(Top) Simulation of the current distribution at resonance for the structure used in this work. (Bottom) The superconducting resonator chip with the couplers shown at points A and C. The third coupler is attached to the lid of the housing, so it is not visible in the photo.
A driving signal at and two low frequency probing signals, and , are fed into the device under test (6) after passive conditioning with a UTE Microwave CT-1395-NT ferrite isolator (2), a Merrimac PD-20–10 lumped element isolated combiner (3), a band pass filter (4), and a 400 MHz low pass filter (5). The output of the DUT is further cleaned with an optional band pass filter before entering the HP 8566B Spectrum Analyzer (7). and were generated by an Agilent 8648C signal generator and a Rhode & Schwartz SMB100A Signal Generator, respectively. was generated with an Agilent E4421B Signal Generator with frequency sweeping capability.
Measurement of the power reflected from the devices under test using a −20 dB M/A-COM KS-21603L7 directional coupler. from Port 1 and from port 2 are used in Eq. (3) to compute the reflection coefficients.
(a) Calibration of surface current density to the measured output power at 78.0 K. (b) Second and third order IMD curves, both exhibiting a slope less than unity, even for a driving current density below 50 A/m.
Close to the third order IMD at 101.2 K has become considerably larger than the second order IMD, and both curves exhibit a slope of unity as expected.
Article metrics loading...
Full text loading...