Harmonic distortion and intermodulation products in the microstrip amplifier based on a superconducting quantum interference device

The harmonic distortion and intermodulation products have been measured for a microstrip amplifier based on a dc superconducting quantum interference device. When the flux bias is adjusted to maximize the gain, in general bot h second harmonic and a series of odd harmonics are observed. The magnitude of the third harmonic is in good agreement with a simple model. The magnit ude of the second harmonic, however, depends critically on the flux bias an d is generally a minimum when the gain is slightly less than the maximum va lue. Similar results are found for the two lowest order intermodulation pro ducts. (C) 2001 American Institute of Physics.