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Coplanar Air-bridge C_AIR



Symbol :

Illustration :

Parameters :

C_LTYP = ID of coplanar transmission line applied at port 1 and port 2
C_BTYP = ID of airbridge type definitions
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 :

  1. C_AIR represents a single bridge as the connection of ground planes. Such bridges are necessary in CPW-circuits in order to suppress the higher order modes. The bridge dimensions are defined using the line addressed by C_LTYP and the bridge addressed by C_BTYP.
  2. For C_AIR, TYPE=0 and TYPE=-1 in selected C_BTYP is not allowed.
  3. The parameter TYPE in selected C_BTYP and the parameter CEN_MET in selected C_LTYP can not have the same value.
  4. If L in applied C_BTYP is set to a positive non-zero value, two coplanar lines of length L are connected to the bridge. Note that the distance between the reference planes is given by 2*L+2*BG+BW.
  5. The parameters of the dielectric material under the bridge is defined C_TECH. The index DIE_IDX in selected C_BTYP indicates, which dielectric layer (0, 1 or 2) is used for the bridge (see C_AIRTYP in chapter 4 for more information).
  6. If L1 and L2 in selected C_GRID are not set to -1 (auto sizing), the minimum values for L1 and L2 are:
    L1min=W+2*S+2*GW

    L2min=8*DL+BW+2*BG
  7. 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_AIR element, a p-network is used. The equivalent circuit parameters are derived from electric quasi-static FD-calculations. The losses within the bridge itself are taken into account. The connected line 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).

Layout :

  1. For C_AIR, two type of air-bridges are possible. If TYPE=1 in selected C_BTYP and the GND_MET=2 in applied C_LTYP, the ground planes is in both metal level.

  2. In the current version, no dielectric layer is drawn.
  3. 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


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