variable capacitor in ADS

HI
i want to have a variable capacitor in ads.this capacitor is a model of a mems microphone.please help me
and help me for matching this capacitor with microphone amplifier
thanks for your help

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i want to have a capacitor that variable with voltage and have a flat response frequency in a simple range

I have not done this myself, but you can use Symbolically Defined Devices (SDD) components.
There is an example in the ADS examples, and it is documented in the online help:

Using Symbolically Defined Devices (SDD)
Location: SHPEESOF_DIR/examples/Tutorial/SDD_Examples_wrk

hi volker
thanks for your help
please help me for matching this capacitor that frequency response in 20-20KHZ
AND define a amplifier for mems microphone