The evolution of wireless communication systems is witnessed every day by their users. Currently, 4G meets the needs of the users in terms of data-rate and latency. 4G is spreading to the world and dominating the worldwide market. However, ever-increasing user demands for higher data-rate, lower latency, and an increased number of users are generating new challenges that 4G could not manage to meet the demands. To overcome the challenges in 4G, the institutions are studying the next generation (5G) communication systems. With the introduction of 5G, the utilization of various new technologies such as full-duplex becomes necessary to meet the demand for higher data-rate and lower latency. With the in-band full-duplex operation, the spectrum e ciency is doubled theoretically. The improvements in the SiGe BiCMOS technology have made them be a good candidate for low-cost and high-performance transceivers. In this thesis, the design of an electrical balance duplexer based in-band full-duplex system for 5G (28 GHz) communication systems implemented in IHP's 0.13 m SiGe BiCMOS technology is presented. The electrical balance duplexer is constructed with a hybrid transformer and an impedance tuner to suppress the leakage from the transmitter to the receiver by reducing the mismatch between the antenna and balance port impedances. The duplexer achieves isolation between the transmitter and receiver sides more than 40 dB for various antenna impedances at 28 GHz. The transmitter gain of the system is more than 30 dB by achieving OP1dB of 12 dBm whereas the receiver gain of 5 dB is obtained. The minimum noise gure of the receiver is 8.2 d
