This book delves into wireless communication, focusing on 5G and 6G applications, mm and THz wave generation, material innovations, machine learning integration, and applications. It covers computational methods for optimizing mm-wave and THz devices. With the crowded microwave spectrum, mm-wave and THz frequencies are ideal for next-generation applications. 5G technology enhances data speeds, reduces delays, and minimizes energy use. While 5G uses MIMO and mm-wave, the THz band offers more spectrum for 6G, promising higher data rates. THz technology is used in wireless communications, remote sensing, and chemical analysis. This book is a valuable resource for THz technologists, covering research trends, computational methods, and topics like THz passive circuit modeling, mm-wave device simulation, and graphene applications in 6G.