How do I calculate the minimum detectable velocity of a radar from its wavelength and dwell time?
Minimum Detectable Velocity
Improving MDV requires: longer coherent processing time (but limited by target acceleration and range migration), narrower antenna beam (reduces the angular extent of the clutter, narrowing its Doppler spread), higher radar frequency (finer Doppler resolution for the same processing time, but also increases clutter spectral width proportionally), and adaptive clutter cancellation (STAP, which adapts the clutter rejection filter to reject the actual clutter spectrum, rather than assuming a fixed spectral shape).
| Parameter | Pulsed | CW/FMCW | Phased Array |
|---|---|---|---|
| Range Resolution | c/(2B) | c/(2B) | c/(2B) |
| Velocity Resolution | PRF dependent | Direct from Doppler | Coherent processing |
| Peak Power | High (kW-MW) | Low (mW-W) | Moderate per element |
| Complexity | Moderate | Low | High |
| Typical Application | Surveillance, weather | Altimeter, automotive | Tracking, multifunction |
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
- Interface compatibility: verify impedance, connector type, and mechanical form factor match the system architecture
- Margin allocation: include sufficient design margin to account for manufacturing tolerances and aging effects
Frequently Asked Questions
Why is MDV important?
MDV determines the slowest-moving target the radar can detect. For ground surveillance: personnel detection requires MDV < 0.5-1 m/s. For traffic monitoring: MDV < 2-3 m/s. For airborne GMTI (ground-moving target indication): MDV < 1-3 m/s (detecting slow-moving vehicles on roads). A radar with MDV = 5 m/s would miss walking personnel and slow vehicles.
How does frequency affect MDV?
Higher frequency provides finer Doppler resolution (better MDV from the resolution perspective), but clutter spectral width also scales with frequency (wind-blown clutter Doppler spread is proportional to frequency). The net effect: MDV is approximately independent of frequency for wind-limited clutter. For scanning-limited clutter: higher frequency is worse (wider clutter spectral width).