Build a Basic Radar with SDRs
~160 minAdvancedTX License May Be RequiredBuild a working FMCW radar using a HackRF or PlutoSDR and GNU Radio. Learn matched filtering, range calculation, and Range-Doppler processing.
Hardware
- •HackRF One (preferred) OR PlutoSDR (ADALM-PLUTO)
- •Two 2.4 GHz patch or dipole antennas
- •SMA coax cables and adapters
- •Optional: 10–20 dB attenuator for RX protection
Software / Knowledge
- •GNU Radio 3.10+ installed
- •Python 3 with numpy, scipy, matplotlib
- •Basic familiarity with GNU Radio Companion (GRC)
- •Workshop 1 completed (SDR basics)
- •Understanding of complex (I/Q) signal representation
Radar (Radio Detection And Ranging) works by transmitting a signal, waiting for a reflection from a target, and measuring the time delay. Every radar system, from weather radar to car parking sensors to this SDR experiment, uses the same fundamental principle.
The radar equation — range from time delay
Range (m) = (c × t) / 2
where c = 3×10⁸ m/s (speed of light), t = round-trip time (seconds)
The factor of 2 accounts for the signal traveling to the target AND back. At 1 meter range, the round-trip time is only 6.7 nanoseconds — requiring very precise timing or frequency-based measurement.
Pulsed Radar
Transmit a short burst, then listen. Time from TX to echo = range. Cannot transmit and receive simultaneously.
Weather radar, air traffic control, ship navigation
FMCW Radar (Frequency-Modulated Continuous Wave)
Continuously transmit a chirp (frequency sweep). Mix TX with RX: the beat frequency encodes range. TX and RX simultaneous but need isolation.
Car blind-spot sensors, level gauges, this SDR project
FMCW beat frequency and range
Beat frequency: f_beat = (2 × R × BW) / (c × T_sweep)
R = range (m), BW = sweep bandwidth (Hz), T_sweep = sweep duration (s)
With 100 MHz sweep bandwidth and 1 ms sweep duration: 1 meter of range produces a beat frequency of 667 Hz — easily measurable with an FFT.
Even a basic SDR radar won't detect aircraft — your transmit power will be milliwatts, so expect maximum range of 1–10 meters for objects. This is a learning exercise in radar signal processing, not a surveillance system.