People used passive mixers driving electromechanical stripchart recorders to compare high-stability oscillators in the good old days.
One assumes that there is a purely analog approach to measurement of picosecond changes in delay at 10 MHz using a single oscillator, but I have not seen any methods described, probably because the relevant articles appeared many decades ago. Can anyone suggest some articles to read? Thanks, Joe Gwinn [EMAIL PROTECTED] wrote on 12/04/2008 11:39:55 PM: > > Building a Sub Pico Second phase detector. > > I was inspired to build this project yesterday after > downloading and trying > Ulrich Bangert's 'DF6JB's Plotter 2008-10-10' program with its > unbelievable > flexible user Interface capabilities. http://www.ulrich- > bangert.de/html/downloads.html > What I needed was a Phase detector to use with the 'Plotter' program. > I decided to see what it takes to build a simple high > resolution, sub Pico second, > linear phase logging detector using standard off the self IC's. > > How If works: > The 5 or 10 MHz signal to be measured is buffered and toggles a > synchronous divide by two or four FF. This gives a 2.5MHz > square wave and its complement. > Each side of the flip-flop connects to two of four XOR gates. > > The 10 MHz reference signal goes thru a matching buffer and > then to a pair of synchronous > Flip-Flops that provide a zero and a 90 deg phase shifted 2. > 5MHz square wave. > Each of these goes to two inputs of the XOR gates. The four XOR > phase detectors > are connected to give four PWM type XOR phase detectors, each > separate by 90 deg. > > Each of the four XOR outputs are buffered by a cmos buffer gate > that has been powered by it's own 5 volt reference supply. > The buffer outputs then goes thru a multi-stage passive RC > filter set up to > give two differential filtered PASSIVE + - 5 volt outputs, 90 deg apart. > > Logging Data: > For the most flexible and best performance, two differential > 16 plus bit ADC's > should be used, each connected to one of the dual differential > Phase detectors. > After using the appropriate Analog RC filters, oversampling, > digital filters, and digital > scaling, you get a file with a single column of data to feed > "Plotter" the phase > difference of the two 10 MHz signals. > > The Data scaling and processing: > For simple controlled short term or lower resolution data > taking a PC Multimeter, > if it is isolated so that you can use it differentially will > work. If not you need to add a differential amp. > For best performance, process the phase data from the two > differential phase detectors > through two identical digital filter algorithms. > Doing this real time on a PC or after all the data is recorder > on a XL spread sheet both work for me. > Besides the filtering, the spread sheet or PC needs to also do > the linearizing by > ( K1* Phase1_Data) + (K2 * Phase2_Data). > K1 and K2 are the sine value of their respective Phase detectors. > > One of the several tricks to why this can provide orders of > magnitude better > performance than is generally obtained from similar type phase detectors > is because of the four matched Phase detectors that are added, > subtracted > and combined and linerized in such a way as to cancel the type of errors > found in single XOR phase detectors. > > Preliminary Performance > The noise floor that I have seen while feeding the same low > noise osc, to both inputs, > is around 10 uv peak to peak at low Bandwidths, at zero phase, > using a 6 digit DVM > with a slow filter which corresponds to <<1 ps. Test are still > underway to see what the > lower limit is, and what the sensitivity to the environment is. > > This is just the start of an on going learning project, It is > just at the breadboard stage and > needs to be verified, critiqued, cleaned up and packaged up. > Noted that when working with sub ps resolution, extra care > needs to be taken. > Although it looks to be a standard digital circuit, It is not. > It is a very sensitive Analog circuit > capable of giving 1 part in a million type of resolution. It > can resolve path distance changes > in the 1/100 to 1/1000 of an inch, and needs to be built with > care and 'respect'. > > Another use (beside watching just how noisy your "GOOD " osc is), > It can be used to compare and adjust the freq differences > between two osc > very quickly and with more resolution than most can use. > 1 E-12 freq difference gave several counts per second change on > the DVM, and with the DVM updating at several times a second, > it made fine freq adjustments much easer than slower monitoring ways. > > > If you know of other simple high resolution phase detectors, > or see any problems or improvements > with the idea, I'd like to hear from you. > > Have fun > WarrenS > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi- > bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
