# gammain

Input reflection coefficient of 2-port network

## Syntax

`coefficient = gammain(s_params,z0,zl)coefficient = gammain(hs,zl)`

## Description

`coefficient = gammain(s_params,z0,zl)` calculates the input reflection coefficient of a 2-port network. `s_params` is a complex 2-by-2-by-M array, representing M 2-port S-parameters. `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.

`coefficient = gammain(hs,zl)` calculates the input reflection coefficient of the 2-port network represented by the S-parameter object `hs`.

## Examples

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

``` ckt = read(rfckt.amplifier,'default.s2p'); s_params = ckt.NetworkData.Data; z0 = ckt.NetworkData.Z0; zl = 100; coefficient = gammain(s_params,z0,zl);```

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### Algorithms

`gammain` uses the formula

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

where

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