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.

frequncy multiplier

Status
Not open for further replies.

dudyyy

New Member
hi i have 50MHz crystal oscilltator ,i need a simple frequncy multiplieer circuit that will double this frequncu to 100MHz.

thanx
 
You don't give any indication of what it's for?, but essentially a multiplier is just a class C amplifier with a tuned circuit in the output, so you would have a 100MHz tuned circuit in the output.
 
I would have thought that a 50 Mhz crystal would work Ok as
a 100 Mhz crystal.
Not that i have tried that one,
but other crystals i have used have been Ok at double their cycles.
 
You're referrng to 'overtone' crystals, which are designed to work at a multiple of their 'real' frequency. It's quite likely that a 50MHz crystal is already an overtone one, and requires an oscillator circuit with a 50MHz tuned circuit in order to run at that frequency.
 
Most of these crystals are actually 3rd or 5th overtone already, some even as high as 7th and 9th, and will be designed to run in an Oscillator tuned to pick the overtone used. Pretty much anything above about 4-5Mhz will be an overtone of some fundamental according to the guys I have spoken to at CMC and Q-Tec. If you can live with the current accuracy of the 50Mhz crystal you have, design a PLL based Oscillator around it to give you the required 100Mhz :)
 
tunedwolf said:
Pretty much anything above about 4-5Mhz will be an overtone of some fundamental according to the guys I have spoken to at CMC and Q-Tec.

No, higher ones than those are commonplace - such as the 20MHz ones we hang on PIC's - these can't be overtone ones as there's no tuning. However, they also probably aren't as accurate and stable as lower frequency ones multiplied up. You might notice that the 18F series use an internal PLL to generate higher clock speeds, presumably because of the difficulty of sourcing higher ones?.

Going back to my early 145MHz amateur radio days, we used crystal controlled equipment (it was pre-PLL tuning), the most common were 12MHz and multiplied 12 times, although some radios used 8MHz multiplied by 18 instead.
 
Hi

i feel better to use a ring modulator cct using 4 diodes and two tranformers. if the input and carrier freq are the same, then the output would be double, provided DUDYYY's oscillator is outputing 50MHz.
of course he has to fabricate transformers using torroid cores and try to use high frequency diodes
 
Last edited:
mvs sarma said:
Hi

i feel better to use a ring modulator cct using 4 diodes and two tranformers. if the input and carrier freq are the same, then the output would be double, provided DUDYYY's oscillator is outputing 50MHz.
of course he has to faricate transformers using torroid cores and try to use high frequency diodes

A bit over complicated though?, and it's NOT the way it's usually done, frequency multiplying is a very standard technique and very easy to do - certainly easier than trying to wind 100MHz toroids!.

If you're looking for different ways of doing it?, a PLL with a divide by 2 circuit in the feedback is another obvious way.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top