To measure quickly and accurately the frequency characteristics of a circuit.
A synthetic waveform memory 24 stores previously the waveform data of pseodo-white noise signals obtained by synthesizing a plurality of sine waves having different frequencies, and the stored waveform data is converted into analog signals by a D/A converter 25 and fed to a circuit to be measured 1, and the spectrum of signals given from the circuit 1 is fed to a spectrum analyzer 30. By a frequency dividing ratio changing means 26, the frequency spacing of the sine waves contained by the pseodo-white noise signal is set over the analyzing band width of the spectrum analyzer 30, and the frequencies of the sine waves are put identical to the analytical frequencies of the spectrum analyzer 30.
MORI TAKASHI
MATSUDA TOSHIYUKI
