Would anyone happen to know how a chip like this one:
http://cds.linear.com/docs/Datasheet/5598f.pdf ...manages to generate an
internal 90 degree phase shift from an LO input over the very wide range of
5MHz-1600MHz? The data sheet says it uses a "poly-phase phase shifter." I'm
guessing... some adjustable analog phase shifters (that can provide up to 90
degrees of phase shift at 5MHz) that are controlled by a feedback loop that's
looking to null the product of the LO and the (ostensibly 90 degree shifted)
LO?

Seems like this is a bit easier to work with than chips that require 2x or 4x
inputs to generate their 90 degree LO shifts!

Anyone have a favorite IQ modulator that'll work on 2m (and perhaps 70cm too)?
The data sheet's detail of "industry standard pin-out" would suggest that
there are others...

Thanks,
---Joel