### Problem

How do I obtain 3dB Bandwidth of a bandpass Filter?

### Solution

Use the **marker()** function in output equations to calculate the 3D bandwidth of a filter.

- Add two
**Auto Search markers**. Right click inside the graph >**Add Auto Search Marker**, select**Value**, and enter**-3**. Click somewhere on the left side of the trace to add the first 3dB point. - Similarly add another -3db marker on the right side of the trace for second 3dB point
- In
**Output Equations**, add the following equations to get the values of markers**Fl=marker("Filter Response","m1")****Fh=marker("Filter Response","m2")****BW_3dB=(Fh[1]-Fl[1])/1e9**BW_3dB is divided by 1e9 to get the values in GHz as the output equations returns values in base unit and for frequency it is Hz.

- Plot the BW_3dB output equation in a graph as shown below