Detailed Presentation on Momentum - Part 1 of 3
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Agilent EEsof EDA Detailed Presentation on Momentum - Part 1 of 3 This document is owned by Agilent Technologies, but is no longer kept current and may contain obsolete or inaccurate references. We regret any inconvenience this may cause. For the latest information on Agilent’s line of EEsof electronic design automation (EDA) products and services, please go to: www.agilent.com/find/eesof Using Momentum Solution process • Select Mode • Substrate definition • Port Setup • Mesh Generation • Planar Solve • Enable regular Momentum or Momentum RF • Display Results • Define Substrate and Metallization (pre-compute option) • Modify the type and impedance of ports • Describe a possible Substrate enclosure • Create/modify Momentum Component to be used in EM/circuit co-simulation or co-optimization • Define Mesh parameters (pre-compute option) •Setup and Perform a Momentum simulation (planar solve) • Setup and Perform a Momentum optimization (geometric perturbation based) • Display Visualization (S-parameters, current density, transmission line parameters) and Radiation patterns • Export 3D files for HFSS Momentum Seminar momentum_01_02 Page 1 Using Momentum: Selecting the Analysis Mode Click this submenu to toggle the analysis mode • Solution process • Select Mode • Momentum MomentumRF • MomentumRF Momentum • Substrate definition • Port Setup • Mesh Generation • Planar Solve • Display Results Momentum Seminar momentum_01_02 Page 2 Momentum versus MomentumRF: A Snapshot Momentum features: Momentum RF features: • Full-Wave EM Simulation • Quasi-Static EM Simulation • Rooftop Basis Function • Star/Loop Basis Functions • Rectangular and Triangular Cells • Polygonal cells • For most passive geometry • Best for geometrically complex designs • Full accuracy for all circuit sizes • For electrically small designs (≤ λ/2) • No inherent upper frequency limit • Upper frequency depends on size • Potential instability at f <kHz to MHz • Results stable down to DC • Port Calibration • Port Calibration • Box and Waveguide inclusion • No Box / Waveguide Modes • Includes all radiation modes • For designs that don’t radiate • Display 2D and 3D Radiation Patterns • No Radiation Patterns • Great for 1st pass results, even for large designs (> λ/2) • Simulation time and memory decrease by ~10X-25X Momentum Seminar momentum_01_02 Page 3 Momentum versus MomentumRF Electrically Small condition for Momentum RF… How do I know? Status window provides rule of thumb frequency for which the structure is “electrically small” D ≤ λ/2 Momentum Seminar momentum_01_02 Page 4 Momentum versus MomentumRF Planar EM Simulation Basics Physical Design • Substrate • Metallization • Ports Method of Moments • Meshing • Rooftop functions B2(r) B1(r) I1 I2 B3(r) I3 λ/10 Hey…where did this equation come from? Momentum Seminar J(r) = I1B1(r) + I2B2(r) + I3B3(r) momentum_01_02 Page 5 Maxwell’s Equations ∇×E = -･B/･t ∇×H = J + ･D/･t ∇·D = ρ ∇·B = 0 Faraday’s Law Ampere’s Law Gauss’s Law No Name (Gauss’s Law for Magnetism) where E = Electric Field Intensity Vector H = Magnetic Field Intensity Vector D = Electric Flux Density (Electric Displacement Vector) B = Magnetic Flux Density Vector James C. Maxwell If one then transforms these equations to the integral form, the mixed potential integral equation in very general form as a linear integral operator equation follows: Here, J(r) represents the unknown surface currents and E(r) the known excitation of the problem. The Green's dyadic of the layered medium acts as the integral kernel. The unknown surface currents are discretized by meshing the planar metallization patterns and applying an expansion in a finite number of subsectional basis functions B1(r), ..., BN(r): Ohhhh…sorry I asked. Momentum Seminar momentum_01_02 Page 6 Momentum versus MomentumRF Planar EM Simulation Basics Method of Moments B1(r) I1 Maxwell’s Equations [Z].[I]=[V] I1 Equivalent Circuit [Z] = [R] + jω[L] + 1/jω Momentum Seminar I2 ≤λ/10 Matrix Equation [C]-1 L11 C11 B3(r) B2(r) L12 L13 I2 R22 L22 I3 L23 I3 L33 C22 C12 momentum_01_02 Page 7 Momentum versus MomentumRF Fullwave versus Quasi-Static: Fullwave 1 e − jkR R Fullwave EM Maxwell’s Equations •Fullwave electric & magnetic Green’s functions Matrix Equation •Includes space and surface radiation [Z].[I]=[V] •[L(w)] & [C(w)] are complex and frequency dependent •[Z(w)] matrix reload CPU intensive Equivalent Circuit [Z] = [R] + jω[L(ω)] + 1/jω [C(ω)]-1 [S] Momentum Seminar momentum_01_02 Page 8 Momentum versus MomentumRF Fullwave versus Quasi-Static: Quasi-Static Quasi-Static EM 1 e − jkR R ≈ R1 (1 − jkR + ...) Maxwell’s Equations •Electro- and magneto-static Green’s functions Matrix Equation [Zo].[I]=[V] •Near field / low freq approximation L(w) = L0 + L1wR + L2(wR)2 + … C(w) = C0 + C1wR + C2(wR)2 + … Equivalent Circuit [Zo] = [R] + jω[Lo] + 1/jω [Co]-1 [S] Momentum Seminar • Neglects far field radiation • [L0] & [C0] are real and frequency independent • [Z0] matrix reload very fast momentum_01_02 Page 9 Momentum versus MomentumRF A Summary of Effects Included Layout DC Spice Spice model Momentum RF Momentum MW S parameters S parameters RF MW • quasi-static inductance . . . . . . • quasi-static capacitance . . . . . • DC conductor loss (s) . . . . . . . . • DC substrate loss (s) . . . . . . . . • dielectric loss (tan d) . . . . . . . . . . . . . . . . . . . . . . . . . . . • skin effect loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • substrate wave radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • space wave radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Momentum Seminar momentum_01_02 Page 10 Using Momentum: Creating Substrate Stack-ups and Mapping Layout Layers as Metallization Layers • Solution process • Select Mode • Substrate definition • Port Setup • Mesh Generation • Planar Solve • Display Results Momentum Seminar momentum_01_02 Page 11 Using Momentum: Creating Substrate Stack-ups and Mapping Layout Layers as Metallization Layers Once you have created or imported your artwork… Momentum Seminar momentum_01_02 Page 12 Using Momentum: Creating Substrate Stack-ups and Mapping Layout Layers as Metallization Layers …be sure to define (or open) your substrate stack-up and map the metallization layers Momentum Seminar momentum_01_02 Page 13 Using Momentum: Creating Substrate Stack-ups and Mapping Layout Layers as Metallization Layers Greens Function Substrate Calculation Time Student’s Guide A-36 Momentum Seminar momentum_01_02 Page 14 Using Momentum: Creating Substrate Stack-ups and Mapping Layout Layers as Metallization Layers A note on layout layer conductivity Conductivity defined as: • Perfect Conductor (lossless) • σ (Real, Imaginary) • σ (Real, thickness) • Impedance (Real, Imaginary) The parameters selected are applied toward a conductor loss algorithm, this does NOT affect the layout thickness Momentum Seminar momentum_01_02 Page 15 Using Momentum: Creating Substrate Stack-ups and Mapping Layout Layers as Metallization Layers: Loss Model used in Strip Conductors • Momentum treats all conductors as having zero thickness. However, the conductivity and thickness can be specified to approximate frequency dependent losses in the metallization patterns. • Momentum uses a complex surface impedance for all metals that is a function of conductor thickness, conductivity, and frequency. • At low frequencies, current flow will be approximately uniformly distributed across the thickness of the metal. Momentum uses this minimum resistance and an appropriate internal inductance to form the complex surface impedance. • At high frequencies, the current flow is dominantly on the outside of the conductor and Momentum uses a complex surface impedance that closely approximates this skin effect. • At intermediate frequencies, where metal thickness is between approximately two and ten skin depths, the surface impedance transitions between those two limiting behaviors. • This surface impedance is added to the Method of Moments approach that is used for Momentum in general. • The formula used is a combination of a high-frequency conductivity and a low-frequency bulk resistivity. The formula is such that both approaches (LF bulk behavior HF surface impedance) transition seamlessly. • The formula is: • Z = coth(γ) * Zc •where Zc = the HF impedance and coth(γ) is the correction for finite thickness • Zc = 0.5 * sqrt(j * µ0 * ω/(σ + j * ε0 * ω )) • γ = 0.5 * thickness * sqrt(j * µ0 * ω * (σ + j * ε0 * ω)) •where ω = 2 * π * f •and σ = conductivity = 1/resistivity [in Siemens/meter] We will examine a “thick conductor” method later in this seminar • The meshing density can affect the simulated behavior of a structure. A more dense mesh allows current flow to be better represented and can slightly increase the loss. This is because a more uniform distribution of current for a low density mesh corresponds to a lower resistance Momentum Seminar momentum_01_02 Page 16 Using Momentum • Solution process • Select Mode • Substrate definition • Port Setup • Mesh Generation • Planar Solve • Display Results Momentum Seminar momentum_01_02 Page 17 Placing and Defining Ports Considerations Keep the following points in mind when adding ports to circuits to be simulated using Momentum: • The components or shapes that ports are connected to must be on layout layers that are mapped to metallization layers that are defined as strips or slots. Ports cannot be directly connected to vias. • Make sure that ports on edges are positioned so that the arrow is outside of the object, pointing inwards, and at a straight angle. • Make sure that the port and the object you are connecting it to are on the same layout layer. For convenience, you can set the entry layer to this layer; the Entry Layer listbox is on the Layout tool bar. • A port must be applied to an object. If a port is applied in open space so that is not connected to an object, Momentum will automatically snap the port to the edge of the closest object. This will not be apparent from the layout, however, because the position of the port will not change. • If the Layout resolution is changed after adding ports that are snapped to edges, you must delete the ports and add them again. The resolution change makes it unclear to which edges the ports are snapped, causing errors in mesh calculations. Note Do not use the ground port component (Component > Ground) in circuits that will be simulated using Momentum. Either add ground planes to the substrate or use the ground reference ports. (Ground port component toolbar button: Momentum Seminar ) momentum_01_02 Page 18 Placing and Defining Ports Description of Momentum Port Types Placement Type of layer Edge Strip or Slot Edge or Surface Strip Two ports with opposite polarity Edge Strip • Coplanar Two ports with opposite polarity Edge Slots • Common Mode Two ports with the same polarity Edge Strip • Ground Ref. An explicit ground reference for a Single or Internal port. Edge or Surface Strip Port Type General Description • Single (default) Calibrated to remove mismatch at port boundary (might also call this a transmission line port) •Internal Not calibrated (might also call this a direct excitation port) • Differential CPW NOTE: For finite ground planes, use Ground Reference ports and Internal port on center conductor. Momentum Seminar momentum_01_02 Page 19 Placing and Defining Ports Single Port Properties • It is connected to an object that is on either a strip or slot metallization layer. • It can be applied only to the edge of an object. • The port is external and calibrated. The port is excited using a calibration process that removes any undesired reactive effects of the port excitations (mode mismatch) at the port boundary. This is performed by extending the port boundary with a half-wavelength calibration (transmission) line. The frequency wavelength selected during the mesh or simulation process is used to calculate the length of the calibration line. For more information about the calibration process, refer to "Calibration and De-embedding of the S-parameters" on page A-7 in the Momentum manual. • The port boundary can be moved into or away from the geometry by specifying a reference offset. S-parameters will be calculated as if the port were at this position. • When two or more single ports are on the same reference plane, coupling effects caused by parasitics affects the S-parameters. The calibration process groups the ports so that any coupling in the calibration arms is included in the S-parameter solution. • If the port is connected to an object on a strip layer, the substrate definition must include at least one infinite metal layer: a top cover, ground plane, or a slot layer, or a ground reference must be used in addition to the port. • If the port is connected to an object that is on a slot layer, the port has polarity. Tip It is not necessary to open the Port Editor dialog box to assign this port type. Any port without a port type specified is assumed to be a single port. Momentum Seminar momentum_01_02 Page 20 Placing and Defining Ports Defining a Single Port • Choose Momentum > Port Editor. • Select the port that you want to assign this type to. • In the Port Editor dialog box, under Port Type, select Single. • Enter the components of the port impedance in the Real and Imaginary fields, and specify the units. • You can shift the port boundary, also referred to as the port reference plane. Shifting the boundary enables a type of de-embedding process that effectively adds or subtracts electrical length from the circuit, based on the characteristic impedance and propagation characteristic of the port. Enter the offset in the Reference Offset field, and select the units. A positive value moves the port boundary into the circuit, a negative value moves the port boundary away from the circuit. • Click Apply to add the definition to the port. Momentum Seminar momentum_01_02 Page 21 Placing and Defining Ports Single Port: Avoiding Overlap (of calibration arm) Be aware that when using single ports, the calibration arm applied to a port may be long enough to overlap another element in the circuit. In this case, the port will be changed to an internal port type, and no calibration will be performed on it. If this occurs, a message will be displayed during simulation in the Status window indicating the change. Momentum Seminar momentum_01_02 Page 22 Placing and Defining Ports Single Port: Applying Reference Offsets Reference offsets enable you to reposition single port types in a layout and thereby adjust electrical lengths in a layout, without changing the actual drawing. S-parameters are returned as if the ports were placed at the position of the reference offset. Why Use Reference Offsets? The need to adjust the position of ports in a layout is analogous to the need to eliminate the effect of probes when measuring hardware prototypes. When hardware prototypes are measured, probes are connected to the input and output leads of the Device Under Test (DUT). These probes feed energy to the DUT, and measure the response of the circuit. Unfortunately, the measured response characterizes the entire setup, that is, the DUT plus the probes. This is an unwanted effect. The final measurements should reflect the characteristics of the DUT alone. The characteristics of the probes are well known, so measurement labs can mathematically eliminate the effects of the probes, and present the correct measurements of the DUT. There are significant resemblances between this hardware measurement process and the way Momentum operates. In the case of Momentum, the probes are replaced by ports, which, during simulation, will feed energy to the circuit and measure its response. The Momentum port feeding scheme also has its own, unwanted effect: low-order mode mismatch at the port's boundary, although this is eliminated by the calibration process. However, in order for this calibration process to work well, it is necessary that the fundamental mode is characterized accurately. This can only be accomplished when the distance between the port boundary and the first discontinuity is sufficiently large, that is, there exists a feedline that is long enough to provide this distance. Momentum Seminar momentum_01_02 Page 23 Placing and Defining Ports Single Port: Allowing for Coupling Effects If you have two or more single ports that lie on the same reference plane, the calibration process will take into account the coupling caused by parasitics that naturally occurs between these ports. This yields simulation results that more accurately reflect the behavior of an actual circuit. The figure below helps illustrate which ports will be grouped in order for the calibration process to account for coupling among the ports. In this setup, only the first two ports will be grouped, since the third port is an internal port type and the fourth port is on a different reference plane. Note that even though the second port has a reference offset assigned to it, for this process they are considered to be on the same plane and their reference offsets will be made equal. If you do not want the ports to be grouped, you must add a small thickness of metal to the edge of the object that one of the ports is connected to. The ports will no longer be on the same plane, and will not be considered part of the same group. Momentum Seminar momentum_01_02 Page 24 Placing and Defining Ports Internal Port Properties • Internal ports enable you to apply a port to the surface of an object in your design. By using internal ports, all of the physical connections in a circuit can be represented, so your simulation can take into account all of the EM coupling effects that will occur among ports in the circuit. These coupling effects caused by parasitics are included in your simulation results because internal ports are not calibrated. • You should avoid geometries that allow coupling between single and internal ports to prevent incorrect Sparameters. • An example of where an internal port is useful is to simulate a bond wire on the surface on an object. Another example of where an internal port is necessary is a circuit that consists of transmission lines that connect to a device, such as a transistor or a chip capacitor, but this device is not part of the circuit that you are simulating. An internal port can be placed at the connection point, so even though the device is not part of the circuit you are simulating, the coupling effects that occur among the ports and around the device will be included in your simulation. • Internal ports are often used in conjunction with ground references. Momentum Seminar momentum_01_02 Page 25 Placing and Defining Ports Internal Port Properties • • • • It can be applied to the interior of a circuit by applying it to the surface of an object. It can be applied to the edge of an object. It can be applied to objects that are on strip layers only. The orientation of the port is not considered if it is on the surface of an object. (For a description of port orientation, refer to "Adding a Port to a Layout" on page B-5 in the Momentum manual.) • No calibration is performed on the port. Because no calibration is performed on the port, the results will not be as accurate as with a single port. However, the difference in accuracy is small. Defining an Internal Port •Choose Momentum > Port Editor. •Select the port that you want to assign this type to. •Click Apply. Momentum Seminar momentum_01_02 Page 26 Placing and Defining Ports Illustration of Internal Port Excitation: Direct Point Feed direct excitation point feed Momentum Seminar momentum_01_02 Page 27 Placing and Defining Ports Illustration of Internal Port Excitation: Direct Line/Edge Feed direct excitation line feed Momentum Seminar momentum_01_02 Page 28 Placing and Defining Ports Differential Port Properties Differential ports should be used in situations where an electric field is likely to build up between two ports (odd modes propagate). This can occur when: • The two ports are close together • There is no ground plane in the circuit or the ground plane is relatively far away • One port behaves (to a degree) like a ground to the other port, and polarity between the ports is developed. • The ports are connected to objects that are on strip metallization layers. • The electric field that builds up between the two ports will have an effect on the circuit that should be taken into account during a simulation. To do this, use differential ports. Differential ports have the following properties: • They can be applied to objects on strip layers only. • They are assigned in pairs, and each pair is assigned a single port number. • Each of the two ports is excited with the same absolute potential, but with the opposite polarity. The voltages are opposite (180 degrees out of phase). The currents are equal but opposite in direction when the ports are on two symmetrical lines, and the current direction is approximated for other configurations. • The two ports must be on the same reference plane. Momentum Seminar momentum_01_02 Page 29 Placing and Defining Ports Differential Port Numbering Note: Port numbers for differential ports are treated in the following manner: on the layout, you will continue to see the port numbers (instance names) that were assigned to each port when they were added to the layout. Use the Momentum Port Editor dialog box to identify which pair of ports will be treated as a differential port. When Momentum simulates designs containing non-consecutive port numbers, the ports are remapped to consecutive numbers in the resulting data file. The lowest port number is remapped to 1, and remaining numbers are remapped in consecutive order. The port numbers are not changed in the design itself. A message in the Status window announces the change, and lists the mappings. For example, if you are simulating a design with ports numbered 1 and 3, the following status message informs you of the changes: Layout has non-consecutive port numbers. Output files will have consecutive port numbers. layout port -> output port 1 -> 1 3 -> 2 Also, when you view results, you will see S-parameters for the differential port numbers. In the example above, the layout would show p1, p2, p3, p4. The S-parameter results will be for combinations of the original P1 and P3 only. Momentum Seminar momentum_01_02 Page 30 Placing and Defining Ports Defining a Differential Port • Choose Momentum > Port Editor. • Select the port that you want to assign this type to. Note the port number. • In the Port Editor dialog box, under Port Type, select Differential. • Under Polarity, make sure that Normal is selected. • Click Apply. • Select the second port. • In the Port Editor dialog box, under Port Type, select Differential. • Under Polarity, select Reversed. • Under Associate with port number, enter the number of the previously-selected port. • Click Apply. • Repeat these steps for other differential port pairs in the circuit. • Click OK to dismiss the dialog box. Momentum Seminar momentum_01_02 Page 31 Placing and Defining Ports Illustration of Differential Port Excitation: Direct Point Feed 1.i direct excitationn line feed -1.i line feed ground reference Student’s Guide A-32 Momentum Seminar momentum_01_02 Page 32 Placing and Defining Ports Coplanar Port Properties This type of port is used specifically for coplanar waveguide (CPW) circuits. It is similar to a differential port, but coplanar ports are applied to objects on slot layers (that is, where slots are used in the design). Coplanar ports should be used in situations where an electric field is likely to build up between two ports. This can occur when: • The two ports are close together • Polarity between the ports develops • The ports are connected to objects that are on slot metallization layers • The electric field that builds up between the two ports will have an effect on the circuit that should be taken into account during a simulation. To do this, use coplanar ports. Coplanar ports have the following properties: • They can be applied to objects on slot layers only. • They are assigned in pairs. • Each of the two ports is excited with the same absolute potential, but with the opposite polarity. The voltages are opposite (180 degrees out of phase). The currents are equal but opposite in direction when the ports are on two symmetrical lines, and the current direction is approximated for other configurations. • The two ports must be on the same reference plane. Momentum Seminar momentum_01_02 Page 33 Placing and Defining Ports Coplanar Port Polarity Be careful when assigning polarity to coplanar ports. An incorrect choice of polarity can change the phase of transmission type S-parameters by 180 degrees. To verify polarity, zoom in on a coplanar port. You will notice two sets of arrows applied to the port. One appears when you add the port component to the circuit. The second will appear after the mesh is computed. It indicates the direction of the voltage over the slot. Momentum Seminar Note: Port numbers for CPW ports are treated similar to the manner in which differential ports are treated. momentum_01_02 Page 34 Placing and Defining Ports Defining a Coplanar Port Note • • • • • • • • • • • • Momentum Seminar Coplanar ports can be applied to objects on slot layers only. Choose Momentum > Port Editor. Select the port that you want to assign this type to. Note the port number. In the Port Editor dialog box, under Port Type, select Coplanar. Under Polarity, make sure that Normal is selected. Click Apply. Select the second port. In the Port Editor dialog box, under Port Type, select Coplanar. Under Polarity, select Reversed. Under Associate with port number, enter the number of the previously-selected port. Click Apply. Repeat these steps for other differential port pairs in the circuit. Click OK to dismiss the dialog box. momentum_01_02 Page 35 Placing and Defining Ports Coplanar Port Example: examples/Momentum/Microwave/CPW_bend_prj Momentum Seminar momentum_01_02 Page 36 Placing and Defining Ports Coplanar Port Example: examples/Momentum/Microwave/CPW_bend_prj Momentum Seminar momentum_01_02 Page 37 Placing and Defining Ports Coplanar Port Example Momentum Seminar Note: Visualization displays the magnetic currents (not the electrical currents) for slot metallizations. Therefore, slots are visualized and not metal. momentum_01_02 Page 38 Placing and Defining Ports Common Mode Port Properties Note: Can also be utilized for “thick conductor” simulations (more on this later) Use common mode ports in designs where the polarity of fields is the same among two or more ports (even modes propagate). The associated ports are excited with the same absolute potential and are given the same port number. Common mode ports have the following properties: • They can be applied to objects on strip layers only • A ground plane or other infinite metal (such as a cover) is required as part of the design • Two or more ports can be associated • Associated ports are excited with the same absolute potential (and same polarity) • The ports must be on the same reference plane Note Port numbers for common ports are treated in the following manner: on the layout, you will continue to see the port numbers (instance names) that were assigned to each port when they were added to the layout. Use the Momentum Port Editor dialog box to identify which group of ports will be treated as a common port. Also, when you view results, you will see S-parameters for the common port numbers. In the example above, the layout would show p1, p2, p3. The S-parameter results will be for combinations of P1 only. Momentum Seminar momentum_01_02 Page 39 Placing and Defining Ports Defining a Common Mode Port • • • • • • • • • • Choose Momentum > Port Editor. Select the port that you want to assign this type to. Note the port number. In the Port Editor dialog box, under Port Type, select Common Mode. Click Apply. Select the second port. In the Port Editor dialog box, under Port Type, select Common Mode. Under Associate with port number, enter the number of the port that you selected first. Make sure that the value in the Associate with port number field is the same for additional ports. For example, if you were associating three ports and the first port was assigned as port 1, for the second and third port, the value entered into the Associate with port number field would be 1. (For the first port you choose, no value is entered in this field.) Click Apply. Repeat these steps for other common mode ports in the circuit. Click OK to dismiss the dialog box. Momentum Seminar momentum_01_02 Page 40 Placing and Defining Ports Ground Reference Port Ground references enable you to add explicit ground references to a circuit, which may be necessary if implicit grounds are in your design. Implicit ground is the potential at infinity, and it is made available to the circuit through the closest infinite metal layer of the substrate. Implicit grounds are used with internal ports and with single ports that are connected to objects on strip metallization layers. There are instances where the distance between a port and its implicit ground is too large electrically, or there are no infinite metal layers defined in the substrate. In these cases, you need to add explicit ground references to ensure accurate simulation results. For more information on using ground references, refer to "Simulating with Internal Ports and Ground References" on page A-10 in the Momentum manual. You can apply ground references to the surfaces of object. The object must be on strip metallization layers. Note: Multiple ground reference ports can be associated with the same port. To be associated with a single port, the ground reference port should be a port attached to an edge of an object in the same reference plane as the single port. Momentum Seminar momentum_01_02 Page 41 Placing and Defining Ports Defining a Ground Reference Port • Choose Momentum > Port Editor. • Select the port that you want to assign as the ground reference. • In the Port Editor dialog box, under Port Type, select Ground Reference. • Under Associate with port number, enter the number of the single or internal port that you want to associate with this ground reference. Make sure that the distance between the port and ground reference is electrically small. • Click Apply. Momentum Seminar momentum_01_02 Page 42 Placing and Defining Ports CPW with Finite Ground Planes using INTERNAL and GROUND REF ports • Ports 1 and 2 are internal. • Ports 3, 4, 5, and 6 are ground reference . The grounds are associated with the internal port using the editor. Momentum Seminar momentum_01_02 Page 43 Placing and Defining Ports Remapping Port Numbers Some designs contain non-consecutive port numbers. This results in simulation data files that are difficult to use. When Momentum simulates designs containing non-consecutive port numbers, the ports are remapped to consecutive numbers in the resulting data file. The lowest port number is remapped to 1, and remaining numbers are remapped in consecutive order. The port numbers are not changed in the design itself. A message in the Status window announces the change, and lists the mappings. For example, if you are simulating a design with ports numbered 37 and 101, the following status message informs you of the changes: Layout has non-consecutive port numbers. Output files will have consecutive port numbers. layout port -> output port 37 -> 1 101 -> 2 Port number remapping is done only for sampled and AFS CITIfiles and their corresponding S-parameter datasets. It is not done for Visualization and far field files. The remapping is done at the CITIfile level, and propagates to the dataset file. After remapping, all datasets are in sync with the new port numbering. Momentum Seminar momentum_01_02 Page 44 For more information about Agilent EEsof EDA, visit: Agilent Email Updates www.agilent.com/find/emailupdates www.agilent.com/find/eesof Get the latest information on the products and applications you select. www.agilent.com For more information on Agilent Technologies’ products, applications or services, please contact your local Agilent office. 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