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

[John B. Stephensen]

Inserting phase shifts in the RF, LO or IF all work for beamforming. All of
these methods are approximating the difference in arrival time at each
antenna for a plane wave with a phase shift that is eventually translated to
RF.

73,

John
KD6OZH

----- Original Message ----- 
From: "Murray Lang" <murray.lang at metoceanengineers.com>
To: <hpsdr at lists.hpsdr.org>
Sent: Tuesday, September 05, 2006 01:12 UTC
Subject: Re: [hpsdr] My doubts about I/Q beam-forming


> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Ken,
>
> No I don't, but I'll try to look it up. I've seen an article on (RX)
> beamforming with "SDR" where they directly sample the RF using a separate
> A/D for each line and synchronise the LO clocks. I believe a similar
result
> can be achieved by synchronising clocks on multiple QSDs/QSEs. But here
the
> phase adjustment is through RF PLLs.
>
> My posting was actually a continuation of an earlier discussion where it
> was proposed that beamforming could be manipulated via I/Q. I wasn't
> comfortable with it at the time, but couldn't explain why beyond a vague
> worry about I/Q frequency response.
>
> Murray - VK6HL
>
> At 08:36 AM 5/09/2006, Ken - N9VV wrote:
> >Hi Murray, I am probably way off base here, but there was an article in
> >QEX this past month about what looks like what might be beamforming for
> >microwave freqs using phased arrays and SDR/DSP. Do you have access to a
> >copy of QEX?
> >de ken n9vv
> >
> >
> >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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