diff --git a/Common/operator_base.cpp b/Common/operator_base.cpp
new file mode 100644
index 0000000..09b98e8
--- /dev/null
+++ b/Common/operator_base.cpp
@@ -0,0 +1,53 @@
+/*
+*	Copyright (C) 2010 Thorsten Liebig (Thorsten.Liebig@gmx.de)
+*
+*	This program is free software: you can redistribute it and/or modify
+*	it under the terms of the GNU General Public License as published by
+*	the Free Software Foundation, either version 3 of the License, or
+*	(at your option) any later version.
+*
+*	This program is distributed in the hope that it will be useful,
+*	but WITHOUT ANY WARRANTY; without even the implied warranty of
+*	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*	GNU General Public License for more details.
+*
+*	You should have received a copy of the GNU General Public License
+*	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "operator_base.h"
+
+Operator_Base::Operator_Base()
+{
+	Init();
+	m_MeshType = Processing::CARTESIAN_MESH;
+}
+
+Operator_Base::~Operator_Base()
+{
+
+}
+
+std::string Operator_Base::GetDirName(int ny) const
+{
+	if (ny==0) return "x";
+	if (ny==1) return "y";
+	if (ny==2) return "z";
+	return "";
+}
+
+void Operator_Base::Init()
+{
+	dT = 0;
+	for (int n=0;n<3;++n)
+		discLines[n]=NULL;
+	for (int n=0;n<6;++n)
+		m_BC[n]=0;
+}
+
+void Operator_Base::Reset()
+{
+	for (int n=0;n<3;++n)
+		delete[] discLines[n];
+	Init();
+}
diff --git a/Common/operator_base.h b/Common/operator_base.h
new file mode 100644
index 0000000..50cd306
--- /dev/null
+++ b/Common/operator_base.h
@@ -0,0 +1,93 @@
+/*
+*	Copyright (C) 2010 Thorsten Liebig (Thorsten.Liebig@gmx.de)
+*
+*	This program is free software: you can redistribute it and/or modify
+*	it under the terms of the GNU General Public License as published by
+*	the Free Software Foundation, either version 3 of the License, or
+*	(at your option) any later version.
+*
+*	This program is distributed in the hope that it will be useful,
+*	but WITHOUT ANY WARRANTY; without even the implied warranty of
+*	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+*	GNU General Public License for more details.
+*
+*	You should have received a copy of the GNU General Public License
+*	along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef OPERATOR_BASE_H
+#define OPERATOR_BASE_H
+
+#include "tools/global.h"
+#include "FDTD/processing.h"
+#include "string"
+
+class Operator_Base
+{
+public:
+	//! Get the timestep used by this operator
+	double GetTimestep() const {return dT;};
+
+	//! Get the number of cells or nodes defined by this operator
+	virtual double GetNumberCells() const {return 0;}
+
+	//! Get the number of timesteps satisfying the nyquist condition (may depend on the excitation)
+	unsigned int GetNumberOfNyquistTimesteps() const {return 0;}
+
+	//! Returns the number of lines as needed for post-processing etc. (for the engine, use GetOriginalNumLines())
+	virtual unsigned int GetNumberOfLines(int ny) const {return numLines[ny];}
+
+	//! Get the name for the given direction: 0 -> x, 1 -> y, 2 -> z
+	virtual std::string GetDirName(int ny) const;
+
+	//! Get the grid drawing unit in m
+	virtual double GetGridDelta() const {return 0;}
+
+	//! Get the mesh delta times the grid delta for a 3D position (unit is meter)
+	virtual double GetMeshDelta(int n, const unsigned int* pos, bool dualMesh=false) const {UNUSED(n);UNUSED(pos);UNUSED(dualMesh);return 0.0;}
+
+	//! Get the disc line in \a n direction (in drawing units)
+	virtual double GetDiscLine(int n, unsigned int pos, bool dualMesh=false) const {UNUSED(n);UNUSED(pos);UNUSED(dualMesh);return 0.0;}
+
+	//! Get the node width for a given direction \a n and a given mesh position \a pos
+	virtual double GetNodeWidth(int ny, const unsigned int pos[3], bool dualMesh = false) const {UNUSED(ny);UNUSED(pos);UNUSED(dualMesh);return 0.0;}
+
+	//! Get the node area for a given direction \a n and a given mesh position \a pos
+	virtual double GetNodeArea(int ny, const unsigned int pos[3], bool dualMesh = false) const {UNUSED(ny);UNUSED(pos);UNUSED(dualMesh);return 0.0;}
+
+	//! Get the length of an FDTD edge (unit is meter).
+	virtual double GetEdgeLength(int ny, const unsigned int pos[3], bool dualMesh = false) const {UNUSED(ny);UNUSED(pos);UNUSED(dualMesh);return 0.0;}
+
+	//! Get the area around an edge for a given direction \a n and a given mesh posisition \a pos
+	/*!
+		This will return the area around an edge with a given direction, measured at the middle of the edge.
+		In a cartesian mesh this is equal to the NodeArea, may be different in other coordinate systems.
+	*/
+	virtual double GetEdgeArea(int ny, const unsigned int pos[3], bool dualMesh = false) const {UNUSED(ny);UNUSED(pos);UNUSED(dualMesh);return 0.0;}
+
+	//! Snap the given coodinates to mesh indices
+	virtual bool SnapToMesh(double* coord, unsigned int* uicoord, bool lower=false, bool* inside=NULL) {UNUSED(coord);UNUSED(uicoord);UNUSED(lower);UNUSED(inside);return false;};
+
+	//! Set the boundary conditions
+	virtual void SetBoundaryCondition(int* BCs) {for (int n=0;n<6;++n) m_BC[n]=BCs[n];}
+
+protected:
+	Operator_Base();
+	virtual ~Operator_Base();
+
+	virtual void Init();
+	virtual void Reset();
+
+	//! boundary conditions
+	int m_BC[6];
+
+	//! The operator timestep
+	double dT;
+
+	Processing::MeshType m_MeshType;
+	unsigned int numLines[3];
+	double* discLines[3];
+	double gridDelta;
+};
+
+#endif // OPERATOR_BASE_H
diff --git a/Common/readme.txt b/Common/readme.txt
index 89192f3..37e9a22 100644
--- a/Common/readme.txt
+++ b/Common/readme.txt
@@ -1,5 +1,6 @@
 readme for openEMS/Commen
 
 - This folder contains all classes common for all numerical solver included in openEMS (currently only FDTD)
+	- Operator-Base class
 	- Engine-Interface classes
 	- Commen processing classes
diff --git a/FDTD/operator.cpp b/FDTD/operator.cpp
index ecef166..0e96dd3 100644
--- a/FDTD/operator.cpp
+++ b/FDTD/operator.cpp
@@ -31,11 +31,9 @@ Operator* Operator::New()
 	return op;
 }
 
-Operator::Operator()
+Operator::Operator() : Operator_Base()
 {
-	m_MeshType = ProcessFields::CARTESIAN_MESH;
 	Exc = 0;
-	dT = 0;
 	m_InvaildTimestep = false;
 }
 
@@ -55,14 +53,14 @@ Engine* Operator::CreateEngine() const
 
 void Operator::Init()
 {
+	Operator_Base::Init();
+
 	CSX = NULL;
 
 	vv=NULL;
 	vi=NULL;
 	iv=NULL;
 	ii=NULL;
-	for (int n=0;n<3;++n)
-		discLines[n]=NULL;
 
 	MainOp=NULL;
 	DualOp=NULL;
@@ -75,11 +73,7 @@ void Operator::Init()
 		EC_R[n]=NULL;
 	}
 
-	for (int n=0;n<6;++n)
-		m_BC[n]=0;
-
 	Exc = 0;
-	dT = 0;
 }
 
 void Operator::Reset()
@@ -88,8 +82,6 @@ void Operator::Reset()
 	Delete_N_3DArray(vi,numLines);
 	Delete_N_3DArray(iv,numLines);
 	Delete_N_3DArray(ii,numLines);
-	for (int n=0;n<3;++n)
-		delete[] discLines[n];
 	delete MainOp;
 	delete DualOp;
 	for (int n=0;n<3;++n)
@@ -102,15 +94,7 @@ void Operator::Reset()
 
 	delete Exc;
 
-	Init();
-}
-
-string Operator::GetDirName(int ny) const
-{
-	if (ny==0) return "x";
-	if (ny==1) return "y";
-	if (ny==2) return "z";
-	return "";
+	Operator_Base::Reset();
 }
 
 double Operator::GetMeshDelta(int n, const unsigned int* pos, bool dualMesh) const
diff --git a/FDTD/operator.h b/FDTD/operator.h
index 55a01cf..f4e27e4 100644
--- a/FDTD/operator.h
+++ b/FDTD/operator.h
@@ -22,13 +22,14 @@
 #include "tools/AdrOp.h"
 #include "tools/constants.h"
 #include "excitation.h"
+#include "Common/operator_base.h"
 
 class Operator_Extension;
 class Engine;
 class TiXmlElement;
 
 //! Abstract base-class for the FDTD-operator
-class Operator
+class Operator : public Operator_Base
 {
 	friend class Engine;
 	friend class Operator_Ext_LorentzMaterial; //we need to find a way around this... friend class Operator_Extension only would be nice
@@ -73,27 +74,22 @@ public:
 	inline virtual void SetII( unsigned int n, unsigned int x, unsigned int y, unsigned int z, FDTD_FLOAT value ) { ii[n][x][y][z] = value; }
 	inline virtual void SetIV( unsigned int n, unsigned int x, unsigned int y, unsigned int z, FDTD_FLOAT value ) { iv[n][x][y][z] = value; }
 
-	virtual void SetBoundaryCondition(int* BCs) {for (int n=0;n<6;++n) m_BC[n]=BCs[n];}
 	virtual void ApplyElectricBC(bool* dirs); //applied by default to all boundaries
 	virtual void ApplyMagneticBC(bool* dirs);
 
 	//! Set a forced timestep to use by the operator
 	virtual void SetTimestep(double ts) {dT = ts;}
-	double GetTimestep() const {return dT;};
 	bool GetTimestepValid() const {return !m_InvaildTimestep;}
 	virtual double GetNumberCells() const;
 
-	//! Returns the number of lines as needed for post-processing etc. (for the engine, use GetOriginalNumLines())
-	virtual unsigned int GetNumberOfLines(int ny) const {return numLines[ny];}
-	//! Returns the number of lines as needed for the engine etc. (for post-processing etc, use GetOriginalNumLines())
+	unsigned int GetNumberOfNyquistTimesteps() const {return Exc->GetNyquistNum();}
+
+	//! Returns the number of lines as needed for the engine etc. (for post-processing etc, use GetNumLines())
 	virtual unsigned int GetOriginalNumLines(int ny) const {return numLines[ny];}
 
 	virtual void ShowStat() const;
 	virtual void ShowExtStat() const;
 
-	//! Get the name for the given direction: 0 -> x, 1 -> y, 2 -> z
-	virtual string GetDirName(int ny) const;
-
 	virtual double GetGridDelta() const {return gridDelta;}
 	//! Get the mesh delta times the grid delta for a 3D position (unit is meter)
 	virtual double GetMeshDelta(int n, const unsigned int* pos, bool dualMesh=false) const;
@@ -141,8 +137,6 @@ protected:
 
 	ContinuousStructure* CSX;
 
-	int m_BC[6];
-
 	//! Calculate the field excitations.
 	virtual bool CalcFieldExcitation();
 
@@ -158,7 +152,6 @@ protected:
 
 	//Calc timestep only internal use
 	virtual double CalcTimestep();
-	double dT; //FDTD timestep!
 	double opt_dT;
 	bool m_InvaildTimestep;
 	string m_Used_TS_Name;
@@ -177,10 +170,6 @@ protected:
 	double* EC_L[3];
 	double* EC_R[3];
 
-	int m_MeshType;
-	unsigned int numLines[3];
-	double* discLines[3];
-	double gridDelta;
 	AdrOp* MainOp;
 	AdrOp* DualOp;
 
diff --git a/FDTD/process_efield.cpp b/FDTD/process_efield.cpp
index dc91a54..f65b7b7 100644
--- a/FDTD/process_efield.cpp
+++ b/FDTD/process_efield.cpp
@@ -19,7 +19,7 @@
 #include "time.h"
 #include "process_efield.h"
 
-ProcessEField::ProcessEField(Operator* op, Engine* eng) : Processing(op)
+ProcessEField::ProcessEField(Operator_Base* op, Engine* eng) : Processing(op)
 {
 	Eng = eng;
 }
diff --git a/FDTD/process_efield.h b/FDTD/process_efield.h
index 9f01315..bf1d9f2 100644
--- a/FDTD/process_efield.h
+++ b/FDTD/process_efield.h
@@ -19,6 +19,7 @@
 #define PROCESS_EFIELD_H
 
 #include "processing.h"
+#include "engine.h"
 
 /*! \brief Process E-field at a point
 
@@ -28,7 +29,7 @@
 class ProcessEField : public Processing
 {
 public:
-	ProcessEField(Operator* op, Engine* eng);
+	ProcessEField(Operator_Base* op, Engine* eng);
 	virtual ~ProcessEField();
 
 	virtual void InitProcess();
diff --git a/FDTD/process_hfield.cpp b/FDTD/process_hfield.cpp
index df8acf9..55cac59 100644
--- a/FDTD/process_hfield.cpp
+++ b/FDTD/process_hfield.cpp
@@ -19,7 +19,7 @@
 #include "tools/global.h"
 #include "process_hfield.h"
 
-ProcessHField::ProcessHField(Operator* op, Engine* eng) : ProcessEField(op, eng)
+ProcessHField::ProcessHField(Operator_Base* op, Engine* eng) : ProcessEField(op, eng)
 {
 }
 
diff --git a/FDTD/process_hfield.h b/FDTD/process_hfield.h
index f089b11..22e00ce 100644
--- a/FDTD/process_hfield.h
+++ b/FDTD/process_hfield.h
@@ -28,7 +28,7 @@
 class ProcessHField : public ProcessEField
 {
 public:
-	ProcessHField(Operator* op, Engine* eng);
+	ProcessHField(Operator_Base* op, Engine* eng);
 	virtual ~ProcessHField();
 
 	virtual void InitProcess();
diff --git a/FDTD/processcurrent.cpp b/FDTD/processcurrent.cpp
index 864b6a1..2ebe466 100644
--- a/FDTD/processcurrent.cpp
+++ b/FDTD/processcurrent.cpp
@@ -20,7 +20,7 @@
 #include "engine_interface_fdtd.h"
 #include <iomanip>
 
-ProcessCurrent::ProcessCurrent(Operator* op) : ProcessIntegral(op)
+ProcessCurrent::ProcessCurrent(Operator_Base* op) : ProcessIntegral(op)
 {
 	m_TimeShift = op->GetTimestep()/2.0;
 	m_dualMesh = true;
diff --git a/FDTD/processcurrent.h b/FDTD/processcurrent.h
index e0ce15e..224eeca 100644
--- a/FDTD/processcurrent.h
+++ b/FDTD/processcurrent.h
@@ -23,7 +23,7 @@
 class ProcessCurrent : public ProcessIntegral
 {
 public:
-	ProcessCurrent(Operator* op);
+	ProcessCurrent(Operator_Base* op);
 	virtual ~ProcessCurrent();
 
 	//! Integrate currents flowing through an area
diff --git a/FDTD/processfields.cpp b/FDTD/processfields.cpp
index dc39a37..b35ce96 100644
--- a/FDTD/processfields.cpp
+++ b/FDTD/processfields.cpp
@@ -21,7 +21,7 @@
 #include "processfields.h"
 #include "engine_interface_fdtd.h"
 
-ProcessFields::ProcessFields(Operator* op) : Processing(op)
+ProcessFields::ProcessFields(Operator_Base* op) : Processing(op)
 {
 	m_DumpType = E_FIELD_DUMP;
 	// vtk-file is default
diff --git a/FDTD/processfields.h b/FDTD/processfields.h
index 83ae51d..22321fc 100644
--- a/FDTD/processfields.h
+++ b/FDTD/processfields.h
@@ -26,7 +26,7 @@
 class ProcessFields : public Processing
 {
 public:
-	ProcessFields(Operator* op);
+	ProcessFields(Operator_Base* op);
 	virtual ~ProcessFields();
 
 	enum FileType { VTK_FILETYPE, HDF5_FILETYPE};
diff --git a/FDTD/processfields_td.cpp b/FDTD/processfields_td.cpp
index 42edd7c..7c6277c 100644
--- a/FDTD/processfields_td.cpp
+++ b/FDTD/processfields_td.cpp
@@ -16,11 +16,12 @@
 */
 
 #include "processfields_td.h"
+#include "Common/operator_base.h"
 #include <iomanip>
 #include <sstream>
 #include <string>
 
-ProcessFieldsTD::ProcessFieldsTD(Operator* op) : ProcessFields(op)
+ProcessFieldsTD::ProcessFieldsTD(Operator_Base* op) : ProcessFields(op)
 {
 	pad_length = 8;
 }
diff --git a/FDTD/processfields_td.h b/FDTD/processfields_td.h
index 36e86ef..cc57ca1 100644
--- a/FDTD/processfields_td.h
+++ b/FDTD/processfields_td.h
@@ -23,7 +23,7 @@
 class ProcessFieldsTD : public ProcessFields
 {
 public:
-	ProcessFieldsTD(Operator* op);
+	ProcessFieldsTD(Operator_Base* op);
 	virtual ~ProcessFieldsTD();
 
 	virtual int Process();
diff --git a/FDTD/processing.cpp b/FDTD/processing.cpp
index e952f83..916fe78 100644
--- a/FDTD/processing.cpp
+++ b/FDTD/processing.cpp
@@ -17,11 +17,13 @@
 
 #include "tools/global.h"
 #include "tools/useful.h"
+#include "Common/operator_base.h"
+#include <algorithm>
 #include "processing.h"
 #include "time.h"
 #include <climits>
 
-Processing::Processing(Operator* op)
+Processing::Processing(Operator_Base* op)
 {
 	Op=op;
 	Enabled = true;
@@ -126,13 +128,13 @@ void Processing::AddFrequency(double freq)
 		cerr << "Processing::AddFrequency: Requested frequency " << freq << " is too high for the current timestep used... skipping..." << endl;
 		return;
 	}
-	else if (nyquistTS<Op->Exc->GetNyquistNum())
+	else if (nyquistTS<Op->GetNumberOfNyquistTimesteps())
 	{
 		cerr << "Processing::AddFrequency: Warning: Requested frequency " << freq << " is higher than maximum excited frequency..." << endl;
 	}
 
 	if (m_FD_Interval==0)
-		m_FD_Interval = Op->Exc->GetNyquistNum();
+		m_FD_Interval = Op->GetNumberOfNyquistTimesteps();
 	if (m_FD_Interval>nyquistTS)
 		m_FD_Interval = nyquistTS;
 
diff --git a/FDTD/processing.h b/FDTD/processing.h
index bd74c99..9faa538 100644
--- a/FDTD/processing.h
+++ b/FDTD/processing.h
@@ -25,22 +25,29 @@ typedef std::complex<double> double_complex;
 #include <iostream>
 #include <fstream>
 #include <cmath>
-#include "Common/engine_interface_base.h"
-#include "operator.h"
-#include "engine.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <iostream>
+#include <string>
+#include <vector>
 
+#include "Common/engine_interface_base.h"
+
+class Operator_Base;
+
+using namespace std;
 
 class Processing
 {
 public:
-	Processing(Operator* op);
+	Processing(Operator_Base* op);
 	virtual ~Processing();
 
+	enum MeshType { CARTESIAN_MESH, CYLINDRICAL_MESH};
+
 	//! Set the interface to the engine. Each processing needs its own engine interface. This class will take ownership and cleanup the interface on deletion!
 	void SetEngineInterface(Engine_Interface_Base* eng_if);
 
-	enum MeshType { CARTESIAN_MESH, CYLINDRICAL_MESH};
-
 	virtual void SetName(string val) {m_Name=val;}
 
 	virtual void InitProcess() {};
@@ -84,7 +91,7 @@ public:
 
 protected:
 	Engine_Interface_Base* m_Eng_Interface;
-	Operator* Op;
+	Operator_Base* Op;
 	MeshType m_Mesh_Type;
 
 	unsigned int m_precision;
diff --git a/FDTD/processintegral.cpp b/FDTD/processintegral.cpp
index 1944166..f9ded38 100644
--- a/FDTD/processintegral.cpp
+++ b/FDTD/processintegral.cpp
@@ -18,7 +18,7 @@
 #include "processintegral.h"
 #include <iomanip>
 
-ProcessIntegral::ProcessIntegral(Operator* op)  : Processing(op)
+ProcessIntegral::ProcessIntegral(Operator_Base* op)  : Processing(op)
 {
 	m_TimeShift = 0.0;
 	m_Results=NULL;
diff --git a/FDTD/processintegral.h b/FDTD/processintegral.h
index 961e706..5a43372 100644
--- a/FDTD/processintegral.h
+++ b/FDTD/processintegral.h
@@ -51,12 +51,12 @@ public:
 	virtual int Process();
 
 protected:
-	ProcessIntegral(Operator* op);
+	ProcessIntegral(Operator_Base* op);
 
 	//! timeshift to be used in TD and FD data, e.g. 0.5*dT in case of current based parameter
 	double m_TimeShift;
 
-	vector<FDTD_FLOAT> TD_Values;
+	vector<double> TD_Values;
 	vector<double_complex> FD_Values;
 
 	double *m_Results;
diff --git a/FDTD/processmodematch.cpp b/FDTD/processmodematch.cpp
index 69b80ea..b04b3e6 100644
--- a/FDTD/processmodematch.cpp
+++ b/FDTD/processmodematch.cpp
@@ -17,9 +17,10 @@
 
 #include "processmodematch.h"
 #include "CSFunctionParser.h"
+#include "Common/operator_base.h"
 #include "tools/array_ops.h"
 
-ProcessModeMatch::ProcessModeMatch(Operator* op) : ProcessIntegral(op)
+ProcessModeMatch::ProcessModeMatch(Operator_Base* op) : ProcessIntegral(op)
 {
 	for (int n=0;n<2;++n)
 	{
diff --git a/FDTD/processmodematch.h b/FDTD/processmodematch.h
index 4104f7e..f68b10d 100644
--- a/FDTD/processmodematch.h
+++ b/FDTD/processmodematch.h
@@ -25,7 +25,7 @@ class CSFunctionParser;
 class ProcessModeMatch : public ProcessIntegral
 {
 public:
-	ProcessModeMatch(Operator* op);
+	ProcessModeMatch(Operator_Base* op);
 	virtual ~ProcessModeMatch();
 
 	virtual void InitProcess();
diff --git a/FDTD/processvoltage.cpp b/FDTD/processvoltage.cpp
index 72f0ff0..8d94b6b 100644
--- a/FDTD/processvoltage.cpp
+++ b/FDTD/processvoltage.cpp
@@ -18,7 +18,7 @@
 #include "processvoltage.h"
 #include <iomanip>
 
-ProcessVoltage::ProcessVoltage(Operator* op) : ProcessIntegral(op)
+ProcessVoltage::ProcessVoltage(Operator_Base* op) : ProcessIntegral(op)
 {
 }
 
diff --git a/FDTD/processvoltage.h b/FDTD/processvoltage.h
index 4bec349..91768ce 100644
--- a/FDTD/processvoltage.h
+++ b/FDTD/processvoltage.h
@@ -24,7 +24,7 @@
 class ProcessVoltage : public ProcessIntegral
 {
 public:
-	ProcessVoltage(Operator* op);
+	ProcessVoltage(Operator_Base* op);
 	virtual ~ProcessVoltage();
 
 	virtual double CalcIntegral();
diff --git a/openEMS.pro b/openEMS.pro
index c556a8b..6f00cd4 100644
--- a/openEMS.pro
+++ b/openEMS.pro
@@ -86,9 +86,10 @@ SOURCES += main.cpp \
     FDTD/engine_cylindermultigrid.cpp \
     FDTD/engine_ext_cylindermultigrid.cpp \
     FDTD/operator_ext_upml.cpp \
-	FDTD/engine_ext_upml.cpp \
+    FDTD/engine_ext_upml.cpp \
     Common/engine_interface_base.cpp \
-    FDTD/engine_interface_fdtd.cpp
+    FDTD/engine_interface_fdtd.cpp \
+    Common/operator_base.cpp
 HEADERS += tools/ErrorMsg.h \
     tools/AdrOp.h \
     tools/constants.h \
@@ -132,9 +133,10 @@ HEADERS += tools/ErrorMsg.h \
     FDTD/engine_ext_cylindermultigrid.h \
     tools/aligned_allocator.h \
     FDTD/operator_ext_upml.h \
-	FDTD/engine_ext_upml.h \
+    FDTD/engine_ext_upml.h \
     Common/engine_interface_base.h \
-    FDTD/engine_interface_fdtd.h
+    FDTD/engine_interface_fdtd.h \
+    Common/operator_base.h
 QMAKE_CXXFLAGS_RELEASE = -O3 \
     -g \
 	-march=native