firlp2lp

Transform FIR Type I lowpass to FIR Type 1 lowpass with inverse bandwidth

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Syntax

g = firlp2lp(b)

Description

g = firlp2lp(b) transforms the Type I lowpass FIR filter b with zero-phase response Hr(w) to a Type I lowpass FIR filter g with zero-phase response [1 - Hr(π-w)].

When b is a narrowband filter, g will be a wideband filter and vice versa. The passband and stopband ripples of g will be equal to the stopband and passband ripples of b, respectively.

example

Examples

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Open Live Script

Create a narrowband lowpass filter to use as a prototype. Display its zero-phase response.

b = firgr(36,[0 0.2 0.25 1],[1 1 0 0],[1 5]);

zerophase(b)

Figure contains an axes object. The axes object with title Zero-Phase Response, xlabel Normalized Frequency ( times pi blank rad/sample), ylabel Amplitude contains an object of type line.

Convert the prototype filter to a wideband lowpass filter. Add to the plot the zero-phase response of the new filter.

h = firlp2lp(b);

hold on
zerophase(h)

Figure contains an axes object. The axes object with title Zero-Phase Response, xlabel Normalized Frequency ( times pi blank rad/sample), ylabel Amplitude contains 2 objects of type line.

Convert the previous filter back to a narrowband lowpass filter. Add to the plot the zero-phase response of the new filter.

g = firlp2lp(h);

[gr,w] = zerophase(g);
plot(w/pi,gr,'--')
hold off

Figure contains an axes object. The axes object with title Zero-Phase Response, xlabel Normalized Frequency ( times pi blank rad/sample), ylabel Amplitude contains 3 objects of type line.

Input Arguments

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Type 1 lowpass FIR filter coefficients with zero-phase response Hr(w), specified as a row vector.

Data Types: single | double

Output Arguments

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Transformed Type 1 lowpass FIR filter coefficients with zero-phase response 1-Hr(pi-w), specified as a row vector.

Data Types: single | double

References

[1] Mitra, Sanjit Kumar, and James F. Kaiser, eds. Handbook for Digital Signal Processing. New York: Wiley, 1993.

Version History

Introduced in R2011a

See Also

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