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IEEE Transactions on Magnetics

Investigation of an electronically tuned 100 GHz superconducting phase shifter

Elie K. Track, Zhongxiang Shen, H. Dang, Masoud Radparvar, S. M. Faris

Published Mar 1, 1991• 9 citations
Publisher

Abstract

Turnable superconducting millimeter-wave phase shifters are discussed. The tuning mechanism is based on inductance modulation of NbN microstrips by excess quasiparticle injection. When measured by a DC method, using the interference patterns and resonances of specially designed DC SQUIDs, the inductance of NbN microstrips can be varied by up to 300%. Based on these results, superconducting microstrip interferometers to operate as low-power 100 GHz phase shifters were designed and fabricated. The 100 GHz signal is coupled into and out of the interferometers by finline antennas. Amplitude modulation of the output is used as the criterion for phase shift in one of the interferometer branches. Thin superconducting films (thinner than the penetration depth) and dielectric layers are needed to achieve tunability of the inductance. The conflicting requirements of tunability and efficient signal coupling are quantified in the interferometer testing, and the range of parameter optimization is bracketed. The elements of this required optimization are presented.

DOI
10.1109/20.133769

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The distributed Josephson inductance phase shifter

D.J. Durand, J. Carpenter, E. Ladizinsky +4 more

The authors report on a novel microwave phase shifter featuring rapid electronic adjustment, continuous phase control true time delay operation, high device fault tolerance, and very broadband operation. By coupling a large number of superconducting quantum interference devices (SQUIDs) to a superconducting microstrip transmission line, a variable magnetic medium in which the wave velocity is controlled electronically is created. The authors have measured 60 degrees phase shift at 10 GHz, and wideband operation from 5 to 15 GHz for an 8-cm-long Nb transmission line coupled to 1600 SQUIDs, each containing a single Nb/AlO/sub x//Nb tunnel junction. The observed phase shift corresponds to a change in wave velocity of about 1 part in 60.>

IEEE Transactions on Applied Superconductivity•Mar 1, 1992•25 citations
Turnable superconducting millimeter-wave phase shifters are discussed. The tuning mechanism is based on inductance modulation of NbN microstrips by excess quasiparticle injection. When measured by a DC method, using the interference patterns and resonances of specially designed DC SQUIDs, the inductance of NbN microstrips can be varied by up to 300%. Based on these results, superconducting microstrip interferometers to operate as low-power 100 GHz phase shifters were designed and fabricated. The 100 GHz signal is coupled into and out of the interferometers by finline antennas. Amplitude modulation of the output is used as the criterion for phase shift in one of the interferometer branches. Thin superconducting films (thinner than the penetration depth) and dielectric layers are needed to achieve tunability of the inductance. The conflicting requirements of tunability and efficient signal coupling are quantified in the interferometer testing, and the range of parameter optimization is bracketed. The elements of this required optimization are presented.
A novel approach to modulating the inductance of a superconducting microstrip is described. This approach could be the basis for numerous practical applications, such as phase-shifters and high-frequency tuning elements. The physical mechanisms involved are quasiparticle injection, gap suppression, and penetration-depth modulation. The authors have investigated the modulation of the penetration depth of niobium and niobium nitride films by excess quasiparticle injection. To this effect, all niobium and all-niobium-nitride SQUID (superconducting quantum interference device) circuits were designed and fabricated. These circuits allow quasiparticle injection into the inductive element of the SQUID. This injection is achieved by optical irradiation through an opening in a Nb reflective layer which partially masks the rest of the circuit or electronic current injection through a tunnel junction overlaid on the microstrip inductance. Penetration-depth modulation is achieved with both methods. The magnitude of the effect varies from 10% to over 200% change in inductance.>
Abstract : A Terahertz Imaging Radar System which exploits superconductive electronics for all of its major components is described in this report. In particular, the importance of the superconducting millimeter (mm) wave phase shifter in the development of such systems has been fully investigated. The experimental and theoretical results presented here are better than we expected to achieve under Phase I of the project. Conventional technology is unable to provide that high frequencies required to obtain small apertures for target acquisition. Superconducting technology offers a high performance, very broadband and low power, mm and sub-mm wave phase shifter based on superconducting microstrips. The physics of the non-equilibrium superconductivity underlying the operation of the superconducting microstrip phase shifter has been studied. Theoretical analysis and numerous experimental results show that superconducting stripline modulation leading to phase velocity reduction and subsequent phase shift is achievable by quasi-particle injection. A digital N-bit phase shifter based on the superconducting microstrip transmission line is proposed for development. The implementations of such a mm and sub-mm wave phase shifter will fulfill a crucial need in the development of the Terahertz Imaging Radar.
A Terahertz Imaging Radar System which exploits superconductive electronics for all of its major components is described in this report. In particular, the importance of the superconducting millimeter(mm)-wave phase shifter in the development of such systems was fully investigated. The experimental and theoretical results presented are better than the authors expected to achieve under Phase I of the project. Conventional technology is unable to provide the high frequencies required to obtain small apertures for target acquisition. Superconducting technology offers a high-performance, very broadband and low-power, mm- and sub-mm wave phase shifter based on superconducting microstrips. The physics of the non-equilibrium superconductivity underlying the operation of the superconducting microstrip phase shifter has been studied. Theoretical analysis and numerous experimental results show that superconducting stripline modulation leading to phase velocity reduction and subsequent phase shift is achievable by quasi-particle injection. A digital N-bit phase shifter based on the superconducting microstrip transmission line is proposed for development. The implementations of such a mm and sub-mm wave phase shifter will fulfill a crucial need in the development of the Terahertz Imaging Radar.
This article presents a low-temperature superconductor (LTS)-based microwave phase shifter. The device utilizes a superconducting hybrid coupler monolithically integrated with two tunable reflective loads. An array of radio frequency superconducting quantum interference devices (rf-SQUIDs) is used to achieve inductive tuning in reflective loads, resulting in a broadband true time delay phase shift. The rf-SQUIDs are current controlled using an on-chip dc bias circuitry. The proof-of-concept fabricated device provides excellent RF performance in theX{X}X- and Ku -band with a phase shift of 49° at 10 GHz and 67° at 15 GHz. The insertion loss is < 1.5 dB for the entire range from 8 to 18 GHz. The methods to further improve the obtained phase shift are discussed. The overall device has a chip footprint of 0.6 mm2 and is fabricated using MIT-Lincoln Lab (MIT-LL) SFQ5ee eight-layer Niobium (Nb)-based superconducting fabrication process.
We implement a broadly tunable phase shifter for microwaves based on superconducting quantum interference devices (SQUIDs) and study it both experimentally and theoretically. At different frequencies, a unit transmission coefficient, |S21| = 1, can be theoretically achieved along a curve where the phase shift is controllable by the magnetic flux. The fabricated device consists of three equidistant SQUIDs interrupting a transmission line. We model each SQUID embedded at different positions along the transmission line with two parameters, capacitance and inductance, the values of which we extract from the experiments. In our experiments, the tunability of the phase shift varies from 0.07 × π to 0.14 × π radians along the full-transmission curve with the input frequency ranging from 6.00 GHz to 6.28 GHz. The reported measurements are in good agreement with simulations, which is promising for future design work of phase shifters for different applications.
The authors report on a novel microwave phase shifter featuring rapid electronic adjustment, continuous phase control true time delay operation, high device fault tolerance, and very broadband operation. By coupling a large number of superconducting quantum interference devices (SQUIDs) to a superconducting microstrip transmission line, a variable magnetic medium in which the wave velocity is controlled electronically is created. The authors have measured 60 degrees phase shift at 10 GHz, and wideband operation from 5 to 15 GHz for an 8-cm-long Nb transmission line coupled to 1600 SQUIDs, each containing a single Nb/AlO/sub x//Nb tunnel junction. The observed phase shift corresponds to a change in wave velocity of about 1 part in 60.>