Method for High Precision Radar Distance Measurement and Synchronization of Wireless Units

In this paper we present a novel approach for high precision synchronization of wireless units. A concept similar to the standard FMCW (frequency-modulated continuous wave) radar principle is used to estimate the offset in time and in frequency between two radar units. It allows for a synchronization of both offsets significantly below 100 ps and 10 Hz, respectively. This highly accurate synchronization is used in a prototype system to measure the distance between wireless units similar to a secondary radar. The prototype operates within the 5.8 GHz ISM-Band and uses a bandwidth of 150 MHz. With the setup presented the distance between two radar units is measured with a standard deviation of less than 4 cm over a range of 250 m. The broadband measurement principle is robust towards multipath interference. It can be extended to other frequency bands and is well-suited for direct integration into communication channels.