| With the rapid development of mobile communication technology in recent years,the number of mobile users has increased dramatically,and mobile data traffic will also explode.However,spectrum resources are very scarce.Therefore,the contradiction between the large number of users and the shortage of spectrum resources is becoming increasingly prominent.To solve this problem,smart antenna technology came into being.The smart antenna improves the capacity and quality of the communication system by controlling the beam direction and shape of the antenna,and is realized by methods such as beam switching technology and reconfigurable technology.The antenna array is one of the key components in the smart antenna system.The most commonly used are linear arrays and rectangular planar arrays,but these two antenna arrays are not easy to provide omnidirectional angular beam scanning,and the beam shape and gain will change during the scanning process.,And the ring array antenna can make up for the above shortcomings,therefore,this paper has studied beam switching/reconfigurable ring array antenna and achieved the following results:(1)According to the basic theory of the ring array antenna,the directionality and change law of the ring array were investigated through MATLAB simulation,and the effects of the radius wavelength ratio,the number of array elements and the current of the array elements on the pattern were mainly explored.Through simulation,the conditions and array element current distribution required to form a double beam in the horizontal plane are obtained,and the beam switching function is realized by an amplitude control method that cyclically changes the array element current size.(2)An embedded microstrip fed printed monopole antenna with a working frequency range of 3.4GHz to 3.6GHz was designed.Using the printed monopole antenna as the array element,a 6-element circular array antenna was designed and used.HFSS electromagnetic simulation software performs simulation optimization to realize the radiation characteristics of the unidirectional beam.In order to make the unidirectional beam have better directivity,a 7-element circular array antenna loaded with a central array element is designed,and a full range of beam switching is realized through amplitude control.On this basis,the designed antenna array was physically processed and tested,and the maximum gain of the unidirectional beam was 1.5dBi,the front-to-back ratio was about 7dBi,the 3dB lobe width was about 90°,and the amplitude control method was adopted.To achieve beam switching,the beam after switching is not much different from the beam before switching,which verifies the simulation results.(3)A quasi-Yagi antenna designed as a balun-fed printed dipole antenna is used as the active vibrator,and the working frequency band is 3.4GHz?3.6GHz.The bias circuit controls the conduction and cut-off of the diode in the antenna,so that the pattern can be reconstructed.Then,the reconfigurable quasi-Yagi antenna is used as an array element antenna to form an 8-element circular array antenna.A parallel switch circuit structure is used to design an RF switch circuit to control the operation of two array antennas at different positions.By switching the working array elements,beam scanning in 16 directions can be achieved and cover the entire horizontal plane.On this basis,a microstrip fed printed monopole antenna was designed as an active quasi-Yagi antenna,as an array element,an 8-element circular array was formed,and the circular array was physically processed and tested,The test shows that the maximum gain of the state 1 beam is about 4.8dBi,the front-to-back ratio is about 10dBi,and the maximum gain direction is about 40°;the maximum gain of the state 2 beam is about 5dBi,the front-to-back ratio is about 8dBi,and the maximum gain direction is about 55°,Compared with the simulation,the performance of the measured results is slightly reduced,but the simulation results are verified. |
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