Signal processing of an IVQ-3005 Radar Module

Question

I'm going to use that module for detecting range, velocity and angle, for that radar. https://www.innosent.de/fileadmin/media/dokumente/datasheets/180222_Datenblatt_IVQ-3005.pdf

So I have read a lot of radar techniques and I'm going to use the mode FMCW, and the modulated signal will be a sawtooth (chirps).

I have 4 signals I1, Q1, I2, Q2.

I need to confirm my understanding of the signal processing algorithms

First steps.

• I1, Q1, I2, Q2 to ADC
• Add I1 + I2, Q2 + Q2
• Multiply the result from 2 by conjguate of 2
• Apply FFT on the rows of the 2D signal I/Q to get the range
• Apply fft on the cols of the 2D signal I/Q to get the velocity
• Apply a third FFT but don't know on which block?
• Find peaks of each FFT block to get the Range, Velocity, Range.

Would someone tell me if the steps are correct or not? Would someone explain what considerations should I take care of?

According the answer, I wrote a basic algorithm, hope that's correct

    /* FFT length must be a power of 2 */
    #define FFT_LENGTH 16
    #define M 4            /* must be log2(FFT_LENGTH) */
    #define ECHO_SIZE 12

    void main()
    {
      int            i,j,k;
      float          tempflt,rin,iin,p1,p2;
      static float   mag[FFT_LENGTH];
      static COMPLEX echos[ECHO_SIZE][FFT_LENGTH];
      static COMPLEX last_echo[ECHO_SIZE];

    /* read in the first echo */
      for(i = 0 ; i < ECHO_SIZE ; i++) {
         last_echo[i].real = getinput();
         last_echo[i].imag = getinput();
      }

 // Read in the Second channgel
// Add first channel I/Q to second channel.


      for(;;) {
        for (j=0; j< FFT_LENGTH; j++){

    /* remove stationary targets by subtracting pairs (highpass filter) */
          for (k=0; k< ECHO_SIZE; k++){
            rin = getinput();
            iin = getinput();
            echos[k][j].real = rin - last_echo[k].real;
            echos[k][j].imag = iin - last_echo[k].imag;
            last_echo[k].real = rin;
            last_echo[k].imag = iin;
          }
        }
    /* do FFTs on each range sample */
        for (k=0; k< ECHO_SIZE; k++) {

          fft(echos[k],M);

          for(j = 0 ; j < FFT_LENGTH ; j++) {
            tempflt  = echos[k][j].real * echos[k][j].real;
            tempflt += echos[k][j].imag * echos[k][j].imag;
            mag[j] = tempflt;
          }
    /* find the biggest magnitude spectral bin and output */
          tempflt = mag[0];
          i=0;
          for(j = 1 ; j < FFT_LENGTH ; j++) {
            if(mag[j] > tempflt) {
              tempflt = mag[j];
              i=j;
            }
          }
    /* interpolate the peak loacation */
          p1 = mag[i] - mag[i-1];
          p2 = mag[i] - mag[i+1];
          sendout((float)i + (p1-p2)/(2*(p1+p2+1e-30)));
        }
      }
    }

Answer 1

The output of an FMCW radar with linear ramp modulation (triangle or sawtooth waves) is a group of tones, one per target. The frequency of each tone gives the range of the corresponding target, and the rate at which the frequency changes gives the range rate (radial velocity). To make these measurements, you can simply add the two receiver channels together.

To measure AOA (angle of arrival), you need to compare the phase angles of the two receiver channels, as derived from the I and Q data. This processing has to be done for each target tone as well. Keep in mind that the phase "wraps" at angles greater than about ±27°, according to the datasheet.

One FFT on a block of data will help you identify target tones. But I don't know what you have in mind when you apply a second FFT.