### Where To Find This Example

#### AWR Version 14

#### AWR Version 13

### Design Notes

**Lange Coupler Feed Manifold - Paramameterized EM Structure**

This example shows a parametric AXIEM model for the feed manifolds of a four-finger microstrip Lange coupler on 15mil Alumina.

__Overview__

The microstrip Lange coupler model in MWO does not include the feed manifolds; i.e. the connection between the external lines and the coupler. One way to model the manifolds is by using EM simulations, but that usually means a fixed set of dimensions for the manifold. A parametric EM model of the manifold reshapes to fit the following dimensions, but it requires EM simulations when the dimensions are changed:

WO: width of external microstrip line

Mtr: miter ratio (0 creates a rectangular manifold, 0.5 is the maximum miter)

W: width of coupler fingers (same as W on MLANGE2)

S: spacing of coupler fingers (same as S on MLANGE2)

The model in this example is an EM structure whose schematic includes: parameter definitions, and circuit elements whose dimensions are functions of the parameters, connected together in a manner that results in the desired layout shape and port locations.

__EM Structure__

“LFAX” is the manifold for the connections to one end of a 4-finger Lange coupler. The schematic primarily consists of two mitered bends (MBEND) whose widths are WO, and offset steps (MSTEPO) to position the connections to the fingers. Two of the fingers are centered so their edges align with the innermost end of the bends, and the third is 2*(W+S) to the left. Since MSTEPO adds no metal to the layout, its width dimensions (W1 and W2) have no effect on the simulation results, and can be set large, to accommodate the offsets. To ensure proper snapping where 3 elements are connected together (one MBEND and two MSTEPO), the layout cells for the MSTEPOs were edited to explicitly set the connections for face (or port) 2. Additional lines are added to allow de-embedding. Using a microstrip coupled line element (MCLIN) for two of the de-embedded lines makes it easy to control the spacing between the bends.

In case WO < 3W+2S, the variable LO adds some length to the external connection side of the manifold, so that it extends far enough to connect to both fingers.

__Schematic__

“Top” shows the microstrip Lange coupler model (MLANGE2), and the EM subcircuit connected to it. Equations are used to set variables for dimensions, so that the parameters of the coupler and the manifolds can be varied together.

__Graph__

"Lange Frequency Response" shows the s-parameters of “Top”, the Lange coupler model with EM simulated manifolds.