# DDS Signal generation

Discussion in 'Electronic Design' started by [email protected], Feb 16, 2007.

1. ### Guest

Hello,
I would like to design a signal generator.
the signal as the following form : cos(cos w1).sin(w2)
with w1~ 10Mhz and w2~50kHz
amplitude and frequency of the signal have to be digitally controlled.
What do you think about such a solution?

Thank you.
y.

2. ### Rich GriseGuest

Depends on what the teacher wants.

Good Luck!
Rich

3. ### John LarkinGuest

Easy in an FPGA. Two phase accumulators, two sine lookup tables, one
multiplier, all feeding a dac. I did a similar thing recently, 8
channels, 32 MHz Nyquist, but the multiply was just used as a slow
gain scaler.

John

4. ### Guest

Actually, this is not a student project!
I'm not familiar with using discussion groups, and perhaps is my
problem not very well explained!

Thank you for yout suggestion.
Yes, I was thinking about a FPGA, but I'm not familiar with this
technology, since I usually work with uC's. I think I'll study this
option a bit further!
In fact, DDS seems not to be really done for a "real-time" modulation
as I wouls like to design.

5. ### Tom BruhnsGuest

You should look at the Analog Devices web site. They make several DDS
chips, and some of them integrate most (or perhaps all) of what you
want into one part. I assume that the function you originally posted
is not quite correct, and that you want to amplitude modulate one
sinusoid (high frequency) by another (much lower frequency). Or did
you really mean the cosine of a cosine wave, times a sine wave?

DDS is most certainly done for real-time modulation. It's done for
arbitrary modulating waveforms as well as for sinusoids or other
repetitive waveforms.

Cheers,
Tom