Doppler Frequency-Shift Unit for Digital-Analog Automobile Radar Target Simulator

Importance of radar target simulators moves up with ongoing fast development of radar sensors. Especially, this concerns the FMCW sensors used widely in automotive industry. The simulators are necessary for both radar calibration, and simulation of different traffic scenarios. The digital target simulators based on digital signal processing belong to the most advanced devices. But their practical deployment can be limited by relatively high latency of used digital circuits, and related high minimum detection range. That is why relatively simple analog simulators can also find their use. One problem connected with design of analog units relates to generation of Doppler frequency shifts corresponding to simulated target radial velocities. Usually, an IQ mixer equipped with two DACs, two anti-aliasing filters and one μ-controller is employed. The presented paper shows that substantially simpler and more efficient structure can be used. It is based on directly digitally-controlled phase shifter, and offers low insertion loss, wide frequency bandwidth, wide range of settable Doppler frequencies, high suppression of non-linear products and very good stability.