S
Sommes
- Jan 1, 1970
- 0
How to adjust the oscillation frequency from the output frequency of 1MHz
crystal oscillator?
Thanks
crystal oscillator?
Thanks
Sommes said:How to adjust the oscillation frequency from the output frequency of 1MHz
crystal oscillator?
Thanks
Sommes said:How to adjust the oscillation frequency from the output frequency of 1MHz
crystal oscillator?
Thanks
Crystal oscillators are quite stable, but you pay for that with a verySommes said:I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz
What I think is I have to use crystal oscillator to make stable oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.
Please let me know the right track...Thanks...
A variable capacitor, or varicap diode in series with one of the capacitors
wil give you upto a few 100ppm adjustment depending on crystal.
a PLL will alow u to adjust it in discrete jumps, or u can just divide it by
any binary number with a pre setable counter
or multiply witha mixer/multiplier to get twice the frequency, or filter out
the 3,5 harmonics etc.
You are going to divide the 1 MHz by 1000 to get 1 KHz, right?Sommes said:I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz
What I think is I have to use crystal oscillator to make stable
oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.
Please let me know the right track...Thanks...
Paul said:Well if you mix it and filter, you could get *any* other frequency,
not just a multiple or a discrete step!
Sommes said:I am doing a analog project.
The topic: High stability variable oscillator
Select and test an appropriate digital oscillator circuit for producing an
accurate variable oscillation from 1kHz to 1MHz
What I think is I have to use crystal oscillator to make stable oscillation.
I will chose 1MHz crystal oscillation...after I may need to adjust 1MHz to
1KHz range.
Please let me know the right track...Thanks...
Gareth said:You say it is an analog project? I think that would rule out things
like Phase Locked Loops (PLLs) and synthesizers.
One easy way to get a frequency which is variable from 1KHz to 1MHz
would be to use a 555 timer. This will be nowhere near as accurate as a
crystal but it may be accurate enough for your project. I don't know,
but have a look at:
http://www.doctronics.co.uk/555.htm
Another option would be to use an oscillator IC, e.g LTC6900, which can
be adjusted from 1 KHz to 20 MHz. See:
http://www.linear.com/pc/productDetail.do?navId=H0,C1,C1010,C1096,P2186
Again this is nowhere near as accurate as a crystal, but may do what you
want.
How can you do that (unless you have another variable oscillator to mix
it with, which seems a bit pointless)?
Gareth said:How can you do that (unless you have another variable oscillator to mix it
with, which seems a bit pointless)?
Gareth.
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Norm Dresner said:See comments in-line
producing 1MHz
Not really. Starting with a square wave it's moderately easy to create
a triangle and not all that hard to approximate a sine wave either. There's
really nothing much like a PLL to get accuracy (but not necessarily
short-term precision). Or Direct Digital Synthesis. DDS is expensive but
it'll put out very nice sine waves of rather controllable frequencies.
For accuracy, nothing beats a crystal -- unless it's a better crystal or an
atomic clock which, I'm pretty sure is out of the OP's budget. But the
question of accuracy may be a red herring. It might be sufficient to have a
555 with a digital frequency readout and a 10-turn pot for time setting. Of
course, that doesn't produce very good stability. And if it's an analog
output that the OP really wants directly from the oscillator then the 555's
binary output isn't what would get him a good grade.
What about the venerable "Intersil" 8038 (or whoever makes it these
days) or one of the Exar things like the (IIRC) 2240 which has it's own
binary divider.
Norm
Tam/WB2TT said:This is used to get a wide range oscillator. For instance, the HP 8601 used
something like a 300 MHz xtal osc and 300 - 400 MHz VCO to get 1 - 100 MHz
output. Highly unstable; primary use was as a sweep generator.
Tam