IQ-Transmitter Digital Predistortion for an OFDM Radar

Digital Predistortion (DPD) has been extensively researched to improve the performance of communication systems in terms of power-efficiency, Signal-to-Noise Ratio (SNR) and reducing out-of-band emissions to fulfill spectral masks. The progress in digitally-modulated radars enables the application of transmitter-based compensation algorithms with the aim to improve the accuracy of the radar measurement and opens a new research field. Digital modulation schemes such as Orthogonal Frequency Division Multiplexing (OFDM) typically require a high instantaneous bandwidth and crest factor, which impose high linearity requirements on the used analog hardware. This work presents first results on the predistortion of IQ-modulator and power amplifier imperfections for an OFDM radar system operating at 72 GHz. Measurement results from an anechoic chamber prove the potential of DPD for radar by showing an improvement in sidelobe reduction greater than 5 dB.