Go to www.awrcorp.com
Back to search page Click to download printable version of this guide.

Homogeneous Stratified Substrate Definition: PCSUB

Symbol

Summary

PCSUB provides stratified homogeneous substrate definition used either for stripline (optional cover present) or microstrip (no cover) PCnCLIN, PC1LIN schematic elements. Substrate may be elevated over the infinite backing ground plate, thus providing suspended substrate. All layers may have arbitrary height and are made of the same material. Each layer may carry any number of conductors. All conductor on the same layer have the same thickness; thickness may vary between layers. The number of conductors is specified in the PCnCLIN model. In addition to metallic cover, PCSUB may define side perfectly conducting walls thus confining the whole structure into metallic box.

PCSUB models PCB (Printed Circuit Board) or LTCC/HTCC (Low/High Temperature Cofired Ceramic) substrate.

Topology

Open grounded substrate (no cover)

Open suspended substrate (no cover)

Covered grounded substrate

Covered suspended substrate

Parameters

Name Description Unit Type Default
N Number of substrate dielectric layers   1
Er Substrate relative dielectric constant   Er[1]
Tand Substrate loss tangent   0
H Heights of substrate layers (vector) Length H[2]
ErC Relative dielectric constants of layer adjacent to cover   1
TandC Loss tangent of layer adjacent to cover   0
HC Cover height over the substrate Length H[2]
HB Substrate elevation over the backing ground plane Length H[2]
T Conductors thicknesses (vector) Length T[2]
Rho Metal bulk resistivity relative to gold   1
Cover Switch "Metallic Cover" / "No Cover"/Metallic Box   "No Cover"
Gnd Switch "Suspended Substrate" / "Grounded Substrate"   "Grounded Substrate"
SW Separation of vertical metallic walls from extreme left/right conductors (optional) Length L[2]
Name Substrate name Text PCSUB1[2]

[1] User-modifiable default. Modify by editing under $DEFAULT_VALUES in the default.lpf file in the root installation directory. See “Nonlinear Oscillator Analysis” for details.

[2] Modify only if schematic contains multiple substrates. See “Using Elements With Model Blocks” for details.

Parameter Details

N. Number of dielectric layers that may carry conductors on their top surface. Layers are enumerated from top to bottom. Note that if switch parameter Cover is set to "Metallic Cover" the topmost layer adjacent to cover is not included in count; likewise, if switch parameter Gnd is set to "Suspended Substrate" the bottom air layer is not included in count.

Er. Relative dielectric constant is the same for all N layers.

Tand. Substrate loss tangent is the same for all N layers.

H. Heights of substrate layers are specified as values of vector H components. User can assign values to vector components via array of constants (or equation variables) on the corresponding parameter field (for example, {10,20,20,10}). The same assignment might be implemented in equation. Model PCnCLIN checks if the length of vector H is equal to the specified number of layers N.

ErC. If switch Cover is set to "Metallic Cover" this parameter specifies relative dielectric constant of a layer that adjoins the cover. If switch Cover is set to "No Cover" parameter ErC is not used.

TandC. If switch Cover is set to "Metallic Cover" this parameter specifies loss tangent of a layer that adjoins the cover. If switch Cover is set to "No Cover" parameter TandC is not used.

HC. Specification of height over the substrate HC is mandatory if switch Cover is set to "Metallic Cover". If switch Cover is set to "No Cover" parameter HC is not used.

HB. Specification of substrate elevation over the backing ground plane is mandatory if switch Gnd is set to "Suspended Substrate".If switch Gnd is set to "Grounded Substrate" parameter HB is not used.

T. Thicknesses of conductors for each layer are specified as values of vector T components. All conductors on the same layer have similar thickness. This thickness may vary between layers. Each dielectric layer must have corresponding entry in vector T even if this specific layer does not carry conductors. For example, if model PC1LIN (single line model) is used and number of layers is five, vector T must contain five entries no matter that only one entry corresponds to the layer that carries single conductor. All entries may be set to the same value. User can assign values to vector components via array of constants (or equation variables) on the corresponding parameter field (for example, {1,2.5,2,4}). The same assignment might be implemented in equation. Model PCnCLIN checks if the length of vector T is equal to the number of dielectric layers that may carry conductors (that is, N if switch Gnd is set to "Grounded Substrate" and N+1 if Gnd is set to "Suspended Substrate").

Rho. All conductors have the same metal bulk resistivity relative to gold Rho.

Cover. This switch can be set to one of three selections: "Metallic Cover", "No Cover", "Metallic Box." "Metallic Cover" provides a covered structure typical for striplines; HC, ErC, TandC are used. "No Cover" provides an open structure typical for microstrips; HC, ErC, TandC are not used. Selection "Metallic Cover" implies that layer immediately under the cover is excluded from layer count; material properties of this layer are defined via parameters ErC and TandC. Selection "Metallic Box" installs metallic cover (see above) and adds side metallic walls thus confining the whole structure into rectangular metallic box. Note that distance from the leftmost conductor to the left wall is always equal to the distance from the rightmost conductor to the right wall; this distance is set by parameter SW.

Gnd. This switch can be set to one of two selections: "Suspended Substrate" or "Grounded Substrate." "Suspended Substrate" provides an elevated structure typical for suspended substrates. Selection "Metallic Cover" implies that air layer adjacent to the ground plane is excluded from substrate layer count; material properties of this layer are defined inside the model. Nevertheless, this air layer potentially may carry conductors (obviously, conductors, if any, are affixed to the substrate but they stick out downwards and are recessed into the air layer) so suspended substrate uses HB and demands vector T to be of length N+1. "Grounded Substrate" places a backing ground plane back to back with substrate; in this case vector T has length N and HB is not used.

SW. Distance from the leftmost/rightmost conductor to the left/right wall. The parameter is used only if switch Cover is set to "Metallic Box." Model implies that structure sits symmetrically between side walls.

Implementation Details

Figures in Topology section demonstrate various implementations of PCSUB. Note that suspended substrate (parameter Gnd is set to "Suspended substrate") implies that layer N+1(air) is placed automatically under the layer N; grounded substrate (parameter Gnd is set to "Grounded substrate") implies that ground plane immediately backs layer N.

Covered substrate (parameter Cover is set to "Metallic Cover") implies that additional unnumbered layer (carrying cover) is automatically placed over layer 1. Material parameters of this layer must be set via parameters ErC and TandC.

Layout

This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.

Recommendations for Use

PCSUB must be either present on the schematics that contain elements using PCSUB or be placed in the Global Definitions window. In the latter case, models using a global definition of PCSUB must refer to it explicitly.

Elements Used with PCSUB

LINES
PCnCLIN
PC1LIN

Legal and Trademark Notice