Transmission of coded pulses and matched receivefiltering can improve the ultrasound imaging penetration depthwhile preserving the axial resolution. This paper shows that thepulse compression technique may be integrated in a low-costscanner to be profitably used also in spectral Dopplerinvestigations. By operating on beamformed, demodulated anddown-sampled data in the frequency domain, a single digital signalprocessor is proved sufficient to perform both pulse compressionand (multigate) spectral Doppler algorithms in real-time.

Simulations, phantom and in vivo experiments demonstrate thatthe transmission of (2.5 μs or 5μs long) linear frequency modulatedchirps with bandwidths over the range 1.6-5.4 MHz, rather thanof corresponding sine burst pulses, provide SNR improvementsvery close to theory. Even in the presence of selective tissueattenuation, SNR gains up to 11dB and 13.3dB have been obtainedfor the short and the longer chirp, respectively. This may beimportant in clinical Doppler applications where the neededpenetration depth is not achieved with sufficient SNR unless verylong bursts are transmitted.