Coplanar Cross-Junction C_CROSS

Symbol :

Illustration :

Parameters :

C_LTYP1 = ID of coplanar transmission line applied at port 1
C_LTYP2 = ID of coplanar transmission line applied at port 2
C_LTYP3 = ID of coplanar transmission line applied at port 3
C_LTYP4 = ID of coplanar transmission line applied at port 4
C_BTYP1 = ID of airbridge applied at port 1
C_BTYP2 = ID of airbridge applied at port 2
C_BTYP3 = ID of airbridge applied at port 3
C_BTYP4 = ID of airbridge applied at port 4
C_SUB = ID of coplanar substrate definition
C_GRID = ID of simulation control data
TEMP = ID of element temperature definition used for noise computation

Notes/Equations/References :

The C_CROSS module represents a junction between four coplanar lines. The dimensions of lines are defined using data items addressed by C_ LTYP1 to C_LTYP4 (see C_LINTYP in chapter 4). The dimensions of the air-bridges at ports are defined in data items addressed by C_BTYP1 to C_BTYP4(see C_AIRTYP in chapter 4).



If the feed lines defined by C_LTYP1, C_LTYP2 C_LTYP3 or C_LTYP4 have different levels (CEN_MET) an inter metal via is automatically included in the cross structure.



For a Cross-junction without air bridges, the applied line types must have the same CEN_MET and GND_MET (see Layout).



The keyword TYPE of the respective C_BTYP data item controls if the structure contains bridges or not. Normally bridges are necessary to suppress odd mode excitation. Note that due to the applied air bridge additional feed lines with a length defined in the respective C_BTYP data item are connected to the Cross-junction structure. This additional feed line connects the reference plane with bridge. There is no line between bridge and Cross-junction itself (see Illustration).


The keyword TYPE of the bridge applied at each port and the center line level CEN_MET of the line type applied on the same port can not have the same value.



If the Keyword TYPE in one of the C_BTYP data items is set to –1 , the TYPE of the other C_BTYPs data items have also to be –1.



All C_BTYPs must have the same DIE_IDX.



If the Keyword TYPE in one of the C_AIRTYP data items is set to 0 and the Parameter BG and BW are nonzero values, these Parameter will not set automatically to zero. This means that the total size of the discontinuity is not changed if only the TYPE is set to zero (see Layout).



If L1 and L2 in selected C_GRID are not set to -1 (auto sizing), the minimum values for L1 and L2 are:



L1_min= max(W1+2*S1, W3+2*S3) +2*max(GW1, GW3, BW2+BG2+4*DL{C_GRID}, BW4+BG4+4*DL{C_GRID})

L2_min= max(W2+2*S2, W4+2*S4) +2*max(GW2, GW4, BW1+BG1+4*DL{C_GRID}, BW3+BG3+4*DL{C_GRID})



See notations in chapter 4 (Important Note!) for the correct selection of the C_LTYP and C_BTYP.

Equivalent Circuit :

For the modeling of the C_CROSS element, the below network is used. The equivalent circuit parameters are derived from quasi-static FD-calculations. The losses (metal losses as well as dielectric losses due to the dielectric layer used for the bridge) within the cross-junction itself are also taken into account. The connected line at ports are modeled as C_LIN elements and are represented by their characteristic impedance Z_L and phase constant b. There is no limitation due to the length of connected lines (L in selected C_BTYPs).

Layout :

For C_CROSS, different combination of bridge types at ports are possible. If the applied line types have different center line levels (CEN_MET) an inter metal via is automatically included in the cross structure.



For a cross without air-bridges, the applied line types must have the same center level CEN_MET


In the current version, no dielectric layer in bridge region is drawn.



If the parameter GW_DEF in C_PROCES is set to a positive non-zero value, this value is used as ground width for layout generation.