Periodically the topic of Adaptive Predistortion comes up for discussion on this community. Our team has been consistent in our position on this subject but sometimes it is useful to restate what has been said many times before in the interest of clarity. Here is a restatement of the facts:
The FLEX-6000 Series hardware has the necessary connections and internal RF port to port isolation to support adaptive predistortion software. We have verified that transmitter output to receiver input isolation (e.g. ANT1 to RXA) is >80 dB on all bands including 6m, which is more than ample to accommodate adaptive predistortion using an external amplifier in the loop.
FlexRadio remains interested in adaptive predistortion technology but we have not in the past nor will we now make a time frame commitment. Our internal engineering resources are 100% allocated to complete our published road map for v1.x releases through v2.0. We believe that the features committed in those releases are currently of higher priority to the vast majority of our customers than is adaptive predistortion.
- We periodically review and rank our software backlog and feature requests. We look at the ranked priorities and compare the development magnitude for each feature to the available engineering resources within a release cycle. Based on those factors, we make decisions on what features make the cut in the release planning process. So far adaptive predistortion has not made the cut. That doesn't mean it won’t make the cut in a future release.
Like Bob says... "We stand behind you ..." In fact, I'm sure others, like myself, stand in front and help try and respond to those who want to interfere with the current roadmap. We ALL want everything (hihi); but, most of us are perfectly happy with the path FRS has chosen. That is not to say some would not have preferred a different sequence (hihi); however, I'm enjoying each and every update. (Bugs included... Heck, I love a challenge.
73's and keep up the great work!
It is just a positive event for a absolutely state of the art transmitter .One that exceeds the present possibilities . And smart companies Like Flex will implement it .
The statement has always been sooner would be better.
So the next time someone asks if you would like that million dollar signal. Try saying NO.
When Flex does have the time to implement Pure signal or whatever they call it It will be the best .
Just remember the fastest and shortest distance between 2 points isn't a straight line ,
What would be nice is if APD could eliminate ALL the high energy harmonics so you could eliminate post PA filters all together.
I wonder if this could be accomplished with a different PA topology (vs push-pull) along with APD. Imagine maybe parallel amps with one side used primarily to negate harmonics, all controlled with APD. Execution gets very complex very quickly...
Going form -16 to -53 on IMD3 is pretty darn impressive though!
slides 20&21 shows the correction algorithm - doesn't look complicated but the transcendentals take time to compute. Converting to FPGA code I won't comment on.
In this blog:
that author states only IMD is corrected so it seems harmonics are not. Also he states:
"badly tuned linear amp stages" can't be corrected. To me that's the crux of the problem in the worse offenders.
If we are looking at the present implementation of "Pre or clear signal " the code is already out there Yes In open source .
The hardware is already in the Flex to accomplish this event .
According to Flex the flex was built with the ability to do this.
So there is a relatively easy to follow Open source programming " call it a guide " that if anyone wanted to do this Anyone!!!! it could be utilized . If just to start things off.
And Now putting the entire package into the FPGA isn't a real smart idea.
I think it would benefit anyone thinking about this , a simple You Tube on a present system using the reduction would explain far more than any techno papers that were written that started this whole thing .
What you would find that there is USER necessities presently to set this up. You would find that there is ,When adapted this way, secondary programming which can reside in the processor that can accomplish this A/B comparison. This gives a relative easy way to continually improve or modify it .
Simple statement . And I can give you the techno analysis .
As it has been named It compares the wave form of a transmitted signal in the band pass (PRE) and compares it with the output of the transmitted signal (Both of equal strength) the difference in this wave form is sees and measures it corrects / shifts to match the template .
This goes for any and all difference it sees (In that band pass) compared to the algorithm it uses as a template.
The result in the real world is (Seen and heard every day) a CLEAN IMD reduced SIGNAL Which can be displayed( using the most harsh of tests the 2 tone test) . The test just about every manufacturer stays away from .
And 200K Well will take time (Programming time) Someone else did it with volunteers .(A true ham spirit)
I am glad we are actually understanding what benefits we would get. And how significant utilization of absolutely any system that reduces IMD is fantastic .
And I am glad some day Flex will Implement it .
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