CHAPTER 6 Windowing In the preceding chapter, we developed a technique for calculating filter coefficients to generate a desired frequency response. Our desired filter response will generate an infinite number of coefficients, and we have to decide how many coefficients to keep, and throw away or truncate the rest. As the previous plots show, as the number of coefficients grows larger, the transition region from passband to stopband grows smaller, and the stopband rejection or attenuation increases. X C i e Àjoi Frequency response ¼ HðoÞ ¼ i¼À1 to 1 The smaller transition region, or steepness of the transition from passband to stopband, is due to higher frequency components in the frequency response. The higher indexes of "i" in the frequency response correspond to higher frequency complex exponentials. Complex exponentials have a sinusoidal characteristic, so to get a quick response, we must use higher frequency exponentials.