signal (version 0.5)

fir2: FIR filter generation

Description

FIR filter coefficients for a filter with the given order and frequency cutoffs.

Usage

fir2(n, f, m, grid_n = 512, ramp_n = grid_n/20, window = hamming(n + 1))

Arguments

n

order of the filter (1 less than the length of the filter)

f

band edges, strictly increasing vector in the range [0, 1] where 1 is the Nyquist frequency. The first element must be 0 and the last element must be 1. If elements are identical, it indicates a jump in frequency response.

m

magnitude at band edges, a vector of length(f).

grid_n

length of ideal frequency response function defaults to 512, should be a power of 2 bigger than n.

ramp_n

transition width for jumps in filter response defaults to grid_n/20. A wider ramp gives wider transitions but has better stopband characteristics.

window

smoothing window. The returned filter is the same shape as the smoothing window.

Value

• The FIR filter coefficients, an array of length(n+1), of class Ma.

References

Octave Forge http://octave.sf.net

See Also

filter, Ma, fftfilt, fir1

Examples

f = c(0, 0.3, 0.3, 0.6, 0.6, 1)
m = c(0, 0, 1, 1/2, 0, 0)
fh = freqz(fir2(100, f, m))
op = par(mfrow=c(1,2))
plot(f, m, type = "b", ylab = "magnitude", xlab = "Frequency")
lines(fh$f / pi, abs(fh$h), col = "blue")
# plot in dB:
plot(f, 20*log10(m+1e-5), type = "b", ylab = "dB", xlab = "Frequency")
lines(fh$f / pi, 20*log10(abs(fh$h)), col = "blue")
par(op)