Reconfigurable Antenna Based On Liquid Water Loading

With the rapid development of wireless communication,the wireless communication equipment is also developing towards miniaturization,multi-function and multi-band.Antenna is one of the key devices of the RF front-end,its performance requirement is becoming more and more demanding.In addition to the continuous improvement of the traditional antenna structure to meet the current communication needs,the enthusiasm for exploring new antenna technology is becoming stronger and stronger.With the development of fluid antennas,especially the emergence of liquid water antennas,which have opened up a new direction for the new antenna technologies.Liquid water antennas break the traditional idea of using solid objects as antenna radiators.The liquid water has a high dielectric constant,which is easy to conformal,easy to adjust volume,environmental protection,and renewable resources and so on,which has a very broad research prospect in the fields of miniaturization wireless communication and biomedical antennas.Taking the research of novel liquid water antenna as a starting point,this paper focuses on the reconfigurable antenna based on liquid water,with the aid of 3D printing technology.The main contents and innovations are as follows:1.Based on the basic principle of Yagi antenna,a two-element Yagi antenna with a single metal column,or a single liquid water column,or a liquid water dielectric array as a passive element,and a metal monopole antenna as an active element is studied.Finally,a pattern reconfigurable antenna is designed by using liquid water dielectric array as passive elements.A pattern reconfigurable antenna is obtained which can switch the omni-directional radiation pattern to a directional radiation pattern,and also realize different gains and different beam pointings.2.Based on the idea that the traditional solid-state dielectric grating reflector has strong reflection characteristics on electromagnetic waves,a dielectric grating composed of several liquid water pillars is innovatively proposed to replace the traditional solid-state dielectric grating,an arc-shaped water dielectric grating reflector compose of multiple liquid water pillars is designed.First,a hollow pipe made of synthetic resin material is obtained by using 3D printing technique.Since a resin material has a low dielectric constant and the thickness of the pipe wall is very thin,so the hollow pipe has a particular weak reflection effect on electromagnetic waves.However,when the hollow pipe is filled with liquid water to form a mixed medium with high dielectric constant,it will enhance the reflection capacity on electromagnetic waves greatly.By optimizing the number of hollow pipes,the height of the hollow pipes,the radius of the hollow pipes,the arrangement period of the hollow pipes and other relative parameters,a water dielectric grating reflector with good reflection characteristics can be obtained.Utilizing the natural fluidity of liquid water,the water can be manually pumped in and pump out by using a micropump or syringe,in order to achieve the states of having water("On")and without water("Off)in the dielectric grating reflector.The two states,that is,the on/off switching function of the liquid dielectric grating reflector is realized.Taking a planar circular monopole antenna as a verification example,when the water grating reflector is at “On” state,the pattern of the planar circular monopole antenna changes from approximately omnidirectional to directional radiation.Finally,a three-beam reconfigurable antenna is realized by using three sets of water dielectric grating reflectors.2.A frequency and pattern reconfigurable antenna is designed.Conventional liquid water antennas need PCB boards as the substrate for designing antennas.This method requires the liquid water dielectric block to be bonded to the circuit board,resulting in a complicated post-processing process and a certain assembly error.The synthetic resin material which is commonly used in the 3D printing technology,has a similar dielectric constant to that of PCB board.So that the dielectric substrate printed by resin material can be used instead of conventional PCB boards.Therefore,the proposed antenna is formed by using 3D printing technology except for the feeding part,which simplifies the design process of the fluid antenna.The peoposed frequency and pattern reconfigurable antenna consists of a driving element and five directional elements.The driving element is excited by an L-shaped metal microstrip line,and the five directional elements are linearly arranged respect to the driving element with a certain interval.The operating frequencies can be tunable by controlling the height of the liquid water of the driving element;the antenna beam-widths and gains can be tunable by controlling the number of directional elements.4.The radiation characteristics of the rectangular slot coupled-fed antenna and H-type slot coupled-fed antenna are studied respectively.The liquid water switches are fabricated by using 3D printing technology.The water switches are loaded on the appropriate position of the slot of the antenna,so that the antenna has the function of frequency reconfiguration.The proposed antenna with three tunnable frequencies is realized by loading two water switches on the rectangular slot coupled-fed antenna,and the proposed antenna with five tunnable frequencies is realized by loading four water switches on the H-shaped slot coupled-fed antenna.