R. Barkans, S. Migla, N. Tihomorskis, J. Ratners, V. Kurtenoks and A. Aboltins, “High-Resolution Sampling of UWB Radar Echoes Using Waveform Crossing and TDC Techniques,” 2025 Photonics & Electromagnetics Research Symposium – Fall (PIERS-Fall), Chiba, Japan, 2025, pp. 1-5, doi: 10.23919/PIERS-Fall62445.2025.11394564.
Abstract:
To provide a millimeter-range spatial resolution of UWB radar, the received down-converted echoes must be sampled at rates above 50GSa/s. Employing regular (ADC)-based sampling techniques at such high sampling rates leads to extremely high costs and power consumption for radar systems. Employing time-to-digital conversion in radars instead of analog-to-digital conversion opens new possibilities for high-bandwidth signal acquisition. Widely available commercial time-to-digital converters (TDCs) provide single-shot time resolution in the range of 20−50ps, which leads to a spatial resolution of 6−10mm. The mentioned technique is widely used in LiDAR; however, due to the complex nature of echoes, it cannot be directly applied to radar systems. As TDC provides information about single threshold level crossing, straightforward employment of TDC leads to a very low dynamic range of a sampler, low sensitivity and worsened signal-to-noise ratio (SNR). To increase the dynamic range of the TDC-based sampler, the authors explore using radar echo crossing with an alternating sampling waveform of a much lower frequency to obtain amplitude and timing information. In this research, the authors explore time-domain (TD) sampling using a custom 4-channel time tagger based on ScioSense GPX2 chips in conjunction with an envelope detector and a custom comparator board driven by a 1.266 MHz sawtooth waveform for stroboscopic sampling of 28 GHz pulsed radar echoes arriving with a period of 160 ns. Research is devoted to designing novel signal acquisition methods and signal processing techniques for radar envelope reconstruction and exploring the techniques’ limitations in communication and sensing applications.