Patent ID: 6229386
Filing Date: 2001-05-08
Classification: G06F,H03D

Abstract:
A digital FM demodulation circuit sampling an input analog FM signal and digitally detecting the sampled input signal, said circuit comprising:an arctangent circuit into which a second signal that is delayed from the sampled input signal for a constant time and a third signal that is different in phase at 90 degrees from the second signal are inputted, and which outputs a corresponding arctangent value based on a result of a division of the two input signals, andsaid arctangent circuit including:roundoff means for sequentially rounding the division result to one of a plurality of typical values;ROM address unit for selecting an arctangent value corresponding to the rounded typical value from a ROM table containing typical arctangent values, and outputting the selected arctangent value;polarity detection means for detecting whether the division result is a negative value; anda polarity correction unit which changes a polarity of the outputted arctangent value, andwherein if said polarity detection unit judges that the division result is a negative value, said polarity correction unit changes the polarity of the output arctangent value to negative.