ie3d教程chap10.docx

1、ie3d教程chap10Chapter 10 Simulation of RF and Microwave FiltersPlanar filters are important components in RF, wireless, and microwave circuits and systems. IE3D is a general-purpose electromagnetic simulator. It certainly can be applied efficiently to the analysis and design of different kinds of plan

2、ar and 3D filters. A filter normally consists of multiple closely coupled resonators. If we adjust the resonant frequencies of the resonators and the coupling between the resonators properly, we can achieve high performance filters. To design a filter, we can certainly start from the IE3D directly.

3、However, no matter how fast it is, IE3D is still a full-wave EM simulator. It would be nice that we can start from some initial geometry. For this reason, we have developed the FilterSyn module for the Ie3dLibrary.Section 1. Ie3dLibrary, the Parameterized and Object-Oriented 2nd Interface for IE3D.

4、Ie3dLibrary is the 2nd interface developed for IE3D. We have been using the MGRID, the default interface for the IE3D in the previous chapters. As you can see, MGRID is a very powerful graphic interface. It allows you to construct and edit complicated structures with all details. The fundamental ele

5、ments of MGRID are polygons and vertices. MGRID allows you to control the shape, size, and orientation of polygons and the locations of vertices. We can construct almost any kind of shapes easily. However, polygons and vertices are low level objects. Consider a filter, it may consist of many differe

6、nt polygons. There are relations between different polygons of a filter. On the MGRID, we can change the shape and size of a polygon easily. However, if some dimensions of an object are determined by many vertices or polygons, it may be tedious to change them by changing each polygon one by one. For

7、 this reason, we introduced the Ie3dLibrary. The basic elements of Ie3dLibrary are the objects of pre-defined shapes. The dimensions of the objects can be changed any time after it is created as a building block for a large circuit. For example, we can divide a circuit as objects of T-junctions, cro

8、ss-junctions, Y-junctions and straight lines, etc. on the Ie3dLibrary. We can connect different objects using some default snapping scheme. After the circuit is built, we can still change each elements dimensions. When we change the dimensions of an object, Ie3dLibrary will preserve the connectivity

9、 between the objects. We can also define tuning variables with a dimension of an object described as a formula referencing the tuning variables. When we change the tuning variables, the dimension defined by the formula is updated automatically. Building a large structure with pre-defined object shap

10、es becomes much simplified on the Ie3dLibrary. In IE3D 12, IE3DLIBRAY is much improved. Boolean objects and operations, void objecs are introduced and they extend the geometry modeling capability of IE3DLIBRARY to a next level. We have also implement the FastEM Design Kit discussedin Chapter 5 into

11、IE3DLIBRARY. The combinations of equation-based geometry modeling, Boolean objects and operations and FastEM Tuning and Optimization make IE3D and IE3DLIBRARY much more capable than before. A separate document on using IE3DIBRARY is provided. Interested users please read the document for more inform

12、ation in using this great layout and parameterization tool. Section 2. Using FilterSyn Module for Ie3dLibrary for Initial Design. The FilterSyn module is basically a menu item on the Ie3dLibrary. The FilterSyn is not considered as part of the IE3D. We will demonstrate how to use the FilterSyn to get

13、 initial design in the examples in this chapter. Those users who did not purchase the FilterSyn will not be able to use the FilterSyn module to create the initial design. You can get the created geometry files from FilterSyn from the .ie3dsamples directory. If you are interested in the license of Fi

14、lterSyn module, please contact us at: info. The FilterSyn deals with low-pass, bandpass, and bandstop filters. It covers coaxial, microstrip, stripline/LTCC, and stripline-like structures. It contains analytical models of the following filters: stepped impedance low-pass filters, open-circuited stub

15、 low-pass and bandstop filters, parallel-coupled bandpass filters, gap-coupled bandpass filters, and combline and interdigital bandpass filters. There are 4 types of low-pass filters, 20 types of band-pass filters, and one type of band-stop filters. Each filter type can be used as an object of the I

16、e3dLibrary. We will demonstrate how to use it in the following.Step 1 Run Ie3dLibrary. An empty Ie3dLibrary main window pops up. Select File-New command. Ie3dLibrary will prompt you for the New Project Wizard. Select Start a New FilterSyn Project, and select OK. The dialog “Filter Simulation and Syn

17、thesis Module for Ie3dLibrary” comes up. Figure 10.1 The FilterSyn dialog for Ie3dLibrary.Step 4 Check Low-Pass in Filters group and check Microstrip in Transmission Lines group. We will get the picture shown in Figure 10.1. There are 2 types of Low-Pass Microstrip Filters available.Figure 10.2 The

18、Simulation and Synthesis Setup dialog for the low-pass filter.Step 5 Please select Microstrip Stepped-Impedance Low-Pass Filter on the list. If you do not have the FilterSyn license, Ie3dLIbrary will give you a warning. Please skip this section and go to Section 3. If you have the FilterSyn license,

19、 the setup dialog for the filter type comes up. The parameters for the object are divided into 3 groups: (1) Common Parameters, (2) Simulation Parameters, and (3) Synthesis Parameters. If we are simulating a microstrip stepped-impedance low-pass filter with pre-defined parameters, we can enter the c

20、orresponding parameters in the Common Parameters and Simulation Parameters groups. If we are synthesizing a filter with specified performance requirements, we should enter the parameters in the Common Parameters and Synthesis Parameters group. In our example, we are going to simulate the filter with

21、 the default parameters.Step 4 Click the Simulate button in the dialog (see Figure 10.2). FilterSyn will finish the simulation in no time since it is based upon analytical formulas. Then, it will prompt you for the s-parameter file.Step 5 Please type: .ie3dpracticeoutputlpfa.sp and select Save butto

22、n. The resulting s-parameters are saved into the file and MODUA is invoked to display the s-parameters (see Figure 10.5). You may wonder how accurate the results are. You may want to check the results using IE3D. We are going to create the IE3D model for it. We do not need to enter the polygons base

23、d upon the dimensions. We can create them automatically on the Ie3dLibrary. Step 6 Select OK to close the Microstrip Stepped-Impedance Low-Pass Filter dialog. It will get back to the Filter Simulation and Synthesis Module for Ie3dLibrary dialog. Step 7 While the Microstrip Stepped-Impedance Low-Pass

24、 Filter is still being selected (see Figure 10.1), please select the Create Lib File button. The complete low-pass filter becomes an object of the Ie3dLibrary. It is following the mouse cursor for relocation.Step 8 Click the mouse button somewhere in the Ie3dLibrary window. The object is dropped ont

25、o the window. However, it is still being selected with the corners highlighted (see Figure 10.3). Click at an empty spot to de-select the object. Save it as: .ie3dpracticelpf1.ie3. The extension “.ie3” is for Ie3dLibrary. You will see two red-dots on the two ends of the filter. They are the possible

26、 connection points for the object. You can connect other objects to the edges with red-dots only.Figure 10.3 LPF1 dropped onto Ie3dLibrary.Section 3. Using LineGauge for Transmission Line Parameters. If you do not have the FilterSyn license and you have skipped the last section, please open the file

27、: .ie3dsampleslpf1.ie3 on Ie3dLibrary. Save it as: .ie3dpracticelpf1.ie3. We are going to discuss the other features here. We are going to add a 50-ohm line section to each end of the filter. What is the width of a 50-ohm microstrip line with a 10-mil-thick substrate of dielectric constant 9.9? It d

28、oes not matter whether you know it, because you can use the LineGauge Transmission Line Synthesis Tool to do the synthesis. The basic edition of the LineGauge is free of charge. You can analyze and synthesize simple transmission lines such as microstrip, stripline, and coplanar waveguide using the b

29、asic edition of the LineGauge. For the professional version of the LineGauge, please contact Zeland Software, Inc.Step 9 Run LineGauge. Select Microstrip in the listbox. Select Length Unit = mil. Enter the Frequency = 3 GHz, Relative Permittivity = 9.9, Substrate Height h = 10 mils, Strip Thickness

30、= 0.1. Then, enter Key Electrical Parameters as: Zc = 50 and Electrical Length = 30 degrees. Select the button Electrical-Physical Parameters. LineGauge will calculate the physical parameters based upon the common parameters and the electrical parameters and yields the Strip Width =9.49 mils and the

31、 Length = 128 mils (see Figure 10.4). The 30-degrees (or 128 mils) is an arbitrarily chosen and it is not critical. We will add a 50-mil-long section of transmission line to each end.Figure 10.4 The LineGauge window.Section 4. Connecting Objects on Ie3dLibrary.Step 1 Please select Edit-Basic Paramet

32、ers dialog. Please make sure the length unit is “mil”. It is possible the Ie3dLibrary layout may not use the same length dimension as the FilterSyn module. Step 2 On Ie3dLibrary, select Insert-Strip Objects. You will see a sub-menu with more than 10 menu items comes up. Each menu item corresponds to a parameterized object of pre-defined shape. Please select Insert-Strip Objects-Straight Strip command. The dialog for Straight Strip object comes up (see Figure 10.5). Enter Length = 50 mils and the Width = 9.49 mils. Select the Z = 10 mils. There is a parameter for Strip Type. It defin