Carl Pixley was my topology professor at U Texas, Austin. His class was taught by the "Moore method"; students discover and present the proofs on their own. Carl would inspire us to persevere by giving advice in the form of "Pixley Principles". One of my favorites was "...if there is a problem you can't do, there is a simpler one you can't do; do that one first!"

This talk gives a gentle introduction to active sonar. Taking Carl's advice, the simple problem to be done first is: estimate the range and velocity of an object from the echo of a signal it returns. Assume no noise and no clutter.