Analytical study of the two first period-doubling bifurcations in a three-d
imensional system is reported. The multiple scales method is first applied
to construct a higher-order approximation of the periodic orbit following H
opf bifurcation. The stability analysis of this periodic orbit is then perf
ormed in terms of Floquet theory to derive the critical parameter values co
rresponding to the first and second period-doubling bifurcations. By introd
ucing suitable subharmonic components in the first order of the multiple sc
ale analysis the two critical parameter values are obtained simultaneously
solving analytically the resulting system of two algebraic equations. Compa
risons of analytic predictions to numerical simulations are also provided.