signal modulation using variable capacitor

I am making a model of a capacitive MEMS accelerometer and I want to implement signal modulation by changing the reactance of the capacitance, for this I change the capacitance as shown in Figure 2 and apply the voltage shown in Figure 3 to the capacitor, but I can not get the envelope of the signal, it is the same as the output

Answer 1

[Vinay]

Hi @Semen Stolbov,

The variable capacitor block is currently not displaying the expected charging and discharging pattern. Instead, it is showing the input voltage at the output side. This issue arises because the 'voltage sensor' block is measuring the voltage across the capacitor, which is actually the input voltage.

To observe the charging and discharging pattern across the capacitor, we need to connect a passive element in series with the capacitor, as shown below.

The envelope of the voltage output can be observed by connecting a diode before the capacitor to hold the voltage across the capacitor in the negative cycle of the input voltage.

Kindly refer to the below documentation of 'variablr capacitor' for more details:

https://in.mathworks.com/help/releases/R2023a/sps/ref/variablecapacitor.html

I hope this would resolve the query!