import unicodedata
import re


def ascii_uppercase_alphanum(s, decoding='utf-8'):
    """Convert a string to alphanumeric ASCII uppercase characters."""
    if type(s) is float:
        return s
    nfkd = unicodedata.normalize('NFKD', s)
    only_ascii = nfkd.encode('ASCII', 'ignore')
    upper = only_ascii.upper()
    decoded = upper.decode(decoding)
    alphanum = ' '.join(m.group(0) for m in re.finditer('[A-Z0-9]+', decoded))
    return alphanum