Shaping the driving pulse signal envelope in an ultrasonic sonar transmitter

摘要

An ultrasonic sonar transmitter generates a reference signal based on a clock signal of a specific frequency and a control signal made up of binary values 0 and 1 for controlling how the level (High or Low) of a carrier drive signal should change, and generates an analog signal constituting the carrier drive signal by pulse-duration-modulating the reference signal. Produced from the carrier drive signal, a driving pulse signal is shaped into a curved waveform having a gradually rising leading edge and a gradually falling trailing edge as the amplitude of the carrier drive signal is gradually increased and decreased based on the control signal. Undesirable frequency components and ringing are supressed. False readings caused by another ship transmitting on a close frequency can be prevented.