The Design Of A Circularly Polarized Antenna Array

In recent years, wireless communication technology has been developed considerably.As a key member of the communication system, Antenna’s performance directly affects thecommunication quality of a wireless communication system. With the wide application ofsatellite communications, radar, mobile communications, RFID and other communicationtechnologies, electromagnetic environment has been more complex. Therefore, a singlepolarized antenna could not meet demand. Circularly polarized antenna can receive anywave and has the characteristics of rotation orthogonal and anti-interference. So it getsextensive concern. In this paper, a circularly polarized antenna array for undergroundcommunication has been proposed. In underground communication system, antenna isfixed in underground mines or tunnels. A high-gain antenna have the characteristics ofgood resistance to absorption of the rock and transmission loss. At the same time,circularly polarization wave has the ability of anti-interference.In this paper, based on the circularly polarized antenna and array antenna theory, acircularly polarized array antenna working at5.8GHz is presented. It has four identicalcircularly polarization unit as main radiator. Adopting sequential rotation technique,feeding network can generate four excitation signals of equal amplitude and90ophasedifference to drive circularly polarization wave.In this paper, adopting a circular microstrip patch as its infrastructure, a circularlypolarized antenna unit is proposed. Then the circularly polarized antenna unit is applied tothe antenna array. The antenna works on a substrate with the dielectric constant of2.65anda thickness of3mm. The simulation results show that center frequency of the antenna is5.8GHz. The antenna provides the peak gain of12.3dBi, the axial ratio bandwidth of7%and the input return loss less than-10dB bandwidth is about9%. At last, two physicalantennas are fabricated with the size of90*90mm~2. From a vector network analyzer andmicrowave chamber, the measurement results show that one has a gain of9.18dBi,3-dBaxial ratio bandwidth of3.5%and the relative bandwidth of28%. The other one has a gainof10.59dBi, return loss is-8.2dB. The proposed antenna has the advantages of smaller size with high gain, compact constructure and easy to integrate. What I am suggesting is thatthere is not calibration in microwave chamber on5GHz. So the results about gain and axialratio are for reference, but the return loss and pattern test is reliable.