| 摘要 |
<p>The invention relates to a method in which a phase modulated or frequency modulated signal can be directly generated with a PLL frequency synthesizer. With an interpolating synthesizer it is possible to create a very dense output frequency (fx) raster, so that the pulses received in the phase comparator (63) both from the reference signal (fo) branch and from the voltage controlled oscillator VCO (65) are lengthened in lengthening means (62, 69; 67, 68; k1, L+ DELTA L; k2, L) by a desired amount. The numbers k1 and k2 are proportional to the amount of lengthening. When these integers now further are changed proportionally to the modulating signal, the change of the integers causes a change of the time difference of the pulses received by the phase comparator (63). This change of the time difference further causes a change in the output signal (fx) of the voltage controlled oscillator. The method is particularly well suited to provide digital quadrature phase modulation QPSK or quadrature amplitude modulation QAM, in which the shift from one carrier phase to another has a predetermined size and waveform as a function of time. <IMAGE></p> |
