OFDM Radar With Subcarrier Aliasing—Reducing the ADC Sampling Frequency Without Losing Range Resolution

Many radar applications require a high range resolution, entailing the necessity for a large signal bandwidth. When employing an orthogonal frequency-division multiplexing (OFDM) radar system in its standard implementation, the radar system must operate at a high sampling frequency to ensure covering the entire signal bandwidth, thus imposing significant challenges on its implementation. Therefore, methods for reducing the sampling frequency are topic of recent research. In this work, a method for reducing the analog-to-digital converter (ADC) sampling frequency at the receiver without losing range resolution is proposed. This is achieved by activating only a fraction of the subcarriers at the transmitter, while simultaneously allowing for systematic aliasing due to undersampling in the receiver. This aliasing is designed such that the active subcarriers do not interfere with each other, which ensures a simple separation of them in the frequency domain. The proposed concept, denoted as subcarrier aliasing (SA), allows reducing the ADC sampling frequency in the receiver, but lacks in reducing the digital-to-analog converter (DAC) sampling frequency in the transmitter. However, the key asset of SA-OFDM lies in the properties of its waveform, making it especially suitable for joint radar and communication applications over other waveforms, e.g., stepped-carrier OFDM.