Changes

===Defining Ports & Modeling Feeds in Practical Applications===

[[Image:FDTD48.png|thumb|450px|EM.Tempo's Port Definition dialog.]]Ports are used to order and index sources for circuit parameter calculations like S/Y/Z parameters. In EM.Tempo, you can define ports at the location of the following types of sources: lumped, distributed, microstrip, CPW, coaxial and waveguide. If the physical structure in your project workspace has N sources, then N default ports are defined, with one port assigned to each source according to their order in the navigation tree. You can define any number of ports equal to or less than the total number of sources in your project.

If your physical structure has two or more *Lumped sources, but you have not defined any ports, all the lumped *Distributed sources excite the structure simultaneously. However, when you assign N ports to the *Microstrip port sources *CPW port sources, then you have a multiport structure that is characterized by an N×N scattering matrix, an N×N impedance matrix, and an N×N admittance matrix. To calculate these matrices, [[EM.Cube]] uses a binary excitation scheme in conjunction with the principle of linear superposition. In this binary scheme, the structure is analyzed N times. Each time one of the N *Coaxial port-assigned sources is excited, and all the other *Waveguide port-assigned sources are turned off.

For Every time you create a new source with one of the computation above types, the program asks if you want to initiate a new port and associate it with the newly created source. If the physical structure of your project workspace has N sources, then N default ports are defined, with one port assigned to each source according to their order in the S-parameters navigation tree. You can define any number of ports equal to or less than the total number of sources in [[your project.  If your physical structure has two or more sources, but you have not defined any ports, all the sources will excite the structure simultaneously during the simulation. However, when you assign N ports to the sources, then you have a multiport structure that is characterized by an N×N scattering matrix, an N×N impedance matrix, and an N×N admittance matrix. To calculate these matrices, EM.Tempo]]uses a binary excitation scheme in conjunction with the principle of linear superposition. In this binary scheme, the source associated with each structure is analyzed a total of N times. Each time one of the N port -assigned sources is excited separately with , and all the other ports port-assigned sources are turned off. In other words, the FDTD solver runs a "port sweep" internally. When the jth ''j''th port is excited, all the S_ij parameters are calculated together based on the following definition: