Traveling wave electrode transmission line filter

## Keywords

electrical, unidirectional

## Ports

Name | Type |
---|---|

input | Electrical Signal |

output | Electrical Signal |

## Properties

### General Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines the name of the element. |
Traveling Wave Electrode | - | - |

Defines whether or not to display annotations on the schematic editor. |
true | - | [true, false] |

Defines whether or not the element is enabled. |
true | - | [true, false] |

Defines the element unique type (read only). |
Traveling Wave Electrode | - | - |

A brief description of the elements functionality. |
Traveling wave electrode transmission line filter | - | - |

Defines the element name prefix. |
TW | - | - |

Defines the element model name. |
- | - | - |

Defines the element location or source in the library (custom or design kit). |
- | - | - |

Defines the local path or working folder $LOCAL for the element. |
- | - | - |

An optional URL address pointing to the element online help. |
- | - | - |

### Standard Properties

Name | Default value | Default unit | Range |
---|---|---|---|

The interaction length of the modulator. |
0.01 | m | [0, +∞) |

Defines if the loss is constant or frequency dependent. Frequency dependency can be linear (~1/f), square root [~1/sqrt(f)] or from a table. |
constant | - | [constant, linear, square root, table |

Defines the microwave loss. |
0 | dB/m | [0, +∞) |

Central frequency of operation. |
1 | Hz | [0, +∞) |

Defines whether or not to load frequency dependent attenuation values from an input file or to use the currently stored values. |
false | - | [true, false] |

The file containing the frequency dependent attenuation values. Refer to the Implementation Details section for the format expected. |
- | - | - |

The table containing the frequency dependent attenuation values |
<2> [1, 0] | - | - |

### Standard/Source Impedance Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines if the impedance is constant or frequency dependent. |
constant | - | [constant, table |

Defines the source resistance. |
50 | Ohms | [0, +∞) |

Defines the source reactance. |
0 | Ohms | (-∞, +∞) |

Defines whether or not to load impedance values from an input file or to use the currently stored values. |
false | - | [true, false] |

The file containing frequency dependent impedance values. Refer to the Implementation Details section for the format expected. |
- | - | - |

The table containing the frequency dependent impedance values. |
<3> [1, 50, 0] | - | - |

### Standard/Characteristic Impedance Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines if the impedance is constant or frequency dependent. |
constant | - | [constant, table |

Defines the characteristic resistance. |
50 | Ohms | [0, +∞) |

Defines the characteristic reactance. |
0 | Ohms | (-∞, +∞) |

Defines whether or not to load impedance values from an input file or to use the currently stored values. |
false | - | [true, false] |

The file containing frequency dependent impedance values. Refer to the Implementation Details section for the format expected. |
- | - | - |

The table containing the frequency dependent impedance values. |
<3> [1, 50, 0] | - | - |

### Standard/Terminating Impedance Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines if the impedance is constant or frequency dependent. |
constant | - | [constant, table |

Defines the terminating resistance. |
50 | Ohms | [0, +∞) |

Defines the terminating reactance. |
0 | Ohms | (-∞, +∞) |

Defines whether or not to load impedance values from an input file or to use the currently stored values. |
false | - | [true, false] |

The file containing frequency dependent impedance values. Refer to the Implementation Details section for the format expected. |
- | - | - |

The table containing the frequency dependent impedance values. |
<3> [1, 50, 0] | - | - |

### Standard/Junction Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines the junction resistance. |
0 | ohm.m | [0, +∞) |

Defines if the junction capacitance is constant or voltage dependent. |
constant | - | [constant, table |

Defines the junction capacitance. |
0 | F/m | [0, +∞) |

Defines whether or not to load measurements from an input file or to use the currently stored values. |
false | - | [true, false] |

The file containing the measurement data. Refer to the Implementation Details section for the format expected. |
- | - | - |

A matrix editor for users to read the element current data values. |
<30,2> [-3, -2.896551724, -2.793103448,...] | - | - |

### Waveguide Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines if the microwave index is constant or frequency dependent. |
constant | - | [constant, table |

Defines the the microwave group index. |
4 | - | [0, +∞) |

Defines whether or not to load microwave index values from an input file or to use the currently stored values. |
false | - | [true, false] |

The file containing frequency dependent microwave index values. Refer to the Implementation Details section for the format expected. |
- | - | - |

The table containing the frequency dependent microwave index values. |
<2> [1, 4] | - | - |

Defines the waveguide group index. |
3 | - | [0, +∞) |

### Numerical Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines if the modulator response uses the frequency dependent modulation reduction factor or the frequency dependent average voltage as the transfer function. |
modulation reduction factor | - | [modulation reduction factor, modulation voltage |

### Numerical/Digital Filter Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Defines the operation of the internal time varying digital filter. |
interpolate | - | [interpolate, update |

Defines whether or not to use a single tap digital filter to represent the element transfer function in time domain. |
false | - | [true, false] |

Defines the method used to estimate the number of taps of the digital filter. |
fit tolerance | - | [disabled, fit tolerance, group delay |

Defines the mean square error for the fitting function. |
0.001 | - | (0, 1) |

Defines the window type for the digital filter. |
rectangular | - | [rectangular, hamming, hanning |

Defines the number of coefficients for digital filter. |
256 | - | [1, +∞) |

Defines the number of coefficients for digital filter. |
4096 | - | [1, +∞) |

Defines the time delay equivalent to a number of coefficients for digital filter. |
0 | s | [0, +∞) |

Defines whether to use the initial input signal to initialize filter state values or to set them to zero values. |
false | - | [true, false] |

### Diagnostic Properties

Name | Default value | Default unit | Range |
---|---|---|---|

Enables the frequency response of the designed filter implementation and the ideal frequency response to be generated as results. |
false | - | [true, false] |

The number of frequency points used when calculating the filter frequency response. |
1024 | - | [2, +∞) |

The upper frequency limit for the calculated graph. |
50e+009 | Hz | (0, +∞) |

## Results

Name | Description |
---|---|

diagnostic/normalized average voltage | The normalized average voltage vs. frequency. |

diagnostic/response #/transmission | The complex transmission vs. frequency corresponding to the ideal and designed filter. |

diagnostic/response #/gain | The gain vs. frequency corresponding to the ideal and designed filter. |

diagnostic/response #/error | Mean square error comparing the frequency response of the designed filter implementation with the ideal frequency response. |

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## Implementation Details

Since the 2017b R3 release, the Traveling Wave Electrode element implements two options for the transfer function, namely the "modulation reduction factor" and the "modulation voltage". The "modulation reduction factor" is defined as:

$$ r(\omega)=\left|\frac{V_{avg}(\omega)}{V_{avg}(0)}\right| $$ |
(1) |

and with the source impedance impact normalized away, the electrode output voltage with this option ("modulation reduction factor") is independent of source voltage, because the voltage is normalized to itself at ω=0.

The absolute response output is given by the option "modulation voltage", which is simply represented by V_{avg}(ω). With this transfer function option, the electrode output is impacted by the source impedance and overall, the larger the impedance mismatch between the device and source, the smaller the voltage on the device, and the smaller the phase-shift.

For more implementation details of Traveling Wave Electrode, please see the application example Traveling Wave Modulators for more information.

## Related Publications

- Hao Xu et al., "Demonstration and Characterization of High-Speed Silicon Depletion-Mode Mach–Zehnder Modulators", IEEE Journal of Selected Topics in Quantum Electronics, Vol. 20, No. 4 (2014)