Frequency identifying device

Abstract

A window function calculator applies a Hann window function to Vd (n) to obtain a numeric value Vw (n). For twenty successive numeric values Vw(n) for every twenty numeric values (N=20), each of the Fourier calculators to executes Fourier calculation. Further, the SRSS calculators to calculate square root of sum of squares of SIM and COS components of respective orders of the results of Fourier calculation as numeric values A 2 , A 3 , A 4 , A 5 . A subtractor calculates a numeric value Ci=A 3 −A 5 , while a subtractor calculates a numeric value Si=A 4 −A 2 . A Frequency calculator calculates a numeric value Fi=(m+1+2*ATAN2 (Ci, Si)/π)/(NT), which indicates the frequency identified. An amplitude calculator doubles the square root of the sum of squares of the numeric values Ci and Si, and calculates a numeric value Ai that indicates the amplitude of the frequency identified.

1 . A frequency identifying device, comprising:
 a sampler for sampling an N number of input signals in a constant cycle T;   a window function calculator for multiplying the N number of samples by a window function; and   an identifier for identifying, from data outputted from the window function calculator, a frequency of a single signal between a frequency (m+1)/(NT) and a frequency (m+2)/(NT), with a resolution higher than 1/(NT), based on eight values, including COS components and SIN components of m-order (m being a natural number less than N/2−4), m+1 order, m+2 order, and m+3 order, namely, C(m), C(m+1), C(m+2), C(m+3), S(m), S(m+1), S(m+2), and S(m+3), obtained by applying Fourier conversion to the N number of data items with an NT cycle as a first order.   
     
     
         2 . The frequency identifying device according to  claim 1 , wherein when a function of a square root is denoted as SQRT, the identifier calculates Si=SQRT(C(m+2)̂2+S(m+2)̂2)−SQRT(C(m)̂2+S(m)̂2) and Ci=SQRT(C(m+1)̂2+S(m+1)̂2)−SQRT(C(m+3)̂2+S(m+3)̂2), and identifies a frequency Fi, based on values of a numeric value Ci and a numeric value Si. 
     
     
         3 . The frequency identifying device according to  claim 2 , wherein when an arc tangent function of two variables is denoted as ATAN2, the identifier calculates Fi=(m+1+2*ATAN2(Ci, Si)/π)/(NT) to thereby identify the frequency Fi. 
     
     
         4 . The frequency identifying device according to  claim 1 , further comprising an amplitude identifier for identifying an amplitude of a signal of a frequency Fi, based on a value of 2*SQRT(Cî2+Sî2). 
     
     
         5 . The frequency identifying device according to  claim 1 , wherein the identifier identifies a phase of a signal of a frequency Fi, based on the frequency Fi and a value of ATAN2(C(m+1), S(m+1)) or a value of ATAN2(C(m+2), S(m+2)). 
     
     
         6 . A signal removal device, comprising:
 a sampler for sampling an N number of input signals in a constant cycle T;   a window function calculator for multiplying the N number of samples by a window function;   an identifier for identifying, from data outputted from the window function calculator, a frequency of a single signal between a frequency (m+1)/(NT) and a frequency (m+2)/(NT), with a resolution higher than 1/(NT), based on eight values, including COS components and SIN components of m-order (m being a natural number less than N/2−4), m+1 order, m+2 order, and m+3 order, namely, C(m), C(m+1), C(m+2), C(m+3), S(m), S(m+1), S(m+2), and S(m+3), obtained by applying Fourier conversion to the N number of data items with an NT cycle as a first order, and   a digital notch filter for receiving inputs of the frequency identified by the frequency identifying device and the input signal and removing a component of the frequency identified from the input signal.   
     
     
         7 . The signal removal device according to  claim 6 , wherein when a function of a square root is denoted as SQRT, the identifier calculates Si=SQRT(C(m+2)̂2+S(m+2)̂2)−SQRT(C(m)̂2+S(m)̂2) and Ci=SQRT(C(m+1)̂2+S(m+1)̂2)−SQRT(C(m+3)̂2+S(m+3)̂2), and identifies a frequency Fi, based on values of a numeric value Ci and a numeric value Si. 
     
     
         8 . The signal removal device according to  claim 7 , wherein when an arc tangent function of two variables is denoted as ATAN2, the identifier calculates Fi=(m+1+2*ATAN2(Ci, Si)/π)/(NT) to thereby identify the frequency Fi. 
     
     
         9 . A frequency identifying device, comprising:
 a sampler for sampling an N number of input signals in a constant cycle T;   a window function calculator for multiplying the N number of samples by a window function;   an identifier for identifying, from data outputted from the window function calculator, a frequency of a single signal between a frequency (m+1)/(NT) and a frequency (m+2)/(NT), with a resolution higher than 1/(NT), based on eight values, including COS components and SIN components of m-order (m being a natural number less than N/2−4), m+1 order, m+2 order, and m+3 order, namely, C(m), C(m+1), C(m+2), C(m+3), S(m), S(m+1), S(m+2), and S(m+3), obtained by applying Fourier conversion to the N number of data items with an NT cycle as a first order, and for identifying a phase of a signal of a frequency Fi, based on the frequency Fi and a value of ATAN2(C(m+1), S(m+1)) or a value of ATAN2(C(m+2), S(m+2)), and   a digital signal generator for generating a signal having a frequency, an amplitude, and a phase that are the same as those which are identified by the frequency identifying device, based on the input signal, and   a subtractor for subtracting the signal generated by the digital signal generator from the input signal.