Nonperiodic Flux to Voltage Conversion of an Arithmetic Series Array of   dc SQUIDs
  A theoretical study on the voltage response function <V> of a series array of dc SQUIDs is presented in which the elementary dc SQUID loops vary in size and, possibly, in orientation. Such series arrays of two-junction SQUIDs possess voltage response functions vs. external magnetic field B that differ substantially from those of corresponding regular series arrays with identical loop-areas, while maintaining a large voltage swing as well as a low noise level. Applications include the design of current amplifiers and quantum interference filters. 
Ch. Haeussler, J. Oppenlaender, and N. Schopohl