One of the challenging tasks of designing a sonar system is to build a single channel or multi-channel receiver, that is able to amplify interested weak echo signal, filter out noises, sample the conditioned signal and convert it into digital domain. The receiver is often the determinant part of system performance. Upon getting the task, an engineer has to make decisions on several indexes for his receiver, and one of them is the dynamic range of the receving gain.
When a sonar system is designed ot work for a range of hundreds of meters, echo signal from targets at different distances will experiance a transmission loss difference, which might be over 120dB, one opinion is that the receiver must compensate all the transmission loss difference among the whole working ranges, and the best way to do that is to use an ADC that has a bit number of over 16, and then use a VGA whose dynamic range can cover the transmission loss difference between the nearest and the utmost working range.
Well that is not easy for most low and medium frequency sonar systems that can work within hundreds of meters. On the other hand, even if we can do that, will that help to improve system performance?
In my opinion, the maximal dynamic range that a receiver can achieve is decided by its input electronic noise level and the ADC bit number, please see the detailed analysis in the attached file.
Thank your for your time!