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(Obsolete) Offset Microstrip Step Width (Mode Matching): MSTEPO



This element is OBSOLETE and is replaced by the Microstrip Step In Width Offset (EM Based) (MSTEPX) element.



MSTEPO$ is a Microstrip iCell and has no parameters. See “Intelligent Cells (iCells)” for more information.

Name Description Unit Type Default
ID Element ID Text SL1
W1 Conductor width @ node 1 Length W[1]
W2 Conductor width @ node 2 Length W[1]
Offset Centerline offset dimension Length 0 um
Modes # of Higher order modes   8
MSUB Microstrip substrate definition Text MSUB#[2]

[1] User-modifiable default. Modify by editing under $DEFAULT_VALUES in the default.lpf file in the root installation directory. See AWR Microwave Office Layout Guide for details.

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

Implementation Details

The model assumes a Quasi-TEM mode of incident and reflected propagating waves and also calculates the stored energy in higher order evanescent waves. The model is based on the Full Wave Solution of an equivalent parallel plate wave guide impedance step and incorporates the effects of dispersion and the frequency-dependent nature of the parasitic inductance and capacitance. The model does not incorporate the resistive effects due to radiation or dielectric and conductive losses. The parameters W1, W2 (Strip Widths) and Offset are lengths entered in the default length units. The parameter MSUB specifies the Microstrip Substrate element, which defines additional cross sectional parameters of the transmission line. The Modes parameter (Number of Higher Order Odd and Even order Modes) indicates the number of modes to sum to determine the amount of stored energy in the junction. The amount of energy stored in the higher modes is increased due to the ability of the asymmetric step to excite odd ordered modes. As the number of modes increases, the accuracy and calculation time increases. Further, as the aspect ratio (W1/W2) deviates away from unity (1) the number of modes required for a given accuracy increases.


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:

  1. Select the item in the layout.

  2. Right-click and choose Shape Properties to display the Cell Options dialog box.

  3. Click the Layout tab and select a Line Type.

  4. Click OK to 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.


0.05 ≤ W1 or 2/H ≤ 20 Recommended εr ≤ 16.0 Recommended
T/Wmin ≤ 0.5 Recommended Offset ≤ |W1 - W2|/2
T/H ≤ 0.5 Recommended 0.05 ≤ W1/W2 ≤ 20 Recommended
1 ≤ Modes ≤ 30 Recommended  


[1] Menzel, W. and Wolff, I. "A Method of Calculating the Frequency Dependent Properties of Microstrip Discontinuities" IEEE Trans. On MTT Vol.25 pp.,107-112 February 1977

[2] Chu, T.S., Itoh, T. and Shih, Y.C. "Comparative Study of Mode-Matching Formulations for Microstrip Discontinuity Problems" IEEE Trans. on MTT Vol-33 No.10 Oct. 1985

[3] Chu, T.S. and Itoh, T. "Analysis of Microstrip Step Discontinuity by the Modified Residue Calculus Technique" IEEE Trans. on MTT Vol-33 No.10 Oct. 1985

[4] Gupta, K.C. "Microstrip Lines and Slotlines" Artech 1996 pp.190

[5] Itoh, Tatsuo, "Numerical Techniques for Microwave and Millimeter-Wave Passive Structures" John Wiley & Sons Inc. 1989 p. 466-472

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