response by changing their own radiation characteristics,and completed the integrated design purpose of filtering and radiation.