| 摘要 |
PURPOSE:To achieve modulation which has a high response speed by an FSK modulator for digital data transmission used for the VHF and UHF bands, by multiplying the output of a voltage-controlled oscillator by N and by performing frequency division according to the space and mark of input data after frequency conversion. CONSTITUTION:The output of a voltage control oscillator 1 which varies in frequency with an input voltage is multiplied by N through a multiplier 2, whose output is processed through the frequency conversion of a mixer 3 by using a local frequency fL. Its output is led to a variable frequency divider 4, which performs frequency division at different frequency division ratios according to the mark and space of the input data, and a phase difference between its output and a reference signal with a reference frequency fr is detected by a phase comparator 5, whose output is made into a direct current through an LPF6. The output of the oscillator 1 is passed through a BPF7 to eliminate spuriousness. For this purpose, the output of the oscillator 1 is multiplied by N through the multiplier 2 to increase the response speeds of the mark and space of the input data. |
