[hpsdr] My doubts about I/Q beam-forming

[Murray Lang]

I would have thought the accuracy required would be orders of magnitude 
greater than for sideband suppression.
We're talking about phase shifts of small fractions of a wave length at 
10s, 100s or 1000s of MHz.

Murray
VK6HL

At 02:46 PM 5/09/2006, John B. Stephensen wrote:
>Fortunately, mixers are linear for amplitude and phase. The accuracy
>required isn't any more than for sideband suppression.
>
>73,
>
>John
>KD6OZH
>
>----- Original Message -----
>From: "Murray Lang" <murray.lang at metoceanengineers.com>
>To: "Robert McGwier" <rwmcgwier at gmail.com>
>Cc: <hpsdr at hpsdr.org>
>Sent: Tuesday, September 05, 2006 03:10 UTC
>Subject: Re: [hpsdr] My doubts about I/Q beam-forming
>
>
> > ***** High Performance Software Defined Radio Discussion List *****
> >
> > Hi Bob
> >
> > My doubts were confined only to the concept of beamforming using the I/Q
> > signal to adjust the phase. I just can't see how a signal from a sound
>card
> > (say) can possibly accurately adjust the phase of an RF carrier to within
>a
> > small fraction of the RF wavelength. I don't doubt that it can adjust it,
> > just not to any useable accuracy.
> >
> > Murray
> > VK6HL
> >
> > At 10:49 AM 5/09/2006, Robert McGwier wrote:
> > >Murray:
> > >
> > >So long as the total bandwidth of the signal or band of interest is small
> > >compared to the carrier,   beam forming by adjustment of the LO's by
> > >analog phase shifters or by simple phase rotations in software all will
> > >work to do beam forming.   If you want you can read all sorts of
> > >literature about "narrow band" phased arrays.  Beam forming by simple I/Q
> > >rotation will indeed work so long as all the LO's, A/D's,  etc.  in the
> > >system of coherent.   They cannot be wandering around or independent of
> > >each other and still have the rotation by multiplication do beam
> > >forming.  So while not completely trivial in hardware,  it is a pretty
> > >simple concept.
> > >
> > >Bob
> > >N4HY
> > >
> > >
> > >
> > >Murray Lang wrote:
> > >>***** High Performance Software Defined Radio Discussion List *****
> > >>
> > >>My doubts about the ability to do RF beam-forming via I/Q have clarified
> > >>somewhat.
> > >>
> > >>Beam-forming would seem feasible given that you can modulate a carrier
> > >>any way you like with I/Q. However, the *resolution* of that modulation
> > >>is limited by the I/Q bandwidth and dynamic range. To accurately and
> > >>steadily control the phase of an RF carrier to within a small fraction
>of
> > >>its wavelength would require an I/Q  bandwidth of the same order as the
>RF.
> > >>
> > >>Would it not?
> > >>
> > >>Murray - VK6HL
> > >>
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