This book presents an unconventional approach for implementing chipless radiofrequency identification (RFID) systems and related sensors. Contrary to most state-of-the-art chipless-RFID systems, the proposed approach is based on time domain and the tags are read through near field. The book discusses different aspects of these chipless-RFID systems, including tag and reader design, strategies to enhance the data density and capacity, tag programming and erasing, tag implementation in plastic and paper substrates, and synchronous tag reading, among others. A tolerance analysis and validation of the different systems, as well as prospective applications, are also included. The book also offers a comprehensive overview of the state-of-the-art in chipless-RFID technology, including a comparative analysis, which is extended also to chip-based RFID systems. Readers are expected to be familiar with RF/microwave engineering technology. Besides master's and postgraduate students, the book is intended for researchers in the field of radiofrequency identification (RFID) technology, and may be of interest for engineers working in the areas of wireless communications, automatic identification, security, authentication, microwave and wireless sensors, as well as those dealing with internet of things (IoT) and smart systems. .