What does the C mean in CW Doppler radar?

What does the C mean in CW Doppler radar? It means continuous, as in continuous-wave radar. A continuous-wave radar transmits an essentially uninterrupted radio signal rather than sending separated pulses and waiting for echoes to return.

In Doppler radar, the returning signal is compared with the transmitted wave. Motion by the target changes the received frequency through the Doppler effect. The frequency difference, called the Doppler shift, reveals the target’s radial speed—its motion toward or away from the radar.

A basic continuous-wave radar is especially useful for measuring velocity, but it does not automatically provide a target’s range. Since the transmitter is always radiating, there is no individual pulse’s travel time to use as a direct distance measurement. More elaborate systems can add range information through modulation or other techniques.

CW should not be confused with “coherent,” even though coherence is important in many radar designs. “Continuous-wave” describes the transmission pattern. Pulsed radar, by contrast, sends brief bursts and commonly determines range from the time delay between transmission and echo.