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Dividing a 40MHz FM-signal

Question asked by Thomas on Mar 21, 2011
Latest reply on Apr 20, 2011 by leoxu

Dear All,


I'm new to DDS and not an electronic application engineer, too, so be patient with me .

My background is physics and measurement science.


In our laboratory we have to cope with 40 MHz carrier frequency sinusoidal fm-signals from Laser-Interferometry.

The signals have a modulation bandwidth of up to 20 MHz!  i.E 30 MHz to 50 MHz actual freuqency.

The frequency of modulation is up to 50 kHz (sometimes even more).

For short measurements, we sample these directly at 200MS/s and do a digital demodulation.

For longer measurements, the amount of data quickly becomes prohibitive.


Now, the idea is to use a DDS like the AD9834 and use it as a frequency divider:

Let's say set the phase angle increment to 2*pi/40 and use our 40 MHz fm signal (may be after

conditioning) as clock input to the DDS.

In theory this should divide the carrier frequency (to 1MHz) as well as the modulation bandwidth.

Thus we would have to sample a signal in the range of 0.75 MHz to 1.25 MHz.


Is that feasible with a DDS device?


Thanks in advance for the support,