| 摘要 |
PURPOSE:To use an amplitude limiting circuit in a base band, to make a multiplying circuit unnecessary, and to simplify constitution of a circuit by limiting an object to be detected, to a frequency modulated wave modulated by a binary digital signal. CONSTITUTION:A signal whose frequency is modulated by a binary digital signal is inputted to an input terminal 11, and four signals which have obtained the output of an oscillator 30 of a frequency being roughly equal to its center frequency by a phase difference separating circuit 35 are mixed 21-24 to be used as a local oscillating signal. A desired frequency is extracted by making its output pass through LPFs 31-34 and the band of noise is limited. Subsequently, it is binary-coded 41-44, and signals I1, Q1, I2 and Q2 are obtained. The signals I1, Q1 and I2, Q2 are inputted to exclusive OR circuits 62, 61, respectively, and signals I1Q1 and I2Q2 are obtained. A reference signal Z is generated from the signal I1Q1, and exclusive OR X of the signal I1Q1 and Z is derived. By differentiating the signal I2Q2, a signal dI2Q2 is obtained as a clock pulse, and the signal X is brought to an FF90. In such a way, the detection can be executed by a simple circuit. |
