As a former Bell Labs design supervisor in the cellular wideband linear
amplifier design area, I can say that predistortion schemes as well as
feedforward linearization were being studied intensely and resulted in many
patents at BTL and elsewhere. It was a very complex problem both
practically and theoretically. The simpler means of incorporating
predistortion quickly became inadequate to meet FCC requirements as mobile
telephony moved away from its FM roots.
Bob W2WG
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Paul
Christensen
Sent: Friday, May 03, 2013 8:35 PM
To: amps@contesting.com
Subject: Re: [Amps] Pre-Distortion Linearizer
> Check out US Patent 4588958 by Allen Katz K2UYH. It's a common way to
> linearize solid state PAs for the cellular market back in the day.
Great info, Jeff. Looks like K2UYH has multiple, related linearization
patents. Also, thanks for passing on the references.
In looking at his patent citations, work really accelerated around the time
of the cellular industry explosion. I imagine AT&T/Bell Labs was faced
with similar spectral efficiency issues with its Long Lines carrier
microwave systems, but they had more usable licensed spectrum way up at 6 &
11 GHz where fixed, point-to-point communication is possible at those
wavelengths -- but not roving communications.
Often when the subject of pre-distortion comes up, the usual questions is
"why doesn't manufacturer X have this technology?" Peering through the
patent data is one reason why. It's easy for us to want the technology --
not so easy for the manufacturers to wade through the intellectual property
landmines or secure licensing agreements.
Paul, W9AC
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