fdesign.peak

Peak filter specification

Syntax

```d = fdesign.peak(specstring, value1, value2, ...) d = fdesign.peak(n,f0,q) d = fdesign.peak(...,Fs) d = fdesign.peak(...,MAGUNITS) ```

Description

```d = fdesign.peak(specstring, value1, value2, ...)``` constructs a peaking filter specification object `d`, with specification set to `specstring` and values provided for all members of the `specstring`. The possible specification options, which are not case sensitive, are listed as follows:

• 'N,F0,Q' (default)

• 'N,F0,Q,Ap'

• 'N,F0,Q,Ast'

• 'N,F0,Q,Ap,Ast'

• 'N,F0,BW'

• 'N,F0,BW,Ap'

• 'N,F0,BW,Ast'

• 'N,F0,BW,Ap,Ast'

where the variables are defined as follows:

• N - Filter Order (must be even)

• F0 - Center Frequency

• Q - Quality Factor

• BW - 3-dB Bandwidth

• Ap - Passband Ripple (decibels)

• Ast - Stopband Attenuation (decibels)

Different specification options, resulting in different specification objects, may have different design methods available. Use the function `designmethods` to get a list of design methods available for a given specification. For example:

```>> d = fdesign.peak('N,F0,Q,Ap',6,0.5,10,1); >> designmethods(d) Design Methods for class fdesign.peak (N,F0,Q,Ap): cheby1```

`d = fdesign.peak(n,f0,q) ` constructs a peaking filter specification object using the default ```specstring ('N,F0,Q')``` and setting the corresponding values to `n`, `f0`, and `q`.

By default, all frequency specifications are assumed to be in normalized frequency units. All magnitude specifications are assumed to be in decibels.

`d = fdesign.peak(...,Fs)` constructs a peak filter specification object while providing the sampling frequency of the signal to be filtered. `Fs` must be specified as a scalar trailing the other values provided. If you specify an `Fs`, it is assumed to be in Hz, as all the other frequency values provided.

`d = fdesign.peak(...,MAGUNITS)` constructs a notch filter specification while providing the units for any magnitude specification given. `MAGUNITS` can be one of the following: `'linear'`, `'dB'`, or `'squared'`. If this argument is omitted, `'dB'` is assumed. The magnitude specifications are always converted and stored in decibels regardless of how they were specified. If `Fs` is provided, `MAGUNITS` must follow `Fs` in the input argument list.

Examples

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Design a Chebyshev Type II peaking filter with a stopband attenuation of 80 dB.

```d = fdesign.peak('N,F0,BW,Ast',8,.65,.02,80); Hd = design(d,'cheby2',SystemObject=true);```

View the frequency response of the filter.

`filterAnalyzer(Hd)`

Version History

Introduced in R2011a