| 摘要 |
<p>PURPOSE:To eliminate the need for a digital multiplier and perform discrete Fourier transform on real-time basis only by addition and subtraction by obtaining a discrete Fourier transform component in the form of the amplitude and phase angle of a sine wave outputted from a digital comb line filter. CONSTITUTION:An input signal is converted by an A/D converter 1 into a digital signal, which is written in an input memory 2 or 3. An adder/subtracter 4 performs convolutional arithmetic between the input signal and a rectangular wave. Higher harmonics of degree 3, 5, 7, etc., in the obtained convoluted waveform are removed by the comb line filter 8. The sine wave outputted by the comb line filter 8 is inputted to a peak value detecting circuit 9 and a zero-cross point detecting circuit 10 for one period to obtain its amplitude and phase angle. Those are equal to the Xk and arg(Xk) of the (k)th DET component Xk.</p> |
