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Can class D/E do SSB?

PostPosted: Thu Jan 26, 2012 11:32 am
by ND9B
Can a class D or E amplifier be modulated to produce SSB output? Looking at a SSB envelope, it seems to me you could produce SSB if the modulating signal followed the outline of one-half of the SSB envelope. The other half of the envelope would be reconstituted by the output tuned circuit just like regular AM and class C. (There must be a flaw in my reasoning, or transmitters would already be doing this!)

ND9B

Re: Can class D/E do SSB?

PostPosted: Sat Jan 28, 2012 5:59 pm
by Gilly
Hi Bobby

No it cann't....just carrier based like AM / CW etc.....

The whole idea of this mode of operation is to tranverse through the linear region as quickly as possibe to turn the fets fully on and then fully off....etc:
The result is high efficiency.....
The term amplifier probably is best not to be used for this mode.......just transmitter....the amount of output power developed is how the output circuitry is setup etc:

Wayne

Re: Can class D/E do SSB?

PostPosted: Wed Feb 01, 2012 11:49 am
by steve_qix
You're almost there! This system is known as Envelope Elimination and Restoration (EER).

In its essentials, EER systems work by demodulating the envelope and capturing (essentially) the audio, and at the same time sending the signal through a hard limiter to capture the phase information.

Image

The hard part is keeping the phase constant in both the modulator and the RF amplifier under all conditions. There are also other techniques including pre-distortion of the demodulated envelope to compensate for anomalies which happen in the modulation and combination process. The level of amplitude modulation as compared to the phase information is critical. There are lots of articles about this available on the Internet.

I have personally never seen one of these, but I know they are out there!

Re: Can class D/E do SSB?

PostPosted: Thu Feb 02, 2012 4:47 am
by Gilly
This might be of interest ..... although I will stick to the usual methods of amplifying SSB I feel...

http://sigma.ucsd.edu/research/articles/2005/2005_9.pdf


Wayne

Re: Can class D/E do SSB?

PostPosted: Mon Feb 13, 2012 9:21 pm
by kb3ouk
October 2010 QST, page 37, has a Class E linear amplifer that uses EER.
Shelby

Re: Can class D/E do SSB?

PostPosted: Thu Feb 16, 2012 3:07 pm
by W4NEQ
... BUT, just thinking out loud, without working the details ... I think you could make a giant PSK31 transmitter if your encoder had separate amplitude (to PWM) and phase (to RF vfo) outputs. Lets see, 1500 watts peak output at 92% eff ... at super narrow bandwidth, could have amazing coverage on 160.