4.2 Measurement Accuracy

The measurements of the timestamps at the transmitter and receiver is performed at a frequency of 6.048 GHz that results in a time resolution of ~165 ps, which corresponds to the distance resolution of +/-4.95 cm. Due to physical effects like jitter and channel effects for the wireless transmissions, the achievable accuracy is less, i.e., the distance measurement variations are higher. The following figure shows a measurement distribution of 1000 measurements at a distance of 100 cm. The mean value for the distance is 97.2 cm with a standard deviation of 6.2 cm.

In addition to the distance, the figure shows the measured time-of-flight with a mean value of 2.74 ns and a standard deviation of 0.21 ns.

The Time-of-Flight (ToF) in this example does not include the distance between the ATA8352 device and the antenna, which is an offset of about 2 * 6.5 cm = 13 cm, corresponding to a ToF offset of 0.43 ns. The calculated distance shown in the preceding figure includes this offset of 13 cm.

For larger distances or in situations with low Signal-to-Noise Ratio (SNR), an additional offset occurs due to the shift of the first path signal necessary to capture the timestamps (refer to Figure 5-23 in the ATA8352 Impulse-Radio Ultra-Wideband (IR-UWB) Transceiver User's Guide (DS50003125). This offset will lead to a shift in the captured timestamps and, finally, into an uncertainty of the calculated position.

The following figure shows the histogram of the measured distances of the previous figure, with mean value and standard deviation.