Architectures of millimeter-wave (mm-wave) fully-integrated frequency-division duplex (FDD) transmitting-receiving (T/R) front-end (FE) modules include a duplexer (DUX), power amplifier (PA), and low noise amplifier (LNA) on a single semiconductor substrate to facilitate the development of system on a chip (SoC) for mm-wave 5th Generation (5G) wireless communications applications. The first FE module adopts a passive DUX consisting of Wilkinson power divider and ground-center-tap transformer to achieve high isolation between PA output and LNA inputs. Another FE module combines the advantages of passive DUX and power-efficient cancellation circuits to accomplish high TX-RX isolation and low noise performance at the same time. The DUX can stand alone as a single unit in a system and is used together with external PA and LNA provided in the system, or it can include its own internal PA and LNA to form a DUX FE module.