[[File:RF45.png|thumb|450px|The top view of layout of the microstrip double step structure.]]
[[File:RF46.png|thumb|450px|The RF.Spice schematic of the microstrip double step.]] The characteristic impedance Z0 of a microstrip line is inversely proportional to its width as you saw in the previous section. When you connect two microstrip lines of different widths directly to each other, you create a transmission line discontinuity, which is called an impedance step. In this part of the tutorial lesson, you will analyze a circuit composed of two back-to-back 2.3mm-to-5mm and 5mm-to-2.3mm impedance steps with a 10mm-long, 5mm-wide, microstrip segment in between. You will use 50Ω input and output lines as shown in the opposite figure. A list of the microstrip line segments you need to place in your schematic is given in the table below. Place the parts and connect them as shown. Place two "Net" Markers called "IN" and "OUT" (keyboard shortcut: Alt+N) at the input and output of your circuit.
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Place the parts and connect them as shown below. Place two "Net" Markers called "IN" and "OUT" at the input and output of your circuit.
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[[File:RF46.png|thumb|500px|The schematic of the microstrip double step structure.]]
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</table>
Run a Network Analysis of the double step circuit, with Port 1 defined between node IN and the ground and Port 2 defined between node OUT and the ground . Set the frequency sweep to go from 100MHz to 6GHz with the linear steps of 10MHz. Instead of the Smith chart, this time choose a Cartesian graph type with amplitude only for the S-[[parameters]].