Hal Murray wrote: >> Surely it would be much simpler (in principle at least) to just to add >> sufficient Gaussian phase noise to the GPS receiver clock so that >> potential coherence problems are virtually eliminated. >> > > It doesn't look reasonable to me, but I'm not good at this sort of math. > > The clock is, say, 40 MHz. That's 25 ns, so the output jitter will be 25 ns > p-p. > > If you are at the top of a hanging bridge, you have to add enough noise to > hide a 12.5 ns offset. Will a typical GPS receiver still work with that much > trash on its clock signal? What sort of noise spectrum would you use? > Hal
The noise only really needs to be added to the PPS positioning algorithm/hardware. In principle (if you can get at the firmware) it would be possible to implement noise shaping using a sigma delta modulator (possibly with added noise dithering to break up idle patterns - like hanging bridges) so that the short term PPS positioning noise increases but the average position is more stable. This may be useful when a long time constant PLL is used to discipline an oscillator with the PPS output of the receiver. Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts