| 摘要 |
PROBLEM TO BE SOLVED: To expand the measuring range of frequency deviation by a phase- orbit method in a digital phase modulation system. SOLUTION: A frequency f0 of a coherent signal S11, which is the reference signal of a quasi-synchronous detecting part 12, is made variable so as to follow a signal under test Sin. As the method for determining the frequency f0, the values of a lower-limit frequency (f2) and an upper-limit frequency (f3) of an occupied bandwidth are used. As the processing sequence, at first the upper-limit frequency (f3) and the lower-limit frequency (f2) in the spectrum distribution of the signal under test Sin are obtained. Then, the central frequency f0 is found from the upper-limit frequency (f3) and the lower-limit frequency (f2), and frequency deviation S16 is obtained at the same time. Then, the signal S11 without modulation of the frequency f0 is used, and the quasi-synchronous detection is performed. Furthermore, frequency deviation S13 is obtained by a phase-orbit method, the frequency deviations S13 and S16 are added and the result of measurement of the frequency deviation S17 of the test signal uner test Sin is found. |
