This study presents a multi-band scalable positioning system that not only provides accurate means of navigation but also seamlessly extends the maximum number of reference and mobile nodes. Time synchronisation is carried out wirelessly, hence minimising the required hardware to easily set up the system. Due to its high precision and immunity to radio frequency interferences, a multi-band frequency modulated continuous wave (FMCW) radar system is designed particularly to handle the core time measurements. Large parts of the radar front-end are fully integrated in an application-specific integrated circuit. Furthermore, in order to withstand the complex indoor conditions, the system engages a particle filter based tracking algorithm as a data fusion platform. The measurements were evaluated in several practical conditions and compared with the state-of-the-art techniques. The evaluation scenarios include areas with line-of-sight and non-line-of-sight conditions. A root mean square positioning error of <17 and 31 cm was achieved in a coverage area of around 500 m², in both outdoor and indoor conditions, respectively. To the best of the authors' knowledge, the proposed system outperforms the current commercial systems not only in the aspect of positioning error, but also in the coverage efficiency.