some doc changes

src/openqlab/analysis/servo_design.py

@@ -231,7 +231,7 @@ class Differentiator(Filter):
 
 class Lowpass(Filter):
     """
-    Create a 2nd-order lowpass filter with variable quality factor `second_parameter`.
+    Create a 2nd-order lowpass filter with variable quality factor `second_parameter` (might be referenced as `Q` in the description).
 
     The default `second_parameter` of ``1/sqrt(2)`` results in a Butterworth filter with flat passband.
 
@@ -279,7 +279,7 @@ class Notch(Filter):
     corner_frequency: :obj:`float`
         Frequency to remove from the spectrum
     second_parameter: :obj:`float`
-        Quality factor of the notch filter. Defaults to 1.
+        Quality factor of the notch filter. Defaults to 1. Referenced as `Q` in description.
     """
 
     def __init__(self, corner_frequency, second_parameter=1, enabled=True):