Lyudmila V. Filippenko

First Implementation of a superconducting integrated receiver at 450 GHz

An integrated quasioptical receiver consisting of a planar double dipole antenna, superconductor‐insulator‐superconductor mixer and a superconducting local oscillator (LO) with matching circuits has been designed, fabricated and tested in the frequency range 360–490 GHz. A flux‐flow oscillator (FFO) based on unidirectional and viscous flow of magnetic vortexes in a long Josephson tunnel junction, is employed as a local oscillator. All components of the receiver are integrated on a 4 mm×4 mm×0.2 mm crystalline quartz substrate using a single Nb–AlOx–Nb trilayer. The lowest DSB noise temperature of 470–560 K has been achieved within a frequency range of 425–455 GHz.

Superconducting millimeter wave oscillators and SIS mixers integrated on a chip

All-refractory material superconducting millimeter-wave oscillators have been designed and investigated experimentally with different superconductor-insulator-superconductor (SIS) mixers integrated on the same chip. Tested structures include a flux-flow oscillator (FFO) based on a long Josephson junction, a coupling section, and an SIS detector with tuned out junction capacitance. Coupling sections were designed as multistep microstrip quarter-wave impedance transformers. All junctions have been fabricated on the basis of a high-quality trilayer Nb-AlO/sub x/-Nb process. Microwave oscillations in the frequency range 75-500 GHz have been detected experimentally. The level of delivered power was estimated from the pumped I-V curve of the strongly coupled single junction detector. Coupled power levels higher than 0.1 mu W at 256 GHz were achieved. A spectral linewidth of the FFO of less than 1 MHz has been estimated experimentally. The first attempt to create an integrated receiver based on an FFO and an SIS array mixer integrated on the same chip was made in the 2-mm wavelength band.<<ETX>>

Superconducting integrated receiver for TELIS

TELIS (Terahertz and submm Limb Sounder) is a cooperative European project to develop a three-channel heterodyne balloon-based spectrometer for measuring a variety of atmospheric constituents within the lower stratosphere. The 600-650GHz channel is based on a phase-locked Superconducting Integrated Receiver (SIR). SIR is the on-chip combination of a low-noise SIS mixer with quasioptical antenna, a superconducting Flux Flow Oscillator (FFO) acting as Local Oscillator (LO) and an SIS harmonic mixer (HM) for FFO phase locking. A number of new solutions was implemented in the new generation of SIR chips. To achieve the wide-band performance of the spectrometer, a side-feed twin-SIS mixer with 0.8 /spl mu/m/sup 2/ junctions integrated with a double-dipole (or double-slot) antenna is used. A Fourier transform spectrometer (FTS) test demonstrated a possibility to obtain the required instantaneous bandwidth for the SIS mixer. To ensure the autonomous operation of the phase-locked SIR on the balloon a number of approaches for the PLL SIR automatic control have been developed.

A one-dimensional tunable magnetic metamaterial

We present experimental data on a one-dimensional super-conducting metamaterial that is tunable over a broad frequency band. The basic building block of this magnetic thin-film medium is a single-junction (rf-) superconducting quantum interference device (SQUID). Due to the nonlinear inductance of such an element, its resonance frequency is tunable in situ by applying a dc magnetic field. We demonstrate that this results in tunable effective parameters of our metamaterial consisting of 54 rf-SQUIDs. In order to obtain the effective magnetic permeability μr,eff from the measured data, we employ a technique that uses only the complex transmission coefficient S₂₁.

Integrated sub-MM wave receivers

The concept of a fully integrated superconducting receiver looks very attractive for sub-mm space astronomy where low weight, power consumption and volume are required. The possibility to integrate on a few chips the different planar components: a SIS mixer, a superconducting local oscillator (LO), an intermediate frequency amplifier followed by superconducting circuits for digitizing and processing of down converted signals, is discussed. A first implementation of a real integrated quasioptical receiver for frequencies up to 500 GHz is described. The one-chip receiver comprises a double dipole antenna, parallel biased SIS array mixer and Josephson Flux Flow Oscillator (FFO) with matching circuits. The results of extensive investigations of the integrated receiver as well as design and investigation of novel superconducting elements are presented.<<ETX>>

Towards a Phase-Locked Superconducting Integrated Receiver: Prospects and Limitations

Presently a Josephson flux flow oscillator (FFO) appears to be the most developed superconducting on-chip local oscillator for integrated submillimeter-wave SIS receivers. The feasibility of phase locking the FFO to an external reference oscillator at all frequencies of interest has to be proven for practical FFO implementation in radio astronomy and other spectral applications. A linewidth of a phase-locked FFO as low as 1 Hz has been measured relative to an external reference oscillator in the frequency range 270–440 GHz on steep Fiske steps in the low damping regime. The increase of the intrinsic linewidth at higher voltages due to an abrupt increase of the internal damping considerably complicates phase locking of the FFO. Comprehensive measurements of the FFO radiation linewidth have been performed using an integrated harmonic SIS mixer. Results on FFO linewidth and spectral line profile have been compared to theory in order to optimize the FFO design. The influence of FFO parameters on radiation linewidth, particularly the effect of the differential resistances associated both with the bias current and the applied magnetic field, has been studied. Two integrated receiver concepts with phase-lock loop have been developed and experimentally tested. 2002 Published by Elsevier Science B.V.

Phase locked 270-440 GHz local oscillator based on flux flow in long Josephson tunnel junctions

The combination of narrow linewidth and wide band tunability makes the Josephson flux flow oscillator (FFO) a perfect on-chip local oscillator for integrated sub-mm wave receivers for, e.g., spectral radio astronomy. The feasibility of phase locking the FFO to an external reference oscillator is demonstrated experimentally. A FFO linewidth as low as 1 Hz (determined by the resolution bandwidth of the spectrum analyzer) has been measured in the frequency range 270–440 GHz relative to a reference oscillator. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. The results of residual FFO phase noise measurements are also presented. Finally, we propose a single-chip fully superconductive receiver with two superconductor–insulator–superconductor mixers and an integrated phase-locked loop.

Superconducting chip receivers for imaging application

Experimental details of a unique superconducting imaging array receiver are discussed. Each pixel contains an internally pumped receiver chip mounted on the back of the elliptical microwave lens. Each chip comprises a quasi-optical SIS mixer integrated with a superconducting flux-flow oscillator (FFO) both fabricated from the same Nb/AlO/sub x//Nb trilayer on a silicon substrate. Properties of the integrated lens antenna were studied using an externally pumped reference SIS mixer which showed antenna sidelobes below /spl sim/17 dB and a receiver double side band noise temperature, T/sub RX/(DSB), below 100 K within the frequency range 460-500 GHz that is close to the quantum noise. For the imaging array T/sub RX/(DSB)=150 K has been measured at 500 GHz using the internal flux-flow oscillator as a local oscillator (LO). A balanced SIS mixer was tested showing T/sub RX/(DSB)<100 K within the range of 480-510 GHz using the internal LO. A computer system was developed to control simultaneously the dc bias of the SIS mixer and the frequency and power provided by FFO. The system also performs automatic optimization of the receiver noise temperature.

LINEWIDTH OF SUBMILLIMETER WAVE FLUX-FLOW OSCILLATORS

A reliable technique for wide band measurements of the spectral linewidth of superconducting oscillators integrated on‐chip with superconductor‐insulator‐superconductor (SIS) detectors has been developed. The spectral linewidth of flux‐flow oscillators (FFO) based on the unidirectional and viscous flow of magnetic vortices in a long overdamped Josephson tunnel junction was measured in the frequency range 250–580 GHz, and a linewidth as low as 200 kHz was obtained at 450 GHz. Also stable frequency locking of a FFO to very high (≤60th) harmonics of an external microwave reference source has been demonstrated. The proposed technique may improve the sensitivity, frequency resolution, and stability of the fully superconducting integrated submillimeter wave receiver.

An integrated 500 GHz receiver with superconducting local oscillator

An integrated quasioptical receiver consisting of a planar double-dipole antenna, SIS mixer and superconducting Flux-Flow Oscillator (FFO) with matching circuits has been designed, fabricated and tested in the frequency range 420-530 GHz. The integrated receiver is very suitable for space applications because of its low size, mass and power consumption. All components of the receiver are integrated on a 4 mm/spl times/4 mm/spl times/0.2 mm crystalline quartz substrate using a single Nb-AlO/sub x/-Nb trilayer. The successful operation of the integrated receiver comprising a number of new crucial elements has been demonstrated. A DSB noise temperature as low as 140 K at 500 GHz and a tuning range of more than 100 GHz have been obtained. A comparison of the FFO with conventional external LO has been performed.