Changes

{{projectinfo|Tutorial| Analyzing Microstrip Lines & Discontinuities |RF46.png|In this project, the basic concepts of you will use RF.Spice A/D are demonstrated, 's line designer and a simple voltage divider is modeled line calculator utilities to build and examinedanalyze simple microstrip circuits.|

|All versions|{{download|http://www.emagtech.com/contentdownloads/project-file-download-repository|EMProjectRepo/RFLesson4.Tempo zip RF Lesson 1|[[RF.Spice A/D]] R154}} }}

<b>Analyzing Microstrip Lines, Discontinuities and Filters</b> === What You Will Learn ===

[[RF.Spice A/D]] has a large number of physical line calculators and designers. You can access these tools from the Device Manager. Open [[RF.Spice]]'s Device Manager either from its '''File Menu''' or using the keyboard shortcut {{key|Ctrl+D}}. At the top of Device Manager's '''Tools Menu''', find '''Microstrip Designer''' and open it. For this project, you will use an FR-4 substrate of thickness h = 1.2mm, relative permittivity er = 4.5 and loss tangent tand = 0.02. To design a 50&Omega; microstrip line, enter these values into the designer dialog and set Z0 = 50. The corresponding width value is computed to be 2.3mm.

[[File:RF40.png|thumb|400pxleft|420px|The RF.Spice A/D Microstrip Designer dialog accessible from the Device Manager.]]

In order to verify your design, go back to the [[RF.Spice A/D]] Workshop and place a "Microstrip Line" part on the schematic either using '''Menu > Parts > [[Transmission Lines]] > Physical [[Transmission Lines]] > Microstrip Line''' or using the keyboard shortcut {{key|Alt+T}}. The following is a list of parts needed for this part of the tutorial lesson:

! scope="row"| XTL1XMS1

| Defaults: w = 2.3, h = 1.2, er = 4.45, len = 20, tand = 0.02

<table><tr><td>[[File:RF44.png|thumb|540pxleft|640px|The property dialog of the Microstrip Line device.]]</td></tr></table> 

[[File:RF42.png|thumb|400pxleft|420px|left|A simple microstrip circuit with a resistive load termination.]]

Run a Network Analysis of this simple circuit, with Port 1 defined between node IN and the ground. Use the following [[parameters]]:

[[File:RF43.png|thumb|750px|left|720px|Smith chart for the return loss of the basic resistor-terminated microstrip line segment.]]

[[File:RF41.png|thumb|360px|The RF.Spice Microstrip Calculator dialog.]]Next, you will use the Device Manager's "Microstrip Calculator" to find the effective permittivity of your 50&Omega; microstrip line and its guide wavelength at 2GHz. Open the '''Line Calculator''' from the '''Tools Menu''' of Device Manager. Enter the [[parameters]]: w = 2.3mm, h = 1.2mm, er = 4.45, len = 20mm, tand = 0.02, as shown in the figure below.  

In the other parts of this tutorial lesson and the next one, you will use very wide and very narrow microstrip line segments. Repeat the same calculations for microstrip width values of 0.5mm and 5mm. The results are summarized in the table below. :

[[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 50&Omega; 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.

| L1 XMS1 || 2.3mm || 5mm || 50&Omega;

| L2 XMS2 || 5mm 2.3mm || 10mm 5mm || 3050&Omega;

| L3 XMS3 || 2.3mm 5mm || 5mm 20mm || 5030&Omega;

<table><tr><td>[[File:RF45.png|thumb|left|540px|The top view of layout of the microstrip double step structure.]]</td></tr></table> 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.  <table><tr><td>[[File:RF46.png|thumb|left|540px|The schematic of the microstrip double step structure.]]</td></tr></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]].You should get a graph like the one shown below.

| valign="bottomtop"|[[File:RF47.png|thumb|800px|left|Graph of s11 and s21 parameters of the double step circuit over the frequency range 500MHz-6GHz.]]

The [[RF.Spice]] In the circuit shown above assumes that of the previous section, the microstrip line segments of different widths are were directly connected to each other, and it ignores you ignored the effect of the step discontinuity. However, [[RF.SpiceA/D]] also provides a number of microstrip discontinuity models for you to increase the accuracy of your modeling. One of these devices is the two-port "Microstrip Step", which can be accessed from the [[Schematic Editor]]'s ''Menu > Parts > RF Menu under the "Components > Microstrip Discontinuities" groupComponents > Microstrip Step'''. The opposite figure shows the property dialog of this device. It assumes that the first microstrip (w1) at Port 1 is always wider than the second one (w2) at Port 2. Therefore, in order to use this device as a junction from segment L1 to L2, you have to flip it horizontally (keyboard shortcut: {{key|Ctrl+F}}) so that its Port 2 and 1 are connected to L1 and L2, respectively. Use another instance of the same device, but without flipping, as a junction from segment L2 to L3.  The following is a list of parts needed for this part of the tutorial lesson:

| valign="bottomtop"|[[File:RF51.png|thumb|450px|The property dialog of the Microstrip Step device.]]| valign="bottom"|[[File:RF48.png|thumb|520px|The RF.Spice schematic of the microstrip double step including step discontinuity models.]]

| valign="bottomtop"|[[File:RF49.png|thumb|800px|left|Graph of s11 and s21 parameters of the double step circuit with step discontinuity models over the frequency range 500MHz-6GHz.]]

[[Image:Back_icon.png|40px]] '''[[RF.Spice_A/D#RF.Spice_A.2FD_Tutorial 2FD_Tutorials | Back to RF.Spice A/D Tutorial Gateway]]'''