Hmmm. I haven't studied 'em, but is this an image canceling mixer? I
recently ran across an article about them (don't even remember where), but
didn't look closely enough to understand it. Probably the same as the
phasing method of SSB generation. Now, where the heck was that???...

--
Steve N, K,9;d, c. i My email has no u's.


"hello" wrote in message
...

I have a question about the design of 2nd mixer in the IC-7800.
From : http://www.icom.co.jp/world/products...7800/index.htm
man could see that Icom use an oscillator with outputs in quadrature and
then sum the mixer outputs after a 90° phase shifter.

What I don't understand , is why do they do the 90° phase shift in the
analog domain ?
Using 2 mixers with a quadrature oscillator is very common in the DSP
world (IQ demodulation). But in general , it's followed by 2 A/D
converters and if phase shift is needed to reject a side band, it's done
digitaly...
I don't think that Icom choose this design just to save an A/D in the
IC-7800 ....

any clues ?

Thierry
F4DWV