The requirements on window length for resolving closely tuned sinusoids was discussed in §5.5.2. This section considers this issue for the Kaiser window. Table 3.1 lists the parameter required for a Kaiser window to resolve equal-amplitude sinusoids with a frequency spacing of rad/sample [1, Table 8-9]. Recall from §3.9 that can be interpreted as half of the time-bandwidth of the window (in cycles).
Kaiser and DPSS Windows Compared
Kaiser Windows and Transforms