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IEEE Transactions on Microwave Theory and Techniques

A hybrid phase shifter circuit based on TlCaBaCuO superconducting thin films

G. Subramanyam, Vikram J. Kapoor, K. B. Bhasin

Published Mar 1, 1995• 5 citations

Abstract

A superconductor-semiconductor hybrid reflection-type phase shifter circuit has been designed, fabricated, and characterized for 180/spl deg/ phase bit with center frequency of 4 GHz and bandwidth of 0.5 GHz for operation at 77 K. All of the passive components of the phase shifter circuit such as input/output feed lines, 3 dB Lange coupler, impedance matching networks, and transmission lines consisted of thallium based superconducting TlCaBaCuO thin films of 4000 /spl Aring/ thickness on lanthanum aluminate substrate. Metal-Schottky field-effect-transistors (MESFET's) on GaAs semiconductor were used as active devices for switching action (on-state and off-state) in the phase shifter circuit. The phase shift and insertion losses were investigated as a function of frequency from 3.6 to 4.6 GHz at 77 K. The circuit exhibited a fairly flat response of 180/spl deg/ phase shift with a maximum deviation of less than 2/spl deg/ and a maximum insertion loss of 2 dB for on-state and 2.2 dB for off-state conditions over 0.5 GHz bandwidth at 4 GHz. The insertion losses were also fairly flat within the bandwidth. The insertion losses were constant between 50 and 80 K, giving the circuit a large range of operation at or below 77 K. The performance of this circuit as compared to a gold microstrip-semiconductor circuit designed identically was superior by a factor of 1.5, and may be due to lower conductor losses and lower surface resistance in the superconducting microstrips.>

DOI: 10.1109/22.372102

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A superconductor-semiconductor hybrid reflection-type phase shifter circuit has been designed, fabricated, and characterized for 180/spl deg/ phase bit with center frequency of 4 GHz and bandwidth of 0.5 GHz for operation at 77 K. All of the passive components of the phase shifter circuit such as input/output feed lines, 3 dB Lange coupler, impedance matching networks, and transmission lines consisted of thallium based superconducting TlCaBaCuO thin films of 4000 /spl Aring/ thickness on lanthanum aluminate substrate. Metal-Schottky field-effect-transistors (MESFET's) on GaAs semiconductor were used as active devices for switching action (on-state and off-state) in the phase shifter circuit. The phase shift and insertion losses were investigated as a function of frequency from 3.6 to 4.6 GHz at 77 K. The circuit exhibited a fairly flat response of 180/spl deg/ phase shift with a maximum deviation of less than 2/spl deg/ and a maximum insertion loss of 2 dB for on-state and 2.2 dB for off-state conditions over 0.5 GHz bandwidth at 4 GHz. The insertion losses were also fairly flat within the bandwidth. The insertion losses were constant between 50 and 80 K, giving the circuit a large range of operation at or below 77 K. The performance of this circuit as compared to a gold microstrip-semiconductor circuit designed identically was superior by a factor of 1.5, and may be due to lower conductor losses and lower surface resistance in the superconducting microstrips.>

Superconducting circuit quantum electrodynamics experiments with propagating microwaves require devices acting as beam splitters. Using niobium thin films on silicon and sapphire substrates, we fabricated superconducting 180° microstrip hybrid ring couplers, acting as beam splitters with center frequencies of about 6 GHz. For the magnitude of the coupling and isolation, we find −3.5±0.5 dB and at least −15 dB, respectively, in a bandwidth of 2 GHz. We also investigate the effect of reflections at the superconductor-normal conductor contact by means of low temperature laser scanning microscopy. Our measurements show that our hybrid rings are well suited for on-chip applications in circuit quantum electrodynamics experiments.

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 the

{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.

This letter presents a low-temperature superconductor (LTS)-based

{X}

- and

{K}

-band analog ultra-wideband phase shifters realized by coupling an array of radio-frequency superconducting quantum interference devices (rf-SQUIDs) to a microwave transmission line (TL). The proposed device is realized using MIT-LL SFQ5ee eight-layer niobium-based process. The device is designed by distributing 2256 rf-SQUIDs coupled throughout the line exhibiting experimental analog current-controlled phase shift of 130° and insertion loss variation of 0.46 ± 0.23 dB in

{X}

-band at

{f} _{c}

= 10 GHz. In the

{K}

-band, a phase shift of 328° and insertion loss of 2.5 ± 1 dB in

{K}

-band at

{f} _{c}

= 22.5 GHz is observed. Theoretical analysis of the phase shifter is discussed.

We present here the design and characterization of an intermediate frequency (IF) assembly comprising a compact 90° hybrid chip (coupled line coupler - Lange coupler- coupled line coupler), two bias-T circuits for biasing the superconductor-insulator-superconductor (SIS) mixers, and two transmission-line circuits. Specifically, the miniaturized three-section hybrid chip fabricated using thin-film technology utilizes superconducting Niobium (Nb) transmission lines, air bridges to connect the fingers of the Lange coupler (middle section), and is complemented with two bias-T circuits with integrated MIM capacitors. The assembly was designed to ensure amplitude and phase imbalances better than 0.6 dB and ±2°, respectively. Experimental verification of the assembly at 4 K shows good agreement between the measurements and simulations with amplitude imbalance of 0.5 dB and maximum phase imbalance of ±2°. The ALMA band-5 (163-211 GHz) receiver will include such assembly. The receiver tests shows sideband rejection ratio better than 15 dB over the entire RF band, i.e., a systematic improvement of 3-9 dB as compared with the previously reported results.

In the 2SB receivers, the rejection ratio is determined, among other factors, by the performance of the quadrature hybrids. We present here the design and characterization of an intermediate frequency (IF) assembly comprising a compact 90° hybrid chip (coupled line coupler – Lange coupler– coupled line coupler), two bias-T circuits in order to bias the Superconductor-Insulator-Superconductor (SIS) mixers. Specifically, the miniaturized 3-section hybrid chip made using thin-film technology utilizes superconducting Niobium (Nb) transmission lines and air bridges to connect the fingers of the Lange coupler (middle section). The assembly is complemented with two bias-T circuits with integrated MIM capacitors. The assembly was designed to have the amplitude and phase imbalance better than 0.6 dB and ±2.5° respectively. Experimental verification of the assembly at 4 K shows good agreement between the measurements and simulations with amplitude imbalance of 0.5 dB and maximum phase imbalance of ±2°.

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.