How do on-chip 90 degree phase shifters work?
 

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

How do on-chip 90 degree phase shifters work?
 

On Wed, 01 Jul 2009 14:25:07 -0700, Joel Koltner wrote:

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...

When you find out, let us know...


--
http://www.wescottdesign.com

How do on-chip 90 degree phase shifters work?
 

On Jul 1, 2:25*pm, "Joel Koltner" wrote:
....

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...
....

1GG7-4225?? :-)

Of course, there are others from places like Analog Devices, Hittite,
Maxim etc.

I'm not sure how they work, but suppose that something similar to
what's used for an audio phase shift network for use generating SSB
could be used. At RF frequencies, the capacitors would not be large,
and clearly it's not terribly difficult to integrate well-matched
capacitors (e.g. in ADC converters). Perhaps I can probe some of my
contacts to find out more...

Cheers,
Tom

How do on-chip 90 degree phase shifters work?
 

"K7ITM" wrote in message
...
"I'm not sure how they work, but suppose that something similar to
what's used for an audio phase shift network for use generating SSB
could be used."

I suspect it's actually something a bit simpler in that the LO is supposed to
be one frequency (perhaps with harmonics) and not something that moves around
quickly (hence the idea that you can just use a feedback loop and track it),
whereas with audio you're dealing with a whole bunch of frequencies at once
(in a sense) and have to phase-shift them all 90 degree simultaneously.

I was planning on designing (or at least implmenting -- all the real design
was by those filter guys decades back) an audio phase shift network, but since
you need an IQ (-like) modulator anyway, and since I already needed a
microcontroller for this design, I'm thinking these days it's just as easy to
perform a Hilbert transform inside the microcontroller and spit out the audio
and it's phase-shifted version on two DAC pins and call it good.

---Joel

How do on-chip 90 degree phase shifters work?
 

Joel,

You might find some answers in these papers:

http://www.eecg.toronto.edu/~kphang/...ng_IQphase.pdf

http://www.ee.ucla.edu/~razavi/paper.../RCICC97_1.pdf

Roger

How do on-chip 90 degree phase shifters work?
 

Thanks Roger, Dong's paper there was quite useful.