Outline. Darren Wang ADS Momentum P2

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2 Outline Momentum Basics: Microstrip Meander Line Momentum RF Mode: RFIC Launch Designing with Momentum: Via Fed Patch Antenna Momentum Techniques: 3dB Splitter Look-alike Momentum Optimization: 3 GHz Band Reject Filter Advanced Topic: Coplanar Waveguide Inductor EM simulation Darren Wang ADS Momentum P2

3 Objectives Know the use model Momentum with ADS. Determine which circuits are best solved by Momentum. Compare Momentum to Momentum RF. Understand how the Momentum. Use Momentum examples. Simulation procedure. Note on using ADS: it is recommended that you know the basics of using ADS for S-Parameter simulation. However, if you are new to ADS, this course will provide enough basic instructions for you to successful Darren Wang ADS Momentum P3

4 Who is Momentum? 2.5D (vias) simulation tool for passive circuits. Motif style interface (connects to ADS). Layout driven (accepts arbitrary geometry). Method of Moments technique as planar solver. Green s functions used to solve integral equations. Unlimited substrate database for computation. Full microwave or RF mode S-Parameter solutions. Layout look-alike components for ADS simulation. Co-simulation with ADS and optimization. Visualization of current and far-field patterns. Darren Wang ADS Momentum P4

5 When should you use Momentum When no analytical model exists- co-simulate with ADS. Arbitrary geometry on a uniform planar substrate. To determine coupling effects-thin layers and close proximity of metal. To find narrow resonances not found using analytical-based models. To display radiation patterns To display current patterns and density. plot far-fields (antennas, etc.) For CPW: coplanar waveguide results with no slot mode. When 3D solvers take too long or are not required. To optimize (modify geometry) a passive layout to achieve desired results. Momentum has two modes: a regular mode and an RF mode! Darren Wang ADS Momentum P5

6 Method of Moments Method of Moments Maxwell s Equations Matrix Equation [Z][I]= [V] Equivalent Circuit [Z]= [R]+ j [L]+ 1/j [C] -1 Darren Wang ADS Momentum P6

7 How Momentum-Microwave Works-1 Mesh strips, vias, slots with rectangles and triangles. (arbitrary surface mesh) Model surface current in each current cell.( linear distribution) Solve matrix of unknown surface current coefficients. Calculate S-parameters. [Z][I]= [V] [S] Darren Wang ADS Momentum P7

8 How Momentum-Microwave Works-2 Fullwave EM Maxwell s Equations Matrix Equation [Z][I]= [V] Fullwave electric & magnetic Green s functions. includes space and surface radiation. L(w)&C(w) are complex and frequency dependent Z(w) matrix reload CPU intensive. Equivalent Circuit [Z]= [R]+ j [L]+ 1/j [C] -1 [S] Darren Wang ADS Momentum P8

9 How Momentum-RF works -1 Mesh strips, vias, slots with rectangles and triangles. (arbitrary surface mesh) Perform mesh reduction while maintaining integrity of solution. Model surface current in each current cell.( linear distribution) Solve matrix of unknown surface current coefficients. Calculate S-parameters. Darren Wang ADS Momentum P9

10 How Momentum-RF works -2 Quasi-static EM Maxwell s Equations Matrix Equation [Z][I]= [V] Equivalent Circuit [Z]= [R]+ j [L 0 ]+ 1/j [C 0 ] -1 Electro & magneto-static Green s functions. Near field / low freq approximation L (w) = L 0 + L 1 R +L 2 ( R) 2 + C(w) = C 0 + C 1 R +C 2 ( R) 2 + Neglects far field radiation L 0 & C 0 are real and frequency independent. Z(w) matrix reload very fast. [S] Darren Wang ADS Momentum P10

11 Comparison of RF mode to Microwave mode DC 200 GHz Darren Wang ADS Momentum P11

12 Spice, Mom & MomRF Model differences SPICE Momentum RF Momentum MW Spice model S parameters RF mode S parameters MW mode Quasi-static inductance Quasi-static capacitance DC conductor loss (s) DC substrate loss (s) dielectric loss (tgd) skin effect loss substrate wave radiation space wave radiation Darren Wang ADS Momentum P12

13 Overview of the Momentum process Start here: or Start here: * Substrate is computed in Momentum or Can be read from a pre-computed database. ADS interface 1a) Schematic with artwork 1b) Layout artwork MOM interface 2) Define the substrate* 3) Mesh and solve 4) Display Results Mag. [db] S Frequency Darren Wang ADS Momentum P13

14 Example Microstrip line in ADS schematic is transferred to ADS layout for Momentum solution Required Port Schematic components must have artwork that can transfer to layout. If not, draw the geometry or import The artwork into ADS layout. Darren Wang ADS Momentum P14

15 Momentum begins in the ADS layout window Momentum Menu File > Import Microstrip geometry with ports, generated from schematic or can be drawn in layout. more Darren Wang ADS Momentum P15

16 ADS Layout: drawing and layer features 1.Drawing icons Entry Layers POP-UP. Note: Do not use default layer 0 not recognized in momentum Specify the entry layer before drawing strips and slots for momentum. However some layers are reserved for momentum. Darren Wang ADS Momentum P16

17 ADS layout: drawing and layer features Ports for Momentum Snap Modes Use Traces (Pins) and paths (no pins). Darren Wang ADS Momentum P17

18 Momentum Menu commands in the layout window Enable regular Momentum or Momentum RF. Substrate layer and metal/slot/via layer definitions. Port type and impedance settings. Substrate enclosures can be described. Layout component look-alike for schematic. Mesh patterns defined and cleared. Simulation s-parameter setups, including datasets. Optimization setup by parameterizing the layout. Visualize currents and radiation patterns. Save files for use in a 3D tool. Next, some details on substrates Darren Wang ADS Momentum P18

19 Momentum requires these 2 layers definitions Substrate Layers Metallization Layers Strip (metal) or slot (located at the interface of two substrates) Strip (metal) or slot Via extends through substrate Substrate layers can be read from schematic or define in the Substrate Editor (Next slide). Darren Wang ADS Momentum P19

20 Substrate Editor: Substrate Layers tab Update From schematic Means that the MSUB definition is copied from ADS schematic. Next, you define the Metallization (drawing layers) Darren Wang ADS Momentum P20

21 Substrate Editor: Metallization Layers tab 1) Select the Substrate interface -- and then select the layout drawing layer (metal drawing layer). 2) Specify Strip or slot between 2 interfaces or a Via through a substrate layer. After defining the layers, use: Substrate > Precompute. If the definition has already been computed, Momentum will find it in the database. If not, it will compute it. Darren Wang ADS Momentum P21

22 Define the Mesh pattern Global mesh is the default, with default setting. But you have choices. In general, small patterns are more accurate but take more time to solve. Mesh reduction: converts some rectangles and triangles to polygons for fewer currents to solve. Darren Wang ADS Momentum P22

23 Global mesh example with edge mesh 1 - Port 2 - Calibration Line 3 - Mesh 4 Edge Mesh Here, the cell size is the same for all parts of the geometry, except for the edges around each primitive. 3 4 The calibration line Is automatically drawn when the port is defined more on this later. 2 1 Note: you can view the mesh, ports, and reference line before simulating and make adjustments if desired. Darren Wang ADS Momentum P23

24 Primitive mesh example The center primitive of this geometry has a different mesh density (50 cells/wavelength) than the two outside geometries (20 cells/wavelength) 2 1 Darren Wang ADS Momentum P24

25 Port Editor: define port types (Properties) First, you select the port and then you define its properties: Single port (default) is attached to the edge and the calibration reference plane is drawn parallel to the edge Port connector icon in schematic or layout is used to add ports. Darren Wang ADS Momentum P25

26 Summary of port types Darren Wang ADS Momentum P26

27 Simulation control: S-parameters To set up a simulation: choose the sweep type and enter the values. Dataset name can be specified. Default is layout name_mom. Also, data display can automatically open with all S- parameters plotted if box is checked. Darren Wang ADS Momentum P27

28 The momentum solution process Substrate Calculator Green s Function Mesh Generator Planar Solver 2 5 Substrate Database (Archive) S-parameters (ADS dataset) Darren Wang ADS Momentum P28

29 Simulation results: ADS Data Display window Data display window can be automatically named Dataset name: a refers to adaptive AFS. Mag and phase plots for all S-parameters automatically plotted if the box is checked in the simulation control. Or you can open a data display window and plot selected data. You will practice this in the lab exercises. Darren Wang ADS Momentum P29

30 Layout look-alike components for ADS schematics Layout look-alike component created and inserted in ADS schematic. ADS simulation runs Momentum or component can be pre-solved. Inserted look-alike component from ADS library. Parameters Specify how the component can be modified for ADS optimization from schematic. Dataset is created for use by ADS simulator. Darren Wang ADS Momentum P30

31 Using ADS Momentum Examples Click the Examples Icon Each project has numerous designs with solutions. Copy the project into your directory and use it for your design! Spiral Examples Darren Wang ADS Momentum P31

32 Example: spiral inductor with via and hole in ground Purpose of the hole in the ground plane is to reduce capacitance of the inductor to ground. Port1 and port2 are on different layers. Darren Wang ADS Momentum P32

33 Review Simulation procedure 1. Create a physical design 2. Choose Momentum or Momentum RF mode 3. Define the substrate characteristics 4. Solve the substrate (optional) 5. Assign port properties 6. Add a box or a waveguide (optional) 7. Set up and generate a circuit mesh 8. Simulate the circuit 9. View the result Darren Wang ADS Momentum P33

34 1.Create a physical design Physical design created in schematic window: spliter Layout representation Darren Wang ADS Momentum P34

35 2. Momentum or Momentum RF mode Momentum Momentum RF Click here to switch the mode Darren Wang ADS Momentum P35

36 3.Define the substrate characteristic Set substrate Layers here Properties of the selected layer Darren Wang ADS Momentum P36

37 4.Define the substrate characteristics Set Metallization Layers here Darren Wang ADS Momentum P37

38 5.Solve the substrate (Optional) Optional: because the substrate will computed during the simulation if not computed. Choose the frequency a Momentum simulation. Not Needed for a Momentum RF simulation. Darren Wang ADS Momentum P38

39 6. Assign port properties 5 types of ports: - single - internal - Differential - Common mode - Ground reference Darren Wang ADS Momentum P39

40 7. Set up mesh Momentum> Mesh> setup Mesh frequency The number of cells per wavelength Arc Facet Angle Enable appropriate mode: - Edge Mesh - Transmission Line Mesh - Thin Layer overlap extraction Darren Wang ADS Momentum P40

41 8.Generate mesh Enter the frequency you want to use for pre-computation of the mesh The wavelength of this frequency will, in part, determine the number of cells in the mesh Darren Wang ADS Momentum P41

42 9. Simulate the circuit Momentum > Simulation > S-parameters 1. Select the sweep type and the frequency range 3. Click on apply then on simulate 2. Click on Add to frequency Plan List Darren Wang ADS Momentum P42

43 10.View the results Display window Notice the name: mom_spliter _a in mom_spliter_a means the results are taken from the adaptive simulation. Darren Wang ADS Momentum P43

44 Time to do the lab exercise! Lab 1: Momentum Basic: Microstrip Meander Line Lab 2: Momentum RF Mode: RFIC Launch Lab 3: Designing with Momentum: Via-fed Patch Antenna Lab 4: Momentum Techniques: 3dB Splitter Darren Wang ADS Momentum P44

45 Lab 1: Microstrip meander line Start ADS Copy the training project Create the layout Examine the Substrate Examine Port setup Set layer fill View the mesh Run the adaptive simulation View the default data plots Plot the S-21 data S Mag. [db] Frequency Darren Wang ADS Momentum P45

46 On-line Help and Examples On-line ADS Help: -Momentum: Help > Topic and index (F1) Manuals > Simulation > Momentum -Layout: Help > Topic and index (F1) Manuals > Design and Display > Momentum -Search: Help > Topic and index (F1) > Search Examples: -At ADS main menu: View > Example Directory > Momentum > Tools > Example Search Darren Wang ADS Momentum P46

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