We've got a 40db SNR from emitter to receiver at 1m with an integration period of 25microseconds.
We have 16 transmitters in a phased array, so with focusing gains we have SNR*16*16.
100 receivers, SNR gains in SNR*100 as noise power adds-up in N and signal power adds-up in N^2
We correlate on a 20 periods-long (17cm) window. Signal adds-up in N^2 and noise in N again.
We're really close to measuring a mosquito's sonar cross section. But, assuming wings 5mm long and 2mm wide, we can estimate it at 10e-6 m^2. A conservative assumption could be around 1e-6 m^2
From the radar range equation : ((10**(40/10))*16*16*100*20*1e-6/((4*3.14)**2))**(1/4) = 2.4 meters.
It turns out, the radar range equation being in R^(1/4) really helps. It stops growing so quickly that even big cross-section differences have a limited effect on the range. Plus, the physics of SNR are really nice with very large transmit and receiver array.
About the drone turbulence I'm not sure it would have a very significant effect in the ultrasonic band we use (40khz). It probably is more of a problem at 20khz than at 40, and there are a lot of ways we could filter it : either electronically, by looking at the spatial and time distribution of the noise, or mechanically by moving it to a region where airflow isn't that disturbed.
The main problem could be the propellers vibrations. But, because we know what the frequencies are (propeller's RPM are controlled by our flight controller) we can dynamically adapt a very narrow cut-band notch filter to ensure it doesn't make its way to our CFAR detection. Flight controllers use the same method to filter propeller noise into gyroscope reading.
Happy to answer any other questions! Invited you on LinkedIn.