Need help to design a Sine curve multiplier

[Mustahsin]

I need an IC that can multiply a Sine wave having around 80MHz by 3 to make it upto 240MHz. This 240 MHz will be needed for an ADC. Low jitter desirable!...So that IC should take the Sine wave as an input and make the output as logic.

 

[keith1200rs]

You could use a single transistor class C amplifier with tuned load to triple the frequency. If you then want a square wave put it through a comparator.

Keith

 

[Mustahsin]

You could use a single transistor class C amplifier with tuned load to triple the frequency. If you then want a square wave put it through a comparator.

Keith

Hi,

Thank you Keith for the answer.....but, for my application jitter is one of the main issues.....my Point to point jitter limit should be around 10Ps.....so can u suggest any particular product?

 

[keith1200rs]

A tuned multiplier will not increase the jitter. A PLL type approach will. You would risk jitter due to noise when you convert the sine to a square wave.

Mind you, it would be worthwhile looking at the specifications of clock generator and multiplier chips. The only ones I have used, and that was a long time ago, are the ICS ones. They are now part of IDT. This is one I have used https://www.idt.com/sites/default/files/documents/IDT_525,525-03_DST_20100514.pdf but jitter would be too high for your application. There are loads more around now though so it is worthwhile looking on IDTs site.

Keith.

 

[FvM]

A tuned multiplier will not increase the jitter. A PLL type approach will.

Yes, if we ignore a small noise induced jitter contribution of the varactor diode, or whatever is used as frequency multiplier. The succeeding comparator converting the 240 MHz sine into the required square wave will show some more jitter, but 1-2 ps seems realistic. Also insufficiently filtered 80 MHz fundamental spurs appear as jitter.

Under these circumstances, I wonder if it won't be more reasonable to use a ready-made low jitter 240 MHz crystal oscillator?

 

[Mustahsin]

Yes, if we ignore a small noise induced jitter contribution of the varactor diode, or whatever is used as frequency multiplier. The succeeding comparator converting the 240 MHz sine into the required square wave will show some more jitter, but 1-2 ps seems realistic. Also insufficiently filtered 80 MHz fundamental spurs appear as jitter.

Under these circumstances, I wonder if it won't be more reasonable to use a ready-made low jitter 240 MHz crystal oscillator?

Hi,

Sounds convincing!!...Thank you very much to both of u!:-D

---------- Post added at 14:25 ---------- Previous post was at 12:28 ----------

Yes, if we ignore a small noise induced jitter contribution of the varactor diode, or whatever is used as frequency multiplier. The succeeding comparator converting the 240 MHz sine into the required square wave will show some more jitter, but 1-2 ps seems realistic. Also insufficiently filtered 80 MHz fundamental spurs appear as jitter.

Under these circumstances, I wonder if it won't be more reasonable to use a ready-made low jitter 240 MHz crystal oscillator?

Btw....my Sine function signal will have to be synchronous with the ADC.....So, if I will use two different sources, then the Synchronisation between them might be a problem. May be the 240MHz Crystal oscillator's phase will be gradually daviated from my Sine function.....am I right?

Here is the overview of my system:

Sine function (80 MHz) --------->LASER Diode
.
. x 3
. = 240 MHz
ADC (Max 250 MHz)