A Hyperbolic Frequency-Modulated Pulsed Radar for Accurate Sensing Below the Nyquist Rate

Wireless sensing has become integral to futuristic intelligent transportation systems encompassing Internet of Things (IoT) and vehicle-to-everything (V2X) networks. In the context of vehicle-to-infrastructure (V2I) scenarios, employing a monostatic pulsed radar on a roadside unit (RSU) to transmit digital linear frequency-modulated (LFM) pulses presents notable progress in obtaining high-resolution and precise sensing information. However, processing of these signals entails the use of expensive high-rate analog-to-digital converters (ADCs). Moreover, reducing the sampling frequency below the Nyquist rate introduces aliasing, which negatively impacts sensing accuracy. To address these challenges, this article investigates hyperbolic frequency-modulated (HFM) pulsed signals for accurate range and the Doppler information of multiple targets at sub-Nyquist sampling rates. Particularly, the inherent nonlinearity of HFM pulses is used to generate distinct aliases when the sampling is done below the Nyquist rate, enabling precise range information through receiver cross-correlation. Performance analysis and simulation results are provided to demonstrate the superiority of sub-Nyquist HFM pulse compression radar over its linear counterpart in terms of range-Doppler estimation, peak-to-sidelobe ratio (PSLR), integrated-sidelobe ratio (ISLR), and probability of detection.