A new digital FM demodulator for VCRs

This paper presents a new digital FM demodulator using a discriminator with a cosine-shaped S curve. In the present arc-tangent type demodulator, three functional operations are required to calculate the instantaneous frequency. Since the gate count for such functional operations is large, it is necessary for this to be reduced in order to promote system on a chip. Therefore, a cosine type demodulator using one divider is proposed. As a result, the gate count of the functional operations becomes 1.5k gates, equivalent to 1/10 of the present gate count. An experimental VCR using the proposed demodulator implemented on the device is developed to evaluate and confirm the validity of the cosine type demodulator.