Half power bandwidth of a filter

While designing a bandpass filter using inbuilt function fir1,we have to specify the cut off frequencies w=[w1 w2].All elements of Wn must be strictly greater than 0 and strictly smaller than 1, where 1 corresponds to the Nyquist frequency: 0 < Wn < 1.It is written in the documentation of inbuilt function fir1 in MATLAB that "If Wn is a scalar, then fir1 designs a lowpass or highpass filter with cutoff frequency Wn. The cutoff frequency is the frequency at which the normalized gain of the filter is –6 dB".Isn't the cut off frequency corresponds to half power bandwidth or -3dB.How can it be -6dB.

[Mathieu NOE]

hello

yes, the usual definition of the cut off frequency corresponds to half power bandwidth or -3dB

now MathWorks decided that their definition of cut off frequency correspond to half amplitude and not half power , so here comes the - 6dB

you simply have to remember it...