* '''[[#Exciting_Periodic_Structures_Using_Plane_Waves|Periodic Characteristics]]''' for calculating the reflection and transmission coefficients when your periodic structure is excited by a plane wave source.
* '''Domain Energy''' for calculating the total electric and magnetic energy in the computational domain.
* '''[[Hybrid_Modeling_using_Multiple_Simulation_Engines#Generating_Huygens_Surface_Data | Huygens Surface]]''' for collecting tangential field data on a box.
Of [[EM.Tempo]]'s frequency domain observables, the near fields, far fields and all of their associated [[parameters]] like directivity, RCS, etc., are calculated at a certain single frequency that is specified as part of the definition of the observable. To compute those frequency domain data at several frequencies, you need to define multiple observables, one for each frequency. On the other hand, port characteristics like S/Y/Z [[parameters]], VSWR and periodic characteristics like reflection and transmission coefficients, are calculated over the entire specified bandwidth of your project.