![]() Note: This is the general version of the overlap save method using inbuilt ifft,fft functions. ![]() This segmentation of the input data and the fitting of the output data blocks together form the output sequence. The resulting data sequence from the IDFT are given where the first M-1 points are discarded due to aliasing and the remaining L points constitute the desired result from the linear convolution. To begin the processing, the first M-1 point of the first record is set to zero. ![]() To avoid loss of data due to aliasing, the last M-1 points of each data record are saved and these points become the first M-1 data points of the subsequent record. The last L points of Ym(n) are exactly the same as the result from linear convolution. Since the data record is of length N, the first M-1 points of Ym(n)are corrupted by aliasing and must be discarded. The multiplication of the N-point DFTs for the mth block of data yields: Ym(k)=h(k)Xm(k). The circular convolution of each block is computed by multiplying the DFTs of the block and the filter coefficients, and computing the inverse DFT of the product. The input is divided into overlapping blocks which are circularly convolved with the FIR filter coefficients. The impulse response of the FIR filter is increased in length by appending L-1 zeros and an N-point DFT of the sequence is computed once and stored. The overlap-save algorithm 2 also filters the input signal in the frequency domain. Each Data Block consists of the last M-1 data points of the previous block followed by L new data points to form a data sequence of length N=L+M-1.An N point DFT is computed for each data block. In this method, the size of the input data blocks is N=L+M-1 and the DFTs and the IDFTs are of length L.
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