Senior Project Help! F.S.K

[Wicked]

Hello


I am looking for a chip that can help me to produce a 2nd signal (sine
wave).

My input is going to be 20Khz, 5Vpp sine wave coming out of my
oscillator. I would like to feed this signal (Freq. F1) into a "chip"
to produce a 2nd sine wave at Freq. F2. However, this second frequecy
F2 needs to be in phase with my Freq F1 and needs to be a sine
wave.... I am lost as to what Chip I can use to solve this problem.

Thank you for your time!

 

[Gareth]

Hello


I am looking for a chip that can help me to produce a 2nd signal
(sine wave).

My input is going to be 20Khz, 5Vpp sine wave coming out of my
oscillator. I would like to feed this signal (Freq. F1) into a "chip"
to produce a 2nd sine wave at Freq. F2. However, this second
frequecy F2 needs to be in phase with my Freq F1 and needs to be a
sine wave.... I am lost as to what Chip I can use to solve this
problem.

Two different frequency signals cannot be in phase, that is like saying
you want two cars travelling at different speeds to stay next to each other.

If you mean that you want F2 to be some known multiple of F1 then look
at Phase Locked Loops (PLL) and synthesisers.

Look at www.analog.com and www.national.com for PLL and synthesiser chips

If you have a high speed (>>20kHz) digital clock you could use a DDS to
produce the 20 kHz and another DDS from the same clock to produce F2.

Look at www.analog.com for DDS datasheets

Gareth.


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[Wim Ton]

Hello


I am looking for a chip that can help me to produce a 2nd signal (sine
wave).

My input is going to be 20Khz, 5Vpp sine wave coming out of my
oscillator. I would like to feed this signal (Freq. F1) into a "chip"
to produce a 2nd sine wave at Freq. F2. However, this second frequecy
F2 needs to be in phase with my Freq F1 and needs to be a sine
wave.... I am lost as to what Chip I can use to solve this problem.

Thank you for your time!

Is the second frequency a multiple or fraction of the first?

One may think of PLLs or synchronized oscillators. Usually not one standard
chip, but some additional Rs, Cs and Ls as well

Wim

 

[GPG]

Two different frequency signals cannot be in phase, that is like saying
you want two cars travelling at different speeds to stay next to each other.

I think he means phase continuous. This same question was posed here
not so long ago.

 

[Ben Bradley]

Hello


I am looking for a chip that can help me to produce a 2nd signal (sine
wave).

My input is going to be 20Khz, 5Vpp sine wave coming out of my
oscillator. I would like to feed this signal (Freq. F1) into a "chip"
to produce a 2nd sine wave at Freq. F2. However, this second frequecy
F2 needs to be in phase with my Freq F1

I think others are incorrectly interpreting what you're trying to
say.
Since you use the initials F.S.K (perhaps for Frequency Shift
Keying, a common modulation method) in your subject, I suspect you
want to generate a single sine wave, but switch it between two
frequencies, and also when switching frequencies you want the new
frequency start at the same phase the previous frequency stopped at.
There are several ways to do this, surely with one or more analog
sine-wave oscillators (I'm thinking of a voltage-controllable
state-variable filter with 'Q' cranked up to oscillation), and it's
also easily done digitally with direct digital synthesis.
If you already have a fixed-frequency oscillator that you want to
somehow 'process' its output to generate a FSK signal, you will have a
much harder time of it. For FSK it's much easier to start with an
'oscillator' (whether analog or digital, hardware or software) whose
frequency can be varied.

and needs to be a sine
wave.... I am lost as to what Chip I can use to solve this problem.

What chip you use depends on how you do it. I'd think different
ways of skinning a cat requires different tools as well.

 

[Wicked]

Yes, the 2nd freq. needs to be a multiple of the first one. I went on
the Analog devices webpage looking for a chip i can use but I cant
seem to find one. Does anyone know which chips would work? PLEASE
HELP! =)

 

[Winfield Hill]

Wicked wrote...

I am looking for a chip that can help me to produce a 2nd signal
(sine wave).

My input is going to be 20Khz, 5Vpp sine wave coming out of my
oscillator. I would like to feed this signal (Freq. F1) into a "chip"
to produce a 2nd sine wave at Freq. F2. However, this second frequecy
F2 needs to be in phase with my Freq F1 and needs to be a sine
wave.... I am lost as to what Chip I can use to solve this problem.

If you use a VCO (voltage-controlled oscillator) there will be no
sudden output-voltage step or disturbance at the instant when you
change frequency, is that what you mean?

A typical precision VCO is the Maxim MAX038, or for frequencies
below 250kHz, you can consider the older (and unrelated) Intersil
ICL8038, available in stock at Newark.

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Gareth]

Yes, the 2nd freq. needs to be a multiple of the first one. I went on
the Analog devices webpage looking for a chip i can use but I cant
seem to find one. Does anyone know which chips would work? PLEASE
HELP! =)

I was thinking of a PLL. You will also need a loop filter and VCO.
there are several PLL chips on the link below but they are aimed at RF
rather than audio applications so they may not be suitable, but have a look:

http://www.national.com/parametric/0,,1951,00.html

If you want a low multiple of the first frequency it may be easier to
take a harmonic. For example if you put your 20 kHz through an
amplifier which hard limits you should get odd harmonics. You could
then select the one you want with a band pass filter.

I don't know of any single chip that has just takes power and 20 kHz in
and gives out n*20 kHz.


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