Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

OCXO based GPSDO project with high accuracy and stability

Status
Not open for further replies.

Nshin

New Member
I'm requierd to make a GPSDO as a project, my resources are flexable and i have access for an Arduino UNO, some Spartan FPGA device, and an OCXO.(which i currently do not own but will have in the near future.). I will prefer to use either the Arduino or FPGA, and there might be an option to use both but only if necessary. I need to make the GPSDO learn its long-term and short-term deviations and errors and have a Hold-over function for when there is no GPS reception so it can correct itself without the 1PPS. It is more of a learning project but it should also be as high-quality as i can make it.

The main thing I am having trouble with is deciding on the suitable measuring/correcting method and algorithm, as there are more then a few GPSDO implementations on the internet. Basicly, right now I'm trying to look for as many different methods i can find and think of.

I've seen 2 methods i thought could work, one is using a 1PPS from a GPS reciever, and connecting it to either the Ardiuno or the FPGA to measure the GPSDO output frequency (which should be at 10MHz) using a rising edge every second from the 1PPS and calculating the difference between the measurment and the wanted output, using a DAC to correct it through the OCXO. While this method is very simple, there is an obvious accuracy problem with the frequency measuring part, and i can't seem to find a way to fix it without measuring it for a longer time (which will be very inefficient), i thought about some methods using the Arduino timers but i don't think i should count on it on the long-term.

The second method is using a PLL's phase detector and an A/D, and connect it through an Arduino and a DAC to the OCXO's VCO terminal. What I'm having trouble with is understand how the phase detector will act with a 1PPS, (which is basicly a very short pulse), and a regular frequency, and how to understand the deviation from its output.

I would appreciate it very much if anybuddy could either suggest how to improve the methods i spoke of, or suggest any other methods.

*I have seen a thread on GPSDO that was posted not too long ago but my situation is a bit different as i have an additional need of learning the exact deviations of the frequency, and if possible the 1PPS jitter's effect aswell.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top