[Amps] Amplifuzz [TSPA]

[John T. M. Lyles]

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 at transmittersrus.com>
>Subject: [Amps] Amplifuzz
>To: amps at contesting.com
>Message-ID: <$hsh1wRGjS+BFwKO at 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