MMTAPER models a segment of inhomogeneous microstrip line on multilayered substrate GMSUB. The width of microstrip tapers smoothly between ports. This model allows linear and exponential width tapers. The substrate may be suspended, covered by a metal cover, or placed into a metal enclosure.
MMTAPER$ is a Microstrip iCell and has no W1 or W2 parameters. See “Intelligent Cells (iCells)” for more information.
|W1||Conductor width @ node 1||Length||W|
|W2||Conductor width @ node 2||Length||W|
|L||Length of taper||Length||L|
|NL||Number of the substrate layer carrying conductor||1|
GMSUB. Supplies parameters for multilayer dielectric substrate, conductor thickness, conductor metal properties, the presence/absence of metallic cover, and the cover height above the substrate. The GMSUB Cover parameter allows the addition/elimination of an infinite metallic plate acting as a cover/shield. Setting the Gnd parameter to "Suspended substrate" allows elevation of the dielectric stack above the backing ground. The elevation gap is filled with air and the HB parameter specifies its height.
Taper. This parameter provides two options. The "Linear" option provides linear taper, that is, an outline of the strip is a trapezoid. The "Exponential" option provides exponential taper, that is, an outline of the strip is trapezoid-like with longitudinal sides made with concave exponents.
Note that the substrate GMSUB's Cover parameter allows you to model the effect of either PEC substrate cover (Cover = "Metallic Cover") or PEC enclosure (cover + side walls). A secondary substrate parameter SW allows you to control the separation of the right-most/left-most conductor from the respective side wall. Conductor separations from the left and from the right wall are assumed equal.
This model does not impose restrictions on the conductor thickness T (it may be zero, positive, or negative). Negative thickness means that the conductor is recessed into the substrate.
If substrate parameter Gnd = "Grounded substrate" then the number of the substrate layer carrying conductor NL must be within limits 1≤NL≤N, where N is a number of dielectric layers in the substrate stackup . If Gnd = "Suspended substrate" then NL must be within the limits 1≤NL≤N+1. Setting NL = N + 1 implies that the taper line is located onto the air layer underlying the dielectric stack. To enable the conductor (at NL = N + 1) to jut downwards (from the dielectric stack bottom), conductor thickness T should be made negative (T<0).
GMSUB parameter T. T specifies thickness of the taper line metal. Note that the GMSUB parameter T is actually a vector, but MMTAPER uses only the first entry of this vector so you may enter the value of T as a scalar. It is important that the connecting line is located at the same layer (specified by parameter NL). In a multilayer stack configuration often it is convenient to have a separate GMSUB instance for MMTAPER.
This model is constructed from a cascaded series of constant width microstrip transmission lines. Model implementation is based on an EM Quasi-Static technique. The number of sections used is frequency-dependent and is constant as a function of the length divided by the guided wavelength. This model assumes a Quasi-TEM mode of propagation and incorporates the effects of dielectric and conductive losses.
This element uses line types to determine its layout. By default, the layout uses the first line type defined in your Layout Process File (LPF). You can change the element to use any of the line types configured in your process:
Select the item in the layout.
Right-click and chooseto display the Cell Options dialog box.
Click the Layout tab and select a Line Type.
Clickto use the new line type in the layout.
See “Cell Options Dialog Box: Layout Tab ” for Cell Options dialog box Layout tab details.
See “The Layout Process File (LPF)” for more information on editing Layout Process Files (LPFs) and to learn about adding or editing line types.
The layout cell has a local parameter NUM_EXP_POINT that is valid if Taper=Exponential. This parameter specifies the number of points used for drawing a curved outline of exponential taper. The default value of NUM_EXP_POINT is 50.
This is an Cadence® Developed Model. The reference for the straight section Microstrip line follows:
 M.B. Bazdar, A.R. Djordjevic, R.F. Harrington, and T.K. Sarkar, "Evaluation of quasi-static matrix parameters for multiconductor transmission lines using Galerkin's method," IEEE Trans. Microwave Theory Tech., vol. MTT-42, July 1994, pp. 1223-1228.