butterworth_filter_order Function

public pure function butterworth_filter_order(fp, fs, fstop, apass, astop, ftype) result(n)

Computes the minimum order of a Butterworth low-pass or high-pass filter.

Frequencies are specified in Hz and attenuation values are specified in dB. The frequency prewarping matches design_iir_filter. An order of zero indicates an invalid specification.

Arguments

Type	Intent	Optional	Attributes		Name
real(kind=real64),	intent(in)			::	fp	The passband edge frequency, in Hz.
real(kind=real64),	intent(in)			::	fs	The sampling frequency, in Hz.
real(kind=real64),	intent(in)			::	fstop	The stopband edge frequency, in Hz.
real(kind=real64),	intent(in)			::	apass	The maximum passband attenuation, in dB.
real(kind=real64),	intent(in)			::	astop	The minimum stopband attenuation, in dB.
integer(kind=int32),	intent(in),	optional		::	ftype	LOW_PASS_FILTER (default) or HIGH_PASS_FILTER.

Return Value integer(kind=int32)

The minimum filter order.