On Sun, 04 Mar 2007 12:20:18 +1300, Dr Bruce Griffiths wrote: >Arnold Tibus wrote: >> Thanks Bruce, >> 'it generates poses some interesting challenges' >> sounds interesting, could you give some little details >> to get better idea of it? >> many thanks, >> >> Arnold, DK2WT >> >Arnold
>As can be seen from the attached schematic, the 50X frequency multiplier >simplifies achieving around 1 radian of phase shift at 500 MHz. >The corresponding phase shift at 10MHz is only around 1.15 degrees, >which as long as the tank Q isn't too high will not produce a >significant change in amplitude. >A phase shift of more than a few degrees with such a simple circuit will >introduce significant non linearities and amplitude changes. >Having to use a multiplier chain to overcome these problems is an >unnecessary complication and expense when one just wishes to phase >modulate an ADC clock which has a frequency of less than 10MHz. >Calculating the phase noise spectrum requires that the spectrum of the >varactor modulation noise and the tank component values and their >associated parasitics be known with reasonable accuracy. This is >particularly difficult for the varactor, which contributes phase noise. >It is far easier (in principle) to measure the resultant phase noise >spectrum, however doing so isn't a trivial exercise. >In contrast its much easier to calculate the phase noise at the output >of a comparator if the spectral characteristics of the noise signal are >known. >Bruce Bruce, many thanks for the excurse, one never stops learning. Arnold, DK2WT _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
