Millimeter-wave Frequency Range Research Articles

Surface wave communication-based wave guide design concerns for flip chip package-based integrated circuits with bump pitch sizes of 1.2 mm and above

ABSTRACT The flip chip package (FCP) based integrated circuits supports millimetre wave frequency range (30 - 300 GHz), analysing the conditions for optimal signal transmission between the integrated circuits for FCP type being the primary essence of this article. The effective signal transmission occurs through a dielectric-coated conductor structure based on the surface wave communication phenomenon, known as a surface wave communication-based wave guide (SWW). The article focuses primarily on design considerations to build SWW for FCP applications at millimetre wave frequency ranges. The efficiency of the proposed waveguide was investigated in terms of power transmission capacity, voltage standing wave ratio (VSWR) and signal attenuation. The analysis comprises examining these parameters at the frequency range of 50 GHz to 150 GHz while taking into account varied degrees of waveguide dimensions and surface reactance. The measured results show that at the signal frequency of 100 GHz with dielectric and conductor thickness of 0.2 mm and surface reactance of 100 Ω, the suggested waveguide provides efficient signal transmission with approximately 0 dB signal attenuation, ideal high-power flow of 41,000 VA m 2 and VSWR of 1.2. Overall, this article provides insights on the design and performance of SWW for FCP applications at millimetre wave frequency band.

(Invited) Recent Advances and Challenges of MOCVD-Grown AlScN/GaN HEMTs

The allocated frequency bands of next-generation wireless communication networks will be shifting further up in the spectrum to be able to meet the stringent data rate requirements. Doing so, demands higher bandwidth capabilities from the electronic devices in the RF chain. Numerous cutting-edge systems are using AlGaN/GaN-HEMT based components, in particular in the transmit chain, due to their favorable combination of output power and bandwidth capability. Still, this semiconductor technology is approaching an upper bound in this regard, known as the Bode-Fano limit. Devices based on an AlScN/GaN heterointerface have been identified as candidates to push these boundaries and enable components that deliver higher power over a broader frequency range. We report on the status of MOCVD-grown AlScN/GaN HEMTs, their current capabilities but also on challenges that still hamper the exploitation of the material system's full potential.The first reported AlScN/GaN HEMTs were fabricated on epitaxial stacks grown by MBE. However, the majority of commercial GaN-based HEMT technologies is relying on MOCVD-grown epitaxy due to higher growth rate and lower cost of operation. We managed to grow AlScN/GaN heterostructures showing sheet carrier densities (nS) of up to 3·1013cm-2 and mobilities of 1100 cm2/Vs. These results were achieved with a MOCVD reactor that had been modified to cope with the low vapor pressure of the used precursors Cp3Sc and (MCp)2ScCl. Depending on the temperature, the obtained growth rates were as high as 0.015 nm/s. Currently, further precursors with allegedly higher vapor pressure are evaluated that should allow for even higher growth rates, further improving the quality of the fabricated heterostructures. Furthermore, HEMT devices were fabricated on top of the epitaxial wafers that showed power densities (Pout) of up to 8.4 W/mm and power-added efficiencies (PAE) of more than 48 % at a frequency of 30 GHz, even surpassing the current state-of-the-art in terms of combined Pout and PAE of Ga-polar devices.However, there are still a number of unsolved issues visible in most reported AlScN/GaN HEMT devices, regardless of the used growth method. One is concerning the level of leakage currents and the consequential premature soft breakdown. The root cause of this phenomena is not yet fully understood but is believed to originate from poor dielectric/isolating properties of the Sc-containing barrier. This hypothesis is supported by a comparably high level of impurites that is found in the AlScN layers. Minimizing theses residuals by purification of the precursors is, therefore, necessary to further improve the electrical device characteristics. Secondly, transport properties of AlScN/GaN heterointerfaces are not as well studied as more established junctions, e.g., AlGaN/GaN and AlN/GaN. An important parameter that has not been experimentally identified for 2DEGs induced by AlScN/GaN heterojunctions yet, is the saturation drift velocity (vsat). It is of particular importance since the Bode-Fano limit, among other, depends on it. Since the extension of the latter is one of the great promises of AlScN/GaN devices, it is clear that the value of vsat is essential to know in order to make quantitative predictions of the level of improvement that is achievable in terms of bandwidth capability but also with regard to power density.We will give an overview of recent advances of MOCVD-grown AlScN/GaN HEMTs with respect to their capability to extend on the achievable performance level of present GaN-based devices, in particular in the millimeter-wave frequency range. Further, we will benchmark the results against other competing technologies, i.e. GaAs pHEMT and Si-CMOS, to give an outlook of where optimized AlScN/GaN devices can takes us and where they cannot.

A compact and fully integrated FMCW radar transceiver combined with a dielectric lens

Abstract Electronic measurement systems in the THz frequency range are often bulky and expensive devices. While some compact single-chip systems operating in the high millimeter-wave frequency range have recently been published, compact measurement systems in the low THz frequency range are still rare. The emergence of new silicon-germanium (SiGe) semiconductor technologies allow the integration of system components, like oscillators, frequency multipliers, frequency dividers, and antennas, operating in the low THz frequency range, into a compact monolithic microwave integrated circuits (MMIC), which contains most components to implement a low-cost and compact frequency-modulated continuous-wave-radar transceiver. This article presents a single transceiver solution containing all necessary components. It introduces a $0.48\,\mathrm{THz}$ radar transceiver MMIC with a tuning range of $43\,\mathrm{GHz}$ and an output power of up to $-9.4\,\mathrm{dBm}$ in the SG13G3 $130\,\mathrm{nm}$ SiGe technology by IHP. The MMIC is complemented by a dielectric lens antenna design consisting of polytetrafluoroethylene, providing up to $39.3\,\mathrm d\mathrm B\mathrm i$ of directivity and half-power beam widths of 0.95∘ in transmit and receive direction. The suppression of clutter from unwanted targets deviating from antenna boresight more than 6∘ is higher than $24.6\,\mathrm d \mathrm B$ in E- and H-Plane.

Spanning the Spectrum: High-Performance Signal Source Design for the Millimeter-Wave Age

The millimeter-wave (mm-wave) frequency range is consumer wireless technology’s next frontier. Next-generation cellular technologies demand ever-increasing data rates, reduced latency, and robust service for a massive number of users. The mm-wave wireless systems operating in the frequency range from 10 to 100 GHz have the potential to satisfy the requirements presented by these consumer demands <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . High carrier frequencies offer increased communication bandwidths for improved throughput with relatively small fractional bandwidths. Furthermore, because the development of mm-wave wireless and cellular technologies is in its infancy, relatively few external interferers exist at these frequencies. Thanks to the continued scaling of CMOS devices and increased transit and maximum frequencies, the integration of high-performance mm-wave transceivers is more viable than ever before. Transceiver integration further benefits from the decreased size of passive devices with high-frequency operation, decreasing silicon area and minimizing parasitic effects. Thanks to these benefits, 5G hardware research has focused on exploring limitations and establishing design principles for integrated CMOS mm-wave front ends.

Ultra-Thin SSPP-Based Sheet for Suppressing Microwave Radiated Emission in SiP Modules

System-in-Package (SiP) has been facing the problem of excessive radiation leakage. In this article, a novel technique of absorptive sheet is proposed for suppressing unwanted microwave radiated emission in an advanced high-speed SiP module backed with a heat sink. Different from the conventional periodic resonant structure or absorptive film, the electromagnetic energy is consumed based on the mechanism of spoof surface plasmon polaritons (SSPP) in our design. By adjusting the length of the metallic strip to control its k-dispersion characteristics, the SSPP modes could be excited around one frequency point. Therefore, a relatively wide absorption band is created by arranging stepped strips in arrays on a dielectric medium. According to the electromagnetic distribution in the SiP module, SSPP-based absorptive units are circularly arranged to constitute the complete proposed absorptive sheet with adequate absorption efficiency. From the simulated results, the proposed design can provide 90 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> absorption performance covering a wide frequency range of 26.3–31.6 GHz, with a substrate thickness of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{L}$</tex-math></inline-formula> /228 and a total thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{L}$</tex-math></inline-formula> /134, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{L}$</tex-math></inline-formula> is the wavelength at the lowest operating frequency. Finally, the proposed absorptive sheet is fabricated and measured, where measurement results agree well with the simulated ones, which corroborates the feasibility and effectiveness of applying the SSPP-based absorbing techniques for suppressing the radiated emission in microwave and millimeter-wave frequency range in SiP modules.

Method for measuring magnetic susceptibility of magnetic nanoparticles up to millimeter-wave frequency range

A novel method for measuring the complex magnetic susceptibility of magnetic nanoparticles (MNPs) has been developed by a broadband microstrip line-type probe with a frequency range of up to 50 GHz. Two external orthogonal DC fields, Hhard and Heasy, were applied to change the susceptibility of MNPs (Streptavidin coated, 200 nmϕ, number of MNPs about 1010) based on magnetization switching theory. The susceptibility of MNPs in the liquid, solid state, and after biotin-avidin reaction with polymer beads (2 μmϕ, number of polymer beads about 108) was evaluated. A clear FMR frequency of MNPs and the same FMR frequency shift trend as Hhard changed was observed around 2–10 GHz in both liquid and solid states. The susceptibility of MNPs reached maximum when Hhard was 0.1 T which is approximately equal to Heasy (0.135 T). The maximum values of real and imaginary parts increased by a factor of 3.39 and 1.66 compared to when Hhard was 0. The obtained results indicate that the magnetic anisotropy was successfully controlled in the liquid and solid states of MNPs aggregate. Furthermore, after the biotin-avidin reaction of MNPs with polymer beads, the imaginary part of susceptibility showed a decreasing trend regardless of the increase in Hhard, and its half-width expanded by 35.1% at maximum when Hhard was 0.15 T.

Gap Waveguide Technology: An Overview of Millimeter-Wave Circuits Based on Gap Waveguide Technology Using Different Fabrication Technologies

With the fast development of next-generation wireless communication and radar sensing, the millimeter-wave frequency band is becoming more and more important due to its rich spectrum, wide bandwidth, and ability to support the miniaturization of antennas and circuits <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> , <xref ref-type="bibr" rid="ref2" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[2]</xref> , <xref ref-type="bibr" rid="ref3" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[3]</xref> , <xref ref-type="bibr" rid="ref4" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[4]</xref> . High-performance, low-loss, and low-cost millimeter-wave circuits and modules are the key elements for wireless front-end systems. For planar transmission lines, such as microstrip lines and coplanar waveguides, they are very easy to integrate with other circuits for low-cost and low-profile physical designs. However, the high insertion loss and radiation loss from planar transmission lines limit their applications at the millimeter-waveband. As for rectangular and cylindrical waveguides, their main application is in the areas of low loss and high power handling, but their 3D structure is difficult to integrate with other planar passive and active circuits. The substrate-integrated waveguide (SIW) is a better way to merge the advantages of planar transmission lines and rectangular waveguides, but it still suffers from dielectric losses at the millimeter-wave frequency range.

30-GHz Low-Phase-Noise Scalable Multicore Class-F Voltage-Controlled Oscillators Using Coupled-Line-Based Synchronization Topology

In this letter, low-phase-nose multicore class-F voltage-controlled oscillators (VCOs) using coupled-lined-based synchronization topology are proposed. Compared to traditional resistance-coupled multicore VCOs, the proposed coupled-line-based topology improves the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> of the small inductors in the millimeter-wave frequency range. Mode ambiguity is eliminated for a robust oscillation startup. Quad-core and oct-core VCO prototypes are designed and implemented in 65-nm CMOS process, which exhibit a measured frequency tuning range of 20.5% centered at 31.32 GHz. The quad-core VCO has a measured phase noise (PN) of −134.33 dBc/Hz and a corresponding FoM of 191.32 dBc/Hz at 10-MHz offset from 28.28 GHz. The oct-core VCO has a measured PN of −137.23 dBc/Hz and a corresponding FoM of 191.08 dBc/Hz at 10-MHz offset from 28.16 GHz.

Generation of complicated millimeter-wave beams based on a wideband high-transmission polarization-independent complex-amplitude metasurface.

Complex amplitude modulation metasurfaces (CAMM) that can independently control both amplitude and phase have fostered a broad research interest worldwide due to its more robust wave manipulation capability than metasurfaces that can only adjust phase. Although many CAMM structures have been reported, they still suffer from limitations such as low transmittance, complicated structure, polarization dependence, high cost, and difficulty in fabrication. This work proposes a high-transmission polarization-independent CAMM operating in an ultra-wide millimeter-wave frequency range from 30 to 50 GHz realized by cost-effective and easily implementable manners. Three CAMMs are designed to generate complicated millimeter-wave beams like holographic imaging beam, Airy beam, and vortex knot beam. The presented simulation and experimental results clearly demonstrate the effectiveness of the CAMMs. This work presents a new paradigm for CAMM that can be readily extended to other frequency bands. It may also advance further applications of millimeter-wave beams in communication, imaging and detection.

Amplitude Non-Uniformity of Millimeter-Wave Vortex Beams Generated by Transmissive Structures

We investigate the origin of non-uniformity in an orbital angular momentum (OAM) beam generated by a transmissive structure in the millimeter-wave frequency range. This work includes the study of amplitude non-uniformity including modal composition analysis using the angular spectrum method (ASM) for OAM beams generated by spiral phase plates (SPPs) and flat-surface metamaterial structures (MSs). The dependency of the axial dimension, over which the OAM beam transforms from a Gaussian beam, on the amplitude non-uniformity of both the structures has been rigorously analyzed. For experimental verification, we designed a perforated planar dielectric slab to convert the Gaussian beam into an OAM beam of order 2 with improved amplitude uniformity. Within the manufacturing limitations, the design of the transmissive MS was fabricated and tested to obtain optimum amplitude uniformity in the generation of OAM beams and to compare with simulation results.

A Miniaturized Ultra-Wideband Radar for UAV Remote Sensing Applications

This letter presents a novel approach to build a compact lightweight unmanned aerial vehicle (UAV) radar for remote sensing applications. The proposed radar exploits the recent advancement of an automotive radar chip for broadband chirp generation and rapid data processing. To compensate for the path losses and improve penetration at the millimeter-wave (mm-wave) frequency range, up- and down-converters are developed to generate an ultra-wideband (UWB) (3.25–5.15 GHz) chirp signal. The total payload of the radar is 2.5 kg. The proposed radar is installed on an UAV and tested in the field at a 100-m altitude above the ground surface. The results show that the compact low-power UWB radar can be used to map vegetation and soil moisture with fine resolution.

Design and performance analysis of a low-pull-in-voltage RF MEMS shunt switch for millimeter-wave therapy, IoT, and 5G applications

Recent advancements in wireless communication systems utilize miniaturized devices based on microelectromechanical system technology for present and future 5G wireless applications. Nowadays, RF devices are utilizing frequencies up to 30 GHz with substantial signal propagation that leads to a slow data rate. On the other hand, there is a huge spectrum available in the millimeter-wave frequency range of 30–300 GHz. The millimeter-wave spectrum is attractive for the development of smart systems based on 5G technology. In this paper, a low-pull-in-voltage capacitive type RF MEMS switch is proposed to operate at frequencies above 30 GHz. The switch is proposed with a new iterative meandering technique where the span length of each section in the meanders differs relative to the first section. A low pull-in voltage of 1.8 V is achieved with a large capacitance ratio of 63. The switch exhibits low insertion loss of −0.24 dB at 41 GHz and possesses high isolation of −46.7 dB at 38 GHz. The design is validated by comparing the theoretical and simulated results, and the switch can be efficiently utilized for millimeter-wave applications.

Design, developments, and applications of 5G antennas: a review

AbstractAs the demand for high data rates is increasing day by day, fifth-generation (5G) becomes the leading-edge technology in wireless communications. The main objectives of the 5G communication system are to enhance the data rates (up to 20 Gbps) and capacity, ultra-low latency (1 ms), high reliability, great flexibility, and enhance device to device communication. The mentioned objectives lead to the hunting of the millimeter-wave frequency range which lies from 30 to 300 GHz for 5G wireless communications. To design such high capacity, low latency, and flexible systems, antenna design is one of the crucial parts. In this paper, a survey is presented on various antenna designs with their fabrication on different types of substrates such as Rogers RT/duroid 5880, Rogers RO4003C, Taconic TLY-5, etc., at different 5G frequency bands. The different configurations of antennas that covered antenna arrays, multiple-input multiple-output (MIMO) antennas, phased antennas, and beamforming antennas are discussed in detail with their applications. The design of MIMO antennas in the 5G frequency band occupied less space so mutual coupling reduction techniques are required for maintaining the required gain, efficiency, and isolation. This paper is also focused on the mutual coupling reduction techniques and diversity in MIMO antennas.

Load-Pull Setup Development at 185 GHz for On-Wafer Characterization of SiGe HBT in BiCMOS 55 nm Technology

This article aims to discuss challenges and performances of a passive load-pull test bench dedicated to the G-band frequencies. The first task of this work is the development of the setup to perform high power generation, impedance generation, and high-power dynamic of measurement. The solution proposed is the association of an external power system of source and detectors, with an integrated synthesizer of impedance. The proposed system requires several analysis steps in order to be validated. On the other hand, special care is dedicated to the calibration of the scalar measurement in the millimeter-wave frequency range. Then, due to the unknown phase at the input and output of the device under test (DUT), scalar measurement can lead to high inaccuracy. Hence, an adaptive calibration is proposed and applied to the measurement of a bipolar transistor at 185 GHz. We highlight the effect of the missing phase information on the accuracy of measurement. Results of the measurement are discussed.

Integrated Stacked Parallel Plate Shunt Capacitor for Millimeter-Wave Systems in Low-Cost Highly Integrated CMOS Technologies

This letter presents a stacked parallel plate (SPP) shunt capacitor (SC) that benefits from metal stack increment with process nodes advancement. It demonstrated high quality (Q) factor and high self-resonance frequency (SRF), promoting the design of analog integrated circuits (IC) in low-cost highly-integrated CMOS technologies at millimeter-wave (mm-wave) frequency range. As a proof-of-concept, an analytical-equation based design method is also proposed and three ac-grounded capacitors: 300-fF, 600-fF and 900-fF, are implemented in STMicroelectronics (STM) 55-nm process. Characterization is performed up to 100 GHz. An effective capacitance density of 0.8 fF/μm2 is obtained. Measurements show Q-values reaching up to 14.7 at 100 GHz and equivalent input series resistances with flat wide band behavior reaching at most an average of 0.55 Ω. SRFs of 140 GHz for the 900-fF SPP-SC up to 368 GHz for the 300-fF SPP-SC are also determined from measurements: the highest SRFs for such large capacitances to the authors’ knowledge.

A Wideband Antenna for mm-Wave Antenna-in-Package Application

Antenna-in-Package has been widely applied for millimeter-wave systems that integrate the MMIC chip and antenna into one package. For organic substrate Antenna-in-Package solutions, probe feeding and aperture-coupled feeding patches are generally used as radiation units. In this work, a patch antenna is proposed using coupled resonation; a wideband, high-gain and compact 3-D antenna package integration is realized. An equivalent circuit model is analysed for the coupled structure. &#x03BB;/4 coupled line is adopted for impedance matching, the whole antenna is designed on the same thick radiation patch substrate, with less organic substrate lamination layers. For millimeter-wave Antenna-in-Package structures, vias are generally used for vertical interconnections, which function well in the lower millimeter-wave frequency range. For operation frequency higher than 100GHz, design difficulties may be encountered for via interconnection, with performance degeneration on impedance matching and transmission loss. This work integrates a H-shaped slot instead of vias on an organic substrate, realizing a high frequency and wideband mm-wave transition. An interconnection structure is also adopted to convert a microstrip line to differential microstrip line in the feeding network. Antenna prototype with 2&#x00D7;4 radiation array is designed for verification purpose at 20GHz frequency range with simulated bandwidth of 23%. The prototype is fabricated with separate PCB boards assembled with screws, measured antenna gain is 12.7dBi-13.5dBi. The proposed structure provides a wideband and low-loss solution for potential higher frequency mm-wave Antenna-in-Package applications.

16-element CPW Series Fed Millimeter-wave Hexagonal Array Antenna for 5G Femtocell Applications

AbstractA 16-element coplanar waveguide series fed hexagonal array antenna is proposed at millimeter-wave frequency range. In this paper, the analysis is initiated from a single-element hexagonal patch then extended to 1×2 array, 1×4 array, and 4×4 series fed hexagonal patch array antennas. The idea behind this design is to improve fractional bandwidth stage-wise with improved gain maintaining constant efficiency with all the structures. The 16-element array antenna is fabricated on Rogers RT Duriod 5880™substrate withɛr= 2.2 and 0.508 mm thickness. This array antenna exhibits low return loss at 28 GHz with a reflection coefficient value of −31.02 dB including almost 102% radiation efficiency and attained a maximum gain value of 8.98 dBi. The results are quite comparable with simulated 4×4 array antenna using the HFSS tool. The size of the proposed antenna is quite small which will be best suited for 5 G Femtobase stations to provide indoor communications at millimeter-wave frequencies.

Dielectric properties of CaO–B2O3–SiO2 glass-ceramic systems in the millimeter-wave frequency range of 20–60 GHz

The dielectric and structural properties of the as-quenched melts of three CaO–B2O3–SiO2 compositions (denoted CBS-1, CBS-2, and CBS-3) were investigated to determine their suitability for use in millimeter-wave applications. The CBS-1 glass-ceramic exhibited the lowest coefficient of thermal expansion (CTE = 3.2 ppm/°C), lowest dielectric constant (εr = 4.04) at 60 GHz, and highest dielectric loss (tan δ = 0.0029) at 60 GHz, which were attributed to the presence of quartz (SiO2) as the major phase. In contrast, as the major phase constituent of the CBS-2 and CBS-3 glass-ceramics was β-CaSiO3, they presented relatively high CTEs (6.6 and 5.9 ppm/°C, respectively), relatively high dielectric constants at 60 GHz (6.29 and 7.61, respectively), and relatively low dielectric losses at 60 GHz (0.0020 and 0.0012, respectively). The CBS-1 glass-ceramic exhibited the highest dielectric loss because of the presence of SiO2 as the major phase constituent as well as lattice scattering induced by the high glassy phase content. The thermal conductivities (κ) of the CBS-1, CBS-2, and CBS-3 glass-ceramics were determined to be 2.43, 1.06, and 0.82 W/mK, respectively. Structural analysis using Raman and Fourier transform infrared spectroscopy revealed an absence of nonbridging oxygen in the CBS-1 glass-ceramic, while the high CaO content (>40 mol%) of the CBS-2 and CBS-3 glass-ceramics triggered the formation of nonbridging oxygen in the tetrahedral silicate units. The increase in CaO content of the glass-ceramics increased the number of nonbridging oxygen atoms, thereby resulting in the relaxation of the structure. Consequently, the CBS-2 and CBS-3 glass-ceramics exhibited low thermal conductivity. All the prepared glass-ceramics presented high electrical resistivities of greater than 5 × 1011 Ω cm. The CBS-1 glass-ceramic displayed the highest breakdown strength of 15.20 kV/mm. Overall, the excellent microwave dielectric properties and thermal properties of the CBS glass-ceramics will facilitate the utilization of these materials in millimeter-wave applications.

Near-Field Scanning Millimeter-Wave Microscope Operating Inside a Scanning Electron Microscope: Towards Quantitative Electrical Nanocharacterization

The main objectives of this work are the development of fundamental extensions to existing scanning microwave microscopy (SMM) technology to achieve quantitative complex impedance measurements at the nanoscale. We developed a SMM operating up to 67 GHz inside a scanning electron microscope, providing unique advantages to tackle issues commonly found in open-air SMMs. Operating in the millimeter-wave frequency range induces high collimation of the evanescent electrical fields in the vicinity of the probe apex, resulting in high spatial resolution and enhanced sensitivity. Operating in a vacuum allows for eliminating the water meniscus on the tip apex, which remains a critical issue to address modeling and quantitative analysis at the nanoscale. In addition, a microstrip probing structure was developed to ensure a transverse electromagnetic mode as close as possible to the tip apex, drastically reducing radiation effects and parasitic apex-to-ground capacitances with available SMM probes. As a demonstration, we describe a standard operating procedure for instrumentation configuration, measurements and data analysis. Measurement performance is exemplarily shown on a staircase microcapacitor sample at 30 GHz.

Planar Offset Short Applicable to the Calibration of a Free-Space Material Measurement System in W-Band

The electrical properties of materials and their dependence on frequency and temperature are indispensable in designing electromagnetic devices and systems in various areas of engineering and science for both basic and applied researches. A free-space transmission/reflection method measuring the free-space scattering parameters of a material under test (MUT) located at the middle of transmit/receive antennas in a free space is suitable for non-destructively testing the MUT without prior machining or physical contact in high-frequency range. This paper describes a planar offset short applicable to the calibration of a quasi-optic based free-space material measurement system in the millimeter-wave frequency range. The measurement results of the dimensional and electrical properties for the three fabricated planar offset shorts with the phase difference of 120° between the reflection coefficients of the planar shorts in the W-band (75–110 GHz) are presented.