[fix] IIR function

mbtrack2/tracking/rf.py

@@ -1492,10 +1492,11 @@ class ProportionalIntegralLoop():
             T = self.ring.T1 * self.every
             alpha = np.cos(omega*T)-1
             tmp = alpha * alpha - 2 * alpha
+            print(tmp)
             if tmp > 0:
                 self.IIRcoef = alpha + np.sqrt(tmp)
             else:
-                self.IIRcoef = self.every * self.ring.T1 * cutoff * 2 * np.pi
+                self.IIRcoef = T * cutoff * 2 * np.pi
         self.IIRout = self.cav_res.Vc
 
     def IIR(self,input):