Henry Kiefer wrote:

So the phase shifter is NOT for flatten the group delay variance (source is
the Tayloe mixer low-pass)?
If I understand your question correctly, that is true. The IQ output
from the Tayloe mixer (or any IQ mixer) is not upper and lower
sideband. To get those you must do further signal processing, which
usually involves shifting the I and Q channels ninety
degress with respect to each other then summing or subtracting the
channels depending on which sideband you want.

Is multiplying I with Q enougth to demodulate FM as in a quadrature
demodulator?
I cannot find a suitable theory page to look for.

I can't either. The IQ signals multiplied do not make an FM quadrature
detector as the phase does not really shift much over the NBFM
bandwidth. There may be a clever way to extract FM more direcly from
the IQ channels without first detecting a sideband, but I don't know
it.

Thank you for given the link to Peregrine. I read the datasheet. How do you
mix it?

Maybe the wrong part? I'm talking about the PE4140 FET ring mixer.
You use two, driven with LOs ninety degress out of phase with respect
to each other.

At the moment I prefer the Tayloe mixer because of it's simplicity.
BTW: They have a nice low-power consumption PLL being compatible to
National.

At TI I found nice tinylogic capable of switching like a 4066 down to 500ps
...
Should be possible to run the mixer at 150MHz with it.

Yeah--digital just keeps getting better. Good luck.


How much dynamic range do I need? I thought about 100dB?
If I recall theory I loss 2dB if limiting the signal to remove AM sensitivy.techniques,

You need good dynamic range up to the limiter. This can be done with
analog circuits as discussed. After the limiter an A/D converter is
not even needed in theory--a fast-running timer hooked to a digital
port could do the trick. I don't remember any loss by removing AM in
the limiter (since all the the information is contained in the
frequency of the signal), but my theory is in the distant past, back
when FM meant 'funny math'.

Regards,
Glenn