[hpsdr] An high dynamic QSD front-end

[Richard Hosking]

Two questions:
(1) What would be the effect of using a passive network to provide a suitable 
load for the mixer outside the GBW of the opamp? (ala terminating ring diode 
mixers)
(2) What about the source of I/Q clock signals as far as noise goes? In 
particular some of the circuits i have seen use dividers that dont follow 
a "Gray code" sequence - does this contribute extra noise? 

Richard

On Monday 15 January 2007 07:20, Ahti Aintila wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Jim,
>
> Your message came before I had time to close the computer. Just a short
> answer.
>
> OPA1632 still has some gain bandwidth left on 30 MHz. I admit that my
> scope shows a little more than ground potential at the integrator
> input, still obviously marginally better than the passive capacitor
> alone. Wider sampling pulses of 180 degree further improve the
> situation compared to the 90 degree case. Considering also the low
> saturation levels of the AK5394A and differential inputs, not so much
> gain is needed.
>
> 73, Ahti OH2RZ
>
> On 15/01/07, Jim Miller <jim at jtmiller.com> wrote:
> > i'm still left puzzled how any of the active integrators deal with all of
> > the signals outside their gain bandwidth capability.
> >
> > they only present a virtual ground to frequencies at which they have
> > significant excess gain.
> >
> > what am i missing?
> >
> > 73
> >
> > jim ab3cv
>
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