  This paper presents a renormalization approach to many-particle systems. By
starting from a bare Hamiltonian ${\cal H}= {\cal H}_0 +{\cal H}_1$ with an
unperturbed part ${\cal H}_0$ and a perturbation ${\cal H}_1$,we define an
effective Hamiltonian which has a band-diagonal shape with respect to the
eigenbasis of ${\cal H}_0$. This means that all transition matrix elements are
suppressed which have energy differences larger than a given cutoff $\lambda$
that is smaller than the cutoff $\Lambda$ of the original Hamiltonian. This
property resembles a recent flow equation approach on the basis of continuous
unitary transformations. For demonstration of the method we discuss an exact
solvable model, as well as the Anderson-lattice model where the well-known
quasiparticle behavior of heavy fermions is derived.
