| 摘要 |
PROBLEM TO BE SOLVED: To exactly discriminate the digital phase modulating system of an input signal from unknown radio equipment by finding an estimated carrier frequency from the frequency area data of an unknown digital phase modulated signal, detecting that frequency, operating it, finding the symbol point of phase modulation and displaying data provided by detecting and operating that frequency again. SOLUTION: A down converter 12 converts the radio wave of unknown radio equipment received by an antenna 10 to an intermediate frequency signal and a data spectrum analyzer 14 converts that signal to digital frequency component data and stores them in a memory. Afterwards, a computer 16 finds the estimated carrier frequency from the digital frequency component data in the memory and finds an orthogonal coordinate by detecting and operating time area data based on this frequency. Further, the symbol point of phase modulation is found at the respective points of these coordinate data and a true carrier frequency is found from this symbol point. Then, the time area data are detected and operated again based on the found carrier frequency and the provided symbol point is displayed on a coordinate plane. |
