CalcDrudeMaterial
=================
```{function}  CalcDrudeMaterial(f, eps_r, kappa, plasmaFreq, t_relax)
```
Full definition:
```{code-block} matlab
eps_drude = CalcDrudeMaterial(f, eps_r, kappa, plasmaFreq, t_relax)
```

Calculate the Drude type dispersive material constant

arguments:
- f:           frequeny range of interest
- eps_r:       eps_r infinity
- kappa:       conductivity (losses)
- plasmaFreq:  (vector) plasma frequencies
- t_relax:     (vector) relaxation time (losses)

return:
- eps_drude: the complex relative permitivity

Example:

    % silver (AG) at optical frequencies (Drude model) [1, p. 201]
    f = linspace(300e12, 1100e12, 201);
    eps_model = CalcDrudeMaterial(f, 3.942, 7.97e3, 7e15/2/pi, 0, 1/2.3e13);

    figure
    plot(f,real(eps_model))
    hold on;
    grid on;
    plot(f,imag(eps_model),'r--')

See also: CalcDebyeMaterial, CalcLorentzMaterial

* [1] Rennings, Andre: "Elektromagnetische Zeitbereichssimulationen
      innovativer Antennen auf Basis von Metamaterialien."
      PhD Thesis, University of Duisburg-Essen, September 2008



-----------------------
author: Thorsten Liebig (2013)