Microstrip Impedance Matching - bandwidth, sensitivity and physical size improvement

I need to make an impedance matching circuit using microstrip lines.

Zin --> MATCHING CIRCUIT --> ZL

The input impedance (Zin) is 50Ω. The impedance at the load is 50 - j 500Ω. Design frequency of 900MHz.

The board I am required to use is the Taconic RF-35. It has a thickness of d = 1.524mm, dielectric constant ξr = 3.5 and loss tangent σ = 0.002.

The magnitude of S11 at the design frequency must be less than -10dB. The size of the circuit is of particular importance. How can I make the microstrip impedance matching circuit smaller?

To start, I got the normalized load impedance of 1 - j 10Ω and plotted that on a Smith chart.

Now I have to use the Smith chart to find what inductance and/or capacitance I should use to match the two ports. After I get those numbers, I could used lumped elements to do the matching, but I must use microstrip lines instead.

After finding the required matching numbers, I will use an open stub to do the matching, I think. My questions are:

1) How do I improve the bandwidth (~900MHz)?
2) How do I reduce the physical size of the impedance matching circuit?
3) How do I increase the voltage sensitivity of the impedance matching circuit?

You can use AWR to simulate. More stubs, smaller size, ans wider bandwidth.

What is AWR? I found the company website, but there are tons of products! Which would I use for this specific application?

Microwave Office

OK - I got a copy of Microwave Office 2002. I did a tutorial and found how to place the strips, place the ports and run simulations.

What I can't figure out is how to place Zin of 50Ω at input port 1.

Please help!

Also, I couldn't find smith chart tool in the AWR Office 2002 suite. Is there one to do impedance matching? I can make a smith chart plot after running an analysis, but how does that assist in impedance matching?


When I get results I can graph the S11, S12, etc. Which one would show the bandwidth?

Port1 is 50ohms, don't need place any Zin anymore.
S21 should show the bandwidth.
S11 show the VSWR, when you add Graph, you select Smith, then show on smith chart.
I suggest you start to lear the getting started of AWR.

Yo_Mommas_Pimp said:

1) How do I improve the bandwidth (~900MHz)?
2) How do I reduce the physical size of the impedance matching circuit?
3) How do I increase the voltage sensitivity of the impedance matching circuit?

Click to expand...

1-To improve bandwidth, you should use multisection matching circuit
2-To reduce the physical dimesions of your circuit, you should use high Er-for instance-alumina substrate (Er>9.6)
3-Voltage sensitivity ?? I couldn't understand your question..