1. A radar system comprising: an array antenna including a plurality of antenna elements each of which outputs a reception signal in response to at least one arriving wave; and a signal processing circuit in which a learned neural network has been established; wherein the signal processing circuit: receives the reception signals; inputs the reception signals or a secondary signal generated from the reception signals, to the neural network; performs computation by using the reception signals or the secondary signal, and data of the learned neural network; and output a signal indicating a number of the at least one arriving wave from the neural network.