Study on pulse form design for monostatic MIMO sonar systems

Active sonar systems typically consist of a transmitter (or transmitter array) and a receiver array and are known as a Single-Input-Multiple-Output (SIMO) system. A Multiple-Input-Multiple-Output (MIMO) sonar, on the other hand, uses multiple transmitters in order to emit different transmitter pulses into the same area. In a monostatic array, this allows the travel time information to be multiplied, resulting in high angular resolution at comparatively low hardware cost if the transmitter pulses can be separated from each other in the receive-side signal processing. This separation can be achieved by transmitting in different frequency or time windows, but this leads to a limited bandwidth or an increased overall ping period. In this paper, a method based on coding techniques and correlation filters are used for pulse separation, which means that the aforementioned limitations no longer apply. In doing so, this paper demonstrates various coding methods and the transmitted pulses generated by them for a monostatic MIMO sonar system. For comparison standard sonar pulses, such as linear frequency modulated (LFM), as well as hyperbolic frequency modulated (HFM) pulses are used as well. Furthermore, new approaches such as LFM sequences, LFM chains and orthogonal frequency division multiplexing are comparatively examined for the use of MIMO sonar systems.