IZ6MAF
Neuling
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Ich liebe dieses Forum!
 
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TX IQ Auto Correction
« on: 13. May 2020, 16:08:43 »
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Subject: TX IQ Auto Correction.
I ask the sw programmers who developed the RX Auto IQ Correction: is it possible to develop an TX IQ automatic correction sw routine as indicated in the attached document using the FWD signal as "envelop detector"?
'73 IZ6MAF Paolo
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SP3OSJ
Guest
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Re:TX IQ Auto Correction
« Reply #2 on: 13. May 2020, 18:32:10 »
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Hi Paolo
This is not possible in mcF.
However, OVI40 Andreas predicted this possibility and used two WM8731. Now you only need to do separate RX and TX tracks in the OVI40 RF PCB.
Is there any other problem?
73
Artur
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IZ6MAF
Neuling
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Posts: 23
Ich liebe dieses Forum!
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Re:TX IQ Auto Correction
« Reply #3 on: 13. May 2020, 20:13:59 »
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Sorry if I insist, but I invite you to read the text carefully, the method is based exclusively on a measurement of the DC offset at the output of the RF envelope detector (as the fwd detector) in different operating conditions, and the application of a iteration process. You don't need a second wm8731, maybe at most an RF probe if the FWD reading is not good.
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SP9BSL
positron
alter Hase
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Re:TX IQ Auto Correction
« Reply #5 on: 14. May 2020, 07:38:32 »
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Hi Paolo,
the theory is interesting but we need to - as Andreas wrote earlier - highly modify the tx path. You can see in the paper that there is switch between the mixer and PA I think they did it for some reasons:
1. The PA itself introduces some distortions (IMD) which might have negative impact on the algorithm.
2. The process of the tuning may produce some more artifacts on the output while tuning with unpredictable result for the PA.
Please see the mixer output amplitude requirement to meet the high S/N range because of high full scale STMs ADC input voltage - we need another amplifier there.
There are some assumptions in the paper like gain of the whole path and this would be also tricky.
This modification involves another input of the STM ADC or switching the FWD one.
The final word: we are going into direct digital conversion technique with UHSDR and most of us abandoned the analog mixing concept leaving it as is.
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| « Last Edit: 14. May 2020, 07:54:32 by SP9BSL » |
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73 Slawek
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Author
Tx_IQ_Auto_Correction.pdf
