thanks for your reply crossroads
Your idea would not match my needs. A 2kHz signal would lead to discrete readings as well. There can be a timegap from 0.5ms (1s/2000) to 0.0ms which is unknown.
In my needs the timegap should be always constant, because I am measurening something in the range of sub nanoseconds.
Thats why I need something continous/analog. Once I know the time it needs for the transmitter to send and for the reciever to recieve the signal, I can use that information for my calculations, that rely on really small amount of time.