Matching Network Designer

Design, visualize, and compare matching networks for one-port load

Since R2021a

Description

The Matching Network Designer app lets you design, visualize, and compare matching networks for one-port load.

Using this app, you can:

• Design two- and three-component lumped element matching networks at desired frequencies and unloaded-Q factors.

• Provide source and load impedance as a one-port Touchstone file, scalar impedance, RF circuit object, RF network parameter object, Antenna Toolbox™ object, or as an anonymous function.

  Note

  • To load one-port circuit object to the app, you must set ports to your circuit object using the setports function.

  • To use an Antenna Toolbox object, you must have an Antenna Toolbox license.

  • One-port Touchstone files include S1P, Z1P, and Y1P file types.

• Sort the matching networks using constraints such as operating frequency range and power wave S-parameters.

• Plot power wave S-parameters [1] of the matching network on a Smith™ chart and Cartesian plot.

• Plot voltage standing wave ratio (VSWR) and impedance transformation plots.

• Plot magnitude, phase, real, and imaginary parts of power wave S-parameters of the matching network.

• Export selected networks as circuit objects or power wave S-parameters as sparameters objects.

More

Available Configurations

The app toolstrip contains these network configurations that you can use to design matching networks:

• Pi-Topology

• T-Topology

• L-Topology

• 3-Components

Open the Matching Network Designer App

• MATLAB^® Toolstrip: On the Apps tab, under RF and Mixed-Signal, click the Matching Network Designer app icon.

• MATLAB command prompt: Enter matchingNetworkDesigner.

Examples

Design, Visualize, and Compare Three-Component Matching Networks

Type this command at the command line to open the Matching Network Designer app.

matchingNetworkDesigner

Select New under File section to start a new session. In the New Session window, specify the design requirements:

• Zs Source — Scalar Complex Impedance

• Impedance (Ohms) — 50+2i.

• Zl Load — Touchstone File

• File Name — dipole_example.s1p

• Center Frequency — 1.5e9 and

• Bandwidth — 750e6.

The app only recognizes one-port Touchstone files and converts the center frequency and bandwidth to Hz.

Select Start session. In the toolstrip of the app window, select 3-Components under the Configuration section and select Generate to generate the matching network. From the Matching Network Browser pane, select the nodes. For the purpose of this example, select auto_1. The Quality Factor is populated based on the data entered in the New Session window.

Set constraints to sort the three-component matching networks. To do this, click Manage Constraints. In the Design Constraints window, click button and add the constraints. Set the constraint to:

abs(Parameter) — S11

Condition — <

Goal (dB) — –15

Min Frequency (GHz) — 1.4500

Max Frequency (GHz) — 1.5400

Weight — 1

Select Active and click OK.

The matching networks are sorted based on the constraints and the nodes are rearranged under the Matching Network Browser pane.

Compare the power wave S-parameter results between the nodes. For the purpose of this example, compare the power wave S-parameter results between auto_1 and auto_3 nodes. To do this, select the auto_1 and auto_3 nodes using the Ctrl key. The results are displayed in the Cartesian and Smith plot.

Deselect the auto_3 node. To visualize the impedance transformation of the auto_1 node, select Impedance Transformation under Smith Plot or select the ZTransform window on the right hand side of the app.

Design Narrow-Band Double Tuning L-Section Matching Network for Monopole Antenna

Design a narrow-band double tuning L-section matching network between a resistive source and a capacitive load in the form of a small monopole. This example designs an L-section matching network consisting of two inductors. The equivalent source impedance is 50 ohms and the load is a monopole with resonant frequency of around 1 GHz. The load (antenna) impedance is at 500 MHz, which is half the resonant frequency.

load_antenna = design(monopole,1e9);
sparams_load = sparameters(load_antenna,linspace(0.45e9,0.55e9,101));

To open the Matching Network Designer app, type this command at the command line.

matchingNetworkDesigner

Select New under File section to start a new session. In the New Session window, specify the requirements:

• Zs Source — Scalar Complex Impedance

• Impedance (Ohms) — 50

• Zl Source — S-,Y-, or Z-parameter Object

• Variable Name — sparams_load

• Center Frequency — 500e6 and

• Bandwidth — 10e6.

The app converts the center frequency and bandwidth to Hz.

Select Start Session. In the toolstrip of the app window, select L-Topology under Configuration section and select Generate to generate the matching network. From the Matching Network Browser pane, select the nodes. For the purpose of this example, select auto_1.

To plot the VSWR, select VSWR under Cartesian plot.

Import Custom Matching Network

Design a pi-matching network with circuit objects. For the purpose of this example, the custom pi-matching network consists of two capacitors and an inductor.

Create a circuit object.

ckt = circuit('test_ckt2');

Create two capacitors, C1 and C2 with the capacitance of 3.35 pF and 2.917 pF.

c1 = capacitor(3.35e-12,'C1');
c2 = capacitor(2.917e-12,'C2');

Create a 5.44 nH inductor.

l = inductor(5.44e-9,'L');

Add C1 to the node [1,0] of the circuit object.

add(ckt,[1,0],c1);

Add L to the node [1,2] of the circuit object.

add(ckt,[1,2],l);

Add C2 to the node [2,0] of the circuit object.

add(ckt,[2,0],c2);

Save the circuit object.

save('test_file2.mat','ckt');

Set ports to the circuit object and resave the circuit object in MAT file type.

setports(ckt,[1 0],[2 0]);
save('test_file2.mat','ckt');

Type this command at the command line to open the Matching Network Designer app.

matchingNetworkDesigner

Select New under File section to start a new session. In the New Session window, specify the design requirements:

• Zs Source — Scalar Complex Impedance

• Impedance (Ohms) — 50

• Zl Source — Touchstone File

• File Name — dipole_example.s1p

• Center Frequency — 1.5e9 and

• Bandwidth — 750e6

Select Import Circuit to import the custom pi-matching network designed in this example. Select node test_ckt2 under Matching Network Browser pane.

S11 and S21 plot of the custom pi-matching network is displayed under Cartesian plot.

Related Examples

• Impedance Matching of Small Monopole Antenna

Programmatic Use

matchingNetworkDesigner

matchingNetworkDesigner opens the Matching Network Designer app to design, visualize, and compare one-port narrowband matching networks.

matchingNetworkDesigner(mnnetwork)

matchingNetworkDesigner(mnnetwork) opens a matching network saved using the Matching Network Designer app. mnnetwork is a MAT file.

Tips

• Use this expression to set design constraints: |Parameter| Condition 10^(Goal (dB)/20). For example, |S21| > 10^(-3/20) implies that matching network circuits are sorted with S21 greater than -3 dB as a design constraint. In linear scale the expression can be rewritten as |S21| > 0.7079.

Algorithms

Color Codes in Cartesian Plot

You can use the color codes provided in this table to analyze the Cartesian plot generated in the app. By doing this, you can determine whether your matching network has satisfied the conditions you specified using the Manage Constraints button.

Criteria	S11 and S22	S12 and S21
Pass	Green	Cyan
Fail	Orange	Red

Note

Overlapping regions will result in color mixing.

References

[1] Kurokawa, K. “Power Waves and the Scattering Matrix.” IEEE Transactions on Microwave Theory and Techniques 13, no. 2 (March 1965): 194–202. https://doi.org/10.1109/TMTT.1965.1125964.

[2] Ludwig, Reinhold, and Gene Bogdanov. RF Circuit Design: Theory and Applications. Upper Saddle River, NJ: Prentice-Hall, 2009.

Version History

Introduced in R2021a