The proposed book Essentials of RF Front-end Design and Testing: A Practical Guide for Wireless Systems provides the RF system essentials required to understand, develop, and evaluate the performance of RFwireless systems such as 5G mmWave. It is a system-oriented book which provides several wireless communication disciplines in one volume; the book covers a wide range of topics, including antenna fundamentals, phased array antenna and MIMOs that are crucial for the latest 5G mmWave and future 6G wireless systems, high-frequency transmission lines, RF building blocks that are necessary to understand how various RF sub-systems are interrelated and implemented in wireless systems, and test setups for conducted and Over-The-Air (OTA) transmitter and receiver tests. Also, it covers modulation techniques for analog and digital signals and demodulation, and an overview of Terahertz technology for future 6G wireless systems. The book is intended for graduate engineers and technologists involved in designing, developing, and testing wireless systems, and undergraduate/graduate students towards enhancing their learning experience on RF subsystems/systems characterization. The book places more emphasis on the system's performance and characterization rather than on mathematical proofs.