Radar Target Generation and Detection

Visualization of the results

Implementation steps for the 2D CFAR process

Every cut needs to be from the 2D FFT response RDM. The cut size is identified by chosen Training Cell Band and Guard Cell Band. If we denote Training Cells for Range and Doppler directions as Tr and Td respectively, and Guard Cells for Range and Doppler directions as Gr and Gd respectively, then CUT is a 2D slice of the RDM with following sizes:

        2*Tr + 2*Gr + 1  --> Two portions of Tr (trailing and leading)
                             Two portions of Gr (trailing and leading)
                             A single target in the middle
        2*Td + 2*Gd + 1  --> Same as Range direction

Hence, CUT is a rectangle that has (2*Tr + 2*Gr + 1) * (2*Td + 2*Gd + 1) cells in total. This CUT has a guarding window that is made of Guarding cells and a single target in the middle. The size of this window can be determined similarly, and has (2*Gr + 1) * (2*Gd + 1) total cells in it. Subtracting total cells of guarding window from total cells in CUT gives us total Training Cells.

numTraining = (2*Tr + 2*Gr + 1) * (2*Td + 2*Gd + 1) - (2*Gr + 1) * (2*Gd + 1)

Taking the 2D slice in Matlab is very straightforward, given that target cell is at (ri, di)

trainingSlice = RDM(ri-Tr-Gr:ri+Tr+Gr, di-Td-Gd:di+Td+Gd)

Once we have the slice, anything within the guarding window should be set to 0 so that they do not contribute to the calculation of mean. This can be easily done via

trainingSlice(ri-Gr:ri+Gr, di-Gd:di+Gd) = 0

Now, summing up all elements of trainingSlice will only sum up values in training cells since guarding cells and target cell has been 0-ed out. Then dividing the result by numTraining will give the average noise.

trainingSlice = db2pow(trainingSlice);
mean = sum(trainingSlice) / numTraining;
mean = pow2db(mean);
threshold = mean + offset;

Then we check whether target is above threshold, if so, we set CFAR for that position to 1.

if (RDM(ri, di) > threshold)
        CFAR(ri,di) = 1;
end

Choosing Training and Guarding Band values

I have started choosing values from 8 for Training band on both range and doppler direction, and from 1 for Guard band in both direction as well. After quite a lot of experiments with these values, ended up with final Tr=12, Td=3, Gr=4, Gd=1 and offset=21.