The Generic Open Stub and Generic Short Stub are two one-port devices based on the Generic T-Line device. They represent terminated generic transmission line segments. In the open stub case, the termination load is Z<sub>L</sub> → ∞, and in the short stub case, the termination load is Z<sub>L</sub> = 0. The [[parameters]] of both open and short stub devices are the same as those of the generic T-line device.
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[[File:tline3.png|thumb|300px| The schematic symbol of the Generic Coupled T-Lines device.]]
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=== The Generic Coupled T-Lines ===
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Many passive RF devices such as directional couplers, hybrids and some filter designs involve segments of parallel coupled [[Transmission Lines|transmission lines]]. According to the coupled mode theory, one can define even and odd mode impedances for such [[Transmission Lines|transmission lines]]. The resulting RF structure can be modeled as a four-port network device as shown in the opposite figure. Note that the four-port device has eight pins. Ports 1 and 2 correspond to the input and output of the first transmission line segment, while Ports 3 and 4 correspond to the input and output of the second (coupled) line segment. It is very important to connect and ground the negative pins at the input and output of the two transmission line segments.
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The Generic Coupled T-Lines device has the following [[parameters]]:
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* Z0e: Even Mode Characteristic Impedance in Ohms
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* Z0o: Odd Mode Characteristic Impedance in Ohms
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* eeff: Effective Permittivity
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* len: Physical Length in meters
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This model assumes lossless [[Transmission Lines|transmission lines]].
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[[File:tline4.png|thumb|450px| The schematic symbols of the Generic T-Line Discontinuity devices: (a) Open End, (b) Bend, (c) Step Junction, (d) Tee Junction and (e) Cross Junction.]]
=== Generic T-Line Discontinuities ===
In real practical RF circuits, you often need to transition from one transmission line to another or connect two or more [[Transmission Lines|transmission lines]] together. These transitions can be modeled as [[Multiport Networks|multiport networks]]. [[RF.Spice]] currently offers five generic T-Line discontinuity devices as follows:
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* Generic Open End (a one-port)
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* Generic Bend (a two-port)
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* Generic Step Junction (a two-port)
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* Generic Tee Junction (a three-port)
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* Generic Cross Junction (a four-port)
[[File:tline5.png|thumb|450px| The schematic symbols of the some Physical Transmission Line Discontinuity devices. (Top Row) microstrip components: right-angled bend, mitered bend, tee and cross junctions, (Bottom Row) CPW components: open end, short end, gap and step junction.]]
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=== Physical Transmission Line Discontinuities ===
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Besides the Generic T-Line Discontinuity devices described earlier, [[RF.Spice]] 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.Spice]] 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.
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For more information about physical transmission line discontinuity devices, please refer to [[Glossary_of_Physical_Transmission_Lines_and_Components|Glossary of Physical Transmission Lines and Components]].
=== Physical Line Calculations and Design ===
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</table>
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=== Physical Transmission Line Discontinuities ===
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Besides the Generic T-Line Discontinuity devices described earlier, [[RF.Spice]] 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.Spice]] 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.
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For more information about physical transmission line discontinuity devices, please refer to [[Glossary_of_Physical_Transmission_Lines_and_Components|Glossary of Physical Transmission Lines and Components]].
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== Working with Coupled Transmission Line Devices ==
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[[File:tline3.png|thumb|300px| The schematic symbol of the Generic Coupled T-Lines device.]]
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=== The Generic Coupled T-Lines ===
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Many passive RF devices such as directional couplers, hybrids and some filter designs involve segments of parallel coupled [[Transmission Lines|transmission lines]]. According to the coupled mode theory, one can define even and odd mode impedances for such [[Transmission Lines|transmission lines]]. The resulting RF structure can be modeled as a four-port network device as shown in the opposite figure. Note that the four-port device has eight pins. Ports 1 and 2 correspond to the input and output of the first transmission line segment, while Ports 3 and 4 correspond to the input and output of the second (coupled) line segment. It is very important to connect and ground the negative pins at the input and output of the two transmission line segments.
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The Generic Coupled T-Lines device has the following [[parameters]]:
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* Z0e: Even Mode Characteristic Impedance in Ohms
* Z0o: Odd Mode Characteristic Impedance in Ohms
* eeff: Effective Permittivity
* len: Physical Length in meters
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This model assumes lossless [[Transmission Lines|transmission lines]].
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[[File:tline4.png|thumb|450px| The schematic symbols of the Generic T-Line Discontinuity devices: (a) Open End, (b) Bend, (c) Step Junction, (d) Tee Junction and (e) Cross Junction.]]
=== Analyzing and Designing Physical Coupled Lines ===