Patent ID: 7433907

Claim:
A signal analyzing method of a complex exponential modulation filter bank, which makes K times sampling of an input signal with sampling frequency fs by K times (K is a divisor of number of bands M and a positive integer greater than or equal to 1), and divides it into M complex band signals with equal bandwidth and sampling frequency fsK/M to be outputted, comprising: assuming that a filter coefficient of a linear phase non-recursive type prototype filter is set to h(n) (N is a filter order, 0≦n≦N), and values of first and last filter coefficients are set to zero, and an input signal at sampling time n is set to x(n), a step of calculating a first intermediate signal w 1 (n) from the input signal by (formula 1), where m is an integer; w ⁢ ⁢ 1 ⁢ ( n ) = ∑ i = 0 N / ( 2 ⁢ M ) - 1 ⁢ ⁢ ( - 1 ) i ⁢ x ⁡ ( mM / K - 2 ⁢ Mi / K - n ) ⁢ ⁢ ⁢ h ⁡ ( 2 ⁢ Mi + Kn ) ⁢ ⁢ ⁢ ( 0 ≦ n ≦ 2 ⁢ M / K - 1 ) ( formula ⁢ ⁢ 1 ) a step of calculating a second intermediate signal w 2 (n) from the first intermediate signal by (formula 2) (j is an imaginary unit); w 2( n )=( w 1( n )− jw 1( n+M/K )) K exp(− jπnK /(2 M ))(0≦ n≦M/K− 1) (formula 2) a step of calculating a third intermediate signal W 3 (k) from the second intermediate signal by (formula 3) with fast Fourier transform; and W ⁢ ⁢ 3 ⁢ ( k ) = ∑ n = 0 M / K - 1 ⁢ ⁢ w ⁢ ⁢ 2 ⁢ ( n ) ⁢ exp ⁡ ( - j2 ⁢ ⁢ π ⁢ ⁢ knK / M ) ⁢ ⁢ ( 0 ≦ k ≦ M / K - 1 ) ( formula ⁢ ⁢ 3 ) a step of calculating a complex band output signal X(k, mM/K) at sampling time mM/K in k-th band (0≦k≦M/K−1) from the third intermediate signal by (formula 4) (* is a conjugate complex number, and A is a phase for signal analysis) when k is an even number (k=2l), and by (formula 5) when k is an odd number (k=2l+1) X (2 l,mM/K )= W 3*( l )exp( j π(4 l +1) A /(4 M )) (0≦ l≦M/ (2 K )−1) (formula 4) X (2 l+ 1, mM/K )= W 3( M/K −1− l )exp( jπ (4 l +3) A /(4 M )) (0≦ l≦M /(2 K )−1) (formula 5).