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Doppler Shift Calculator
Calculate the received frequency shift for a moving transmitter or receiver. Used in radar, satellite communications, radio astronomy, and velocity measurement applications.
Calculate Doppler Frequency Shift
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Quick Reference
Doppler Shift Reference Table
Doppler shift at common radar frequencies for various target velocities (one-way, head-on approach, θ = 0°).
| Velocity | 10 GHz (X-band) | 35 GHz (Ka-band) | 77 GHz (W-band) | 94 GHz |
|---|---|---|---|---|
| 30 m/s (108 km/h) | 2.0 kHz | 7.0 kHz | 15.4 kHz | 18.8 kHz |
| 100 m/s (360 km/h) | 6.7 kHz | 23.3 kHz | 51.3 kHz | 62.7 kHz |
| 300 m/s (Mach 0.88) | 20.0 kHz | 70.0 kHz | 154 kHz | 188 kHz |
| 1,000 m/s (Mach 2.9) | 66.7 kHz | 233 kHz | 513 kHz | 627 kHz |
| 7,800 m/s (LEO orbit) | 520 kHz | 1.82 MHz | 4.0 MHz | 4.89 MHz |
Understanding the Fundamentals
What Is the Doppler Effect?
The Doppler effect is the change in frequency of a wave as observed by a receiver moving relative to the source. When a source and receiver move toward each other, the received frequency increases (positive shift). When they move apart, the received frequency decreases (negative shift).
Formulas
One-Way Doppler (Communications):
fd = (v / c) × f0 × cos(θ)
Two-Way Doppler (Radar):
fd = (2v / c) × f0 × cos(θ)
Where:
v = relative velocity, c = speed of light (2.998 × 10&sup8; m/s)
f0 = carrier frequency, θ = angle to line of motion
fd = (v / c) × f0 × cos(θ)
Two-Way Doppler (Radar):
fd = (2v / c) × f0 × cos(θ)
Where:
v = relative velocity, c = speed of light (2.998 × 10&sup8; m/s)
f0 = carrier frequency, θ = angle to line of motion
Applications
- Automotive radar (77 GHz): Forward collision warning, adaptive cruise control, blind spot detection. Target velocities typically 0 to 250 km/h.
- Weather radar (S/C/X-band): Measures precipitation velocity to detect wind shear, tornadoes, and storm rotation.
- Satellite communications: LEO satellites at 7,800 m/s produce significant Doppler that must be compensated in the receiver.
- Air traffic control (L/S-band): Moving target indication (MTI) uses Doppler to separate aircraft returns from ground clutter.
- Speed enforcement: Police radar (K/Ka-band) measures vehicle velocity via the two-way Doppler shift of the reflected signal.
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