bandwidth

R2026b

Calculate and plot absolute bandwidth of antenna or array

Since R2024a

Syntax

bandwidth(object,frequency)

absBW = bandwidth(___)

[absBW,fRES,fL,fU,S] = bandwidth(___)

[___,sweepobj] = bandwidth(___,SweepOption=Value)

[___] = bandwidth(___,Name=Value)

Description

bandwidth(object,frequency) marks the bandwidth on the S₁₁ plot of the antenna or array in the specified frequency range.

absBW = bandwidth(___) calculates and returns the absolute bandwidths absBW for the specified antenna or array at each resonant frequency within the specified frequency range.

[absBW,fRES,fL,fU,S] = bandwidth(___) calculates and returns the absolute bandwidths absBW at each resonant frequency in fRES, and the lower (fL) and upper (fU) bounds for the specified antenna or array. absBW and fRES are empty if no bandwidth or resonant frequency is detected within the specified frequency range. absBW and fRES are vectors when there are more than one bandwidths. S is a vector of all the S₁₁ values across the specified frequency range.

[___,sweepobj] = bandwidth(___,SweepOption=Value) uses the specified frequency sweep interpolation method to calculate the bandwidth of an antenna or array, and additionally returns the interpolation method type and rational fit parameters stored in a frequency sweep object sweepobj.

[___] = bandwidth(___,Name=Value) specifies additional options using one or more name-value arguments. For example, bandwidth(dipole,60e6:1e6:80e6,Threshold=-10) marks the bandwidth on the S₁₁ plot of the dipole antenna in the 60 MHz to 80 MHz range with an S₁₁ threshold of -10 dB.

Examples

Calculate and Plot Bandwidth of Dipole Antenna

This example shows how to calculate and plot the bandwidth of a dipole antenna for different thresholds.

Create Dipole, Calculate and Plot Bandwidth with Default Threshold

Create a dipole operating at 75MHz. Calculate and plot the bandwidth of a dipole for a default threshold of -10dB over a frequency span 50MHz to 100MHz.

h = design(dipole,75e6);
absBW = bandwidth(h,50e6:1e6:100e6)

absBW = 
6.6738e+06

bandwidth(h,50e6:1e6:100e6);

Calculate and Plot Bandwidth with Custom Threshold

Calculate and plot the bandwidth of the same dipole, using a -2dB threshold, over the same frequency span.

absBW = bandwidth(h,50e6:1e6:100e6,Threshold=-2)

absBW = 
3.4303e+07

bandwidth(h,50e6:1e6:100e6,Threshold=-2);

Input Arguments

object — Antenna or array to calculate bandwidth

antenna object | pcbStack object | customAntenna object | customAntennaMesh object | customAntennaGeometry object | infiniteArray object

Antenna or array to calculate bandwidth, specified as one of the following options: an infiniteArray object, or a custom antenna created using either of these:

• Antenna object from antenna catalog.

• pcbStack object.

• customAntenna

• customAntennaMesh

• customAntennaGeometry

• infiniteArray object.

Example: dipole

frequency — Frequency range to calculate bandwidth

positive vector

Frequency range to calculate the bandwidth, 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: Threshold=-2

UseParallel — Option to enable parallel pool

false or 0 (default) | true or 1

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 speed up the bandwidth 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 enables the parallel pool for bandwidth computation.

Data Types: logical

SweepOption — Sweep interpolation method

"direct" (default) | "interp" | "interpWithGrad" | frequencySweep object

Sweep interpolation method, specified as one of the following:

• "direct" — Compute bandwidth using all the specified frequencies.

• "interp" — Interpolate the sweep using rational fitting to compute bandwidth with minimum possible set of frequency points within the specified frequency range.

• "interpWithGrad" — Interpolate the sweep using rational fitting with gradient information to compute bandwidth with minimum possible set of frequency points within the specified frequency range.

• frequencySweep object — Interpolate the sweep using parameters such as error tolerance, number of frequency points, and number of iterations that you set in the frequencySweep object.

Frequency sweep interpolation methods use rational fitting to interpolate results over the frequency range defined by two or more specified frequency points.

When you use an interpolating sweep, the frequencies at which the bandwidth function computes and plots the results can differ from the frequencies in the input frequency vector. The effective set of frequencies depends on SweepOption:

• If SweepOption is a frequencySweep object, the effective frequencies are determined by its NumFreqs property.

• If SweepOption is "interp" or "interpWithGrad", the number of frequency points depends on how many frequencies you provide:

  • If you provide more than 30 frequencies, the sweep uses your frequencies directly.

  • If you provide 30 or fewer frequencies, the sweep uses the default of 100 points across the band.

Sweep Interpolation Methods

Method	When to Use	Trade-off
"direct"	Results at all specified frequencies	High computational cost; slow for large sweeps
"interp"	Faster results with automatic accuracy control and fewer simulations	No control over number of frequency points
"interpWithGrad"	Faster results with gradient information for optimization	Slightly more expensive than "interp"
frequencySweep object	Manual control over frequency resolution, error tolerance, and number of iterations	Requires manual tuning; no adaptive refinement

To use this feature, you need an RF Toolbox™ license.

Example: [absBw,fRES,fL,fU,S,sweepobj] = bandwidth(dipole,[10e6:1e6:180e6],SweepOption="interp")

Data Types: string

Z0 — Reference impedance in ohms to calculate S-parameters

50 (default) | positive real scalar

Reference impedance in ohms to calculate the S-parameters, specified as a positive real scalar. The default reference impedance is 50 ohms.

Example: Z0=75 sets the reference impedance to 75 ohms.

Data Types: double

Threshold — S11 threshold value to calculate bandwidth

-10 (default) | numeric scalar

S11 threshold value to calculate the bandwidth, specified as a numeric scalar in dB.

Example: Threshold=-12 sets the threshold to -12 dB.

Data Types: double

PlotDataTips — Option to enable or disable data tips

true (default) | false

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

absBW — Absolute bandwidth in Hz

positive scalar | positive vector

Absolute bandwidth 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: 30e6

fRES — Resonant frequency in Hz

positive scalar | positive vector

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: 6.67e9

Data Types: double

fL — Lower frequency bound of bandwidth in Hz

positive scalar | positive vector

Lower frequency bound of bandwidth in Hz, returned as scalar for a single resonance or a vector for multiple resonances within the specified frequency sweep.

Example: 6.64e9

Data Types: double

fU — Upper frequency bound of bandwidth in Hz

positive scalar | positive vector

Upper frequency bound of bandwidth in Hz, returned as scalar for a single resonance or a vector for multiple resonances within the specified frequency sweep.

Example: 6.7e9

Data Types: double

S — S11 values in dB for entire frequency sweep

complex vector

S11 values in dB for the entire frequency sweep, returned as a complex vector.

Data Types: double
Complex Number Support: Yes

sweepobj — Frequency sweep interpolation parameters

frequencySweep object

Frequency sweep interpolation parameters, returned as a frequencySweep object.

Tips

• Interpolating frequency sweeps may report results at frequencies that differ from the frequencies you specify. If you require results at exact frequencies, either use the default direct sweep, or set the NumFreqs property of the frequencySweep object greater than or equal to the number of frequencies you provide.

• When using the "interp" or "interpWithGrad" sweep options, provide more than 30 frequency points to have the sweep use your frequency resolution exactly; otherwise the sweep defaults to 100 points across the band.

Version History

Introduced in R2024a

R2026b: Use frequency sweep interpolation to calculate bandwidth

Use the new SweepOption name-value argument to interpolate the frequency sweep for bandwidth calculations. The interpolation methods use rational fitting or rational fitting with gradient information.