[Amps] Pre-Distortion Linearizer / the perennial GI-GO problem

[Leigh Turner]

Yes fully agreed Tom; my comment here had presupposed the use of a decent
exciter!

Amongst the poor and mediocre rigs there are some good ones in the
commercial transceiver marketplace.

Leigh
VK5KLT 

-----Original Message-----
From: Tom Thompson [mailto:tlthompson at qwest.net] 
Sent: Saturday, 4 May 2013 12:42 PM
To: Leigh Turner
Cc: amps at contesting.com
Subject: Re: [Amps] Pre-Distortion Linearizer

As long as the transceiver manufacturers give us transceivers with poor 
IMD, it does little good to get the IMD on the amplifier good, unless 
you home brew your own transceiver.

Tom   W0IVJ


On 5/3/2013 8:39 PM, Leigh Turner wrote:
> That's right Bob, complex indeed. Such linearization and intermodulation
> distortion correction techniques are not the panacea they might first
seem;
> their practical implementation in ham-radio gear is not trivial and the
> costs generally outweigh the meagre gains and benefit. As Paul points out
> the other impediment for commercial equipment manufacturers is the complex
> IP and licensing minefield.
>
> For the average ham it's far easier to run an amplifier conservatively to
> steer well clear of the amplifier's compression transfer curve where the
> gain and Po depart from a linear relationship with input power, i.e.
> practice power and drive back-off to attain maximum linearity.
>
> The majority of common ham-radio amplifier tubes respond nicely to this
> simple approach and yield sufficiently adequate IMD characteristics when
> deployed in a well designed amp.
>
> Compensation techniques to linearize an imperfect amp abound, but are not
> simple to implement in a 1500 Watt PEP Tx system.
>
> Leigh
> VK5KLT
>
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Robert
Carroll
> Sent: Saturday, 4 May 2013 11:37 AM
> To: amps at contesting.com
> Subject: Re: [Amps] Pre-Distortion Linearizer
>
> 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 at contesting.com] On Behalf Of Paul
> Christensen
> Sent: Friday, May 03, 2013 8:35 PM
> To: amps at 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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