Signal Integrity Challenges and Solutions at Cryogenic Temperatures

Abstract

The field of electronics is rapidly evolving and expanding into new frontiers, including cryogenic environments. Cryogenic temperatures below 10 K have become increasingly important in various applications such as quantum computing, superconducting electronics, and space exploration. However, the unique physical properties of materials at these extremely low temperatures present significant challenges for signal integrity in electronic systems.

The dissertation addresses critical signal integrity challenges encountered in the transmission of high-speed digital signals in extremely low-temperature environments. The initial research focuses on the design and implementation of a face-to-face cable connection scheme using flexible thin-film superconducting stripline cables. The work encompasses the mitigation of signal integrity issues, including impedance discontinuities, crosstalk, signal loss, and power dependency. Through extensive simulations using Ansys HFSS and Keysight PathWave ADS and experimental measurements, the dissertation presents an effective interconnect scheme for cryogenic and quantum technology applications. The findings contribute to the advancement of dense signal integration, ensuring reliable and efficient signal transmission in demanding low-temperature environments. The insights gained from this research provide a foundation for the development of robust signal pathways and hold significance for the design and optimization of future cryogenic systems and quantum technologies.

This dissertation also investigates signal integrity challenges at cryogenic temperatures, with a specific focus on the impact of gamma radiation on superconducting microstrip resonators. The work explores the behavior of Nb and Al/Nb/Al embedded resonators before and after exposure to gamma radiation, quantifying changes in their quality factor (Q) values. The Q values of the resonators were extracted and compared at various cryogenic temperatures below 4.2 K after one and four weeks of gamma radiation corresponding to 152 kGy and 608 kGy, respectively. The findings reveal the resilience of these resonators to radiation, with minimal degradation observed in the dielectric loss tangent values.

The research also focused on utilizing very long resonators to characterize material losses and optimize fabrication procedures for superconducting structures for quantum applications. By employing these resonators, a detailed analysis of losses at different frequencies is achieved, enabling the identification of the most suitable fabrication techniques for quantum computation applications. The work addresses signal integrity challenges by investigating losses and frequency-dependent behaviors of superconducting structures. The Q values as high as 1.2 million were measured. Through rigorous measurements and analysis, this research contributes to the understanding and mitigation of signal integrity issues at cryogenic temperatures, paving the way for the development of more efficient and reliable systems for quantum computation.

The experimental investigation is a crucial aspect of this research, as it allows for the validation of theoretical and simulation results and provides insight into the effectiveness of proposed solutions. The results of this research contribute to the development of reliable electronic systems for cryogenic applications. The proposed solutions include the use of special low-temperature cables and connectors to minimize signal attenuation and noise and the selection of appropriate materials with low loss tangent and high thermal conductivity. These solutions are demonstrated through experimental validation and simulation, providing a basis for their application in real-world electronic systems.