How do I calculate the maximum detection range of a radar using the radar range equation?
Radar Architecture Comparison
The choice of radar waveform fundamentally determines the system's range capability, resolution, measurement accuracy, and hardware complexity. Each architecture has distinct advantages that make it optimal for specific applications.
| 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 |
Frequently Asked Questions
Why do automotive radars use FMCW at 77 GHz?
Three factors converge: (1) 77 GHz provides a regulatory allocation of 4-5 GHz bandwidth (76-81 GHz), enabling range resolution under 5 cm for pedestrian and object discrimination. (2) FMCW operates at low power (10-13 dBm EIRP typical), enabling single-chip implementation in SiGe or CMOS at cost under $5 per radar module. (3) The short wavelength (3.9 mm) enables compact antennas with narrow beams from small apertures (2° beamwidth from a 6 cm antenna). Current generation (TI AWR2944, NXP S32R45) integrate 4 TX and 4 RX channels with 4 GHz bandwidth on a single chip.
What is the maximum range of FMCW radar?
FMCW range is limited by transmit power, receiver sensitivity, and beat frequency bandwidth. Automotive: 200-300 meters. Industrial level measurement: 100 meters. Aircraft altimeter: 10,000+ meters. Marine: 50-100 km (25-50W transmit). The beat frequency at maximum range must fall within the ADC bandwidth. For automotive (40 μs sweep, 4 GHz BW): beat frequency at 300m is 80 MHz, requiring an ADC sampling at 160+ MSPS. Increasing range requires either higher power, longer sweep time (slower update rate), or narrower bandwidth (coarser resolution).
Can pulsed radar measure velocity?
Yes, through Doppler processing. A coherent pulsed radar extracts velocity from the phase change of target returns between consecutive pulses. The Doppler shift appears as pulse-to-pulse phase rotation at rate 2*pi*f_d/PRF. Pulse-Doppler processing (FFT across the slow-time dimension) separates targets by velocity and suppresses clutter. The velocity resolution equals lambda/(2*N*T_r), where N is the number of pulses integrated and T_r is the PRI. Pulsed Doppler radar is the primary architecture for airborne and naval fire-control systems requiring simultaneous range and velocity measurement at long range.