IWR1642: Minimum distance to a single target

Hello Todd,

The minimum IF frequency is one of the characteristics for min distance. Since we have a HPF1, HPF2 High Pass filter, this limits the lowest usable frequency. ~150khz.

There are other criteria, in that the FMCW Slope, Mhz/usec creates a calibrated frequency difference proportional to 2 * distance to the object.
The mmwave SDK allows us to change this slope upto 100Mhz / usec.

As an example, if we have a frequency slope of 50Mhz / usec.
1443 (.15 to 15Mhz IF), 1642 (.15 to 5Mhz IF)
Slope - 50Mhz us
Start Freq 77Ghz
6250ksps DFE output rate, 80% bandwidth for 5Mhz IF
450 numADC samples per chirp
72usec per chirp for ADC sampling
End Freq 80.85Ghz
512 point FFT (with 62 zero samples at end of chirp)

.45meters - based on 150khz analog min frequency, it would take a stronger signal to see closer than this
we do have an Rx LNA with gain of 24 to 48db.

if we non-coherently combine 8 chirps to get a higher signal to clutter (noise) (more integration time)
the FFT resolution would be for complex 1x
6250ksps / 512 FFT bins = 12.2khz per FFT bin.
with further signal processing, either zoom FFT, or more non coherent combining, .15meters.

Regards,
Joe Quintal

Wow...Great, comprehensive answer. Thanks.