Novel Design Of Ka-band Microstrip Circularly Polarised Antenna

Millimeter-band antennas are important for the realization of next-generation 5G wireless cellular networks and the Internet of Things(IoT)technology.Due to the available broadband bandwidth,the electromagnetic spectrum can transmit data by multi-gigabit per second for increasing system capacity.Millimeter-band antennas will play a pivotal role in modern wireless communication systems,such as in future 5G communication networks.At the same time,the satellite system can also realize the allweather link of the sky,the earth and the sea.The circularly polarized antenna is an important part of the communication system.Because the circularly polarized antenna with strong mobility is less affected by the faraday rotation effect.The receiver and launcher do not have to keep the same direction.It can accept any linearly polarized wave,the transmitted wave can also be accepted by any linearly polarized antenna.These excellent characteristics make circularly polarized antennas an indispensable part in wireless communication systms,like satellite communications for positioning.At the same time,because the microstrip antenna has many outstanding features,such as smart structure,easy integration,low cost,etc.,it is particularly suitable for making circularly polarized antennas.The impedance bandwidth of common single-layer antennas are relatively narrow,the average gain is below 5dBic.In order to solve this problem,the laminated patch antenna is used in this article to broaden the impedance bandwidth and improve the gain.The design of this article includes these parts:1.Two broadband circularly polarized antenna are proposed.The basic feeding structures of these two antennas are the same.The bottom layer is a microstrip loop feeder.The microstrip loop feeder includes four phase branch converters.Each converter can guarantee phase difference for 90 degrees.The ground plane with a cross slot is in the middle.The top metal layer is the radiating surface.The difference between the two antennas is that they have different radiating structures.The first antenna surface is a square matrix,the second is a patch array with branches on the basis of the square,and the second antenna can increase the gain comparing with the first one.The impedance bandwidth of both antennas is above 30%.The axial ratio bandwidth is about10%,and the gain of the two antennas in the band is greater than 5dBic.The simulation and test results of the two antennas will be discussed.2.The array is designed on the basis of the two units.The T-type power divider with the same power and phase is used to form the antenna into a 2×2 array.The maximum gain of the array will reach 12 dBic.The array uses two units as the basic structure,and the two array antennas are also processed and tested.The processed results of the two antenna arrays are in good agreement with the simulation results.The performance of the antenna array is good so that the array can also be used as unit to form a larger array.In order to verify the performance of the array,we use the 2×2 array as a unit to form 2×4 and 4×4 array.The gain of first array can reach more than 15 dBic in the whole band and the axial ratio bandwidth of second array can reach 14%.3.Based on the broadband circularly polarized antenna,the structure of radiation patch is changed so that a dual-band circularly polarized antenna is proposed.The radiation surface of the antenna has two nested structures.The inner radiation structure is a rectangular patch.The outer radiating structure is a square ring with branches.The antenna with one feeding port can achieve circular polarization in two frequency bands,and the axial ratio bandwidth in dual-band is greater than 7%.The internal gains are all greater than 5dBic.Finally,the structure of the dual-band antenna is also processed and tested.