PulseDoppler

Pulse Doppler refers to a class of systems and processing techniques that combine pulsed transmission with Doppler shift measurement to determine the range and velocity of moving targets. In radar and medical ultrasound, a transmitter emits short pulses and then listens for echoes; by measuring the Doppler shift of the returned signal, the system can estimate the radial velocity of objects relative to the observer. The use of discrete range gates allows simultaneous estimation of target distance and velocity.

In radar, the frequency shift corresponds to the target's line-of-sight speed. The data are organized into range bins and Doppler bins (spectral analysis) to separate stationary clutter from moving targets. Techniques such as pulse-Doppler processing and MTI reduce clutter and improve detection of slow or distant objects. Limitations include velocity aliasing when the Doppler frequency exceeds half the pulse repetition frequency and range-velocity coupling.

In ultrasound, pulse Doppler is widely used to measure blood flow velocity. The Doppler equation relates frequency shift to velocity, angle dependence, and tissue properties. Modern ultrasound devices provide spectral, color-flow, and power Doppler displays to visualize flow characteristics, low-velocity detection, and turbulence.

Applications span weather and aviation radar, maritime radar, geophysical studies, and medical imaging. The technique offers rapid, real-time velocity information with range discrimination but requires careful calibration and handling of aliasing and angle effects.