FMCW Chirp Frequency Error and Phase Noise Measurement

In FMCW radar systems the frequency ramp nonlinearity and the synthesizer phase noise impact the radar’s ranging precision. In this chapter, a measurement method is presented and evaluated to determine the frequency-ramp nonlinearity and phase error during chirping by suppressing the random noise components. The limitations in the reported FMCW chirp characterization approaches are discussed. The impact of instrument settings on the reported FM-error is further discussed and a chirp averaging technique is proposed to validate the synthesized chirps. A method to evaluate the phase noise of the synthesizer during FMCW modulation is proposed. It is shown that, for proper evaluation of chirp parameters, a care needs to be taken when choosing the instrument sampling rate and FM filter bandwidth, along with the instrument accuracy measurement.