Fix filtering logic

Author: AustP

simphony/simulation.py

@@ -571,7 +571,7 @@ def _monitor(self, power: np.ndarray) -> np.ndarray:
         """
         # amplify and filter the signal
         signal = power * self.monitor_conversion_gain
-        if len(signal) > 1:
+        if len(signal[0][0]) > 1:
             signal = self._monitor_filter(signal)
 
         # for every frequency and power, add the electrical noise on top
@@ -605,7 +605,7 @@ def _rf(self, p1: np.ndarray, p2: np.ndarray) -> np.ndarray:
             The second signal (in Watts)."""
         # amplify and filter the difference
         signal = (p1 - p2) * self.rf_conversion_gain
-        if len(signal) > 1:
+        if len(signal[0][0]) > 1:
             signal = self._rf_filter(signal)
 
         # for every frequency and power, add the electrical noise on top