Calculating FIR filter coefficients with the windowing method and Convolution algorithm Please advice how to calculate FIR filter coefficients with the windowing method using the Rectangular Window function and convolution method? What utility or FIR design application can perform this task?
draw your desired frequency response.  uniformly sample that frequency response $\frac{N}{2}$ times from DC up to just below Nyquist.  reflect those $\frac{N}{2}-1$ samples (not the DC values) as complex conjugate in the upper half of the frequency response above Nyquist.  do the inverse FFT.  if it's rectangular window, you're done.