| 摘要 |
PURPOSE:To reduce man-hours for locating a fault location of a demodulation section by half by allowing a demodulator to disconnect a digital signal processing unit of a post-stage and to diagnose itself as to whether or not itself is faulty. CONSTITUTION:When a demodulation section of an input radio signal (s) subject to orthogonal transformation is faulty, at first an error output E0 of a carrier recovery device (CR0) 1 selected by a switch (SW) 2 in a demodulator DEM is integrated by an integrator 16, and a resulting voltage is used as a control voltage V, it is fed to a voltage controlled oscillator VCO 13 and when the said voltage controlled oscillator VCO recovers a correct carrier, it is discriminated that a demodulator DEM 10 is normal and a transversal equalizer TRV EQL 21 in the inside of a digital signal processing unit DSP 20 is faulty. A self diagnostic device selects an error E1 of an output of a carrier recovery device CR1 22 into an error E0 of an output of a carrier recovery device CR0 1 in the said demodulator 10 at a fault of the demodulation section to observe whether or not the frequency and the phase of an output C of the voltage controlled oscillator VCO 13 are correct thereby allowing the demodulation section by itself to diagnose whether or not itself is normal. |
