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Diffstat (limited to 'dpd/README.md')
| -rw-r--r-- | dpd/README.md | 23 |
1 files changed, 18 insertions, 5 deletions
diff --git a/dpd/README.md b/dpd/README.md index b5a6b81..83a2986 100644 --- a/dpd/README.md +++ b/dpd/README.md @@ -8,7 +8,9 @@ Concept ODR-DabMod makes outgoing TX samples and feedback RX samples available for an external tool. This external tool can request a buffer of samples for analysis, can calculate coefficients for the -polynomial predistorter in ODR-DabMod and load the new coefficients using the remote control. +predistorter in ODR-DabMod and load the new coefficients using the remote control. + +The predistorter in ODR-DabMod supports two modes: polynomial and lookup table. The *dpd/main.py* script is the entry point for the *DPD Calculation Engine* into which these features will be implemented. The tool uses modules from the *dpd/src/* folder: @@ -43,10 +45,21 @@ The coef file contains the polynomial coefficients used in the predistorter. The very similar to the filtertaps file used in the FIR filter. It is a text-based format that can easily be inspected and edited in a text editor. -The first line contains the number of coefficients as an integer. The second and third lines contain -the real, respectively the imaginary parts of the first coefficient. Fourth and fifth lines give the -second coefficient, and so on. The file therefore contains 2xN + 1 lines if it contains N -coefficients. +The first line contains an integer that defines the predistorter to be used: +1 for polynomial, 2 for lookup table. + +For the polynomial, the subsequent line contains the number of coefficients +as an integer. The second and third lines contain the real, respectively the +imaginary parts of the first coefficient. Fourth and fifth lines give the +second coefficient, and so on. The file therefore contains 1 + 1 + 2xN lines if +it contains N coefficients. + +For the lookup table, the subsequent line contains a float scalefactor that is +applied to the samples in order to bring them into the range of 32-bit unsigned +integer. Then, the next pair of lines contains real and imaginary part of the first +lookup-table entry, which is multiplied to samples in first range. Then it's +followed by 31 other pairs. The entries are complex values close to 1 + 0j. +The file therefore contains 1 + 1 + 2xN lines if it contains N coefficients. TODO ---- |