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filterStepImpedanceLowPass

Create stepped impedance lowpass filter in microstrip form

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

Description

example

filter = filterStepImpedanceLowPass creates a default stepped impedance lowpass filter. The default filter dimensions are 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

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 default value is a dielectric object with these properties:

  • Name{'CustomDielectric'}

  • EpsilonR3.7

  • LossTangent0.001

  • Thickness1.6e-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.

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

Data Types: string | char

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

Examples

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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]

show(steppedfilter)

Figure contains an axes object. The axes object with title filterStepImpedanceLowPass element contains 6 objects of type patch, surface. These objects represent PEC, feed, CustomDielectric.

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 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 contains 4 objects of type patch.

figure
current(steppedfilter,5e9)

Figure contains an axes object. The axes object with title Current distribution contains 4 objects of type patch.

info(steppedfilter)
ans = struct with fields:
          IsSolved: "true"
          IsMeshed: "true"
       MeshingMode: "auto"
      HasSubstrate: "true"
           HasLoad: "false"
     PortFrequency: []
    MemoryEstimate: "790 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