Engee documentation

rfckt.txline

Creates a common transmission line.

Library

EngeeRF

Description

Use the function rfckt.txline to create transmission lines, the characteristics of which include line losses, line length, loop type and short circuit.

Syntax

Function call

  • h = rfckt.txline() — creates a transmission line object with default properties.

  • h = rfckt.txline(Name=Value) — sets properties specified by one or more arguments of the type «name-value». Unspecified properties retain their default values.

Arguments

Input arguments «name-value»

Specify optional argument pairs as Name=Value, where Name — the name of the argument, and Value — the appropriate value.

Example: rfckt.txline(Z0 = 75) creates a transmission line object with a characteristic impedance 75 Ohms. You can specify multiple pairs «name-value».

# Name — the name of the object

+ "Transmission Line" (by default) | line

Details

The name of the object, set as a string.

This argument is read-only.
Типы данных

String

# NPort — number of ports

+ 2 (by default) | a positive integer

Details

The number of ports specified as a positive integer.

This argument is read-only.
Типы данных

Int64

# AnalyzedResult — calculated values of S-parameters, noise factor, OIP3 and group delay

+ the rfdata.data object

Details

Calculated values of S-parameters, noise factor, OIP3, and group delay, set as an object rfdata.data. For more information, see Algorithms.

This argument is read-only.
Типы данных

function_handle

# lineLength — the physical length of the transmission line, m

+ 0.01 (by default) | scalar

Details

The physical length of the transmission line, specified as a scalar in meters.

Типы данных

Float64

# StubMode — loop type

+ "NotAStub" (by default) | "Series" | "Shunt"

Details

The type of loop specified by one of the following values: "NotAStub", "Series", "Shunt".

# Termination — closing of the transmission loop
"NotApplicable" (by default) | "Open" | "Short"

Details

The short circuit of the transmission loop, set by one of the following values: "NotApplicable", "Open", "Short".

# Freq — frequency values

+ 1e9 | vector

Details

Frequency values in Hz, set as a vector from elements. The values must be positive and correspond to the order of the loss values and the phase velocity.

Типы данных

Float64

# Z0 — characteristic impedance

+ 50 (by default) | vector

Details

The characteristic impedance, specified as a vector in ohms.

Типы данных

Float64

# PV — phase velocity

+ 2.99792458e8 (by default) | vector

Details

The phase velocity or propagation velocity of a homogeneous plane wave on a transmission line, given as a vector from elements in m/s. The phase velocity values correspond to the frequency values specified in the argument Freq.

Типы данных

Float64

# Loss — reduced signal strength
0 (by default) | vector

Details

The decrease in signal power as it passes through the transmission line, defined as a vector from non-negative elements in dB/m.

Типы данных

Float64

# IntpType — interpolation method

+ "Linear" (by default) | "Spline" | "Cubic"

Details

The interpolation method used in the function rfckt.txline, set as one of the following values:

  • "Linear" — linear interpolation;

  • "Spline" — cubic spline interpolation;

  • "Cubic" — piecewise cubic Hermite interpolation.

Output arguments

# h — transmission line object

+ object

Details

A transmission line object containing the following properties:

  • Name — the name of the object as a string, for example "Transmission Line";

  • nPort — number of ports;

  • AnalyzedResult — calculated values of S-parameters, noise factor, OIP3 and group delay;

  • LineLength — length of the transmission line;

  • StubMode — type of train;

  • Termination — shorting of the transmission loop line;

  • Freq — frequency values;

  • Z0 — characteristic impedance;

  • PV — phase velocity;

  • Loss — reduced signal power;

  • IntpType — the interpolation method.

Examples

Creating a transmission line

Details

Let’s create a transmission line using the function rfckt.txline.

using EngeeRF

trl = rfckt.txline(Z0 = 75)

println("Name: ", trl.Name,
        "\nnPort: ", trl.nPort,
        "\nAnalyzedResult: ", trl.AnalyzedResult,
        "\nLineLength: ", trl.LineLength,
        "\nStubMode: ", trl.StubMode,
        "\nTermination: ", trl.Termination,
        "\nFreq: ", trl.Freq,
        "\nZ0: ", trl.Z0,
        "\nPV: ", trl.PV,
        "\nLoss: ", trl.Loss,
        "\nIntpType: ", trl.IntpType)
Name: Transmission Line
nPort: 2
AnalyzedResult: nothing
LineLength: 0.01
StubMode: NotAStub
Termination: NotApplicable
Freq: 1.0e9
Z0: 75.0 + 0.0im
PV: 2.99792458e8
Loss: 0.0
IntpType: Linear

Algorithms

Method analyze considers a transmission line, which can be lossy or lossless, as a two-port linear network. It calculates the property AnalyzedResult for a loop line or a line without a loop, using the data stored in the object properties rfckt.txline, as follows:

  • If we model the transmission line as a line without a loop, the method analyze First, it calculates the ABCD parameters at each frequency contained in the vector of simulated frequencies. Then he uses the function abcd2s to convert ABCD parameters to S parameters.

    Method analyze calculates the ABCD parameters using the physical length of the transmission line and a comprehensive distribution constant , using the following equations:







    where — specified in the argument Z0 the characteristic impedance, and — a vector whose elements correspond to the elements of the frequency vector specified in the input argument Freq functions analyze. Method analyze calculates based on the set properties as , where — attenuation coefficient, and — the wave number. Attenuation coefficient associated with specified losses the ratio

    The wave number is it related to a given phase velocity the ratio

    Phase velocity determined by the properties of the object rfckt.txline. It is also known as the wave propagation velocity.

  • If we model the transmission line as a parallel or serial loop, the method analyze first, it calculates the ABCD parameters at the specified frequencies. Then he uses the function abcd2s to convert ABCD parameters to S parameters.

    If for an argument StubMode the value is set "Shunt", then the two-port network consists of a loopback transmission line that can be closed or opened, as shown in the following figure.

    rfckt coaxial 1

    Here — input impedance of the parallel circuit. The ABCD parameters for the parallel loop are calculated as follows:







    If for an argument StubMode the value is set "Series", then the two-port network is a serial transmission line that can be closed or opened, as shown in the following figure.

    rfckt coaxial 2

    Here — input impedance of the serial circuit. The ABCD parameters for the serial loop are calculated as follows:







Literature

  1. Ludwig, R. and P. Bretchko, RF Circuit Design: Theory and Applications, Prentice-Hall, 2000.