A single-point band is a frequency band that consists of a single point. Single-point bands are useful when designing notch and peak filters.

You can specify single-point bands with the DFD Remez Design VI by entering only one point in the band specs input to describe the frequency response.

For example, suppose you want to design a double-notch filter with notch frequencies at 0.15 Hz and 0.35 Hz. The five bands in this example have the frequency ranges of [0, 0.12], [0.15], [0.18, 0.32], [0.35], and [0.38, 0.5]. All passbands, single-point bands, and stopbands are equally weighted. The following figure shows the magnitude response of the designed 30th order filter:

You might find other uses for single-point band specifications. For example, by adding a single-point band in a transition band, you can force the frequency response to pass close to a particular point. Alternatively, when you encounter transition band anomalies designing a multiband filter, you might be able to remove the anomalies by adding single-point bands within those transition bands.