# firlp2hp

Transform FIR lowpass filter to Type I FIR highpass filter

## Syntax

``g = firlp2hp(b)``
``g = firlp2hp(b,'narrow')``
``g = firlp2hp(b,'wide')``

## Description

example

````g = firlp2hp(b)` transforms the lowpass FIR filter `b` with zero-phase response Hr(w) into a Type I highpass FIR filter `g` with zero-phase response Hr(π-w). Filter `b` can be any FIR filter, including a nonlinear-phase filter.The passband and stopband ripples of `g` will be equal to the passband and stopband ripples of `b`, respectively.```
````g = firlp2hp(b,'narrow')` transforms the lowpass FIR filter `b` into a Type I narrowband highpass FIR filter `g` with zero-phase response Hr(π-w). `b` can be any FIR filter, including a nonlinear-phase filter.```
````g = firlp2hp(b,'wide')` transforms the Type I lowpass FIR filter `b` with zero-phase response Hr(w) into a Type I wideband highpass FIR filter `g` with zero-phase response 1 - Hr(w). NoteThe `b` must be a Type I linear-phase filter. For this case, the passband and stopband ripples of `g` will be equal to the stopband and passband ripples of `b`.```

## Examples

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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 3]); zerophase(b)```

Convert the prototype filter to a narrowband highpass filter. Add to the plot the zero-phase response of the new filter.

```h = firlp2hp(b); hold on zerophase(h)```

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

```g = firlp2hp(b,'wide'); zerophase(g) hold off```

## Input Arguments

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Lowpass FIR filter coefficients, specified as a row vector.

Data Types: `single` | `double`

## Output Arguments

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Type I highpass FIR filter coefficients, returned 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