UWB Ranging and Crystal Offset

Distance between a pair of UWB sensor nodes without common time reference can be obtained by measuring round trip time. Because of difficulties in synchronization and channel estimate, the response delay of impulse UWB node is the order of milliseconds. Comparing with the nanosecond propagation delay, relative crystal offset between UWB nodes introduces big error in two way ranging. This paper estimates relative crystal offset through measuring the ranging frame duration in the counting window after synchronization. Simulation shows the relative crystal offset can be reduced to less than plusmn2 ppm