Abstract: A signal processing technique for improving the axial resolution and/or the sensitivity of an ultrasonic imaging system. This technique also improves the lateral resolution and the depth of field. The technique is based on combining two or more transmit wave functions in an optimal manner to achieve a synthetic waveform which has greater bandwidth and/or energy than the individual wave functions. This scheme operates on the imaging data before the data reaches the envelope detector, while the phase information is still maintained within the signal. Using a synthetic transmit wave design approach, the effective emitted pressure waveform would have a bandwidth which would be wider than the transducer bandwidth with high sensitivity. The synthetic transmit waveform design scheme consists of firing two or more relatively long transmit waveforms for each single A-line in a given focal zone. The frequency spectrum for each of these transmit pulses is centered at a slightly different frequency.

Abstract: A method using a progressive sampling rate technique to maintain the sampling rate at the Nyquist frequency of the I/Q data through a tunable equalization bandpass filter in the front end of the imager and then increasing the sampling rate via axial interpolation to prevent aliasing during the nonlinear detection process. If an envelope detector is used, the bandwidth of the detector output should be approximately double that of the I/Q data. In this case, the sampling rate is doubled (or more) by axial interpolation before envelope detection. A 2-point linear interpolator can be used. Depending on the application, this axial interpolator can be turned on or off automatically by the system. After detection, the signal can be low-pass filtered to restrict the speckle bandwidth prior to log compression.