Low correlation sidelobes are preferred for different radar applications. Sidelobes generated during the pulse compression process are objectionable because a strong echo can mask a weaker target return. Sidelobe reduction techniques are adopted after pulse compressor to reduce sidelobes. Various methods like two sample adder, weighting filters are developed to reduce sidelobes at the receiver section. The reduction of ACF sidelobes for LFM and Barker codes by overlaying with 8 X 8 orthonormal phase code (Binary, P4) was discussed by Mozeson and Levanon. In this paper, most of the autocorrelation function (ACF) sidelobes of various codes such as Barker, ternary and polyphase P4 code are reduced by overlaying them with orthonormal codes. The three types of orthonormal phase codes used are Binary orthonormal phase code, P4 orthonormal phase code and Prometheus Ortho Normal Set (PONS). The peak sidelobe level of each code (Barker, Ternary, and P4) after overlaying with 4 X 4 or 8 X 8 or 16 X 16 orthonormal phase code (Binary, P4, PONS) is compared in this paper. Sidelobes can be reduced to zero with increase in dimension of the orthonormal code. The ambiguity function of all the overlaid signals is plotted.
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