Peak and Mean Power measurements on wideband FMCW radar signal

Modern automotive radar systems occupy very wide bandwidth in order to have a good location resolution. In most cases the bandwidth is a result of frequency modulation or fast frequency hopping techniques, in some cases also pulse modulation is used. Besides the measurement of the frequency variation over time like deviation and linearity, the verification of emissions according to EN or FCC standards is mandatory. ETSI regulations for measuring peak transmission power from radar operating at 77-81 GHz require 50 MHz resolution bandwidth for the measurements. Publications are available that describe the measurements on pulsed UWB or MB-OFDM signals in detail, for frequency-modulated signals the information is limited.

This application note provides information how to perform spectral emission measurements on frequency modulated CW signals with spectrum analyzers using RBW filters with very wide bandwidth, and explains the capabilities and the limiting factors of the Rohde & Schwarz FSW signal and spectrum analyzer to perform this measurement.