| 摘要 |
A digital input signal is input to a real part calculator and an imaginary part calculator. The real part calculator comprises an M-stage shift register formed of an M number of series-connected D-type latch circuits and for delaying the input signal in a stepwise manner where M represents 2 or more positive integers. The imaginary part calculator comprises an N number of series-connected D-type latch circuits for delaying the input signal in a stepwise manner, coefficient registers for storing coefficients corresponding to the respective latch circuits, multipliers for multiplying the output of the latch circuit and the corresponding coefficient thereof, and an adder for adding together all the outputs of the multipliers. Here, N denotes 2 or more positive integers. If N is an odd number, M=(N+1)/2, and, M=N/2 or (N/2)+1 if N is an even number. The coefficient registers store coefficients for enabling the digital filter to perform a Hilbert transformation. The real and imaginary part signals output from the real and imaginary part calculators are input to a phase calculator. The phase calculator comprises a divider for dividing the imaginary part signal by the real part signal, and a calculator for calculating an arctangent of the result of the division. Alternatively, the real and imaginary part signals may be supplied to an envelope calculator, which calculates the root-mean-square of the real and imaginary part signals.
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