... | ... | @@ -21,7 +21,7 @@ If we now equate $`IF_A=IF_B`$ and insert the DDS frequencies $`f_{DDS1}(FTW_1)` |
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{f_{OCXO}\over{f_R}} - 1 = { {2^{48} \cdot 2^2}\over{ 10 (FTW_1 + { {FTW_2}\over{ 2^{10}}}) }}-1
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```
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DDS1 can be used for coarse frequency adjustments. Around a fractional frequency of zero, changing FTW1 by 2 steps changes the output frequency by 1.8e-14 as follows:
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DDS1 can be used for coarse frequency adjustments. Around a fractional frequency of zero, changing FTW1 by 2 steps (AD9912 is a 47-bit DDS!) changes the output frequency by 1.8e-14 as follows:
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```
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uStep output fractional frequency y
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... | ... | @@ -39,4 +39,23 @@ FTW1 dFTW1 y |
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112480039521493 8 -7.1e-14
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112480039521495 10 -8.88e-14
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y change due to 2 steps in FTW1: -1.8e-14
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``` |
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\ No newline at end of file |
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```
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DDS2 is used for fine frequency adjustments. Around a fractional frequency of zero, changing FTW2 by 2 steps changes the output frequency by 1.7e-17 as follows:
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```
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uStep output fractional frequency y
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FTW1 = 112480039521485 (constant)
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FTW2 dFTW2 y
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112589990684047 -10 9.19e-17
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112589990684049 -8 7.46e-17
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112589990684051 -6 5.72e-17
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112589990684053 -4 3.99e-17
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112589990684055 -2 2.26e-17
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112589990684057 0 5.2e-18
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112589990684059 2 -1.21e-17
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112589990684061 4 -2.95e-17
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112589990684063 6 -4.68e-17
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112589990684065 8 -6.42e-17
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112589990684067 10 -8.15e-17
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y change due to 2 steps in FTW2: -1.7e-17
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``` |