Multifrequency radar signals

A multifrequency radar signal is considered. It employs M subcarriers simultaneously. The subcarriers are phase modulated by different sequences that constitute a complementary set. Such a set can be constructed, for example, from the M cyclic shifts of a perfect phase-coded sequence of length M (e.g., P4). The subcarriers are separated by the inverse of the duration of a phase element by yielding orthogonal frequency division multiplexing (OFDM), well known in communications. The signal exhibits a thumbtack ambiguity function with delay resolution of t/sub h//M. The power spectrum is relatively flat, with width of M/t/sub h/. The signal can be constructed by power combining M fixed-amplitude signals. The resulting signal, however, is of variable amplitude.