function [er] = ersoil(f,T,mv);

% Calculation of the complex relative permittivity of moist soil
% for the REBEX-7 and REBEX-8 sites
% using the Dobson et al, 1985, semi-empirical model.
% Soil texture for R8:  16.1% sand, 55.0% silt, 28.9% clay.
% exp(-iwt) time dependence, Imag(er) > 0.
% Brian Hornbuckle, April 16, 2002.  Modified April 13, 2006.

% This function uses the function erwater.m
% which caculates the complex relative permittivity of pure water

% mv = volumetric water content of the soil, m^3 m^-3
% T = temperature, K
% f = frequency, Hz

S = 0.161;  Silt = 0.550;  C = 0.289;

% -------- fitting parameters

alpha = 0.65;
beta = 1.09 - 0.11*S + 0.18*C;

% ------------ soil solids

epsilon_ss = 4.7;			% relative permittivity of soil solids
ro_ss =	2.65;				% particle density (density of soil solids), g cm-3
					% could possibly change this will real data,
					% but epsilon_ss was optimized for this value
ro_bulk = 0.362*1.21 + 0.638*1.09;	% LOW bulk density = 1.21 g cm-3, HIGH bulk density = 1.09 g cm-3
					% 36.2% LOW areas, 63.8% HIGH areas
v_phi = 1 - ro_bulk/ro_ss;		% soil porosity, cm-3 cm-3

ss = (1 - v_phi)*epsilon_ss^alpha;	% soil solids contribution

% ---------- air

a = (v_phi - mv)*1^alpha;		% air contribution

% ---------- free and bound water

fwbw = mv.^beta.*erwater(T,f).^alpha;	% free and bound water contribution

% -------------------

er = (ss + a + fwbw).^(1/alpha);