TLINP4NL simulates a transmission line with isolated (floating) ground terminals. The characteristics of the transmission line are specified as the characteristic impedance and the electrical length at a given frequency. By default, this model provides a partial account for circuit loss (insertion loss only). You can toggle the secondary parameter LossModel to access insertion loss, return loss, and dielectric loss (for example; for microstrips or stripline). Use extreme care with this element as it is meant to work in concert with additional elements which relate the voltages at both ends of the transmission line to the global ground. Unusual and unexpected behavior can result if these additional elements are omitted.

Note that any interaction with the ground on either side of the transmission line is ignored. All current on one conductor is equal and opposite to the current on the other at any given distance along the line. Importantly, this condition is enforced regardless of the length of the transmission line or the operating frequency. The exception to this behavior is at DC (Frequency = 0 Hz) where current on the two conductors can be unequal to allow both conductors to be used for biasing active devices. This change in behavior at DC causes a discontinuity of the model parameters at DC. This discontinuity is expected, and additional circuit components relating the voltage at each end of the transmission line to ground should be added, allowing flexibility in implementing the desired transition to the RF-to-DC performance.

Name | Description | Unit Type | Default |
---|---|---|---|

ID | Element ID | Text | TL1 |

Z | Impedance | 50 | |

NL | Number of wavelengths at F_NL | 0.25 | |

F_NL | Frequency at NL wavelengths | Frequency | 1 GHz |

K | Dielectric constant | 1 | |

A | Loss (dB/m) | 0 | |

F | Frequency for scaling loss | 0 | |

*LossModel | Partial/Full account for conductor and dielectric loss | Partial | |

*TanD | Dielectric loss tangent | 0 | |

*Mur | Relative dielectric permeability | 1 | |

*TanM | Dielectric magnetic loss tangent | 0 | |

*Sigma | Dielectric bulk conductivity (S/m) | 0 | |

*EpsFreqDep | Dielectric constant is frequency dependent (No/Yes) | No | |

*Fmin | Low roll-off frequency of Tand frequency dependence | Frequency | 1kHz |

*Fmax | High roll-off frequency of Tand frequency dependence | Frequency | 1THz |

*Fspec | Er and Tand are specified at this frequency | Frequency | 1GHz |

`* indicates a hidden secondary parameter`

Note that parameters marked by asterisk (*) are hidden/invisible while the control parameter LossModel=Partial (default value). Setting LossModel=Full displays these secondary parameters in the model's Element Options dialog box Parameters tab (except parameters Fmin, Fmax, and Fspec which are visible only when parameter EpsFreqDep=Yes).

**NL** and ** F_NL.** Determine
the frequency-dependence of the electrical length of the line, described as
βL=2πNL(freq/F_NL) where `freq`

is the evaluation frequency. The
length of the line is given as L=(c·NL)/(F_NL√k) where `c`

is the
speed of light in a vacuum.

**A** and **F**. Determine the
frequency-dependence of the attenuation constant. If F is not equal to zero (0.0), then

(dB/m) where `freq`

is the evaluation frequency. If F is
equal to zero, the attenuation is constant versus frequency and is equal to A (dB/m).

**LossModel** is a secondary control parameter that defines how
the model accounts for loss and dielectric parameters. If LossModel=Partial (default value) then
the model accounts for insertion loss (parameter Loss) only. If LossModel=Full then the model
accounts for insertion loss, return loss, dielectric loss, and for frequency-dependent model of
dielectric parameters (for example, for microstrips, stripline, or other).

**NOTE:** The secondary parameter LossModel displays when you
click the Show or hide secondary parameters button on the toolbar of the the
Element Options dialog box Parameters tab. If LossModel=Full, additional
secondary parameters display.

**EpsFreqDep** is a (hidden, secondary) control parameter that
defines if dielectric constant and dielectric loss tangent exhibit predefined
frequency-dependence, suggested in [1]. This dependence is controlled by the three frequency
parameters Fmin, Fmax, and Fspec, and imparts causal behavior to the model. Fmin, Fmax, and Fspec
are hidden (invisible) if EpsFreqDep=No.

The following is a Y-matrix for a grounded transmission line system:

where α+jβ represents the complex propagation constant, `Z`

is
the characteristic impedance of the line and `L`

is the length of the line as
derived from the input parameters.

Applying the equivalent circuit shown above, the Y-matrix of the floating transmission line system can be shown as follows:

At DC, the Y-matrix changes to a model of two wires above a ground plane:

where `R`

is a real resistance approaching zero.

This element does not have an assigned layout cell. You can assign artwork cells to any element. See “Assigning Artwork Cells to Layout of Schematic Elements” for details.

This model, along with additional components can be used to model transmission line baluns and transmission line transformers in which one of the conductors is shielded from ground, like a coaxial line.

**NOTE:** Because the model definition does not include
interactions with the ground, unusual and unexpected results can occur if other components are
not used to relate the voltage on both sides of the transmission line to ground.