# The Uses of a Dual-Band Corrugated Circularly Polarized Horn Antenna for 5G Systems  
[PERSON]  
1 Department of Physics, National Central University, Taoyuan City 230317, Taiwan; [EMAIL_ADDRESS]  
[PERSON]  
2 National Synchrotron Radiation Research Center, Hsinchu City 30076, Taiwan [EMAIL_ADDRESS]  
[PERSON]  
3 Shenzhenjen Jaguar Wave Technology Co. Ltd., Shenzhen 518051, China; [EMAIL_ADDRESS]  
[PERSON]  
1 Department of Physics, National Central University, Taoyuan City 230317, Taiwan; [EMAIL_ADDRESS]  
[PERSON]  
1 Department of Physics, National Central University, Taoyuan City 230317, Taiwan; [EMAIL_ADDRESS]  
[PERSON]  
4 Department of Electrical Engineering, Ming Chi University of Technology, New Taipei City 243303, Taiwan 445  
compared to wireless transmission systems below 6 GHz which scatter and diffuse, the high-frequency millimeter-wave system has difficulty in covering broader indoor spaces. The 5G repeater system will play an important role in solving this issue of inadequate indoor coverage. It will amplify the signal from the outdoor base station and broadcast the signal to indoor environments. Additionally, plans for 5G will include various multi-signal paths and the mismatching of polarization. This paper proposes a novel design that possesses both circular polarization and wide beam width properties that perfectly match the 5G repeater system demand [1]. The application of circularly polarized antennas in communication originated in satellite communication. The polarization plane of a linearly polarized wave will be deflected and lead to a polarization mismatch due to the Faraday rotation effect [2; 3], which is produced by electromagnetic waves passing through the ionosphere. The smaller the elevation angle of the antenna, the greater the impact. However, the Faraday rotation effect has almost no effect on the circularly polarized wave, which makes the circularly polarized antenna extremely important in satellite communications. Circular polarization antennas are also used in general communication systems to reduce polarization mismatch, increase signal coverage, and inhibit multipath errors [1]. The grooved waveguide, iris-loaded waveguide, septum polarizer, and ridge circular waveguide are the main design structures of circularly polarized antennas [4]. In the communication industry, the mm-wave 5G repeater system is the future [5]. The radiated power of the repeater system is about 10 dBm, and the antenna gain is 6 dBi. Based on the linked budget and path loss calculations [6], the signal power will cover about 5\(\sim\)10 m in an indoor environment. The axial ratio will be under 6 dB to mitigate polarization mismatch [7]. Previous research has studied the circular polarized horn antenna in millimeter-wave band. A low-cost circularly polarized horn antenna has a wide band (50-75 GHz) and low axial ratio (AR), as shown in [8]. Circularly polarized horn antennas exploiting open slotted end structures have a wide band (75-110 GHz) and low AR (\(<\) 3 dB) [9]. This seems to provide a solution, but fall short with regards to beam width coverage on 5G repeater antennae. [PERSON] and [PERSON] presented a design for a broad beam width, with a 60 GHz band [10]. Corrugated structure antenna successfully achieved 112 degrees of antenna beam width at 55-62.5 GHz. It will overcome the lack of coverage indoors, but this design still struggles with various applications. In this study, a dual-band circularly polarized horn antenna with broad beam width is presented to solve the issues of indoor coverage and other usage scenarios. Broad beam width can be achieved by using two different corrugated structures. The double ridged waveguide polarizer was used on the horn antenna so that it would have dual-band circularly polarization properties. To ascertain the performance of the proposed antenna, a prototype running at a 5G FR2 band was fabricated. The operation's band frequencies were n257 and n260 [11].