MODELING THE DIRECT-CURRENT SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE COUPLED TO THE MULTITURN INPUT COIL .2.

A complete circuit model of a dc superconducting quantum interference device (SQUID) coupled to a multiturn input coil has been developed. With this model, it is shown that the rf properties of the coupled SQUID can be calculated using only the given parameters of the SQUID. There are no adjustable parameters. The resonant structures in the SQUID characteristics caused by the presence of the input coil have been quantitatively studied. Methods to suppress the resonant structures have also been investigated. It is shown that the present circuit model explains well the experimentally observed rf properties of coupled SQUIDs. The present circuit model is therefore useful for the design of highly sensitive SQUIDs.