# gammain

Calculate input reflection coefficient of two-port network

## Description

example

coefficient = gammain(s_params,z0,zl) calculates the input reflection coefficient of a two-port network. z0 is the reference impedance Z0; its default value is 50 ohms. zl is the load impedance Zl; its default value is also 50 ohms. coefficient is an M-element complex vector.

example

coefficient = gammain(hs,zl) calculates the input reflection coefficient of the two-port network represented by the S-parameter object hs.

## Examples

collapse all

Calculate the input reflection coefficients at each index of an S-parameter array.

s_params = ckt.NetworkData.Data;
z0 = ckt.NetworkData.Z0;
zl = 100;
coefficient = gammain(s_params,z0,zl)
coefficient = 191×1 complex

-0.7247 - 0.4813i
-0.7323 - 0.4707i
-0.7397 - 0.4601i
-0.7470 - 0.4495i
-0.7542 - 0.4389i
-0.7612 - 0.4284i
-0.7682 - 0.4179i
-0.7750 - 0.4075i
-0.7817 - 0.3972i
-0.7883 - 0.3870i
⋮

Define a S-parameters object from a file.

s_params = sparameters('default.s2p');

zl = 100;

Calculate the input reflection coefficients at each index of a sparameters object.

coefficient = gammain(s_params,zl)
coefficient = 191×1 complex

-0.7247 - 0.4813i
-0.7323 - 0.4707i
-0.7397 - 0.4601i
-0.7470 - 0.4495i
-0.7542 - 0.4389i
-0.7612 - 0.4284i
-0.7682 - 0.4179i
-0.7750 - 0.4075i
-0.7817 - 0.3972i
-0.7883 - 0.3870i
⋮

## Input Arguments

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Two-port S-parameters, specified as a complex 2-by-2-by-M array. M is the number of two-port S-parameters.

Data Types: double

Reference impedance, specified as a positive scalar.

Data Types: double

Load impedance, specified as a positive scalar.

Data Types: double

Two-port network, specified as an S-parameter object.

Data Types: function_handle

## Output Arguments

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Input reflection coefficient, returned as a M element complex vector.

## Algorithms

gammain uses the equation:

${\Gamma }_{in}={S}_{11}+\frac{\left({S}_{12}{S}_{21}\right){\Gamma }_{L}}{1-{S}_{22}{\Gamma }_{L}}$

where

${\Gamma }_{L}=\frac{{Z}_{l}-{Z}_{0}}{{Z}_{l}+{Z}_{0}}$

## Version History

Introduced before R2006a