Signal processing apparatus and method
摘要
說明書
Note that S*(k) is a complex conjugate component of S(k).
Here, computation of the frequency shift requires the computations described above with reference to Eq. (1) and Eq. (2), resulting in a very long time required for the computation. However, use of the FFT and the IFFT allows the computation of the frequency shift to be substituted with readout position shifting for an array. Therefore, the computation of Eq. (3) is fast. In addition, S(k) is a signal that has passed through a band-pass filter. Therefore, the multiplication (R(k-ζ) and S*(k)) in Eq. (3) produces a zero result for frequencies outside of a predetermined limited frequency range. Therefore, the computation of Eq. (3) can be performed at a high speed.
As described above, the use of the fast Fourier transform (FFT) and the inverse fast Fourier transform (IFFT) enables the decoding processing unit 222 to perform the correlation computation at a higher speed.
The infinitesimal shift ζ in frequency can vary depending on the frame start position. Thus, at step S276, the decoding processing unit 222 calculates a cross-correlation value α(t) at time t by summing up the absolute value of c(t, ζ) while successively shifting the value of the infinitesimal shift ζ as expressed by Eq. (4) below. α(t)=Σζ=?γ+γ|c(t,ζ)|2??[Math. 4]
