C_CROSS Coplanar Cross-Junction Parameters Notes Equivalent Circuit
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Coplanar Cross-Junction 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_TYP4. The dimensions of the air-bridges at ports are defined in data items addressed by C_BTYP1 to C_BTYP4.

Parameters  

Notes

• If the line types defined by C_LTYP1 to C_LTYP4 have different center line levels (CEN_MET) an inter metal via is automatically included in the bend structure.
• For a cross-junction without air-bridges, the applied line types must have the same center level CEN_MET.
• The keyword TYPE of the selected C_BTYP 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 L defined in the selected C_BTYP are connected to the cross-junction. This additional feed lines connect the reference planes with bridges (see above Illustration). There is no line between bridges and bend structure itself .
• The keyword TYPE of the bridge applied at a 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_BTYPs is set to - 1, the TYPE of the other C_BTYP has to be also - 1.
• All C_BTYPs must have the same DIE_IDX.
• If the Keyword TYPE in one of the C_BTYP 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.
• If L1 and L2 in selected C_GRID are not set to –1 or –2 (auto sizing), the minimum values for L1 and L2 are:

  L1min= max(W1+2S1,W3+2S3)+2max(GW1,GW3,BW2+BG2+4DL,BW4+BG4+4DL)

  L2min= max(W2+2S2,W4+2S4)+2max(GW2,GW4,BW1+BG1+4DL,BW3+BG3+4DL)

Equivalent Circuit  

For the modeling of the C_CROSS element, the illustrated 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 bridges) within the cross-junction itself are taken into account. The connected lines at ports are modeled as C_LIN elements and are represented by their characteristic impedance ZL and phase constant b. There is no limitation due to the length of connected lines (L in selected C_BTYP).