WMB: Advanced Low-Noise Measurement Techniques for Cutting-Edge Room-Temperature and Cryogenic Applications

Presentation Abstract
The measurement of noise temperatures or noise figures of low-noise amplifiers and receivers is a key technique for a multitude of applications. Especially when talking about cutting-edge performance, eg for satellite-based systems at room temperature or quantum computing and radio astronomy at cryogenic temperatures, low-noise measurements become more and more challenging. While noise measurements are very often understood as straight forward, measurements at different ambient temperatures, operating frequencies, or input matching conditions are a major challenge so that low noise temperatures with a low uncertainty are difficult to maintain. This is especially true when the measured performance further improves and gets closer to physical limits. With applications such as array receivers or highly-scaled systems, such as astronomical interferometer or quantum computer, the increasing number of devices under test is a continuously growing requirement and will be addressed. In this workshop, we address several challenges and show state-of-the-art solutions for applications at room temperature and cryogenic conditions; best practices are discussed. This includes noise sources that are a key technology for the characterization and calibration of THz instrumentation ranging from amplifiers to radiometers. Therefore, the first talk will describe the development of noise sources, both diode and transistor based, with a focus on increasing ENR to enable a wide range of applications. In addition, the characterization methods and error analysis of the noise sources will be presented. The characterization of noise parameters is a key technique for device modeling and the assessment of different transistor technologies and devices. Thus, the second talk will focus on the characterization of noise parameters and corresponding conclusions. The following two talks discuss setups and challenges for cryogenic devices. The third talk describes a method for on-wafer noise temperature measurements of low-noise amplifiers using the cold-attenuator approach. Furthermore, a detailed analysis of the measurement uncertainty is presented. The fourth talk discusses an approach in measuring and qualifying cryogenic LNAs for their application in radio astronomical receivers. The basis of the presentation will be the activities for ALMA Band 2 1st stage LNA at W-Band. Here the main RF performance characteristics of effective noise temperature, full two-port s-parameters, amplitude and phase stability need to be verified at a cryogenic temperature of 15K and evaluated against specifications. Current and future projects in radio astronomy require a procedural approach in order to handle production volumes in the order of hundreds of cryogenic components. An increase of production volume is clearly foreseeable for the near future. This necessitates the use of automated processes for measurement and document generation. It is noteworthy that these activities often take place in research institutions, where, traditionally, many components used in cryogenic radio astronomy receivers are still developed, fabricated and tested. The learning and best practice of measurement setups in such demanding environments help also to improve the understanding in an even wider area of applications. Thus, developments, as discussed in this workshop, serve the entire IMS community.