Clock frequency modulation

How do I modulate a given clock signal, without using any other
frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
I have only 1 frequency ie of the clock signal and I need to modulate
that same signal.
Is this possible ?

Any help would be appreciated.
Thnx in advance....


Regards
Apurva

Apurva  Agarwal wrote:
> How do I modulate a given clock signal, without using any other
> frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
> I have only 1 frequency ie of the clock signal and I need to modulate
> that same signal.
> Is this possible ?
>
> Any help would be appreciated.
> Thnx in advance....
>
>
> Regards
> Apurva

What sort of modulation do you want to put on the clock signal? AM, FM,
PM? If the clock originates from an oscillator with a tuning input,
then you could modulate its frequency by changing the DC voltage
applied to that input. If it is a standard two-lead crystal, then you
might be able to pull it one way or the other by changing the component
values around the crystal.

John

Apurva Agarwal wrote:
> How do I modulate a given clock signal, without using any other
> frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
> I have only 1 frequency ie of the clock signal and I need to modulate
> that same signal.
> Is this possible ?


Special relativity, although not practical, makes this possible;)

> 
> Any help would be appreciated.
> Thnx in advance....
> 
> 
> Regards
> Apurva
> 

You could try replacing your clock with a VCXO and modulate it with a 
digital or audio signal.

Thomas

"Apurva Agarwal" <agarwal.apurva@gmail.com> wrote in message 
news:1143186368.104940.94690@e56g2000cwe.googlegroups.com...
> How do I modulate a given clock signal, without using any other
> frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
> I have only 1 frequency ie of the clock signal and I need to modulate
> that same signal.
> Is this possible ?
>
> Any help would be appreciated.
> Thnx in advance....
>
>
> Regards
> Apurva
> 

Apurva Agarwal wrote:
> How do I modulate a given clock signal, without using any other
> frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
> I have only 1 frequency ie of the clock signal and I need to modulate
> that same signal.
> Is this possible ?

If you clarify what you mean by "modulate", your question might have an 
answer.

Jerry
-- 
Engineering is the art of making what you want from things you can get.
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On 23 Mar 2006 23:46:08 -0800, "Apurva  Agarwal"
<agarwal.apurva@gmail.com> wrote:

>How do I modulate a given clock signal, without using any other
>frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
>I have only 1 frequency ie of the clock signal and I need to modulate
>that same signal.
>Is this possible ?
>
>Any help would be appreciated.
>Thnx in advance....

Frequency modulation of a clock without the use of a high(er)
frequency reference clock  is (1) possible and (2) commonly done (in
ASICs) using a DLL.

Here's how:

Pass your reference clock into a tapped delay line.  Fine tune the
delay line so that its length is exactly equal to one period of the
input clock.

Each tap on the delay line then represents a different phase of the
input clock.

Connect the taps to the inputs of a wide multiplexer, to allow you to
select one tap at a time.  The output of the multiplexer is your
output signal.

Apply a counter to the select inputs of the multiplexer.  Slowly
incrementing (or decrementing) the counter will cause the phase of the
output to increment (or decrement) with respect to the input clock.
This is a different way of saying that you have changed the frequency.

Getting this to work without generating glitches or lots of jitter is
left as a exercise for the reader.

Regards,
Allan.

On Sat, 25 Mar 2006 20:08:37 +1100, Allan Herriman
<allanherriman@hotmail.com> wrote:

>On 23 Mar 2006 23:46:08 -0800, "Apurva  Agarwal"
><agarwal.apurva@gmail.com> wrote:
>
>>How do I modulate a given clock signal, without using any other
>>frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
>>I have only 1 frequency ie of the clock signal and I need to modulate
>>that same signal.
>>Is this possible ?
>>
>>Any help would be appreciated.
>>Thnx in advance....
>
>Frequency modulation of a clock without the use of a high(er)
>frequency reference clock  is (1) possible and (2) commonly done (in
>ASICs) using a DLL.
>
>Here's how:
>
>Pass your reference clock into a tapped delay line.  Fine tune the
>delay line so that its length is exactly equal to one period of the
>input clock.

To do this you need a PLL ("fine tune the delay line so that its
length is exactly equal to one period of the input clock") which
requires someone to do this fine tuning; the only way of which I know
is to run a PLL, use replica bias and use twice as many delay elements
in the DLL as that of the PLL so it's outside the requirements of the
OP as it requires PLL, VCO and Ring OSc all at the same time :-)

>Getting this to work without generating glitches or lots of jitter is
>left as a exercise for the reader.

This portion I am curious about though. I have a solution which works
but my glitch suppression is a little bit more complicated than I am
comfortable with. Any references I can look up on this ?

On Sun, 26 Mar 2006 03:52:32 GMT, mk<kal*@dspia.*comdelete> wrote:

>On Sat, 25 Mar 2006 20:08:37 +1100, Allan Herriman
><allanherriman@hotmail.com> wrote:
>
>>On 23 Mar 2006 23:46:08 -0800, "Apurva  Agarwal"
>><agarwal.apurva@gmail.com> wrote:
>>
>>>How do I modulate a given clock signal, without using any other
>>>frequency source(ie. no PLLs, VCOs, Ring osc. etc.)
>>>I have only 1 frequency ie of the clock signal and I need to modulate
>>>that same signal.
>>>Is this possible ?
>>>
>>>Any help would be appreciated.
>>>Thnx in advance....
>>
>>Frequency modulation of a clock without the use of a high(er)
>>frequency reference clock  is (1) possible and (2) commonly done (in
>>ASICs) using a DLL.
>>
>>Here's how:
>>
>>Pass your reference clock into a tapped delay line.  Fine tune the
>>delay line so that its length is exactly equal to one period of the
>>input clock.
>
>To do this you need a PLL ("fine tune the delay line so that its
>length is exactly equal to one period of the input clock") which
>requires someone to do this fine tuning; the only way of which I know
>is to run a PLL, use replica bias and use twice as many delay elements
>in the DLL as that of the PLL so it's outside the requirements of the
>OP as it requires PLL, VCO and Ring OSc all at the same time :-)

You can do it with just the DLL.  No VCO required.
You will need a phase detector to compare the phase at the end of the
delay line with the incoming clock though.

>>Getting this to work without generating glitches or lots of jitter is
>>left as a exercise for the reader.
>
>This portion I am curious about though. I have a solution which works
>but my glitch suppression is a little bit more complicated than I am
>comfortable with. Any references I can look up on this ?

I don't know of any that give useful details, sorry.

Regards,
Allan

Thanx a lot Allan.

--If you clarifyIf you clarify what you mean by "modulate", your
question might have an
answer.

Modulate = FM,  looks like i forgot to mention it.. oops :)

Apurva