Novel Stable and Reliable Readout Electronics for HTS rf SQUID

Conventional readout electronics for radio-frequency SQUIDs exhibit long-term instabilities due to a temperature-dependent frequency drift of their voltage controlled oscillator. A novel electronics with a quartz-controlled synthesizer was developed to solve this problem. The frequency can be adjusted from 450 to 900 MHz with 2 ppm frequency stability, the amplitude range covers more than 60 dB. An adjustable phase shifter for demodulation is implemented to compensate for variable cable length. The total amplification is about 100 dB. The electronics with touchpanel and remote USB control is commercially available with up to three preamplifier units. Because thermal drift is eliminated, it is well suited for outdoor applications, e.g. in geophysics.