Removing autocorrelation function sidelobes by overlaying orthogonal coding on any train of identical pulses

A coherent train of identical Linear-FM pulses is used extensively in radar because of its good range and Doppler resolution. Its relatively high autocorrelation function (ACF) sidelobes are sometimes reduced through spectrum shaping (e.g., non-linear FM, or intrapulse weighting on receive). We show how to completely remove most of the ACF sidelobes, without any increase to the mainlobe width by diversifying the pulses through overlaying them with orthonormal coding. The method applies to any train of identical base pulses. We will demonstrate some base pulses in which the remaining ACF sidelobes are lower than with Linear-FM. The type of orthonormal overlay does not affect the resulting ACF, but does affect the ambiguity function. The same is true with the order of slices in the pulse and the order of pulses.