# resonantFrequency

Calculate and plot resonant frequency of antenna

Since R2024a

## Syntax

``resonantFrequency(object,frequency)``
``resonantFrequency(object,frequency,Method="Sparameters")``
``resonantFrequency(object,frequency,Method="Impedance",Name=Value)``
``resonantFrequency(object,frequency,Method="Sparameters",Name=Value)``
``fRES = resonantFrequency(object,frequency)``
``fRES = resonantFrequency(object,frequency,Name=Value)``
``[fRES,zRES,Z,typRES] = resonantFrequency(object,frequency)``
``[fRES,zRES,Z,typRES] = resonantFrequency(object,frequency,Method="Impedance",Name=Value)``
``[fRES,sRES,S] = resonantFrequency(object,frequency,Method="Sparameters")``
``[fRES,sRES,S] = resonantFrequency(object,frequency,Method="Sparameters",Name=Value)``

## Description

````resonantFrequency(object,frequency)` marks the resonant frequencies on the impedance plot of the specified antenna or array in the specified frequency range. If no resonant frequency is detected in the specified frequency range, this syntax plots the impedance of the specified antenna or array without any marked points.```
````resonantFrequency(object,frequency,Method="Sparameters")` marks the resonant frequencies on the S11 plot of the specified antenna or array in the specified frequency range. If no resonant frequency is detected in the specified frequency range, this syntax plots the S11 of the specified antenna or array without any marked points.```
````resonantFrequency(object,frequency,Method="Impedance",Name=Value)` marks the resonant frequencies on the impedance plot of the specified antenna or array in the specified frequency range with additional options specified by one or more Name-Value Arguments. If no resonant frequency is detected in the specified frequency range, this syntax plots the impedance of the specified antenna or array without any marked points.```
````resonantFrequency(object,frequency,Method="Sparameters",Name=Value)` marks the resonant frequencies on the S11 plot of the specified antenna or array in the specified frequency range with additional options specified by one or more Name-Value Arguments. If no resonant frequency is detected in the specified frequency range, this syntax plots the S11 of the specified antenna or array without any marked points.```
````fRES = resonantFrequency(object,frequency)` calculates and returns the resonant frequencies of the specified antenna or array in the specified frequency range. `fRES` is empty if no resonant frequency is detected in the specified frequency range. `fRES` is a vector when more than one resonant frequencies are detected in the specified frequency range.```
````fRES = resonantFrequency(object,frequency,Name=Value)` calculates and returns the resonant frequencies of the specified antenna or array in the specified frequency range using additional options specified by one or more Name-Value Arguments. `fRES` is empty if no resonant frequency is detected in the specified frequency range. `fRES` is a vector when more than one resonant frequencies are detected in the specified frequency range.```
````[fRES,zRES,Z,typRES] = resonantFrequency(object,frequency)` calculates and returns the resonant frequencies `fRES` and the corresponding impedances `zRES` and resonance type `typRES` (series or parallel) for the specified antenna or array in the specified frequency range. `fRES`, `zRES`, and `typRES` are empty if no resonant frequency is detected within the specified frequency range. `fRES` and `zRES` are vectors, and `typRES` is a string array when more than one resonant frequencies are detected. `Z` is a vector of all the impedance values across the specified frequency range.```

example

````[fRES,zRES,Z,typRES] = resonantFrequency(object,frequency,Method="Impedance",Name=Value)` calculates and returns the resonant frequencies `fRES` and the corresponding impedances `zRES` and resonance type `typRES` (series or parallel) for the specified antenna or array in the specified frequency range using additional options specified by one or more Name-Value Arguments. `fRES`, `zRES`, and `typRES` are empty if no resonant frequency is detected within the specified frequency range. `fRES` and `zRES` are vectors, and `typRES` is a string array when there are more than one resonant frequencies. `Z` is a vector of all the impedance values across the specified frequency range.```

example

````[fRES,sRES,S] = resonantFrequency(object,frequency,Method="Sparameters")` calculates and returns the resonant frequencies `fRES` and the corresponding S11 values `sRES` for the specified antenna or array in the specified frequency range. `fRES` and `sRES` are empty if no resonant frequency is detected within the specified frequency range. `fRES` and `sRES` are vectors when more than one resonant frequencies are detected. `S` is a vector of all the S11 values across the specified frequency range.```
````[fRES,sRES,S] = resonantFrequency(object,frequency,Method="Sparameters",Name=Value)` calculates and returns the resonant frequencies `fRES` and the corresponding S11 values `sRES` for the specified antenna or array in the specified frequency range using additional options specified by one or more Name-Value Arguments. `S` is a vector of all the S11 values across the specified frequency range.```

## Examples

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This example shows how to calculate and plot the resonant frequency of a dipole antenna using Impedance method and S-parameters method.

Calculate and Plot Resonant Frequency using Impedance Method

Create a dipole antenna operating at 75 MHz. Calculate and plot the resonant frequency of a dipole over a frequency span of 50 MHz - 100 MHz.

```h = design(dipole,75e6); resonantFrequency(h,50e6:1e6:100e6);```

Calculate and Plot Resonant Frequency using S-parameters Method

Calculate and plot the resonant frequency of the same dipole, using S-parameters method, over the same frequency span.

`resonantFrequency(h,50e6:1e6:100e6,Method="Sparameters");`

## Input Arguments

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Antenna or array to calculate resonant frequency, specified as one of the following options:

Example: `dipole`

Frequency range to calculate the resonant frequency, specified as a positive vector in Hertz.

Example: `[50e6:5e6:80e6]`

Data Types: `double`

### Name-Value Arguments

Specify optional pairs of arguments as `Name1=Value1,...,NameN=ValueN`, where `Name` is the argument name and `Value` is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Example: `Method="Sparameters"`

Option to enable parallel pool, specified as a logical value. The default value is `false`. Set this option to `true` or `1` to enable the parallel pool. Use parallel pool to speedup the resonant frequency calculations at multiple frequencies for computationally large antennas and arrays. To use this feature, you need a license to the Parallel Computing Toolbox™.

Example: `UseParallel=true`

Data Types: `logical`

Method to use for resonant frequency calculation, specified as either `"Impedance"` or `"Sparameters"`. The default method is `"Impedance"`. When the method is specified as `"Impedance"`, zero-crossings of the reactance are used to find the resonant frequency, and `zRES` and `Z` are the outputs. When the method is specified as `"Sparameters"`, the negative peaks of S11 are used to find the resonant frequency. The output `typRES` (whether the impedance is series or parallel) is supported only when the method is `"Impedance"`.

Example: `"Sparameters"`

Data Types: `string`

Threshold value for impedance or S11, specified as a real scalar in ohms when the `Method` is set to `"Impedance"` or a real scalar in dB when the `Method` is set to `Sparameters`.

Example: `-12`

Data Types: `double`

Reference impedance to calculate the S-parameters, specified as a positive real scalar in ohms. The default reference impedance is 50 ohms. This argument is valid only when the `Method` argument is set to `Sparameters`.

Example: `75`

Data Types: `double`

Option to enable or disable the data tips, specified as a logical `true` to enable or logical `false` to disable the data tips. By default, the data tips are enabled.

Example: Specifying `PlotDataTips=false` disables the data tips on the plot.

Data Types: `logical`

## Output Arguments

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Resonant frequency in Hz of the specified antenna, returned as either positive scalar value for a single resonance or a positive vector for multiple resonances within the specified frequency sweep.

Example: `75.33e6`

Impedance values corresponding to the resonant frequencies, returned as a real or complex scalar or vector. `zRES` is empty when there are no resonant frequencies within the specified frequency range. And `zRES` is a vector when multiple resonances are found within the specified frequency range.

Example: `75`

Data Types: `double`
Complex Number Support: Yes

`S11` values corresponding to the resonant frequencies, returned as a complex vector in dB.

Data Types: `double`
Complex Number Support: Yes

Impedance values over entire frequency range, returned as a complex vector in ohms.

Data Types: `double`
Complex Number Support: Yes

S11 values over the entire frequency range, returned as a complex vector in dB.

Data Types: `double`

Resonance type, returned as a string. The resonance type is either `"Series"`, `"Parallel"` or `"Unclear"`. When the reactance in the impedance plot approaches zero but does not cross it, resonance type is returned as `"Unclear"`.

Example: `"Parallel"`

Data Types: `string`

## Version History

Introduced in R2024a