Waveforms design for modern and MIMO radar

One of the main focus of the research in modern radar systems, as MIMO (Multiple Input Multiple Output) radar and multifunction/multistatic radar, is the waveforms design and optimization in order to get a low degradation in the main lobe (low Signal to Noise Ratio loss), a low Peak Side-Lobe Ratio (PSLR) and good orthogonality properties. In MIMO applications typically M different waveforms, or codes, are required, where M is the number of the transmit elements. In reception the orthogonal property of the M transmitted waveforms permits their separation. Orthogonality may be imposed in time domain, in frequency domain or in signals space. In most radar applications, obtaining the orthogonality in the signals domain is the best choice. Good candidates to design deterministic signals that satisfy the orthogonality requirements are the well-known “up” and “down” chirp (Linear-FM and Non-LFM), the Costas codes, the Alltop sequences and the OFDM signals. Another important class of orthogonal signals are the random signals such as the noise waveforms. In this paper we present the main characteristics of these signals and their comparison through a characterization, including an analysis of the auto and cross correlation functions, and of the spectral properties, with recommendations for practical use.