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Add power of 2 check to QAM #123

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Add power of 2 check to QAM #123

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6 changes: 5 additions & 1 deletion commpy/modulation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -245,7 +245,7 @@ def __init__(self, m):
Parameters
----------
m : int
Size of the QAM constellation. Must lead to a square QAM (ie sqrt(m) is an integer).
Size of the QAM constellation. Must be a power of 2 and lead to a square QAM (ie log2(m) and sqrt(m) are integers).

Raises
------
Expand All @@ -256,6 +256,10 @@ def __init__(self, m):
num_symb_pam = sqrt(m)
if num_symb_pam != int(num_symb_pam):
raise ValueError('m must lead to a square QAM.')

num_bits_symbol = log2(m)
if num_bits_symbol != int(num_bits_symbol):
raise ValueError('Constellation length must be a power of 2.')

pam = arange(-num_symb_pam + 1, num_symb_pam, 2)
constellation = tile(hstack((pam, pam[::-1])), int(num_symb_pam) // 2) * 1j + pam.repeat(num_symb_pam)
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