The Doppler velocity signal refers to a signal whose voltage is proportional to the Doppler frequency shift, obtained by a frequency-to-voltage conversion of the Doppler signal.

See also Autocorrelation, Temporal Mean Velocity, Doppler Effect, Doppler Ultrasound and Maximum Venous Outflow.

The dwell time (also called ensemble length or packet size) is the transmitting duration of ultrasonic waves focused at one place or the Doppler samples for each line of sight. The reduction of the dwell time is of use if threshold pressures are exceeded.
The sensitivity to slow flow and accuracy of Doppler measurement increase with longer dwell times. With increased dwell times, the frame rates decrease and the capability of Color Doppler images to depict fast changes in hemodynamics is limited.

From Fukuda Denshi Co., Ltd.;
'Phased array probes made available for High resolution imaging of full cardiovascular examinations.
By adding Linear and Convex probes, the examination areas are extended to Abdominal and OB/GYN applications.
B-mode (1, 2 displays), M, and B/M-modes can be individually shown.
Optional Doppler unit available for observation of Blood flow information in pulsed and continuous wave Doppler.
Portable with IP (Image Processing), Full Keyboard, and track ball are standard.'

A filter in electronics is a circuit that only passes certain signals. In ultrasound is a filter a device to suppress acoustic or electromagnetic waves of certain frequencies, letting other frequencies pass, e.g. high pass filter, low pass filter. The high pass filter is the wall filter (also called thump filter) used in Doppler devices to eliminate low frequency Doppler shifts caused by clutter. For blood flow measurement, a low pass filter is often used to strip out high frequency noise, leaving only the biological components of interest. Frame averaging is a form of a low pass filter.

From Philips Medical Systems;
'Clinicians are demanding smaller, higher performing systems specifically designed to meet their clinical and operational challenges. The new Philips HD11 system provides an uncompromising platform, plus advanced options in a highly mobile and easy-to-use system.'