Microstrip Impedance Matching - bandwidth, sensitivity and physical size improvement

[Yo_Mommas_Pimp]

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?

 

[tony_lth]

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

 

[Yo_Mommas_Pimp]

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

 

[tony_lth]

Microwave Office

 

[Yo_Mommas_Pimp]

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?

 

[tony_lth]

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.

 

[BigBoss]

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?

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..