PURPOSE: To detect and analyze a chirp signal with high accuracy by calculating an autocorrelation data being the result of retarding a data in a digital high frequency signal memory by a specified time, allowing an FET circuit to decide whether a signal is a chirp signal or a normal signal, and calculating the slope of the chirp signal.

CONSTITUTION: A reception signal inputted to a digital high frequency signal memory DRFM 1 is expressed as cos(2π(f+ft)t), where (t) is a time. The f depicts a slope of a chirp signal in this expression. An autocorrelation device 2 calculates the autocorrelation value retarding a data recorded in the DRFM 1 by a time T0. A chirp signal deciding circuit 5 evaluates the value of the fT0, and decides it to be a normal signal when the value is '0' and discriminates it to be a chirp signal when the value is not '0'. In the case of the chirp signal, the value f is calculated from the value 2fT0. Thus, one FET circuit makes it possible to detect and analyze the chirp signal. Then the detection and analysis accuracy is improved.