SWRZ090C January 2020 – October 2023 AWR2243
Doppler Spur Observed at Certain RF Frequencies
AWR2243 ES1.0, ES1.1
When the instantaneous FMCW Ramp frequency nears certain specific RF frequencies, there can be coupling between the synthesizer's reference and its output, and manifest as frequency glitches or spurs in TX output spectrum.
Implication: In FMCW radar 2D signal processing, this can lead to spurs in a fixed Doppler bin at all range bins. This situation can occur with narrow band chirps, if the FMCW ramp includes or nears 76.8-, 77.4-, 78-, 79.2-, 80.4-, 81-GHz RF frequencies. The affected Doppler bin is a function of chirp timing and RF frequency properties.
Use the device's dithering features to vary idle time, RF frequency and ramp end times to spread the spurs significantly in Doppler dimension so that it does not get detected as spurious targets. Using larger chirp band widths also reduces the spur level.