This study presents a novel frequency modulated continuous wave (FMCW) radar system based on sub-harmonic generation, where a 24 GHz frequency divider-by-10 is used as an active reflector tag. A practical prototype is designed and fabricated on a GF45nm-Silicon on Insulator (SOI) technology for the 24 GHz building blocks, while a GF0.18 μm 7WL Bipolar Complementary Metal Oxide Semiconductor (BiCMOS) technology was used for the 2.4 GHz receiver and baseband. System measurement results show that as opposed to conventional primary radars, the proposed system is immune to strong multi-path interferences resulting from direct reflections of the interrogating signal. The system achieves a ranging precision of 3.7 mm with loop measurements. Moreover, when measured in an indoor environment, the ranging results show a ranging precision and accuracy of 5.8 and 22.3 cm, respectively, which outperform other FMCW radars in the literature.

The design of a 24 GHz frequency divider-by-10 for accurate indoor localisation systems is presented. It is proposed to use frequency dividers as active reflector tags in a frequency-modulated continuous wave indoor localisation system in order to reduce interferences caused by direct reflections of the interrogating signal. Since frequency dividers are subharmonic generators, this allows achieving conversion gain in the reflected signal. The frequency divider is fabricated using GLOBAL FOUNDRIES 45 nm-silicon-on-insulator technology. It consumes only 5.7 mW from a 1 V supply. It has a wide locking range of 33% and an efficiency of 3.58 GHz/mW. To the best of authors' knowledge, the use of frequency dividers as active reflectors was not studied before.