fm modulator

For a FM modulator application, we recommend AC coupling your +- 50 kHz signal to your VTUNE signal. To do this you can connect your +- 50 kHz signal via a capacitor to the 'end' of your loop filter (between C3 and the VTUNE pin).

It is important that your filter loop bandwidth (LBW) is less than the modulation bandwidth. If you're transmitting a 100 kHz signal, you should set the LBW less than or equal to 25 kHz.

Hello rbrennan,

I have a similar question. I would like to use ADF4360-9 as a sound modulator around 6.5 MHz with +/-25 kHz modulation BW. Is this possible? As per the datasheet, the primary output freq is between 65 MHz - 400 MHz. Can I set the output frequency to 65 MHz and the division ratio to 10 and modulate the VTUNE signal as you explained above?

I don't see any reason why this wouldn't work, but you will need to test it yourself.

To get the 65 MHz output, program the VCO output frequency to 65 MHz and DIVOUT = 5. Setting DIVOUT to 5, combined with the divide-by-2 output divider, will result in a 6.5 MHz output.

Also, see this: http://ez.analog.com/message/130663#130663