I am using the following system: Ultrasonic chirp signals with central frequency 100kHz are being transmitted using ultrasonic sensor. After the transmission through the medium(air/solid/liquid/combination) they are being received with hydrophone. The system is being controled by DSP and signal generation and acquisition is obtained via DAC and ADC. Our aim is to detect the time of arrival between transmission and reception. My mentor suggested that I could use something with FFT to observe reflections, but I am struggling to find information on the internet about it. Does anyone have a suggestion how that could be done using FFT, or any other method?

  • $\begingroup$ This needs context. Time of arrival is a time-domain concept, but for certain types of signals it might be sensible to figure out that time through frequency-domain properties or just processing tricks. However, you're telling us absolutely nothing about your system, so what you're asking us is "How do I solve this very broadly stated problem using one of the most ubiquitously used algorithms?", and that's really not precisely enough stated for us to be able to understand what your mentor meant. $\endgroup$ Jun 25, 2020 at 8:10
  • $\begingroup$ Also, ask your mentor about clarification what she or he said, maybe? $\endgroup$ Jun 25, 2020 at 8:10
  • $\begingroup$ I have updated the post with explanation of the system. Unfortunatelly, I cannot obtain more information from my menthor right now, that is why I wanted to try and search about it on my own. $\endgroup$
    – Deanna77
    Jun 25, 2020 at 8:26

1 Answer 1


That sounds like a usual FMCW sonar.

It's technically identical to FMCW radar. So, multiply your receive with your transmit signal, you get a signal at the beat frequency, which is proportional to the range.

Standard FMCW approaches; there's a wealth of info out there.


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