# In digital modulation, how did they get the magnitudes 0.22 and 0.821? Any explanation about how is it derived?

### 1 Answer

- Markus ImhofLv 78 months ago
A little more context would be extremely helpful.

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Still at a loss here - the symbols in QAM usually represent multiple bits, so there isn't a single numerical value (for whatever) that corresponds to a single bit, but rather a combination of numerical values for the i and q amplitudes that correspond to a set of bits (usually 2 to 8 bits per symbol). The values you are quoting _might_ be the amplitude values in a (specific) square 16-QAM, i.e. all possible combinations of these values (including negative sign) will give 16 points in i/q-space, denoting the 16 QAM symbols which can correspond to the binary symbols 0000...1111.

Although, if this is the case, I find the choice of amplitudes strange, as these will give a far lower distance between the points of the inner square.