In recent years, radio frequency identification (RFID) technology has been employed in mainstream applications for asset management, storage of goods, security, transportation and logistics. The RFID sensor has features which can revolutionize the field of automated object identification in conjunction with condition monitoring. In this research, a novel chipless RFID sensor platform is proposed for wireless sensing of tagged objects. Since the proposed chipless RFID sensor does not require any on-board micro-chip and power source, it has great potential for low-cost, maintenance-free, automated and robust applications. The aim of this research is to develop single node multi-parameter sensing chipless RFID sensors in versatile RF sensing applications. This PhD thesis involves developing novel multi-resonator chipless RFID sensor platforms for three potential RF sensing applications: (i) non-invasive radiometric partial discharge (PD) detection and localization of faulty power apparatus, (ii) electromagnetic (EM) sensors for real time environment monitoring, and finally, (iii) RF memory sensors for event detection. Each development involves the problem identification, research hypothesis, physical layer design of the sensor tag, prototype fabrication and experimentation. Finally, a chipless RFID sensor for multiple parameter sensing is proposed for both real-time environment monitoring and event detection. In the first phase of this research, a passive radio frequency (RF) sensor has been developed for non-invasive radiometric detection of simultaneous PD signals in high voltage (HV) apparatus such as transformers, overhead lines, capacitor banks and circuit breakers. The sensor comprises passive multi-resonator circuit and an antenna for capturing PD as well as providing ID of faulty equipment. The low-cost RF sensor is installed in individual HV apparatus for monitoring their PD events. The chipless RFID based PD sensor addresses PD monitoring, PD detection and faulty source identification.In the second phase, a low-cost, printable chipless RFID tag sensor is developed for real-time environment monitoring. The chipless RFID tag sensor provides identification data and monitors a number of physical parameters of tagged objects and the surrounding environment. The RF sensor measures physical parameters such as temperature, humidity, light intensity and pH level of tagged objects. The RFID sensor is based on planar, single-sided resonant scatterers for generating data ID and carrying sensing information in the frequency spectrum. Environment sensing is incorporated using smart polymer materials, which exhibit dielectric change to particular physical parameters. Our proposed chipless RFID sensor comprises a planar multi-slot resonator as an ID generation circuit and an electric field coupled LC (ELC) resonator coated with a smart material layer as a sensing circuit on a compact planar layout. A novel feature of the developed sensor is its ability to combine multiple physical parameter sensing in the same chipless RFID platform for ubiquitous condition monitoring. In this research firstly, a humidity sensor is proposed, as it is one of the most critical physical parameters for environment monitoring. Next, a chipless RFID memory sensor is developed for violation of temperature threshold. The memory sensor uses a smart material which exhibit permanent dielectric change when certain temperature threshold is reached. The sensor operates as a memory device to store occurrence of a particular event. The temperature threshold sensor can also incorporate real time humidity sensing within the same chipless RFID tag platform. Hence a chipless RFID sensor for multiple parameters sensing capability is developed.Reading of chipless RFID sensor is a non-trivial task. A chipless RFID sensor tag is a minute radar target for the reader. New reader architecture to read the tag is proposed in this thesis. The reader comprises RF, digital and power control modules to interrogate the tag sensor, captures backscattered RF response and performs necessary signal processing for data decoding.Finally, the thesis summarizes the major challenges in realizing a fully-printable chipless sensor on flexible substrates. Potential future research directions in sensor fabrication, chipless RFID reader development, and sensor calibration methods are discussed. With its simultaneous identification and sensing capabilities, the low cost fully printable chipless RFID sensor will revolutionise emerging fields such as internet of thing (IoT) and smart cities.