In ultrasonic distance-ranging automotive applications such as ultrasonic park assist (UPA) and blind-spot detection (BSD), ultrasonic waves transmitted by the system are reflected by objects present in the vicinity.
The system receives the reflected wave, or echo, and compares the object’s echo amplitude against a threshold to detect the object.
The echo for objects that are closer to the system is stronger than that for objects that are farther from the system. Hence, it is relatively common for the threshold to be varied with time. The article shows that a variable threshold is not required and that the threshold can remain fixed.
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This article is part of Texas Instruments' 3Q12 Analog Applications Journal (AAJ).