This work describes accurate methods for the characterization of sub-terahertz (sub-THz) devices and pad de-embedding procedures. The extraction of the intrinsic DUT is enabled by generating a precise pad model using two-tier calibration approaches. Moreover, the proposed approaches offer a solution to the designers to preserve precious silicon area by presenting a simplified and potentially parameterizable pad model. Employing two different thru-reflect-line (TRL) calibration kits (calKits) together with the DUT on the same die, this research validates the proposed calibration strategies. This paper uses as DUT at J-band, i.e. a Marchand balun, fabricated using IHP SiGe BiCMOS technology with an aluminum back-end-of-line (BEOL), alongside the mentioned calKits. The goal of the paper is to assess the performance of the DUT and validate two de-embedding methods. Moreover, the pad model offers a way for accurate DUT characterization saving silicon area for future optimized designs.@en

In this paper, we present a low-noise, high-gain readout hardware to be used in conjunction with (sub)mm-wave zero bias detectors, to enable high sensitivity (i.e., ∼-50dBm) and fast (i.e., below a second at -50 dBm) power detection.

The developed hardware employs a cascade of two (COTS) programmable gain amplifier (PGA), capable of reaching up to 90 dB gain (volt to volt), each providing an input referred noise level of 16 nV/√Hz. The signal is then digitized on the same board via a 500 kHz 12bit ADC, providing an SNR of 74 dB. The digitized signal is then readout via an ST microcontroller and transferred to the operator PC via a USB interface. The sensitive bias voltages for the PGAs are provided via the microcontroller, or alternatively can be fed by an external lab grade supply to further improve on the (already high) supply noise rejection from the first stage PGA. The proposed hardware is designed to interface with VDI zero bias detectors, high responsivity and low NEP diodes (around 2000 V/W and below 12 pW/√Hz, respectively) operating in monomodal waveguide bands up to 500 GHz. In this contribution we demonstrate the usage of the developed hardware with WR10, WR6.5, WR5 and WR 3 ZBD diodes.@en

Provides society information that may include news, reviews or technical notes that should be of interest to practitioners and researchers.@en

This review offers a detailed examination of the current landscape of radio frequency (RF) electromagnetic field (EMF) assessment tools, ranging from spectrum analyzers and broadband field meters to area monitors and custom-built devices. The discussion encompasses both standardized and non-standardized measurement protocols, shedding light on the various methods employed in this domain. Furthermore, the review highlights the prevalent use of mobile apps for characterizing 5G NR radio network data. A growing need for low-cost measurement devices is observed, commonly referred to as “sensors” or “sensor nodes”, that are capable of enduring diverse environmental conditions. These sensors play a crucial role in both microenvironmental surveys and individual exposures, enabling stationary, mobile, and personal exposure assessments based on body-worn sensors, across wider geographical areas. This review revealed a notable need for cost-effective and long-lasting sensors, whether for individual exposure assessments, mobile (vehicle-integrated) measurements, or incorporation into distributed sensor networks. However, there is a lack of comprehensive information on existing custom-developed RF-EMF measurement tools, especially in terms of measuring uncertainty. Additionally, there is a need for real-time, fast-sampling solutions to understand the highly irregular temporal variations EMF distribution in next-generation networks. Given the diversity of tools and methods, a comprehensive comparison is crucial to determine the necessary statistical tools for aggregating the available measurement data.

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This contribution presents the measurement strategy to accurately characterize probe-fed high-gain antennas operating in the sub-THz band. First, a near-field technique employing a quasi-optical system is introduced to enable characterization of backside radiating antennas (with respect to the landing pads). The proposed setup employs classical manipulators for probe landing (i.e., above the structure) and linear xyz CNC controlled translation stage. After, the calibration and modelling techniques to allow for an accurate input reflection-coefficient at the antenna input plane, and the estimation of the antenna gain, in a near field planar scanning system, are described in details. The experimental data of an high-gain backside-radiating lens antenna operating in D-band are presented to validate the proposed approach and characterization bench.@en

In this contribution, we describe a reconfigurable surface, designed in 130um SiGe technology, to realize a fully-electronic, planar chopper aiming at passive terahertz imaging applications. This surface consists of subwavelength metallic patches that are interconnected using FET-based varactors. By switching the bias voltage of the varactors between 0V and 1.2V, the reconfigurable surface can switch between a transmissive and opaque state, respectively. The expected transmissivity is simulated to be between 0.2 and 0.9 over a wide frequency band, from 250 GHz to 550 GHz. This chopping solution would enable a high degree of system integration for future passive terahertz cameras.

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In this work we present calibration approaches aimed at mitigating the measurement error in testbenches featuring multiple sensor-nodes and operating over-the-air. Such errors can arise from fluctuations in component responses and mechanical tolerances of the setup. The calibration approaches are detailed for the case of the Antenna Dome measurement setup previously presented by the authors.In the current implementation, the Antenna Dome employs multiple dual linearly-polarized scalar sensing nodes, to enable real-time 2D (theta and phi) radiation pattern acquisition. The variation of the electrical response among the different sensing elements as well as their position, with respect to the nominal one, due to the mechanical tolerances, introduce systematic error in the generated radiation patterns.Over-the-air procedures to linearize the power conversion asymmetry within the dually polarized nodes as well as the linearity response across them are described. Proposed approach provides a reduction of the angular dependent error within ±0.5 dB across the various nodes. Moreover, to minimize the impact of mechanical deviations an over-the-air method is described to transfer the sensor coordinates from the mechanical reference system to the antenna under test one.@en

In this contribution we present an approach to reduce the error arising from the variations of the lumped load, due to process spread, in probe level calibrations. First, full-wave electromagnetic (EM) simulations are employed to generate the nominal standard responses, then a parametric EM simulation of the load structure is used to generate a parametrized model of the standard. The approach is tested using a Short-Open-Load-Reciprocal calibration algorithm and an impedance standard calibration substrates developed on a 150 mm Quartz wafer (400 pm thick). In this process the high fidelity of the lateral dimension of the fabricated structures, realized using IC Photolithography, allows to confine the variations of the load response to only the thin-film resistor thickness spread. The DC response of the load, measured during the calibration step, is used to identify the specific RF response of the probed load from the parametric model. A complete analysis using full-wave EM simulations accounting for process variation is presented together with a set of experimental data up to 67GHz.@en

The evolution of emerging technologies that use Radio Frequency Electromagnetic Field (RF-EMF ) has increased the interest of the scientific community and society regarding the possible adverse effects on human health and the environment. This article provides NextGEM’s vision to
assure safety for EU citizens when employing existing and future EMF-based telecommunication technologies. This is accomplished by generating relevant knowledge that ascertains appropriate prevention and control/actuation actions regarding RF-EMF exposure in residential, public, and occupational settings. Fulfilling this vision, NextGEM commits to the need for a healthy living
and working environment under safe RF-EMF exposure conditions that can be trusted by people and be in line with the regulations and laws developed by public authorities. NextGEM provides a framework for generating health-relevant scientific knowledge and data on new scenarios of exposure to RF-EMF in multiple frequency bands and developing and validating tools for evidence-based risk assessment. Finally, NextGEM’s Innovation and Knowledge Hub (NIKH) will offer a standardized way for European regulatory authorities and the scientific community to store and assess project outcomes and provide access to findable, accessible, interoperable, and reusable (FAIR) data.
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The design of a focal plane array (FPA) for imaging at sub-mm wavelengths generally is a trade-off between resolution and sensitivity. For maximum angular resolution, minimal spacing between FPA elements is desired, which leads to increased losses due to spillover and mutual coupling and therefore deteriorates the imaging sensitivity. This work presents the characterization of an ultra-wideband (200 GHz 600 GHz) FPA with integrated direct-detectors, achieving a tight sampling of the focal plane by implementing overlapping of the feed elements, hence alleviating the penalty in aperture efficiency. The overlapping of the feed elements in implemented using a combination of a dual-polarized connected array configuration resembling a chessboard, and leaky-wave propagation in the CMOS stratification. The measured radiation patterns and aperture efficiency show @en

This article presents the development of a focal plane array (FPA) for terahertz imaging applications with a near diffraction-limited resolution achieved through a very tight sampling of the focal plane. The antenna array is integrated with direct detectors in a 22-nm CMOS technology and operates from 200 to 600 GHz. The tight sampling of the focal plane is realized by using a combination of leaky-wave radiation and a dual-polarized connected array configuration that closely resembles a chessboard. By utilizing both the polarizations in the chessboard design, the number of array elements per unit area is effectively doubled. The geometry of the chessboard array was co-optimized together with that of a silicon elliptical lens to achieve both high aperture efficiency and beam overlap. Measurements in the WR2.2 band of a fabricated demonstrator showed that an aperture efficiency of −4.1 dB was realized at 400 GHz. The average gain roll-off between two diagonally adjacent array elements was measured to be −1.5 dB at 400 GHz. Compared to the reference configuration of an idealized, equivalently sampled hexagonal FPA, the improvement in gain at the edge of coverage yields 1.2 dB, which includes 1.9 dB of ohmic losses in the chessboard array. The agreement between measurements and simulations proved to be within 1 dB from 325 to 475 GHz.

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The continuous advancements in the coverage and sensitivity of terahertz direct-detector imagers places increasing constraints on the test benches needed for characterization. Already, relative differences on the order of a few decibels are observed between simulated and measured performance in the state-of-the-art literature. This contribution elaborates on our experimental strategies to maximize the characterization accuracy and precision of terahertz direct-detection imagers using a broadband, over-the-air measurement procedure. As a demonstration, four elements within a dense detector array were characterized in the WR2.2 band. By optimizing the modulation frequency in the setup for minimal impact of low-frequency noise and interference, a measurement dynamic range up to 30 dB was achieved, including the path loss over 20 cm. The hardware-to-model agreement of the characterized array is below 1 dB between 325 and 450 GHz.

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Organ-on-chip (OoC) is emerging as a key technology for improved pre-clinical drug testing. Monitoring tissues and the artificial microenvironment in OoC devices is critical to recapitulate human physiology; however, sensing is often invasive, superficial, and not continuous over time. This work aims to overcome these issues by proposing dielectric spectroscopy as a non-invasive and time-continuous sensing technique capable of extracting information from multi-layer OoC devices, including distinguishable tissue layers. The presented results set the foundations for this goal by proving this technique’s feasibility, showing excellent correspondence between the experimental and modelled data, and providing design guidelines for application-tailored optimization.@en

In this paper, we present an experimental strategy to analyze the harmonic content of mm-wave frequency extenders using the VNA (absolute) power calibration step, without requiring spectrum analyzers and/or separate downconverters. The spectral purity of the upconverted band of the extenders is a key requirement to enable entirely software-based power control required for the accurate analysis of an (active) device under test. The proposed approach is based on the complementary response provided by the calorimeter-based power meter (i.e. VDI PM5) capable of integrating the entire spectral content of the waveguide band, in respect to the extreme frequency selectivity of the narrow-band mixer-based downconverter of the VNA. This complementary integration bandwidth response allows to compare the two results at each input drive level (at the power calibration setup, in-situ) and link the difference to the increased harmonic content contribution, with respect to the spectral content value at the saturation drive level, i.e. nominal manufacturer specified. The paper presents tests carried out in the WR10 (75–110 GHz) and WR6 band (110–170 GHz). The WR10 resulted in a harmonic contribution on the total output power of a maximum of 0.3 dB down to -33 dBc power back off from saturation level, and less than 1 dB down to -38 dBc while the WR6 the same parameter is less than 1 dB over the entire frequency band excluding the lower frequency points.@en

In this contribution, we describe the modeling approaches and the characterization procedures used to develop accurate standard models for cryogenic, probe-level, calibrations substrates.The key electrical and mechanical parameters of the impedance terminations and the lines used in commercially available impedance standard substrates are first characterized versus temperature. After, these component are simulated using 2.5D EM solvers including their mechanical variation when exposed to cryogenic temperatures, to extract their nominal response at 7 Kelvin. The quality of the resulting calibrations at cryogenic is evaluated first using independent CPW lines on the calibration substrates and then by measuring the response of a transformer-based resonator realized on a Si-based technology.Ambient temperature models are used as a comparison, to highlight the accuracy improvement that can be achieved employing optimized Cryo-EM based models.

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In this contribution, we present a rigorous analysis based on uncertainty propagation techniques to estimate the random variation of the controlled reflection coefficient in mixed-signal load-pull test benches. A digital-to-analog converter is commonly used in these test benches to generate the baseband signal required to synthesize the high-frequency, user-defined injected wave. To study the random noise of the injected wave, which can be mapped to the noise of the controlled reflection coefficient, we employ Jacobian sensitivity functions between the baseband signal and the RF one. First, the baseband integrated rms noise of the up-converter is evaluated, and then the upconverted noise is determined via the derived transfer function. Finally, experimental results to validate the uncertainty control bound of the synthesized reflection coefficients are presented, highlighting a full coverage of the measured reflection coefficients.@en

This contribution presents the development of an electrically small lens antenna using an artificially loaded thermoplastic at 140-170GHz. We will present the on-going development of the Fly’s Eye front end antenna concept that was presented in [1]. The antenna is composed on a dual plastic lens, a core lens and a shell lens, fed by a double slot. The core-lens, being presented in this contribution, is a spherical lens made from an artificially loaded plastic of permittivity 9.5. To the best of our knowledge, this thermoplastic material has not been used for lens antennas in this frequency range before. A 4mm lens prototype has been developed using this material, which includes an antireflective layer synthesized by drilling sub-wavelength holes on the lens contour. Full-wave simulations show a negligible degradation of the performance of the anti-reflection layer compared to an ideal homogeneous matching layer. Physical measurements and antenna measurements confirm that the antenna's performance matches the design specifications.@en

In this study, an efficient power combiner for mm-wave frequency transmitters is investigated. The combiner is based on a parallel plate waveguide (PPW) excited with multiple parallel feeds. The Doherty power combiner scheme is also integrated in the proposed concept, to increase the efficiency of the amplifiers when implementing amplitude modulation. The advantage of the proposed PPW combiner with respect to other concepts, for example, the ones based on substrate-integrated waveguide, is the wider bandwidth and the scalability to an arbitrary number of inputs. Measured results from a demonstrator realised in standard printed circuit board technology are presented. Two variations of the combiner are implemented, one terminated with a 50 Ω coaxial output, and another integrated with an antenna. In the latter case, the waveguide is folded so that both the power combiner and the antenna fit within a half wavelength size, and thus would be compatible with a dense antenna array implementation.

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