Research And Design On A Phased Array Antenna

The development of modern wireless communication technology is accelerating.Antennas play a vital role in wireless communication,and the requirement of antennas is more and more strict.On the one hand,the microstrip antennas have attracted much attention in recent years.Their advantage is that they have a low profile,light weight,diversified electrical properties and so on.On the other hand,because the electrical performance of a single antenna is relatively fixed,it can not meet the requirements of various types of antennas.The antenna array is composed of a lot of antenna elements,and it is the key to sloving the previous question.The antenna array can remarkably improve the whole gain of antennas.The phased array antenna is a new kind of antenna,and it is based on the antenna array.The phased array antenna can change radiation pattern to achieve the purpose of beam scanning by the way of the phase shifter controlling feeding phase of radiation element of the antenna array.There are lots of forms of the phased array antenna.For aircraft or missile carrier,the planar phased array antenna is not always the best solution,and the conformal phased array antenna can be bent to carrier surface,which is more and more popular.The conformal phased array antenna can fit on the surface of the carrier tightly.It has little effect on the performance of the carrier on condition that it can guarantee its electrical properties.What's more,it can also guarantee stealth performance of the carrier,so it can meet the requirement of information warfare.Above all,this thesis decides to design a microstrip conformal phased array antenna.The antenna element is a dual frequency circularly polarized microstrip antenna.The antenna array is composed of seven elements and it is placed on a nonplanar floor.A power divider,some phase shifters and corresponding control circuit are also the key part of the complete phase antenna array system.The main work of this thesis is as follows:1.Design a double fed stacked microstrip antenna.It uses air as the dielectric,and the feed excitation amplitude of its two feeding ports is equal and the phase difference is 90 degrees.It has a good circular polarization performance.The form of the feed network is 3d B branch bridge.As a result,it achieves a good performance of voltage standing wave ratio,gain and axial ratio at both high and low frequencies.2.Design a single fed stacked microstrip antenna.It adds a metal cavity around the microstrip antennas.It uses F4 B as the dielectric,and its dielectric constant is 2.2.Compared with the double fed stacked microstrip antenna,as a result,it has a worse performance of the voltage standing wave ratio,axial ratio.The performance of gain is different,and the gain of the elevation of zero degrees is lower,but it has a wider beamwidth and the gain of the low elevation is higher.Next,it is processed into a physical object and tested,the measured results are in good agreement with simulation results.3.In order to reduce the weight and the cost,the F4 B of the single fed stacked microstrip antenna is replaced by air.According to the actual situation,the antenna is placed on a nonplanar floor during the simulation process.As a result,its gain is different from the gain of the previous antennas.As for the appearance,the height and area will increase to some extent.Next,it is processed into a physical object and tested,the measured results are in good agreement with simulation results.4.Compare the performance of the antenna array composed of the antenna elements designed previously,especially the gain of the beam scanning at a low elevation.Considering the performance of the antenna array and the cost,we decide to use the single fed stacked air microstrip antenna as the phased array antenna element.According to the actual requirements of the phased array antenna,we select the seven antenna elements,which are arranged in the side surface of a cylinder and the cylinder has a bottom surface radius of 2.5 meters.Through the adjustment of distance and rotation angle itself,it can meet the requirements of the antenna array.5.Design a ring power divider to feed the seven antenna elements.It uses F4 B as the dielectric,and its dielectric constant is 2.2.The microstrip lines are densely packed,so the structure of the power divider is compact.As a result,it meets the requirements of the standing wave,transmission loss and isolation.Next,it is processed into a physical object and tested.The measured results are in good agreement with the simulation results.