Ultrasonic echo processing in presence of Doppler shift

An ultrasonic sensing system, comprising:

• a decimator adapted to be coupled to an ultrasonic transducer, the decimator being configured to generate first and second template signals by decimating a transmit signal for transmission through the ultrasonic transducer, the first template signal being generated by the decimator using a first decimation ratio, and the second template signal being generated by the decimator using a second decimation ratio that is different from the first decimation ratio;
• a first correlator coupled to the decimator, the first correlator configured to generate a first output signal by correlating the first template signal with a received signal derived from the ultrasonic transducer;
• a second correlator coupled to the decimator, the second correlator configured to generate a second output signal by correlating the signal derived from the ultrasonic transducer with the second template signal;
• and
• a Doppler shift determination circuit configured to determine a Doppler frequency shift based on the first and second output signals.