Systems and processing algorithms for ultrasound time-of-flight digitizer systems

A system for processing timing information and a received signal corresponding to a sequence of pulses of a pressure wave oscillation received by a receiver to track variations in a distance D calculated from time-of-flight measurements of the pulses, the pressure wave oscillation having a given wavelength and wave period, the system comprising:

• (i) a signal processor for processing the received signal to derive an effective time-of-arrival for each pulse;
• (ii) a timing module associated with said signal processor, said timing module being configured to derive a time-of-flight for each pulse from the timing information and said effective time-of-arrival;
• (iii) a synchronous operation module associated with said timing module and configured to analyze said times-of-flight to identify a state of synchronous operation when at least two successive pressure wave pulses satisfy predefined synchronicity criteria;
• (iv) a monitoring module associated with said timing module and configured to monitor successive time-of-flight measurements to identify a shifted time-of-flight measurement which varies by at least half of the wave period from a predicted time-of-flight value calculated from a number of preceding time-of-flight measurements;
• (v) a shift factor module associated with said monitoring module and configured to identify a shift factor corresponding to an integer multiple of the wave period by which said shifted time-of-flight measurement must be corrected to obtain a corrected time-of-flight measurement falling within half of the wave period from the predicted time-of-flight value;
• and
• (vi) a correction module associated with said timing module and configured to correct the distance D calculated from said shifted time-of-flight measurement by the product of said shift factor and the pressure wave wavelength.

A system for identifying the position of a transmitter of a pulsed pressure-wave signal in at least two dimensions, the system comprising a plurality of interconnected modular receiver units, each of said modular receiver units including:

• (i) a pressure-wave receiver configured to convert a received pressure-wave signal into an electrical signal;
• (ii) a signal processor associated with said pressure-wave receiver and configured to process said electrical signal to generate a detection output indicative of reception of a pulse of the pulsed pressure-wave signal;
• (iii) a timing module associated with said signal processor and responsive to said detection output and an externally supplied synchronization input to measure a time-of-flight of said pulse;
• and
• (iv) an output module associated with said timing module and configured to output data related to said time-of-flight.