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# Coplanar Interdigital Capacitor C_IDC

### Notes :

> The evaluation of the interdigital capacitors will be compared with the corresponding microstrip model of Libra. The best match between CPW and MS edged coupled lines will be achieved with a 50W MS configuration (h=150mm, w=100mm). This FD-simulator version does not take transmission line effects into account. The IDC was assumed to be ideal lumped. This will lead to a simulation inaccuracy especially for long IDC fingers and a small number of fingers. In the new version of COPLAN/ADS, the distributed properties of this element is taken into account. The second example shows the results of the old and new simulation method, where the new simulation has been achieved by utilizing a model of N+2 (N fingers and 2 ground strips) coupled lines instead of a lumped element.
> Equivalent Circuit Parameter (Capacitive) : Cp1 = 49fF, Cp2 = 51fF, Cs = 27fF

Configuration: Feed lines configuration: 50W1, length=1mm; Airbridges: TYPE=2, BW=50, BS=14, BG=8mm MS-Substrate: h=150mm, w=100mm IDC: N=2, WF=25mm, SF=20mm, LF=300mm width of feed line: W=50mm spacing to ground: SGF=30mm (90mm) gap between ground and feed line: S=20mm |

Configuration: Feed lines configuration: 50W1, length=1mm; Airbridges: TYPE=2, BW=50, BS=14, BG=8mm MS-substrate: h=150mm, w=100mm IDC: N=2, WF=25mm, SF=20mm, LF=300mm width of feed line: W=50mm min. spacing to ground: SGF=30mm (90mm) gap between ground and feed line: S=20mm |

Configuration: Feed lines configuration: 50W1, length=1mm; Airbridges: TYPE=2, BW=50, BS=14, BG=8mm IDC: number of fingers: N=5, WF=25mm, SF=20mm, LF=300mm width of feed line: W=50mm min. spacing to ground: SGF=30mm gap between ground and feed line: S=20mm |

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