Determining required SNR for beat signal from ADI FMCW RADAR component

It's the chain:

Triangle frequency shape sent from ADF5901(24 GHz VCO and PGA with 2-Channel PA Output)

Then receive from

ADF5904(4ch 24GHz receiver downconverter) -> ADA8282(RADAR receiver path AFE: 4CH LNA & PGA) 

I have some next stage:

AD817(Op-Amp) summer of 4ch together -> AD817(Op-Amp) sallen-key filter -> Transmit to other board

Seems I need to start through PA power then add max distance noise to it, then noise of receivers chain through their datasheet. Then some MATLAB simulation to determine least possible SNR required?

    •  Analog Employees 
    on Dec 13, 2018 3:34 PM


    Radar detection is based on signal to noise ratio, not signal alone.  In radar SNR is defined as the ratio of the signal power (or energy) to the local noise power (or energy).  This is different than in ADC’s where SNR is defined as the ratio of the signal power to the integrated noise power.

     Also, it appears that you have not included the effects of process gain due to the Doppler FFT and any beamforming.  For the Doppler FFT the process gain is 10 log10( M ) where M is the number of chirps.  It is M, not M/2, since this is a complex to complex FFT.  For the beamforming, if we combine 4 RX into a beam, then we have a process gain (in the beam direction) of ~ 10 log10(K) where K is the number of RX antennas (both real and virtual).  It is approximate, since it does not account for the ‘window’ loss of the beamforming coefficients.  The 10log10(K) is valid for a rectangular window, near boresight of the antenna.  [But as you may know, rectangular windows yield poor antenna side lobes, which are detrimental to system performance.]


    However, if one uses time division MIMO, (applicable for 5904) the signal energy is ½ of what we would get without out it (-3 dB with two TX MIMO).  This is because the virtual and real antennae only receive ½ the energy for each group.

    I hope this helps, regards Brigid.

  • Thanks for answer, as fast as I get a time I will think in your answer but now I have more important question from you if you could please answer: