| 摘要 |
PURPOSE: To decide the reception quality of AM broadcasting by inspecting the characteristic of an inputted broadcasting signal without being based on the measurement of signal density delayed by AGC time constant. CONSTITUTION: An IF signal 25 is provided with an intermediate frequency to be used by a specific receiver and modulated by an audio information signal 26. A corrected IF signal 27 generated from a variable gain block 13 includes a residual carrier noise 28 higher than the upper side cut-off frequency of LPF 15. A pure sine-wave carrier signal 31 is induced from a square wave 30 provided with transition at the zero cross point of the signal 27. At the time of subtracting the pure sine carrier signal from the signal 27 by an adder 20, a noise signal 32 is generated. Otherwise, the pure sine-wave carrier signal can be generated with 180 deg. phase shift with respect to the corrected IF signal by a phase adjuster 18 to add these two signals to generate a noise signal. |
