Measuring VHF Detector Linearity Using a Quantum-Based Source

We demonstrate the use of a Josephson Arbitrary Waveform Synthesizer (JAWS) for linearity measurements of two instruments: an RF power sensor and a fast ADC. The VHF-JAWS source consists of a chip with 12,810 Josephson junctions located in a cryocooler and driven to produce quantum-based ac waveforms at frequencies up to 50.05 MHz and power up to -19 dBm. We first confirm that the device is operating correctly by measuring the dc bias current quantum-locking range and then measure the system output power with an RF power sensor and a high-speed digitizer. After removing an overall scale factor, the ten-nanowatt scale differences between the programmed JAWS values and the measured values indicate better than +/- 0.5 % DUT linearity for frequencies in the VHF band.