Load stabilty improvement in OCXO

[varaprasad]

Can any body suggest the circuit diagram for load stability improvement in OCXO design.Is it possible to get 0.1ppb over 50Ohms±5% load change.Thanks in advance.

 

[Diver300]

0.1 ppb takes a lot of work. What it the temperature stability? How are you setting the oven temperature? Are you using SC cut?

To improve load stability, you need several stages of buffer to isolate the load changes from the crystal.

Make sure that you filter the power lines very well as that is often how the oscillator frequency signals make their way back from the output stage to the oscillator.

 

[RadioRon]

What is the frequency? It might be quite easy to buffer your load by adding a cascade of several line driver amps (in one package) from a logic family.

As was mentioned, you have to pay as much attention to power supply isolation as direct load isolation. Perhaps consider an independent linear regulator (a precision type) dedicated to the OCXO.

 

[varaprasad]

We are working with 10.000MHz TO-8 SC-CUT crystal with sine wave output.Is
there any Logic family IC available for Sine output.We are using Zener based voltage regulator.

 

[RadioRon]

If you need to maintain the sine output, then my logic idea is no good. Better just to use some high frequency op amps or RF gain blocks with high output/input isolation.

Another point worth mentioning is to insure there is no RF noise or feedback radiating back into your oscillator from external sources. Perhaps some RF bypass capacitors on the wiring inputs would be helpful. Also, keep magnetic noise sources like switching regulators away from the output circuitry. You have to be pretty fussy to achieve 0.1 ppb.