Superconducting Integrated Receiver Based on Nb-AlN-NbN-Nb Circuits

Abstract

The Superconducting Integrated Receiver (SIR) comprising in one chip a superconductor-insulator-superconductor (SIS) mixer and a phase-locked superconducting Flux Flow Oscillator (FFO) is under development for the international project TELIS. To overcome temperature constraints and extend operation frequency of the SIR we have developed and studied Nb-AlN-NbN-Nb circuits with a gap voltage Vg up to 3.7 mV and extremely low leakage currents (Rj Rn 30). Based on these junctions integrated microcircuits comprising FFO and harmonic mixer have been designed, fabricated and tested; the radiation from such circuits has been measured at frequencies up to 700 GHz. Employment of NbN electrode does not result in the appearance of additional noise. For example, FFO linewidth as low as 1 MHz was measured at 600 GHz, that allows us to phase lock up to 92% of the emitted by FFO power and realize very low phase noise about 90 dBc. Preliminary results demonstrated uncorrected DSB noise temperature of the Nb-AlN-NbN SIR below 250 K at frequencies around 600 GHz.

Superconducting integrated THz receivers: development and applications

“…This allows us to set any voltage (and any frequency) below V JSC , but for each voltage only a certain set of currents should be used. So, in this case we have the regions of forbidden bias-current values, specific for each voltage below V JSC , instead of the forbidden voltage regions for the Fiske regime in Nb-AlOx-Nb FFO 15 . Special algorithms have been developed for automatic working point selection in flight.…”

The concept of the receiving complex for the “Millimetron” space radio telescope

“…The application of the phase-locked loop to the wideband local oscillators based on Nb-AlO x -Nb and Nb-AlN-NbN structures, whose emission linewidth is equal to several megahertz at frequencies 550-750 GHz, will allow us to significantly reduce the phase noise. In particular, at a frequency of about 600 GHz, the emission linewidth of the wideband Nb-AlN-NbN local oscillator is only 1 MHz, which allows one to significantly reduce the phase noise to −90 dB by using the phase-locked loop [53]. Preliminary measurements (the optimization has not yet been performed) show that the double-sideband noise temperature of SIS mixers integrated with the wideband local oscillator and a part of the phase-locked loop does not exceed 250 K at a frequency of 600 GHz.…”

“…Preliminary measurements (the optimization has not yet been performed) show that the double-sideband noise temperature of SIS mixers integrated with the wideband local oscillator and a part of the phase-locked loop does not exceed 250 K at a frequency of 600 GHz. [53].…”

NbN/AlN/NbN Josephson Junctions on Sapphire for SIS Receiver Applications

“…The electrodes made from niobium exhibit a gap voltage of 2.9 mV, resulting in an upper frequency limit of 700 GHz. In order to overcome this limit, niobium nitride (NbN) or niobium titanium nitride was used in some cases as material of choice for one of the electrodes [7][8][9][10][11][12]. However, in order to achieve ultimate performance, both of the electrodes need to be of materials with high gap voltages, e.g.…”