Hello everyone,

I'm trying to make a very accurate frequency counter. A GPS receiver allows me to have a 1PPS signal that I use as a reference to do my frequency measurement. According to the datasheet this 1PPS has a jitter of 10ns.

In short, the more stable this signal, the more accurate my frequency measurement will be, right?

So I would simply like to remove or reduce this jitter.

Internet friends, do you have any ideas?

 

In short, the more stable this signal, the more accurate my frequency measurement will be, right?

No.

Since you have not given us the schematic, or even a block diagram of the circuit, everything is just a guess.

You don't say if your receiver is a disciplined oscillator. That matters.

IF IF IF you are using the 1 pps signal to gate a counter that is clocked by the signal being measured, then that circuit's best case ambiguity is +/- 1 count. For a 1 kHz signal, that is +/-1 ms. Having a gate width that is *only* 100,000 times more accurate should be good enough. At 1 MHz it still is 100 x better.

Also, know that the propagation delay through a string of counters is significantly greater than 10 ns, and varies with temperature. How this affects your circuit is a mystery.

AND - read up on how GPS timing works. That spec probably is for the receiver itself, not the total error from the satellite atomic clock through the transmitter and the atmosphere. The actual jitter in the receiver output signal will be greater than 10 ns, and it still will be a near-miraculous thing of beauty. The only way to have a timing signal with less jitter is to have a rubidium or cesium standard on your desk.

What is the signal whose frequency you are trying to count, and what is your required precision / accuracy / whatever?

ak

 

You need to state the accuracy you are trying to achieve.
There are two parameters to state, error and long term drift.
Also, what are the range of frequencies you wish to measure?

 

Since you have not given us the schematic, or even a block diagram of the circuit, everything is just a guess.

You don't say if your receiver is a disciplined oscillator. That matters.

I gave the datasheet of the component that I use as a GPS receiver.

For the counting and frequency deduction stage I do this on an FPGA:

Only rather than using the external 10MHz oscillator as a source, I use my GPS receiver to make my measurement window.

Also, know that the propagation delay through a string of counters is significantly greater than 10 ns, and varies with temperature. How this affects your circuit is a mystery.

AND - read up on how GPS timing works. That spec probably is for the receiver itself, not the total error from the satellite atomic clock through the transmitter and the atmosphere. The actual jitter in the receiver output signal will be greater than 10 ns, and it still will be a near-miraculous thing of beauty. The only way to have a timing signal with less jitter is to have a rubidium or cesium standard on your desk.

What is the signal whose frequency you are trying to count, and what is your required precision / accuracy / whatever?

My objective is to measure at least with an accuracy of 0.1Hz a frequency of maximum 100MHz

 

100MHz ± 0.1Hz translates into 1ppb (1 part in 1000,000,000).

10ns in 1s is 10ppb.

So the answer is no.

 

100MHz ± 0.1Hz translates into 1ppb (1 part in 1000,000,000).

10ns in 1s is 10ppb.

So the answer is no.

Thank you for your answer.

So I can maximum measure 10MHz with 0,1Hz accuracy..

But do you know if the jitter can be reduce ?

 

I gave the datasheet of the component that I use as a GPS receiver.

I completely miss that. Duh.

Apologies.

ak

 

I completely miss that. Duh.

Apologies.

ak

No worries my friend you try to help