Design Of Beamforming Antenna For Building Coverage

Since 21th century,the construction of urbanization in our country has been developing rapidly,which has led to the problem of poor signal coverage in build-intensive areas.The annual growth rate of high-rise buildings in our country has exceeded 20%,the buildings in cities are in one row after another,the average height is constantly rising,and the cities are rapidly expanding into complex three-dimensional spaces.In the areas where buildings are concentrated,the problem of network signals occur frequently,for example,the signal intensity is weakened,the signal coverage is uneven,the blind area exists,poor communication or data transmission due to poor signal quality,and so on.Therefore,in order to meet the demand of the rapid development of the town,it is necessary to carry on the research of the signal three-dimensional coverage technology,thus solve the problem of signal three-dimensional coverage for building concentrated area.At present,one of the effective methods to solve the three-dimensional signal coverage is to obtain the desired radiation pattern in the elevation plane by array antenna beamforming technology.The beamforming antenna array formed by the microstrip antenna array has the advantages of small volume,low cost and easy implementation,and can meet the requirements of a series of beamforming.Therefore,this thesis studies the design and implementation methods of beamforming microstrip antenna arrays.The specific work and results are as follows:(1)In this thesis,the design theory of the microstrip antenna is first studied,and then an antenna unit operating in the LTE-A frequency band is designed by using the slot-coupled microstrip antenna structure.(2)Aiming at the problem of uneven building coverage,a new coverage plan is proposed.In order to achieve the proposed coverage scheme,the antenna array beamforming methods are studied.On this basis,using MATLAB software to write the beamforming code.In the code,the Fast Fourier Transform method is used to calculate the far-field pattern.The advantage of doing this is that you can quickly and easily solve the pattern in the computer.The optimization method for beamforming uses the genetic algorithm,which can accurately obtain the amplitude and phase distribution of each array element satisfying the expected direction pattern.Through the code in MATLAB,we can get the radiation pattern with different number of array elements,different array element spacing,different shaping patterns and different shaped areas.After a series of calculation and optimization,and taking into account of the existing laboratory conditions,finally determined using 8 microstrip antennas array to achieve shaped beam,and get the desired directional pattern of the excitation distribution for array antenna unit.(3)According to the requirement of excitation distribution for array antenna unit,the design methods of feed network are studied.Through the analysis and comparison of many kinds of feeding network scheme,it is finally determined that feed network should be designed with 7 Wilkinson power dividers.In order to realize the feed network,the voltage transmission coefficients from the input port to each output port are deduced first from the amplitude distribution value of excitation.Then calculate the power ratio of each divider,and design each divider according to the working principle of Wilkinson divider.With the help of HFSS simulation software,the power divider is optimized.Finally,seven designed dividers are cascaded into a complete feed network,and the co-simulation and optimization are carried out.(4)The 8-element array is composed according to the design requirements of the array,and then simulated the overall antenna array.By adjusting the phase of the output port for the feed network,the directional pattern characteristic of the array is improved;By adding fan-shaped branches at the bottom of the antenna array,the impedance matching bandwidth of the antenna is increased,and the standing wave ratio in the working frequency band is reduced.Finally,the physical processing is carried out according to the final result,and the antenna array is tested in the microwave dark room.The tested results show that the various indexes of the antenna array basically meet the design requirements.