How do I select the pulse width and bandwidth for a radar to meet specific range resolution and sensitivity requirements?
Pulse Parameters
Example design: require 1.5 m range resolution and 100 km detection range against 1 m² target. Resolution: B = c/(2×1.5) = 100 MHz. From the radar range equation: required pulse energy = 10 mJ. With 10 kW peak power: τ = E/P = 10 mJ / 10 kW = 1 μs. TB = 1 μs × 100 MHz = 100 (20 dB compression gain). With 1 kW peak power: τ = 10 μs, TB = 1000 (30 dB compression gain).
| 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 limits the bandwidth?
Transmitter bandwidth (the PA must amplify the full bandwidth without significant gain variation or phase distortion), antenna bandwidth (must radiate efficiently across the full bandwidth), and receiver/ADC bandwidth (must digitize the full bandwidth with adequate dynamic range). For practical radar: 10-500 MHz bandwidth is common. Wideband radar (> 1 GHz): requires careful component selection and equalization.
What about duty cycle?
Duty cycle = τ × PRF. Higher duty cycle increases the average power (better detection) but reduces the maximum unambiguous range (due to eclipsing) and increases the thermal load on the transmitter. Typical duty cycles: 1-10% for pulsed radar, up to 50% for pulse-Doppler, and 100% for FMCW radar.