  We study self-sustained oscillations (SO) in a Nb superconducting stripline
resonators (SSR) integrated with a DC superconducting quantum interface devices
(SQUID). We find that both the power threshold where these oscillations start
and the oscillations frequency are periodic in the applied magnetic flux
threading the SQUID loop. A theoretical model which attributes the SO to a
thermal instability in the DC-SQUID yields a good agreement with the
experimental results. This flux dependant nonlinearity may be used for quantum
state reading of a qubit-SSR integrated device.
