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filterStepImpedanceLowPass

Create stepped impedance lowpass filter in microstrip form

Since R2021b

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Description

Use the filterStepImpedanceLowPass object to create a stepped impedance lowpass filter in microstrip form.

Three part image from right to left: Default image of a step impedance low-pass filter. Current distribution on the step impedance low-pass filter. S-parameters plot of the step impedance low-pass filter.

The stepped impedance lowpass microstrip filters have a cascaded structure of alternating high- and low-impedance transmission lines. These lines are considerably shorter in length than the design wavelength and act as semi-lumped elements. The high-impedance lines act as series inductors, and the low-impedance lines act as shunt capacitors. This filter structure realizes a Pi LC ladder type of a lowpass filter. You can control the impedance by adjusting the width of the strip. This filter is used in radar, satellite, and terrestrial communications and in electronic counter-measure applications.

Creation

Syntax

filter = filterStepImpedanceLowPass
filter = filterStepImpedanceLowPass(Name=Value)

Description

filter = filterStepImpedanceLowPass creates a default stepped impedance lowpass filter with default property values for a cutoff frequency 5 GHz.

example

filter = filterStepImpedanceLowPass(Name=Value) sets Properties using one or more name-value arguments. For example, filterStepImpedanceLowPass(FilterOrder=10) creates a tenth-order stepped impedance lowpass filter. Properties not specified retain their default values

example

Properties

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Filter order, specified as a positive scalar. The minimum filter order you can specify is 3 and the maximum order is 11.

Example: filter = filterStepImpedanceLowPass(FilterOrder=5)

Data Types: double

Length of the input and output lines in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(PortLineLength=0.0553)

Data Types: double

Width of the input and output lines in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(PortLineWidth=0.0087)

Data Types: double

Width of the low-impedance line in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(LowZLineWidth=0.0553)

Data Types: double

Width of the high-impedance line in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(HighZLineWidth=0.0553)

Data Types: double

Length of the low-impedance line in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(LowZLineLength=0.0553)

Data Types: double

Length of the high-impedance line in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(HighZLineWidth=0.0553)

Data Types: double

Height of the filter from the ground plane in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(Height=0.020)

Data Types: double

Width of the ground plane in meters, specified as a positive scalar.

Example: filter = filterStepImpedanceLowPass(GroundPlaneWidth=0.013)

Data Types: double

Type of dielectric material used as a substrate, specified as a dielectric object. The dielectric material in a filterStepImpedanceLowPass object with default properties have the following properties:

  • Name—{'CustomDielectric'}

  • EpsilonR—3.7

  • LossTangent—0.001

  • Thickness—1.6e-3

Example: d = dielectric("FR4"); filter = filterStepImpedanceLowPass(Substrate=d)

Data Types: string | char

Type of metal used in the conducting layers, specified as a metal object. The type of metal in a filterStepImpedanceLowPass object with default properties is PEC.

Example: m = metal("Copper"); filter = filterStepImpedanceLowPass(Conductor=m)

Data Types: string | char

Flag to add a metal shielding to the PCB component, specified as a logical 0 or logical 1. The default value is logical 0.

Example: IsShielded = true or 1 add a metal shield.

Note

To enable FEM solver required for the metal shield property, download the Integro-Differential Modeling Framework for MATLAB. To download this add-on:

  1. In the Home tab Environment section, click on Add-Ons. This opens the add-on explorer. You need an active internet connection to download the add-on.

  2. Search for Integro-Differential Modeling Framework for MATLAB and click Install.

  3. To verify if the download is successful, run 

    matlab.addons.installedAddons
    in your MATLAB® session command line.

  4. On Windows, to run the IDMF add-on, you must install the Windows Subsystem for Linux (WSL). To install WSL, see Install Linux on Windows with WSL.

    The Windows Defender Firewall can block the PostgreSQL server when using the IDMF add-on. To resolve this issue, you can allow the server to communicate on desired networks if the firewall prompts. Alternatively, you can manually add the executable file of the PostgreSQL server located in <matlabroot>\sys\postgresql\win64\PostgreSQL\bin\postgres.exe. For more information, see https://support.microsoft.com/en-us/windows/risks-of-allowing-apps-through-windows-defender-firewall-654559af-3f54-3dcf-349f-71ccd90bcc5c.

Data Types: logical

This property is read-only.

Metal shield for the PCB component, specified as a shape.Box object. The length and width of the box must be equal to the length and width of the ground plane. The center of the box is at [0 0 Shielding.Height].

Dependencies

To enable the Shielding property, set the IsShielded property to true or 1.

Type of RF connector assembled at the feed locations of the PCB component, specified as a RFConnector object.

Example: Create connector from RFConnector object like this: coaxial = RFConnector adds a coaxial connector.

Dependencies

To enable the Connector property, set the IsShielded property to true or 1.

Object Functions

chargeCalculate and plot charge distribution
currentCalculate and plot current distribution
designDesign stepped impedance low pass filter around desired cut-off frequency
feedCurrentCalculate current at feed port
getZ0Calculate characteristic impedance of transmission line
layoutPlot all metal layers and board shape
meshChange and view mesh properties of metal or dielectric in PCB component
shapesExtract all metal layer shapes of PCB component
showDisplay PCB component structure or PCB shape
sparametersCalculate S-parameters for RF PCB objects
RFConnectorCreate RF connector

Examples

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Open Live Script

Create and view a default stepped impedance lowpass filter.

steppedfilter = filterStepImpedanceLowPass
steppedfilter = 
  filterStepImpedanceLowPass with properties:

         FilterOrder: 3
       PortLineWidth: 0.0034
      PortLineLength: 0.0040
      HighZLineWidth: 5.0000e-04
       LowZLineWidth: 0.0096
     HighZLineLength: 0.0026
      LowZLineLength: 0.0032
              Height: 0.0016
    GroundPlaneWidth: 0.0120
           Substrate: [1x1 dielectric]
           Conductor: [1x1 metal]
          IsShielded: 0


show(steppedfilter)

Figure contains an axes object. The axes object with title filterStepImpedanceLowPass element, xlabel x (mm), ylabel y (mm) contains 6 objects of type patch, surface. These objects represent PEC, feed, CustomDielectric.

Open Live Script

Create and view a stepped impedance lowpass filter with a multilayer dielectric substrate.

sub = dielectric("FR4","Teflon"); 
sub.Thickness =[0.003 0.001];
steppedfilter = filterStepImpedanceLowPass;
steppedfilter.Height = 0.003;
steppedfilter.Substrate = sub;
figure
show(steppedfilter)

Figure contains an axes object. The axes object with title filterStepImpedanceLowPass element, xlabel x (mm), ylabel y (mm) contains 7 objects of type patch, surface. These objects represent PEC, feed, FR4, Teflon.

Plot the charge and current on the filter at 5 GHz.

figure
charge(steppedfilter,5e9)

Figure contains an axes object. The axes object with title Charge distribution, xlabel x (m), ylabel y (m) contains 4 objects of type patch.

figure
current(steppedfilter,5e9)

Figure contains an axes object. The axes object with title Current distribution, xlabel x (m), ylabel y (m) contains 4 objects of type patch.

info(steppedfilter)
ans = struct with fields:
          IsSolved: "true"
          IsMeshed: "true"
       MeshingMode: "auto"
      HasSubstrate: "true"
           HasLoad: "false"
     PortFrequency: []
    MemoryEstimate: "770 MB"

References

[1] Pozar, David M. Microwave Engineering. 4th ed. Hoboken, NJ: Wiley, 2012.

[2] Garvansh, Abhay, Singh Kushwaha, Navita Singh, and Arun Kumar. “Implementation of Stepped Impedance Low Pass Microstrip Line Filter for Wireless Communication.” International Journal of Advanced Research in Computer and Communication Engineering 3, no. 7 (July 2014): 7608–10.

[3] Maity, Budhadeb. “Stepped Impedance Low Pass Filter Using Microstrip Line for C-Band Wireless Communication.” In 2016 International Conference on Computer Communication and Informatics (ICCCI), 1–4. Coimbatore, India: IEEE, 2016. https://doi.org/10.1109/ICCCI.2016.7480008.

Version History

Introduced in R2021b

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See Also

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