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This comprehensive, hands-on review of the most up-to-date techniques in RF and microwave measurement combines microwave circuit theory and metrology, in-depth analysis of advanced modern instrumentation, methods and systems, and practical advice for professional RF and microwave engineers and researchers. Topics covered include microwave instrumentation, such as network analyzers, real-time spectrum analyzers and microwave synthesizers; linear measurements, such as VNA calibrations, noise figure measurements, time domain reflectometry and multiport measurements; and non-linear measurements, such as load- and source-pull techniques, broadband signal measurements, and non-linear NVAs. Each technique is discussed in detail and accompanied by state-of-the-art solutions to the unique technical challenges associated with its use. With each chapter written by internationally recognised experts in the field, this is an invaluable resource for researchers and professionals involved with microwave measurements.

The authors design a cavity-backed Vivaldi antenna (CBVA) for microwave breast measurements. The design criteria for the antenna is shaped by the requirements of the free-space measurement scenario where the receiving and the transmitting antennas are rotated by a mechanical scanner. Later, the authors have performed various breast phantom measurements with the CBVA to reveal its feasibility for microwave tomography.

The state of an itinerant microwave field can be coherently transferred into, stored in and retrieved from a mechanical oscillator with amplitudes at the single-quantum level, and the time to capture and retrieve the microwave state is shorter than the quantum state lifetime of the mechanical oscillator. Mechanical oscillation and quantum state storage In the last decade it has become possible to control macroscopic mechanical oscillators in such a way that they show quantum behaviour. The next step is to exploit this capability to produce useful devices for quantum information applications, in particular as storage elements for quantum states, a role for which mechanical oscillators show promise. One way of achieving this is to embed mechanical oscillators in superconducting circuits where quantum information can be processed in the form of microwave fields. Tauno Palomaki et al . now reach an important goal in this area by showing that the state of a microwave field can be coherently stored in and retrieved from a mechanical oscillator at the single-quantum level. Macroscopic mechanical oscillators have been coaxed into a regime of quantum behaviour by direct refrigeration 1 or a combination of refrigeration and laser-like cooling 2 , 3 . This result supports the idea that mechanical oscillators may perform useful functions in the processing of quantum information with superconducting circuits 4 , 5 , 6 , 7 , either by serving as a quantum memory for the ephemeral state of a microwave field or by providing a quantum interface between otherwise incompatible systems 8 , 9 , 10 , 11 , 12 , 13 , 14 . As yet, the transfer of an itinerant state or a propagating mode of a microwave field to and from a storage medium has not been demonstrated, owing to the inability to turn on and off the interaction between the microwave field and the medium sufficiently quickly. Here we demonstrate that the state of an itinerant microwave field can be coherently transferred into, stored in and retrieved from a mechanical oscillator with amplitudes at the single-quantum level. Crucially, the time to capture and to retrieve the microwave state is shorter than the quantum state lifetime of the mechanical oscillator. In this quantum regime, the mechanical oscillator can both store quantum information and enable its transfer between otherwise incompatible systems.

Researchers at the University of Cantabria in Spain have designed and fabricated a phase switch for use in radio astronomy and other microwave measurement systems. Researcher Enrique Villa described the design of the team's device as a 90° hybrid design based on the use of microstrip bandpass filters. The coupling between the branches is achieved by a broadband MMIC single pole double through switch based on pseudomorphic HEMT transistors. Villa went on to say that taking into account they are based on short-circuited stub π-networks, the phase features of each filter are calculated, and the individual phase expressions enable us to obtain the phase dependence between filters and to consider it as a design parameter.

The paper discusses the results of modeling of thermal radio processes for the purpose of non-destructive testing, diagnosis of dynamic states and prediction in dielectrics by sensing electromagnetic self-radiation in microwave hyperspectral mode. Measurement errors when using radiometric methods of testing have been shown. We have found the specifics of reducing measurement error while increasing the dynamics and resolution of radiometric measurements. We have presented a schematic of a new type of hyperspectrometer with higher performance and frequency resolution.

The effect of temperature on thermoelectric microwave power sensors is researched in order to extend its application field. The fabrication of this microwave power sensor is divided into a front side and a back side processing using GaAs MMIC process and MEMS technology. The measurement results show that the temperature has a significant effect on the performance of thermoelectric microwave power sensors. The obtained temperature coefficient is about 0.488 mV/(W · K), which has an important reference value for the thermoelectric microwave power sensors. The reason is that the accuracy of microwave power measurement will be realised as long as the environment temperature is tracked.

Providing energy from fusion and finding ways to scale up the fusion process to commercial proportions in an efficient, economical, and environmentally benign way is one of the grand challenges for engineering. Controlling the burning plasma in real-time is one of the critical issues that need to be addressed. Plasma Position Reflectometry (PPR) is expected to have an important role in next-generation fusion machines, such as DEMO, as a diagnostic to monitor the position and shape of the plasma continuously, complementing magnetic diagnostics. The reflectometry diagnostic uses radar science methods in the microwave and millimetre wave frequency ranges and is envisaged to measure the radial edge density profile at several poloidal angles providing data for the feedback control of the plasma position and shape. While significant steps have already been given to accomplish that goal, with proof of concept tested first in ASDEX-Upgrade and afterward in COMPASS, important, ground-breaking work is still ongoing. The Divertor Test Tokamak (DTT) facility presents itself as the appropriate future fusion device to implement, develop, and test a PPR system, thus contributing to building a knowledge database in plasma position reflectometry required for its application in DEMO. At DEMO, the PPR diagnostic’s in-vessel antennas and waveguides, as well as the magnetic diagnostics, may be exposed to neutron irradiation fluences 5 to 50 times greater than those experienced by ITER. In the event of failure of either the magnetic or microwave diagnostics, the equilibrium control of the DEMO plasma may be jeopardized. It is, therefore, imperative to ensure that these systems are designed in such a way that they can be replaced if necessary. To perform reflectometry measurements at the 16 envisaged poloidal locations in DEMO, plasma-facing antennas and waveguides are needed to route the microwaves between the plasma through the DEMO upper ports (UPs) to the diagnostic hall. The main integration approach for this diagnostic is to incorporate these groups of antennas and waveguides into a diagnostics slim cassette (DSC), which is a dedicated complete poloidal segment specifically designed to be integrated with the water-cooled lithium lead (WCLL) breeding blanket system. This contribution presents the multiple engineering and physics challenges addressed while designing reflectometry diagnostics using radio science techniques. Namely, short-range dedicated radars for plasma position and shape control in future fusion experiments, the advances enabled by the designs for ITER and DEMO, and the future perspectives. One key development is in electronics, aiming at an advanced compact coherent fast frequency sweeping RF back-end [23–100 GHz in few μs] that is being developed at IPFN-IST using commercial Monolithic Microwave Integrated Circuits (MMIC). The compactness of this back-end design is crucial for the successful integration of many measurement channels in the reduced space available in future fusion machines. Prototype tests of these devices are foreseen to be performed in current nuclear fusion machines.

One of the major goals of Health 4.0 is to offer personalized care to patients, also through real-time, remote monitoring of their biomedical parameters. In this regard, wearable monitoring systems are crucial to deliver continuous appropriate care. For some biomedical parameters, there are a number of well established systems that offer adequate solutions for real-time, continuous patient monitoring. On the other hand, monitoring skin hydration still remains a challenging task. The continuous monitoring of this physiological parameter is extremely important in several contexts, for example for athletes, sick people, workers in hostile environments or for the elderly. State-of-the-art systems, however, exhibit some limitations, especially related with the possibility of continuous, real-time monitoring. Starting from these considerations, in this work, the feasibility of an innovative time-domain reflectometry (TDR)-based wearable, skin hydration sensing system for real-time, continuous monitoring of skin hydration level was investigated. The applicability of the proposed system was demonstrated, first, through experimental tests on reference substances, then, directly on human skin. The obtained results demonstrate the TDR technique and the proposed system holds unexplored potential for the aforementioned purposes.

The strongest volcanic eruption since the 19th century occurred on 15 January 2022 at Hunga Tonga‐Hunga Ha'apai, generating unprecedented atmospheric waves not seen before in observations. We used satellite microwave observations from (a) Advanced Technology Microwave Sounder (ATMS) on board the National Oceanic and Atmospheric Administration (NOAA)‐20 and the Suomi‐National Polar‐orbiting Partnership (SNPP) and (b) Advanced Microwave Sounding Unit (AMSU)‐A on board Meteorological operational satellite (MetOp)‐B/MetOp‐C to study these waves in the stratosphere immediately after the eruption. The NOAA Microwave Integrated Retrieval System (MiRS) was applied to these microwave observations to produce atmospheric temperature profiles. The atmospheric Lamb wave and fast‐traveling gravity waves are clearly revealed in both the brightness temperatures and the MiRS retrieved temperatures, revealing their vertical phase structures. This study is the first attempt to perform a detailed analysis of the stratospheric impact of the Tonga eruption on operational satellite microwave observations and the corresponding MiRS retrievals. Plain Language Summary The strongest volcanic eruption since the 19th century occurred on 15 January 2022 at Hunga Tonga‐Hunga Ha'apai. The microwave instruments onboard the currently operational satellites observed the area in the vicinity of the eruption. The eruption impacts were most obvious at high altitudes (the stratosphere) in the observed microwave brightness temperatures. Additionally, atmospheric temperature profiles have been retrieved using the satellite measured microwave brightness temperatures. The retrieved atmospheric temperature fields also show the impacts of the volcanic eruption in the stratosphere. This study is the first attempt to perform a detailed analysis of the impact of the Tonga volcanic eruption using operational satellite microwave observations and the corresponding retrievals. Key Points Microwave observations from multiple satellites capture stratospheric waves from the Tonga eruption, including Lamb and gravity waves MiRS atmospheric temperature retrievals also resolve wave perturbations in the stratosphere after the eruption The Lamb wave and the lead gravity wave show no apparent phase change with height, whereas the trailing gravity waves do