Yes, you are right. 5650_5650 is sig=ref case. prs10_5650 is sig=prs10 and ref=5650 case.
Since I really want to reduce the noise, what is the best test set you suggest? All the frequency source I have: FE5650 Rb , PRS10 Rb , MV89a*2 OCXO, Thunderbolt GPSDO, 8663-XS*2 OCXO, Wenzel 100M OCXO(not sure). How to analyze the ADEV plot to get information about noise? Thanks 2014-12-13 0:31 GMT+08:00 Bob Camp <[email protected]>: > > Hi > > In your original data: > > Is the blue “5650 to 5650” trace looking at the same source for input and > reference? > > Is the green “PRS10 to 5650” trace looking at two independent sources (one > reference and the other as input)? > > I’m guessing that the answer is yes in both cases. > > Bob > > > > On Dec 12, 2014, at 10:40 AM, Li Ang <[email protected]> wrote: > > > > Hi Bob, > > The job done by linear regression is to reduce the uncertainty. This > > counter is designed to use continous timestamp method. My current design > > can measure 9000 times/second. If I only use the 1st and last one to > > calculate, it's the traditional recipocal + interploator method. This is > > what you can see on the chart named "without linear regression". The > > uncertainty of slope(the frequency ratio of ref and signal ) is > contributed > > by these 2 measurements. With linear regression of all 9000 data within > one > > second, the uncertainty will reduced to smaller one. (I really can't > > remember the ratio. Something like sqrt(9000)). > > > > > > while(1) { > > double t3; //fraction part of refcnt, measured by tdc_gp22 > > double ref_curr; > > uint32_t sig_curr; > > static double ref_start; > > static uint32_t sig_start; > > uint32_t refcnt, sigcnt; > > const uint32_t gate_time = 1000; // 1000ms gate time > > > > if (i == 0) { > > init_regression(&rv); > > cpld_rst(); > > timestamp(&refcnt, &sigcnt, &t3); > > ref_start = refcnt - t3; > > sig_start = sigcnt; > > i++; > > continue; > > } > > > > timestamp(&refcnt, &sigcnt, &t3); > > > > regression_enter_data(&rv, refcnt - t3 - ref_start, sigcnt - > sig_start); > > if (msecond < gate_time) { > > i++; > > continue; > > } else { > > t = regression_slope(&rv) ; // with linear regression > > printf("\r\nFreq=%.*f", 14, t); > > ref_curr = refcnt - t3; > > sig_curr = sigcnt; > > > > t = CalcFreq(ref_curr - ref_start, sig_curr - > > sig_start); // without linear regression > > printf(" Interpolated=%.*f", 12, t); > > > > msecond = 0; > > i = 0; > > } > > } > > > > 2014-12-12 21:18 GMT+08:00 Bob Camp <[email protected]>: > >> > >> HI > >> > >>> On Dec 12, 2014, at 4:04 AM, Tom Van Baak <[email protected]> wrote: > >>> > >>> This large posting is from Li Ang. > >>> /tvb > >>> > >>> ----- Original Message ----- > >>> From: Li Ang > >>> To: Discussion of precise time and frequency measurement > >>> Sent: Thursday, December 11, 2014 7:37 AM > >>> Subject: Re: [time-nuts] Homebrew frequency counter, need help > >>> > >>> > >>> Hi Bob, > >>> I've sent the PCB to the factory and I am waiting for the new board. > >> This time, it's a 4-layer borad and changed from CPLD to FPGA. This is > the > >> first time of FPGA & 4-layer project. Hope everthing be OK. > >> > >> Very nice looking. I hope it works !!! > >> > >>> TPS79333 as the LDO for TDC. Better PSRR and noise spec than before > >> (XC6206). Analog and digital parts have their dedicated LDO. > >>> > >>> > >>> While I'm waiting the the new board. I did a test with PRS10 & FE5650 > >> with current board. It's strange that the 20s adev of "without linear > >> regression" is better than "with linear regression” > >> > >> Be careful pre-processing ADEV data. There are a variety of statistical > >> “traps” you can fall into. An overly simple explanation is that ADEV > looks > >> at noise and that most pre-processing is a filter. Filters take out > noise. > >> Finding one that only takes out the “bad noise” and keeps the “good > noise” > >> can be quite difficult. > >> > >> What exactly are you doing in your linear regression computation? > >> > >> Bob > >> > >>> > >> > .<bottom_layer.GIF><power_plane.GIF><top_layer.GIF><adev.gif>_______________________________________________ > >>> 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. > >> > > _______________________________________________ > > 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. > _______________________________________________ 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.
