Impact of Receiver Thermal Noise and PLL RMS Jitter in Radar Measurements

The accuracy of range and velocity measurements relies on the characteristics of the hardware blocks employed within a radar system. In particular, the two crucial blocks in a radar system are the low noise amplifier (LNA) located at the front of the receiver chain and the phase-locked loop (PLL) used as a signal generator. Thus, the predominant noise sources in the radar system are the receiver’s thermal noise (primarily influenced by the LNA) and the rms jitter of the PLL. The presence of noise in these blocks causes uncertainties in the radar measurements. This work derives the formulation of standard deviation for range and velocity uncertainties for frequency-modulated continuous wave (FMCW) and stepped-frequency continuous wave (SFCW) radars and further validates it through real-world measurement results from a radar in X-band. The study primarily examines the effect of parameters such as the rms jitter and settling time of the signal generator, along with the thermal noise in the receiver on the radar range and velocity measurement. The conclusion drawn from the study is that applications requiring a rapid measurement time with a specified level of accuracy necessitate the integration of a fast-settling PLL in a radar system. Ultimately, the relationship of the specifications of these essential components in the measurement accuracy in radars used in Industry 4.0 can help the designer in developing a robust radar system.