filterStepImpedanceLowPass

Create stepped impedance lowpass filter in microstrip form

Since R2021b

Description

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

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.

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

Properties

FilterOrder — Filter order

3 (default) | positive scalar in the range [3,11]

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

PortLineLength — Length of input and output lines

0.0034 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(PortLineLength=0.0553)

Data Types: double

PortLineWidth — Width of input and output lines

0.0040 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(PortLineWidth=0.0087)

Data Types: double

LowZLineWidth — Width of low-impedance line

0.0096 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(LowZLineWidth=0.0553)

Data Types: double

HighZLineWidth — Width of high-impedance line

5.0000e-04 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(HighZLineWidth=0.0553)

Data Types: double

LowZLineLength — Length of low-impedance line

0.0032 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(LowZLineLength=0.0553)

Data Types: double

HighZLineLength — Length of high-impedance line

0.0026 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(HighZLineWidth=0.0553)

Data Types: double

Height — Height of filter from ground plane

0.0016 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(Height=0.020)

Data Types: double

GroundPlaneWidth — Width of ground plane

0.012 (default) | positive scalar

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

Example: filter = filterStepImpedanceLowPass(GroundPlaneWidth=0.013)

Data Types: double

Substrate — Type of dielectric material

dielectric object

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

Conductor — Type of metal used in conducting layers

metal object

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

IsShielded — Flag to add metal shielding

false or 0 (default) | true or 1

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

Shielding — Metal shielding

shape.Box object

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.

Connector — Type of RF connector

RFConnector object

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

charge	Calculate and plot charge distribution
current	Calculate and plot current distribution
design	Design stepped impedance low pass filter around desired cut-off frequency
feedCurrent	Calculate current at feed port
getZ0	Calculate characteristic impedance of transmission line
layout	Plot all metal layers and board shape
mesh	Change and view mesh properties of metal or dielectric in PCB component
shapes	Extract all metal layer shapes of PCB component
show	Display PCB component structure or PCB shape
sparameters	Calculate S-parameters for RF PCB objects
RFConnector	Create RF connector

Examples

Default Stepped Impedance Lowpass Filter

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)

Create Stepped Impedance Lowpass Filter with Multilayer Dielectric Substrate

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)

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

figure
charge(steppedfilter,5e9)

figure
current(steppedfilter,5e9)

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

R2023b: Metal shielding for step impedance low pass filter

Use the IsShielded, Shielding, and Connector properties to add a metal shield to the filterStepImpedanceLowPass object.