Bandwidth Expansion of the IBFD Communication System Using Balanced Feed Networks

As the generation of mobile technology is evolved, technical requirements are also enhanced. Among the 5G standardization items, the spectral efficiency is critically important, whose requirement the three times higher than the efficiency of the 4G cellular generation. Also, in order to provide the faster data rate, the 5G system bandwidth is much wider than the 4G system. The In-Band Full Duplex (IBFD) can improve the spectral efficiency up to two times. To apply the IBFD system, Self-Interference (SI) must be eliminated. Self-Interference Cancellation (SIC) performance can be divided into the elimination performance of the target frequency and how much band can be eliminated. In this paper, a complex balanced feed network system is designed and evaluated for the wide SIC bandwidth. In this paper, the existing single BFN (Balanced Feed Network) and double-BFN systems are constructed and compared with the performance of the suggested triple BFN system in this paper. As results of the performance evaluation, the SIC removal performance at the target frequency is decreased, compared to the conventional system. However, suppression bandwidth can be widened.