Fig. 2
From: Extended families of 2D arrays with near optimal auto and low cross-correlation
a A Hadamard matrix, H8. b H8*H8 T is diagonal: each row of H8 is maximally different. c An FRT for p = 7. The eight rows are spectrally flat 1D projections. The seven sign patterns on rows 2–8 of (a) build seven distinct FRTs like (c). d The 7 × 7 array reconstructed from FRT (c). All seven arrays exhibit perfect autocorrelation (e). Their 21 cross-correlations are all optimally low, like (f)