Fig. 3
From: Extended families of 2D arrays with near optimal auto and low cross-correlation
a The 6 × 6 pseudo-Hadamard H 6 . b The matrix product H 6 *H 6 T is quasi-orthogonal (c.f. Fig. 2a, b). c A set of six spectrally flat 1D FRT projections for p = 5. Here, the pattern of signs for each 1D projection is fixed by row 2 of (a). Four other distinct FRTs can be built using rows 3–6 of (a). d The inverse FRT of (c) is a perfect pn array. Each of the 5 5 × 5 arrays exhibits perfect autocorrelation, as shown in (e), but the 10 cross-correlations between these arrays, (f), are next-to-optimal (c.f. Fig. 2f)