| 摘要 |
PURPOSE:To realize the demodulation even with a QPSK (Quadrature Phase Shift Keying) signal having the frequency fluctuation of a carrier wave by providing a fixed frequency oscillator, a multiplier, a differentiator and a level detector and also using a resistor that secures a wide lock range, and a frequency variable oscillator using a capacitor and a coil respectively. CONSTITUTION:The QPSK signals supplied to an input terminal 51 and to be demodulated are divided into two routes by a signal processor 52. Then each of these divided signals is multiplied by the output signal of a 1st oscillator 57. In this case, the QPSK signals of one of both routes are multiplied by the output signal of the oscillator 57 having its phase shifted by 90 deg.. Such multiplied signals of both routes are applied to 1st and 2nd LPF 53 and 54 and the output signals of both filters are multiplied by a multiplier 55. These multiplied signals are transmitted through an LPF 56 and applied to a terminal which controls the oscillation frequency of the oscillator 57. Then the signals which are not modulated yet by the QPSK signal are outputted to output terminals 66 and 67 connected to the output parts of both filters 53 and 54. |
