Phase-frequency discriminator for WWV phase-lock - Page 1
Forum section: electronics / projects

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: November 23, 2015, 06:33:13 am
content: Hi all, I'm building a WWV-locked ovenized oscillator as a local frequency standard for my cheap counter. I have all of the pieces of this gizmo figured out and built and working except for the frequency-phase detector. What kind of detector can be used as part of a PLL to lock the ovenized osc? The osc, btw, always comes within 1 Hz of WWV after about 1 hr warmup, but while I can detect the amount of phase error there is with a phase comparator, I dont know if its above or below WWV.

author: richard.cs
author_rank: Super Contributor
timestamp: November 23, 2015, 01:29:47 pm
content: How about a 4046 or it's new and improved version, the 9046? Take a look at phase comparator 2. It is worth reading datasheets for several 4046 versions as they are a bit varied in how much information they include and how they describe the behaviour.http://www.nxp.com/documents/data_sheet/HEF4046B.pdfhttp://www.ti.com/lit/an/scha002a/scha002a.pdfhttp://www.nxp.com/documents/data_sheet/74HCT9046A.pdf

author: Kleinstein
author_rank: Super Contributor
timestamp: November 23, 2015, 09:29:28 pm
content: Usually an ovenuzed oscillator should be rather good. Unless you have a very good reception of the ref. signal, the lock should be rather slow with times in the hours range, which is unpratical for normal use. So you might consider using WWV only for periodic calibration runs, but not a true lock.Otherwise the 4046 should be good enough, unless you have an extemly good signal (e.g. just next to station). However you should consider a digital FLL, not a simple analog PLL.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: November 24, 2015, 07:31:53 am
content: I'm pretty familiar with the 4046 and have used it many times. It contains both a very good digital clocked phase-frequency discriminator and an EXOR gate. The former is good only in fairly noise-free environments which I do not have with WWV and the gate, while it can be used with a low pass filter in noisy environments to extract the frequency difference between them does not give information as to whether the osc is above the ref or below it. The osc is, by the way, an XVCO in a temp-controlled insulated box. At this point what I have is an analog comparator (discrete differential two-quadrant multiplier) to give me difference frequency and display this difference on an LED so I know what the difference is, I dont know if the osc is too high or too low.Anybody know a good, fairly simple frequency discriminator to tune the osc with?

author: Pjotr
author_rank: Frequent Contributor
timestamp: November 24, 2015, 11:57:54 am
content: Quote from: basinstreetdesign on November 24, 2015, 07:31:53 amI would say forget about WWV if the signal is not perfectly clean. It will disturb the phase noise of a good ovenized VCXO more than it helps.In your case you are better off with a good GPS time receiver and onlyfrequencylock it to its 1 PPS output IMHO. But that involves a micro controller and some programming. And long integration times also.