Doppler Aliasing in OFDM Radar - A Method for Reducing the ADC Sampling Frequency without Losing Range Resolution
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The orthogonal frequency-division multiplexing (OFDM) waveform is especially suited for joint sensing and communication applications and has raised attention for radar-driven applications as well. For radar applications, the signal bandwidth determines the achievable range resolution, however, a large signal bandwidth also entails a large sampling frequency that is costly in terms of energy consumption and chip area. Hence, methods for reducing the sampling frequency have become an interesting field of research. In this work, a novel method referred to as Doppler aliasing (DA) - OFDM (DA-OFDM) is proposed, which allows for reducing the sampling frequency, while still benefiting from the same range resolution the entire signal bandwidth offers. This is achieved by allowing for systematic aliasing of the originally orthogonal subcarriers due to undersampling in the receiver. However, by properly modulating the transmit signal, these subcarriers become separable in the receiver in the Doppler domain. This work contains the derivation of the DA-OFDM waveform, a detailed analysis, radar measurement results, the derivation of a suitable communication receiver signal processing scheme, and bit error ratio (BER) simulation results. The latter one will verify the suitability of DA-OFDM for joint sensing and communication applications compared to, e.g., stepped-carrier OFDM.