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[[File:tline6.png|thumb|320px350px| Microstrip Line Calculator.]]

Oftentimes, you may want You often need to design a 50Ω transmission line of a certain type, or calculate and compare the characteristics of several transmission line types. For every physical transmission line type, [[RF.SpiceA/D]] also provides a ten physical transmission line designer tooltools. The designer ignores designers ignore the conductor and dielectric losses and calculates calculate the physical dimensions of the line for a given value of the characteristic impedance Z0. For example, given a substrate with thickness h and relative permittivity ε_r, the "Microstrip Designer" calculates the microstrip width in mm for a given value of Z0 (50 Ohms by default). Some line type like CPW and coaxial line have more than one dimensional parameter that can be varied. For example, CPW has slot width (w) and center strip width (s), while coaxial line has inner and outer conductor radii. In such cases, the Line Designer line designer dialog provides radio button options to fix one parameter and vary the other.

Besides the Generic T-Line Discontinuity devices described earlier, [[RF.SpiceA/D]] also offers a large number of physical transmission line discontinuity devices based on some of the transmission line types listed above. Among these, the microstrip components are more widely used and have more variety. Unlike the generic T-line components which require that you supply the S-parameter data, the physical components are parameterized based on their geometrical and material properties. As a result, you simply enter the physical dimensions and other [[parameters]] and their S-[[parameters]] are automatically calculated by [[RF.SpiceA/D]] during the circuit simulation. In other words, the property dialog of these components contains their physical [[parameters]] only and does not show the values of their S-[[parameters]] as a function of frequency.