As the technology has been evolved from 4G to 5G, data traffic growth has been explosively increasing due to the emergence of various applications. In order to satisfy the tremendous required traffic, it is necessary to improve the frequency bandwidth or the signal-to-noise ratio (SNR) in accordance with Shannon's law. However, since there is a limit in the frequency resource, it has become very important to improve the spectral efficiency. In-Band Full Duplex (IBFD) systems can improve spectral efficiency up to 2 times. In this IBFD system, the Self-Interference (SI) occurs inherently, so the desired received signal cannot be demodulated. Self-Interference Cancellation (SIC) must be required to solve this problem. In this paper, a Balanced Feed Network (BFN) based system is designed and evaluated to improve SIC performance at the target frequency 2.45GHz. Simulation results show that the SIC performance is improved by 3 dB compared to the existing system. However, it is also confirmed that the transmission power is decreased by 3 dB.