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

[John B. Stephensen]

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
> >>
> >>_______________________________________________
> >>HPSDR Discussion List
> >>To post msg: hpsdr at hpsdr.org
> >>Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> >>HPSDR web page: http://hpsdr.org
> >>Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/
> >>
> >>
>
>
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at hpsdr.org
> Subscription help: http://lists.hpsdr.org/listinfo.cgi/hpsdr-hpsdr.org
> HPSDR web page: http://hpsdr.org
> Archives: http://lists.hpsdr.org/pipermail/hpsdr-hpsdr.org/


 1157438769.0