Device and method for detecting and elimination of spurious ultrasonic ranging echoes

A method for distinguishing spurious ultrasonic ranging echoes arising during ultrasonic distance measurement, wherein the method comprises the steps of:

• performing a plurality of ranging intervals at a repetition rate, wherein each ranging interval includes a step of transmitting an ultrasonic pulse toward a datum and then a step of detecting the occurrence of any echo during the ranging interval;
• performing a silent interval which includes a step of detecting the occurrence of any echo during the silent interval but does not include the step of transmitting an ultrasonic pulse;
• and
• changing the repetition rate of ranging intervals if an echo is detected during the silent interval.

An ultrasonic ranging device for determining the distance between the device and a datum, said device comprising:

• an ultrasonic transducer;
• a transmitter circuit coupled to the ultrasonic transducer and including means for periodically transmitting an ultrasonic ranging pulse;
• a receiver circuit coupled to an ultrasonic transducer and including means responsive to received ultrasonic energy for detecting the presence of an echo of a previously transmitted ultrasonic ranging pulse;
• and
• a processor coupled to the transmitter and receiver circuits, wherein the processor includes means for determining a time measure of the distance between the device and the datum by transmitting an ultrasonic pulse toward the datum and then detecting the occurrence of an echo from the datum;
• wherein the processor further includes means for detecting a spurious echo by detecting the occurrence of a delayed echo from a prior transmission of an ultrasonic ranging pulse;
• and wherein the processor further includes means responsive to the detection of any spurious echoes for choosing between multiple echoes to determine the echo from the datum.

An ultrasonic ranging device for determining the distance between the device and a datum, said device comprising:

• an ultrasonic transducer;
• a transmitter circuit coupled to the ultrasonic transducer and including means for periodically transmitting an ultrasonic ranging pulse;
• a receiver circuit coupled to an ultrasonic transducer and including means responsive to received ultrasonic energy for detecting the presence of an echo of a previously transmitted ultrasonic ranging pulse;
• and
• a processor coupled to the transmitter and receiver circuits, wherein the processor includes means for performing a series of ranging intervals at a predetermined repetition rate, wherein each ranging interval includes transmitting an ultrasonic pulse toward the datum and then detecting the occurrence of an echo during the ranging interval;
• wherein the processor further includes means for detecting a spurious echo by detecting the occurrence of an echo without having transmitted an ultrasonic pulse;
• and wherein the processor further includes means for changing the repetition rate of ranging intervals if a spurious echo is detected.