Limiting the power consumption of distance measurement

Hi there, 

I'm looking for some advice on limiting the power consumption of distance measurement, as it seems I cannot simply configure the example code to do a single form of distance measurement ie: IFFT, and after searching, I was not able to find any documentation for how the different forms of distance measurement are calculated within this code. 

Is there any way to do this that I am missing?

Is there any documentation towards how calculations are made that I may use?

Thanks for any help