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Re: [Amps] Amplifuzz [TSPA]

To: "John T. M. Lyles" <jtml@lanl.gov>
Subject: Re: [Amps] Amplifuzz [TSPA]
From: Tomm Aldridge <KD7QAE@ARRL.NET>
Date: Fri, 28 Jan 2005 23:46:33 +0000
List-post: <mailto:amps@contesting.com>
It is actually the NPWM group, not teh Phasex group. I stand corrected.

John T. M. Lyles wrote:
I agree with Philip, I could not find it either on Yahoo groups.

Ampliphase, the RCA tradename for outphasing modulation, goes back to the classic paper by French engineer H. Chireix in Proc of the IRE, Vol. 23, p 1370-1392, dated Nov. 1935. Gaudernack reported on his phase opposition system for AM in Proc. IEEE in Aug, 1938. As far as i know, only Marconi and RCA have built successful high power broadcast transmitters with it, and the New Zealand company Blyth attempted to market solid state MW models about 5 years ago, but pulled it back and converted to conventional PWM, class D. There has been a lot more interest in Outphasing modulation with the advent of personal wireless communications with long battery life. D. C. Cox revised the technology when he wrote his paper on LINC, Linear Amplification with Nonlinear Components, in IEEE Trans. Communications, Vol. com-22, p. 1942-1945 in December 1974.

A recent general reference is Fritz Raab's "Efficiency of Outphasing RF power Amplifier Systems", IEEE Trans. Communications Vol. com-33, #10, p. 1094-1099, Oct. 1985. Also, its in his book with the late Herb Krauss of Virginia Tech, Solid State Radio Engineering. (I was in the first classes under Dr. Krauss to use this textbook in college).

Of interest to the microwave designers is the reuse of the wasted power (as both amplifiers are running full carrier, and when outphased, the RF usually goes into a combining system/load). For instance, R. Landgridge, A Power Re-Use Technique for Improved Efficiency of Outphasing Microwave Power Amplifiers, IEEE Trans. MTT, Vol 47, #8, p. 1467-1470, Aug. 1999. Getting two RF amplifiers to be able to operate at high efficiency while driving reactive loads (when they are summed without a hybrid combiner) during modulation has been one of the problems of this technology. Doing this in a frequency agile way is even more challenging. According to Raab, the resulting efficiency has been likened to class B with all practical aspects such as this. Except that the fidelity of an outphaser is better without the iron transformers in the audio. A good summary report describing most of the high efficiency RF power amplifier configurations was in High Frequency Electronics magazine, in a series of articles, Msy 2003. Should be available online for download.

Five years ago I built a great phase shifter that would swing the RF phase of a 1 - 10 MHz signal by many degrees(360) at an audio rate, extremely linear, using the now obsolete Analog Devices AD639 trigonometry chips in a DSB modulator scheme. This was going to be the front end of an outphasing AM rig made with two nonlinear MOSFET amplifiers, but I since gave it up to concentrate on PDM/PWM modulator with class D rf.

I look forward to hearing about what the PhaseX group comes up with.

73
John
K5PRO



Message: 1 Date: Thu, 27 Jan 2005 17:45:42 +0000 From: Philip de Cadenet <phil@transmittersrus.com> Subject: [Amps] Amplifuzz To: amps@contesting.com Message-ID: <$hsh1wRGjS+BFwKO@philstheboss.freeserve.co.uk> Content-Type: text/plain;charset=us-ascii;format=flowed

Skipp,

I searched PhaseX on Yahoo Groups and it came up zilch.

Can you post the group URL?

Tnx
--
Philip de Cadenet G4ZOW
Transmitters 'R' Us

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