The idea behind this is to encoded data onto the transmitted pulse so that the received pulse can be correlated to reduce error and to give a more accurate reading.

With some quick tests, the transducers has an extremely narrow bandwidth and has low dampening  resulting in long ring times. This makes PSK and FSK very difficult. I have not been able for encode any data into the transmitted pulses. The closest I got was driving the transducers with a function generator and sweeping the frequency. The downside is that the sweep was very slow.