# circular Convolution

Multiplications of time domain vectors of two signals is equivalent to convolutions in frequency domain and also use circular convolutions for when FIR filter design using window method in frequency. if working Discrete Fractional Fourier transform (DFRFT) i.e. on bins between time and frequency domain then which is proper operation (multiplication, convolution or any other operational treatment) gives same effect for FIR filter design using window when DFRFT of window function and FFT of Ideal filter is taken? Please explain with example if possible.

• what do you mean?? do you mean using the FFT (or DFT) and then multiplying by $e^{-j 2 \pi k \tau /N}$ will delay by $\tau$ samples (and $\tau$ can be fractional)? circular convolution is what the DFT does. fractional-delay filters can be done in the time domain with linear convolution. – robert bristow-johnson May 11 '14 at 4:13