Frequency Extension Method for Multirate Radar Target Simulation Systems

Radar target simulation is an important tool for testing and characterizing radar systems. It was shown before, that multi rate radar target simulators allow for highly accurate emulation of moving targets. These multi rate systems are a special case of digital radio frequency memory systems. By using different sampling clocks in the ADCs and DACs, moving targets can be simulated with outstanding realistic behavior, since this multirate system mimics the behavior of the continuous target distance changes perfectly. In this paper, we demonstrate for the first time how the frequency range of the multirate digital target emulation can be extended. We want to apply sub-Nyquist sampling techniques combined with the multirate technique and analyze its effect. It is shown that sub-Nyquist sampling does not change the signal properties; rather, the signals are downconverted via the sampling process, which enables direct coverage of higher frequency bands. This reduces the cost and complexity of hardware designs for multirate radar target simulation compared to previously demonstrated mixer-based down-conversion. We successfully demonstrate a frequency range extension of the baseband system by a factor of more than five.