How does the sidelobe level of the radar antenna affect its clutter rejection capability?
Sidelobes and Clutter
For airborne pulse-Doppler radar: the clutter seen through the sidelobes spans a wide Doppler spread (from the platform velocity resolving along different look angles), creating a clutter ridge in the range-Doppler domain. STAP handles this, but lower sidelobes reduce the required dynamic range of the clutter cancellation, improving the minimum detectable velocity and reducing the computational burden. Every 10 dB reduction in average sidelobe level directly reduces the sidelobe clutter power by 10 dB.
| 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
What sidelobe level do I need?
Ground-based surveillance radar: -25 to -30 dB peak sidelobes (adequate for most environments). Airborne radar: -30 to -40 dB (sidelobe clutter is severe due to high ground reflectivity at shallow grazing angles). Fire control radar: -30 to -35 dB. Space-based radar: -40 dB or lower (very large illuminated area through sidelobes).
How do sidelobes affect jamming?
A jammer outside the main beam enters through the sidelobes. The sidelobe blanking or cancellation system must suppress the jammer. Lower sidelobes reduce the jammer power entering the receiver, improving the system's electronic protection capability. For military applications: sidelobe levels of -30 to -40 dB are essential for jammer resistance.