Ultrasonic signal processor for a hand held ultrasonic diagnostic instrument
A hand held ultrasonic instrument is provided in a portable unit which performs both B mode and Doppler imaging. The instrument includes a transducer array mounted in a hand-held enclosure, with an integrated circuit transceiver connected to the elements of the array for the reception of echo signals. A digital signal processing circuit performs both B mode and Doppler signal processing such as filtering, detection and Doppler estimation, as well as advanced functions such as assembly of multiple zone focused scanlines, synthetic aperture formation, depth dependent filtering, speckle reduction, flash suppression, and frame averaging.
1. A method for reducing signal bandwidth with respect to a signal of an ultrasound device, said method comprising:
receiving ultrasound scan signals in a normalization circuit, wherein said receiving ultrasound scan signals is at an input rate;
coupling ultrasound scan signals to a first finite impulse response filter and producing a first accumulated signal; and
coupling said ultrasound scan signals to a second finite response filter and producing a second accumulated signal,
wherein said first and second finite impulse response filters provide said first and second accumulated signals at a rate less than the input rate.
2. The method of claim 1 , wherein each of said first finite impulse response filter and said second finite impulse response filter comprises a multiplier and an accumulator.
3. The method of claim 1 , wherein said normalization circuit normalizes said ultrasound scan signals for beam and aperture variation.
4. The method of claim 1 , said method further comprising:
multiplying said ultrasound scan signals by a coefficient to produce normalized ultrasound scan signals.
5. The method of claim 1 , wherein said ultrasound scan signals are coupled by a multiplexer to said second finite impulse response filter.
6. The method of claim 1 , wherein coefficients used by said first and second finite response filters to produce said first and second accumulated signals are supplied by a coefficient memory.
7. The method of claim 1 , wherein said first finite impulse response filter produces in phase (I) signal samples.
8. The method of claim 1 , wherein said second finite impulse response filter produces quadrature (Q) signal samples.
9. The method of claim 1 , wherein a coefficient associated with said first finite impulse response filter and used to produce said first accumulated signal is chosen to multiply said ultrasound scan signals by a weighted cosine function.
10. The method of claim 1 , wherein said signal bandwidth is reduced to equal the transducer bandwidth of said ultrasound device.
11. The method of claim 1 , wherein said signal bandwidth is reduced to match the display bandwidth of a display monitor of said ultrasound device.
12. The method of claim 1 , wherein the effective lengths of each of said first and second finite impulse response filters are adjusted.
13. The method of claim 1 , wherein said first and second finite impulse response filters are used to reduce radio frequency noise.
14. The method of claim 1 , wherein the output rate is decimated by a variable factor.
15. The method of claim 9 , wherein a coefficient associated with said second finite impulse response filter and used to produce said second accumulated signal is chosen to multiply said ultrasound scan signals by a weighted sine function.
16. A digital signal processor for use in an ultrasound device comprising:
a normalization circuit configured for receiving and adjusting ultrasound scan signals for beam variation;
a memory configured for storing partially summed ultrasound scan signals from a portion of a full aperture acquired following at least two separate pulse transmissions; and
an adder configured for combining said partially summed ultrasound scan signals to form full aperture signals.
17. The digital signal processor of claim 16 , further comprising:
at least two finite impulse response filters configured for receiving and multiplying ultrasound scan signals, wherein said at least two finite impulse response filters are coupled to said memory by a multiplexer.
18. The digital signal processor of claim 16 , further comprising:
a detection and compression circuit, wherein after said lull aperture signals are formed, said full aperture signals are conducted from said adder to said detection and compression circuit.
19. The digital signal processor of claim 18 wherein said detection and compression circuit is configured to compress and scale said full aperture signals to map them to a desired range of display gray levels.
20. A digital signal processor for use in an ultrasound device comprising:
means for normalizing ultrasound scan signals for at least one of beam variation and aperture variation;
means for multiplying said normalized ultrasound scan signals;
means for forming a synthetic aperture, wherein said means for forming a synthetic aperture uses multiplied normalized scanline signals from said means for multiplying acquired following at least two separate pulse transmissions and combined to form full aperture scan signal;
means for compressing and mapping said full aperture scanlines to a desired range of display gray levels.