Miniaturization Narrow Beam Of Ka-band Antenna

Narrow beam lobe is one of the important tragets about radar especially early warning radar after world war II. The narrow beam antenna has many advantages such as narrow beam, low sidelobe could improved radar antenna’s anti-jamming. It’s important significance on the development radar systems.This thesis mainly researchs includes: antenna antenna unit, Vivaldi antenna design,antenna array arrangement and feeder design, and reflector or lens structure ‘s affect on antenna’s beam and miniaturization.Firstly,this thesis illustrate antenna array as important way to achieve narrow beam antenna lobe,then constrast characteristcs and antenna feeder between Ka band microstrip patch antenna and Vivaldi antenna. Consider about antenna lobe orientation, Vivaldi antenna is choosed array antenna element. During the design Vivaldi antenna, use empirical equations which about slot line of Vivaldi antenna, groove line resonator, Vivaldi antenna’s gradient line and single array antenna’s feeder to analysis Vivaldi antenna size. After determinate antenna size, in order to research antenna’s array, without account of the size and coupling of antenna, we treat Vivaldi antenna as a point antenna, then simulate circular array structure whether influence antenna beam lobe. Let the matrix of Vivaldi antenna far-field as array factor into the far-field equation. It get Vivaldi draw circular array antenna lobe pattern. And then try to use equally space line array to simulation. Compare with two models structure,choose uniform linear array. At last, design the array antenna feeder,compare with Wilkinson power divider and T-centimeter device, choose the T-splitters to Vivaldi array antenna feeders.Research antenna beamwidth suppression, you not only consider their array element distribution arrangement, but choose other method such as reflector and lens antenna. Through simulate reflector antenna to observe its effect to antenna beam width, you could found that even though its restraints antenna lobe, improve side lobe. Analysis this situation, it might the two phase radiation could be overlaied when radiation passed through the reflector. Then try luneberg lens antenna structure, it found the luneberg lens antenna could make antenna beam narrow and increase the antenna gain. According to the electromagnetic wave propagation characteristics in different media, and establishment of rectangular lens. It could increase gain and reduce the antenna beam width. Finally, make this lens structure combine with Vivaldi array antenna, found its limit capacity about lobe beams. By analyzing the results, due to the increasing of gain smaller than itself, therefore the antenna’s narrow beam is ineffective.