function eps_swd_l91r, freq, temp

; This function returns the complex dielectric constant of suspended
; (pure) water droplets as a function of frequency f (GHz) and
; temperature T (deg. C), using the double Debye model of Liebe, Hufford,
; and Manabe (Int. J. IR & mm Waves V.12 (7) July 1991), as modified by
; P. W. Rosenkranz.
;
; converted from F90 to IDL by Chris O'Dell, 9/2003.

; INPUTS :
;
;		freq: 	frequencies (scalar or array), GHz
;		temp: 	scalar, [°C]

; OUTPUT :
;
;		eps:    complex dielectric constant [units: ???]

	theta = 1.0 - 300.0/(273.15 + temp)
  eps0 = 77.66 - 103.3*theta

  eps1 = 0.0671 * eps0
  eps2 = 3.52 + 7.52 * theta
  gamma1 = 20.20  + 146.4*theta + 316.0 * theta^2
  gamma2 = 39.8*gamma1

  eps = eps0 - freq * ((eps0 - eps1)/complex(freq,gamma1) $
  				+ (eps1 - eps2)/complex(freq,gamma2))

  return, eps

END