TABLE OF CONTENTS A window with a flatter passband which reduces the size of the amplitude dips between bins minimizes the amplitude error. A spectral line that falls halfway between the centers of two bins will be attenuated by a much smaller amount. The flattop window has such a characteristic and is shown in Figure 4-19b. Since the response of each bin overlaps considerably more than with the Hanning window, the disadvantage of the flattop window is reduced frequency resolution. The spectral line will appear wider on the spectrum analyzer display, limiting the ability to resolve two closely spaced spectral lines.
The flattop window is considered a high-amplitude accuracy window, having a maximum amplitude error of 0.1 dB (1%). Figure 4-20b shows the spectrum of a sine wave as measured using the flattop window.
