  We use Wegner's flow equation method to investigate the infinite-$U$ periodic
Anderson model. We show that this method poses a new approach to the
description of heavy fermion behaviour. Within this scheme we derive an
effective Hamiltonian where the $c$ and $f$ degrees of freedom are decoupled.
By evaluating one-particle energies as well as correlation functions we find an
electronic structure which comprises two gapped quasiparticle bands. We also
address the lattice Kondo temperature, which shows a typical exponential
dependence on the hybridisation energy. This energy scale exhibits a
significant decrease compared to that of the single impurity Anderson model.
