Test signal injection for Doppler systems

Objective: To evaluate the performance of continuous and pulsed Doppler systems a test signal generator has been developed, simulating an ultrasound radio frequency signal, to be injected by induction into the front-end of an ultrasound Doppler system. Unlike for flow rigs the characteristics of the simulated signal are exactly known and under full control of the user, allowing for an objective interpretation of the test results. Methods: Under software control specific signal characteristics, e.g. ultrasound carrier frequency, clutter frequency, amplitude of clutter signal with respect to Doppler signal amplitude, Doppler signal-to-noise ratio, mean Doppler frequency, shape and width of the Doppler spectral distribution, and its time-dependent behavior can be set and varied. Results: A software package was developed to manipulate the relevant characteristics of the radio frequency signal and to drive a PC compatible plug-in card for signal generation. To illustrate the applicability of the Doppler signal generator some specific examples will be discussed. Conclusion: The proposed test signal generator allows for a variety of Doppler test procedures under controlled and realistic conditions. Copyright 1997 Elsevier Science Ireland Ltd.