== Working with FDTD Simulation Data ==
===Understanding the FDTD Observable Types===
EM.Tempo's FDTD simulation engine calculates all the six electric and magnetic field components (E<sub>x</sub>, E<sub>y</sub>, E<sub>z</sub>, H<sub>x</sub>, H<sub>y</sub> and H<sub>z</sub>) at every mesh grid node at all time steps from t = 0 until the end of the time marching loop. However, in order to save memory usage, the engine discards the temporal field data from each time step to the next. Storage, manipulation and visualization of 3D data can become overwhelming for complex structures and larger computational domains. Furthermore, calculation of some field characteristics such as radiation patterns or radar cross section (RCS) can be sizable, time-consuming, post-processing tasks. That is why EM.Tempo asks you to define project observables to instruct what types of output data you want in each simulation process.
EM.Tempo offers the following types of observableoutput simulation data:
{| class="wikitable"
|-
! scope="col"| Source Simulation Data Type! scope="col"| Observable Type
! scope="col"| Applications
! scope="col"| Restrictions
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Temporal Field Probe |Point Fields]]'''| style="width:250px;" | '''[[Glossary of EM.Cube's Simulation Observables#Temporal Field Probe |Temporal Field Probe]]'''| style="width:300px;" | Monitoring Computing E- and H-field components at a fixed location in both time and frequency domains| style="width:250px;" | Associated with a PEC or thin wire lineNone
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Near-Field Sensor |Near-Field Distribution]]'''| style="width:250px;" | '''[[Glossary of EM.Cube's Simulation Observables#Near-Field Sensor |Near-Field Sensor]]'''| style="width:300px;" | Monitoring Computing E- and H-field components on a planar cross section of the computational domain in both time and frequency domains| style="width:250px;" | Associated with a virtual rectangle stripNone
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Far-Field Radiation Pattern |Far-Field Radiation Characteristics]]'''| style="width:250px;" | '''[[Glossary of EM.Cube's Simulation Observables#Far-Field Radiation Pattern |Far-Field Radiation Pattern]]'''| style="width:300px;" | Monitoring Computing the radiation behavior of your structurepattern and additional radiation characteristics such as directivity, axial ratio, side lobe levels, etc. | style="width:250px;" | Associated with a PEC rectangle stripNone
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Radar Cross Section (RCS) |Far-Field Scattering Characteristics]]'''| style="width:250px;" | '''[[Glossary of EM.Cube's Simulation Observables#Radar Cross Section (RCS) |Radar Cross Section (RCS)]]'''| style="width:300px;" | Monitoring Computing the scattering behavior bistatic and monostatic RCS of your structurea target| style="width:250px;" | Associated with Requires a PEC rectangle stripplane wave source
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Port Definition |Port Characteristics]]'''
| style="width:300px250px;" | Computation '''[[Glossary of EM.Cube's Simulation Observables#Port Definition |Port Definition]]''' | style="width:300px;" | Computing the S/Y/Z parameters and voltage standing wave ratio (VSWR)| style="width:250px;" | Associated with a PEC CylinderRequires one of these source types: lumped, distributed, microstrip, CPW, coaxial or waveguide port|-| '''[[Glossary of EM.Cube's Simulation Observables#Port Definition |Port Voltage, Current & Powers]]'''| style="width:250px;" | '''[[Glossary of EM.Cube's Simulation Observables#Port Definition |Port Definition]]''' | style="width:300px;" | Computing the port voltages, port currents and total port powers in both time and frequency domains| style="width:250px;" | Requires one of these source types: lumped, distributed, microstrip, CPW, coaxial or waveguide port
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Periodic Characteristics |Periodic Characteristics]]'''
| style="width:250px;" | No observable required | style="width:300px;" | Computation of Computing the reflection and transmission coefficients when your periodic structure is excited by of a plane wave sourceperiodic surface| style="width:250px;" | Associated with Requires a hollow PEC boxplane wave source and periodic boundary conditions
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Domain Energy |Domain Energy]]'''
| style="width:300px250px;" | Computation '''[[Glossary of EM.Cube's Simulation Observables#Domain Energy |Domain Energy]]'''| style="width:300px;" | Computing the total electric and magnetic energy in the computational domain| style="width:250px;" | Stand-alone sourceNone
|-
| '''[[Glossary of EM.Cube's Simulation Observables#Huygens Surface |Huygens Surface]]'''
| style="width:250px;" | '''[[Glossary of EM.Cube's Simulation Observables#Huygens Surface |Huygens Surface]]'''| style="width:300px;" | Collecting tangential field data on a boxto be used later as a Huygens source in other [[EM.Cube]] modules| style="width:250px;" | Stand-alone sourceNone
|}