How do I design an SDR-based radar prototype for research and education?

Designing an SDR-based radar prototype for research and education uses the SDR's transmit and receive paths to implement a basic radar system, most commonly an FMCW (frequency modulated continuous wave) radar due to its simplicity and safety (low peak power). The basic FMCW radar architecture uses the SDR's DAC to generate a linear frequency sweep (chirp) that is transmitted through one antenna, and the SDR's ADC to capture the reflected signal through a second antenna. The transmitted and received signals are mixed (either in the SDR's digital processing or with an external analog mixer for better isolation), producing a beat frequency proportional to the target range: f_beat = (2 x R x BW) / (c x T_sweep), where R is the target range, BW is the sweep bandwidth, and T_sweep is the sweep duration. The beat frequency is measured using FFT, converting to range. For moving targets, the Doppler shift across multiple chirps provides velocity information. Suitable SDR platforms include the Analog Devices ADALM-Pluto ($150, 325 MHz-3.8 GHz, 20 MHz BW) for ultra-low-cost demonstrations, or the Ettus USRP B210 ($1,500, 70 MHz-6 GHz, 56 MHz BW) for more capable prototypes with wider bandwidth and better range resolution.