| 摘要 |
PURPOSE:To decrease remarkably power consumption by demodulating a message signal only when its own station has been called, on the assumption that a discriminating signal represented by a digital signal is transmitted prior to a message signal to be communicated. CONSTITUTION:A modulated wave signal of an intermediate frequency band is inputted from an input terminal 300, detected by an orthogonal detector, and base band signals whose phases are different by 90 deg. from each other are obtained in low-pass filters 321, 322. The two base band signals are made to branch, respectively, and one signal and the other signal are inputted to the first receiving circuit 306 and the second receiving circuit 305, respectively. The base band signal which is inputted to the second receiving circuit 305 is converted to a digital value by A/D converters 343, 344, and thereafter, brought to a demodulation and other operation processing by a digital signal processor 345. Subsequently, it is returned to an analog signal by a D/A converting circuit 346, and a transmitting message signal is obtained in an output terminal 310. |
