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International audience; A low-cost dual linearly-polarized transmitarray antenna (TA) is presented for 5G and beyond networks at D-band. This TA is made of 40 40 unit-cells (UCs) and is illuminated by a stepped feed horn with a F/D ratio equal to 0.75. The flat lens panel is based on UCs with six different phase states at the center frequency of 150 GHz (thus leading in average to a 2-bit phase quantization and 0.7-dB insertion loss from 130 to 175 GHz). Each UC is made of only three metal layers and does not include any via connection to guaranty performance robustness with respect to fabrication dispersions. The measured1-dB and 3-dB TA gain bandwidths equal 16.8% and 19.8%, respectively, with a peak gain of 32 dBi, corresponding to an aperture efficiency of 32% at 150 GHz. The measured sidelobe and cross-polarization levels in E and H planes remain below -21 and -37 dB, respectively. An excellent agreement between measured and simulated radiation patterns was observed.

This letter presents a ring-shaped $E$ -plane filtering coupler working at 150 GHz with high performance. The coupler is based on cavity resonators. Unlike the conventional ones, the four resonators in this coupler are all bent along their length direction and connected end to end, forming a closed circle. By adjusting the radius of the circle, three of the resonators work on TE101 mode while the other is on TE102 mode. The coupler can be split through $E$ -plane and the measured response of the coupler has an excellent agreement with the simulation, with a low amplitude imbalance of 0.31 dB, insertion loss of 0.12–0.46 dB, and over 20-dB return loss and isolation.

This article presents two kinds of low-cost antennas for $D$ -band short-distance wireless communication applications. Both the antennas are excited by a substrate integrated waveguide (SIW) feed line based on the printed circuit board (PCB) process. The first type is a stainless-steel-based horn antenna, fabricated by electric-discharging machining (EDM) process and selective laser melting (SLM) 3-D printing, respectively, for reducing cost. To integrate the horn antennas with the SIW feed line, a wideband transition structure from SIW to the rectangular waveguide is designed by suppressing higher order eigenmodes. The experimental data show that the integrated horn antenna can achieve 18.9% (129.5–156.5 GHz) −10 dB impedance bandwidth and a peak gain of 15.46 dBi. The second type of antenna is a single-layer rectangular patch antenna fed by SIW. By locally widening the SIW feed line to generate an equivalent shunt capacitance instead of using complex resonators, a wide impedance bandwidth can be realized. The measured −10 dB impedance bandwidth and the peak gain of the patch antenna are 20.8% (125.3–154.4 GHz) and 7.26 dBi, respectively. The two proposed antennas can provide comparable performance for different application requirements under the premise of a low fabrication cost.

This work focuses on the impact of the build orientation on additively manufactured waveguide-based hybrid couplers for D-band frequency range and relates it to other sources of uncertainty within the overall manufacturing process and measurement instrumentation for the D-band frequency range. The designed specimens are first printed from UV curable photopolymer resin and subsequently metal coated by an electroless silver plating process, which in turn is improved by making use of the slotted waveguide approach. Although the requirements toward geometrical precision to achieve phase errors below 10° are in an order of 0.1 mm, a desktop grade DLP printer is utilized in this work in order to point out the prospects and limitations of additive manufacturing. Furthermore, waveguide paths with bends are part of the model and their impact on the measured attenuation is estimated explicitly.Despite this narrow field of tolerances, one specimen could have been realized, which achieves a measured output magnitude imbalance of 0.7 dB over the frequency range from 120 to 155 GHz while at the same time exhibiting a phase deviation of only

Single atom catalysts (SACs) have received much attention in the nitrogen reduction reaction (NRR) field due to their high atomic utilization and controllable electronic state regulation. It is attractive to explore the mechanism for regulating the electronic state of the active center of single-atom catalysts. Herein, we propose a new regulation mechanism by applying a strain that can change the coordination bond length of Cr–N and quantitatively regulate the electronic state of the active center in Cr-SACs. Based on this mechanism, we achieve an ultra-low 0.174 V over-potential for the NRR in the single Cr-embedded nitrogen-doped graphene (CrN3@graphene) by applying lattice stretch of 2.5% compared to the pristine CrN3@graphene. Computational results show that the d band center, the Cr–N anti-bonding orbital and the spin-polarization state of the single Cr atom can be adjusted by tuning the coordination length of Cr–3N. The applied lattice stretch of 2.5% can transform the spin-polarization state of the single Cr atom from a high-spin-polarization state to low-spin-polarization. This conversion weakened the adsorption capacity of N2 for CrN3@graphene and finally achieved an ultra-low over-potential. Our findings open up a new path of NH3 production by exploiting strained SACs under ambient conditions.

The quality of Li-ion batteries is highly related to the crystallinity of the graphite used in their electrodes. Therefore, the development of two-dimensional detection equipment for evaluating the integrity of graphite electrodes is critical. In this study, a triaxial scanning platform was developed for Raman spectroscopy. Two-dimensional Raman mapping of the defects (D band) and stacking (2D band) of graphite electrodes was performed to determine atomic-level variations caused by charging. Through Raman mapping, the effects of constant-current–constant-voltage (CC–CV) and CC–reFLEX fast charging were compared. The graphite damage from CC–reFLEX fast charging was less extensive than that from CC–CV charging. Furthermore, investigations using the triaxial platform revealed that the graphite on a curved electrode exhibited disordered stacking after several charging–discharging cycles. This phenomenon creates safety concerns.

We demonstrate anomalous reflectors at 140 GHz for the application of 6G communication coverage expansion. The reflectors are designed on cyclo-olefin polymer (COP) substrates on the basis of measured complex permittivity and conductivity at millimeter frequencies obtained with the balanced-type circular disk resonator method. From full-wave simulations, we confirm that nearly perfect anomalous reflection characteristics are realized with suppressed parasitic reflections in undesired directions. The simulated efficiencies excluding the material losses of the reflectors designed with the reflection angle $\theta _{\mathrm {R}}={30}^\circ $ , 45°, 60°, and 75° are 99.5%, 98.9%, 99.7%, and 99.8%, respectively. In addition, we fabricate the designed reflectors on the COP substrates and experimentally evaluate their anomalous reflection performances. The measured overall efficiencies of the reflectors with $\theta _{\mathrm {R}}={45}^\circ $ , 60°, and 75° are 88.0%, 83.6%, and 81.6%, respectively. This is the first demonstration of highly efficient anomalous reflectors in the D-band.

High-energy ball milling (HEBM) combined with powder metallurgy route was used to fabricate carbon nanotube (CNT) reinforced 7055Al composites. Two powder morphology evolution processes (HEBM-1 and HEBM-2) were designed to investigate the dispersion and damage of CNTs during HEBM process. HEBM-1 evolution process involved powder flattening, cold-welding and fracture, while HEBM-2 evolution process consisted of powder flattening and fracture. For HEBM-1, the repetitive fracture and cold-welding process was effective for dispersing CNTs. However, the powder flattening process in HEBM-2 was unsuccessful in dispersing CNTs due to two reasons: (1) the thickness of flaky Al powders exceeded the critical value, and (2) the clustered CNTs embedded in flaky Al powders could not be unravelled. Because of the broadening of D band and the appearance of a new defect-related D’ band, product of ID/IG and full width half maximum of D band, rather than ID/IG, was used to evaluate the actual damage of CNTs. It indicates that the damage of CNTs was severe in powder flattening and fracture stages, while the damage of CNTs was small in powder cold-welding stage.

This article presents a compact 150-GHz transmitter with 12-dBm $P_{\mathrm{ sat}}$ and 17-dB conversion gain. This $D$ -band transmitter is composed of a frequency doubler, a micromixer, a two-stage $g_{m}$ -boosting power amplifier (PA), and an on-chip dielectric resonate (DR) antenna. At sub-terahertz, the output power and the gain are the limiting factors for the transmitter’s performance. In this work, $g_{m}$ -boosting topology is implemented to achieve the 17-dB gain by taking advantage of the base inductor without sacrificing the PA’s stability. The output power of the 150-GHz PA is enhanced by the proposed phase compensation method. In this proposed method, an auxiliary inductor is added for adjusting the phase difference to decrease the introduced loss from power combining and matching networks. The imbalance at the LO port is also reduced by the proposed capacitor and the resistor compensation method. From 140 to 160 GHz, the transmitter delivers more than 8-dBm output power, with the maximum $P_{\mathrm{ sat}}$ of 12 dBm at 148 GHz. This transmitter exhibits a conversion gain of 17 dB and an output 1-dB compression point ( ${\mathrm{ OP}}_{1~{\mathrm{ dB}}}$ ) of 11.4 dBm. The transmitter exhibits the highest output power, the highest ${\mathrm{ OP}}_{1~{\mathrm{ dB}}}$ , competitive conversion gain, and bandwidth among any silicon-based transmitters in $D$ -band, to the best of our knowledge.

A D-band low-loss mixed-mode filter with high selectivity is proposed and analyzed in this article. The transverse quintuplet/triple topology has been employed in the design with coupled overmode cavities using the TE $_{\mathrm {2N,1,0}}$ modes ( $N = 2,3,4, \ldots $ ) and TE $_{\mathrm {2N,1,0}}$ -like modes. Two transmission zeros (TZs) are generated in the upper and lower stopbands. The fractional bandwidth (FBW) and positions of the TZs can be flexibly designed by properly selecting the geometries of the proposed overmode cavity, which determines the frequencies of all resonating modes. To improve the frequency selectivity, multiple coupled overmode cavities, which have different spurious responses and TZs distributions, are cascaded for the designed filter. For demonstration purposes, two types of filter architectures are proposed for two D-band mixed-mode bandpass filters, respectively, which shows the design flexibility of the proposed method. The first filter is realized by cascading multiple overmode cavities through waveguide sections, and the second filter is realized by cascading overmode cavities through slots. Experiments are carried out to verify the second filter with TZs. The measured FBW3 dB is 17.18% from 128.11 to 152.19 GHz, the minimum insertion loss is around 0.33 dB, and the measured rectangle coefficient (BW40 dB/BW3 dB) is about 1.38. The measured results agree well with the designed ones, which verifies the proposed method. The proposed filter can be a good candidate for millimeter-wave and terahertz systems.

A wideband air-filled plate array antenna with multistage impedance matching operated in $D$ -band is proposed in this article. To achieve the wide bandwidth, three stages of impedance matching are introduced in the $2\times 2$ subarray, including the step-profiled horn element, the step-profiled power divider cavity with two resonant points, and a modified E-plane bend transition. The integrated step-profiled horn with simple configuration can realize broadband matching. Wideband T-junctions are combined together to form a corporate feeding network. Essential matching pins are introduced to break through the upper bandwidth restriction of the feeding network. In addition, the square aperture shape of the horn element and the air-filled feeding structure contribute to the high radiation efficiency of the proposed array. To satisfy the fabrication tolerance, the MEMS micromachining technology with a high etching precision is utilized. The experimental results show a wide 1 dB down gain bandwidth of 23.54%. The maximum gain is 33.24 dBi and the peak efficiency is 70.91%.

This paper reports the design and characterization of a D-band front-end receiver, implemented in a 0.13- ${\mu {m}}$ SiGe BiCMOS technology, for use in a direct-detection-based Dicke radiometer architecture. The peak responsivity of the Dicke radiometer is 688 MV/W at 130 GHz, and its minimum value is about 82.6 MV/W at 170 GHz. The Dicke switching frequency is 10 kHz. The noise equivalent power of the Dicke radiometer remains below $20\textit {fW/H}{z}^{\text {1/2}}$ at the frequency range of 110–155 GHz, and its minimum value is about $9.3~\textit {fW/H}{z}^{\text {1/2}}$ at 130 GHz. The implemented radiometer achieves an NETD of 0.13K for a back-end integration time of 30ms. Its total chip area is approximately 1.7mm2, and the overall quiescent DC power consumption is 33.8 mW. To the authors’ best knowledge, the implemented Dicke radiometer achieves the best NETD in the literature.

A 130 GHz fully-integrated fundamental-frequency transmitter (TX) module with 4.4 dBm single-ended measured output power in a 130 nm SiGe technology is presented. The transmitter achieves in measurement a phase noise of −88 dBc/Hz at 1 MHz offset frequency from a 130 GHz carrier and a tuning range of 17 GHz. Its relatively compact size, low power consumption and high output power, enables the TX module to be integrated into more complex D-Band transceiver modules for radar and imaging applications. Due to the available measurement equipment, it was only possible to measure the output power single-ended. The measured single-ended output power is 4.4 dBm. This corresponds well to a simulated maximum differential output power of 8.1 dBm. To the best of the author’s knowledge, the presented chip exhibits one of the highest output power for fundamental-frequency TX modules among the recently reported state-of-the art chips in this frequency range.

Summary Anisotropies in electronic transportations conventionally originate from the nature of low symmetries in crystal structures and were not anticipated for perovskite oxides with crystal asymmetries much smaller than, e.g., van der Waals or topological crystal. Beyond conventional expectations, here we demonstrate pronounced anisotropies in the inter-band Coulomb repulsion-dominated electronic transportation behaviors in the low-dimensional perovskite family of rare-earth nickelates (ReNiO3). The in-plane orbital entropy associated to the in-plane symmetry of the NiO6 octahedron within ReNiO3 causes intrinsic anisotropies for the gradual orbital transition with temperature to regulate their thermistor transportations. Extrinsically imparting biaxial interfacial strains amplifies the anisotropies in the electronic transportation of ReNiO3. It unveils the overlooked role of orbital directionalities within low-dimensional correlated perovskites that triggers anisotropic transportations despite their higher crystal symmetries, and this introduces new freedoms to regulate their correlated transportations.

We present novel three-layer $D$ -band linearly polarized transmitarrays entirely fabricated using standard printed circuit board (PCB) processes. Three flat lenses comprising 1600 elements are designed to generate broadside and scanned beams. All lenses are synthesized using eight unit cells (3 bit phase quantization). The combination of cells comprising probe-fed and aperture-coupled patches is proposed to overcome the design challenges due to technological constraints and achieve a wideband operation. The minimum design feature is $80~\mu \text{m}$ . The tradeoffs in the design of the feed illumination are analyzed using ad hoc numerical tools. A 10 dBi horn is eventually selected as source. The focal-to-diameter ( $F/D$ ) ratio is 0.75 for all lenses. The broadside array attains a peak gain of 33.0 dBi and a −1 dB relative gain bandwidth of 11.7%, i.e., wider than that of state-of-the-art designs, in the 100–300 GHz band, which use more complex technologies and larger focal distances. The performance of the proposed antenna technology demonstrates its potential for low-cost high-capacity wireless backhauls beyond 100 GHz.

Ni3B/Ni heterostructures have been constructed, which exhibit exceptional catalytic performance toward the hydrogen oxidation reaction (HOR) under alkaline media, with the mass activity being about 10 times greater than that of Ni3B and Ni, respectively, ranking among the most active platinum-group-metal-free electrocatalysts. Experimental results and theoretical calculations confirm electron transfer from Ni3B to Ni at the Ni3B/Ni interface, resulting in inter-regulated d-band centers of these two components. This inter-regulation gives rise to optimized binding energies of intermediates, which together contribute to enhanced alkaline HOR activity.

This paper proposes a new concept of designing compact high precision millimeter-wave wideband variable phase shifters. The phase shifter is implemented with a stacked shim with extremely short length of 0.9 mm and two waveguide flange adaptors with length of 0.5 mm. High precision phase shifting is achieved over entire D-band (110-170 GHz) by rotating the shim 90 degrees from aligned to perpendicular with consistent impedance matching performance. In addition, a glide-symmetric holey electromagnetic bandgap (EBG) structure is adopted to avoid wave leakage from the gap between the shim and the flange adaptors. A proof-of-concept (PoC) demonstrator is designed, manufactured, and tested. The measured results show that the designed stacked shim phase shifter with embedded EBG structure ensures return loss higher than 10 dB across 110-170 GHz with a 75 μm airgap between waveguide flanges. The studied phase shifter provides a 0.88° phase shifting with each degree of mechanical rotation. The fabricated PoC phase shifter has a worst-case insertion loss of 0.92 dB and a return loss of 20 dB across the entire 110-170 GHz band and a maximum phase shift of 30°. At 10° phase shifting, the measured insertion loss is lower than 0.52 dB, and return loss is higher than 23 dB, respectively.

A D-band vector millimeter wave (mm-wave) signal generation and propagation scheme employing cascaded intensity modulator (IM) and in-phase/quadrature (I/Q) modulator is proposed and implemented. In experiment, both the IM and I/Q modulator are operating on optical-carrier-suppressing (OCS) mode to generate two pairs of dual single-sideband (SSB) signals, and the undesired optical sidebands are not eliminated by an optical filter. For each pair of dual SSB signals, one is unmodulated the other is vector-modulated, they are located on both sides of the center suppressed carrier. After optical fiber transmission, SSB signals will beat with each other at the photoelectric detection end, thus the electrical mm-wave signals are generated. We experimentally demonstrated 2-Gbaud 16QAM, 4-Gbaud QPSK, and 8-Gbaud QPSK Radio-over-Fiber (RoF) transmission at 130-GHz over 22.5 km standard single mode fiber and 1 m wireless link with a Bit-Error-Rate (BER) under ${3}{{.8}} \times {1}{{0}^{{{ - 3}}}}$ .

This paper proposes a measurement based modeling of D-band indoor channels. Different indoor environments were considered including Line-of-Sight (LOS) and Non Line-of-Sight (NLOS) conditions. Double steering at the transmitter and receiver sides was performed allowing angular characterization of the channel. Path loss, delay spread, angular spread, intra- and inter- cluster characteristics were also modeled. These characteristics were then compared to the ones obtained in other millimeter wave bands for the same environment.

We proposed and experimentally demonstrated a novel and simple method to realize D-band millimeter-wave (mm-wave) single-sideband (SSB) vector signal generation using cascaded one single-drive Mach-Zehnder modulator (MZM) and one push-pull MZM. After the first MZM driven by a radio frequency (RF) signal of 20-GHz, an optical frequency comb (OFC) with six flat carriers was successfully generated. Using the subsequent push-pull MZM driven by 10-GHz SSB vector signals and a photodiode (PD) for detection, we finally generated D-band SSB vector mm-wave signals at frequencies of 130-GHz and 150-GHz, respectively. The experimental results are well consistent with theoretical and simulation analysis. Based on the proposed scheme, 4-Gbaud generated D-band quadrature phase shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) mm-wave signals were transmitted over 10-km/25-km single-mode-fiber (SMF) and 1-m wireless links. The bit-error-rate (BER) performance can reach less than 7% hard-decision forward-error-correction (FEC) threshold of 3.8 × 10-3.

The article presents a monostatic D -band frequency-modulated continuous-wave (FMCW) radar based on a fully integrated monostatic single-channel silicon-germanium (SiGe) transceiver (TRX) chip. The chip is fabricated in Infineon's bipolar-complementary metal-oxide-semiconductor (BiCMOS) production technology B11HFC which offers heterojunction bipolar transistors (HBTs) with an f_{mathrm {T}}/f_{mathrm {max}} of 250 GHz/370 GHz. The monolithic microwave integrated circuits (MMICs) output signal is coupled by a fully differential substrate integrated waveguide (SIW) based coupling network. The output power at the WR-6.5 antenna flange is more than -10 dBm over a bandwidth of 37.5 GHz. For a sweep within a single-loop phase-locked loop (PLL) circuit from 174.5 to 121.5 GHz, a spatial resolution of almost 3 mm with a metallic plate as the target is achieved. The radar provides a small form factor of 2 times 4 times 5 cm3 and low power consumption of 2.2 W at 5 V. Finally, t he capabilities of the sensor for non-destructive testing (NDT) are demonstrated using a millimeter scanner. With radar imaging, it was possible to measure the orientation of the fiber layers up to a depth of 7.03 mm.

This Letter presents a non-galvanic D-band (110-170 GHz) interconnect realised in embedded wafer level ball grid array (eWLB) packaging technology. The interconnect consists of a patch-radiator-based waveguide transition implemented using one of the technology's redistribution layers. The patch radiates to a WR-6.5 standard waveguide perpendicular to its plane. An electromagnetic band-gap structure realised by metal patches is used to suppress undesired modes and improve the performance of the transition. The proposed solution is experimentally verified, and measurement results show that the transition exhibits an average insertion loss of 2 dB across the frequency range 122-146 GHz which, to the best of the authors' knowledge, is the lowest reported loss for a D-band packaging solution in eWLB technology and hence addresses one of the main integration challenges facing millimetre-wave systems.

This paper presents the integration of ${S}/\textit {Ka}/{D}$ -band antennas in a low-temperature cofired ceramic (LTCC) package. Three types of antennas, microstrip patch, grid array, and step-profiled horn, operating at different bands are compactly assembled in the same substrate. For electromagnetic isolation, a specific layout and extra-shielding structures, such as fences of metallic vias and air cavities, are designed to reduce the unwanted coupling between antennas. In addition to the antennas, a cylindrical radome is introduced closely attached to the surface of the LTCC substrate. Since radome acts as a dielectric superstrate, its influence on radiation performance is also taken into consideration, especially for ${D}$ -band operation, where a ring-shaped cavity is introduced to suppress the detrimental propagation of surface waves inside radome and enhance the gain as a consequence of dielectric loading effect. Measured results agree well with simulation. Proposed triband antennas, working at three frequencies 3, 30.5, and 120 GHz, achieve broadside gains of 6.51, 9.74, and 13.36 dBi with −10 dB fractional impedance bandwidths of 15.3%, 6.1%, and 6.5%, respectively.

In this paper, we present a comparative study of S-parameter measurements of electronic components on planar substrates performed with a waveguide module and in a conventional on-wafer probing environment. Measurements were conducted at three well-established measurement laboratories for the investigation of reproducibility at frequencies from 110 to 170 GHz. For the comparison, we fabricated waveguide modules for six passive structures, including devices under test (DUTs). Four of these structures are related to using a second tier calibration to achieve the same reference planes for the waveguide module measurements as used for the on-wafer probing measurements. Additionally, we processed three complete on-wafer calibration sets, including DUTs, equipped with different probe-to-pad interfaces. In this comparison, the DUT measurement from the waveguide module acts as a reference standard, with reduced crosstalk behavior in comparison to the on-wafer measurement. With the waveguide reference, we are able to assess the ability of two techniques to compensate for crosstalk and higher order modes influencing the on-wafer S-parameter measurements. On the one hand, we use a shielded probe-to-pad transition and on the other hand, we use an algorithm-based crosstalk correction scheme. To the best of our knowledge, this is the first time that such a comparison has been undertaken, comparing well-established waveguide calibrations with an equivalent on-wafer calibration.

In this paper, we report formation of single and multilayer graphene synthesized by varied doses of implanted carbon ions in Ni as a host medium. 1 MeV energetic C ions with a dose in the range from 1012 ions/cm2 to 1015 ions/cm2 were implanted in thermally evaporated Ni films on glass and Si substrates. XRD, SEM and AFM were employed to study the structure and morphology of the synthesized graphene. A sharp Raman G band was observed, which overlapped with a very broad Raman D band due to presence of amorphous C in the synthesized structures. The lineshape analysis of Raman 2D bands confirmed the formation of monolayer, bilayers and four layers of graphene layers. The splitting observed in the Raman 2D mode was attributed to the interlayer disorders caused by Ni traces. In the end it was concluded that the dose rate and quality of Ni film were critical for the synthesis of graphene or graphene like multilayered films. The synthesis of graphene was also found to depend on the substrate as adhesion and growth of Ni on various substrates was different. In present experiments, dose of 1015 ions/cm2 of 1 MeV C ions was suitable in case of Si substrates where as 1014 ions/cm2 dose rate was acceptable lower limit for the synthesis of single layer grapheme on glass substrate.

A D-band on–off keying (OOK) transceiver chipset is fabricated in a 65-nm bulk CMOS technology as a low-cost and highly integrative solution to short-distance wireless connectivity. Supplementary transistor modeling is performed for accurate circuit design at mm-wave frequencies. To overcome low transistor $\text{f}_{\mathrm {max}}$ and reduce dc power consumption, the transmitter employs a frequency-multiplier-based architecture with no power amplifier. The receiver adopts a non-coherent architecture consisting of a dc-coupled three-stage differential amplifier and an envelope detector. The OOK transmitter exhibits a measured output power of −9.8 dBm and an on–off level difference of 13.2 dB at 134.1 GHz. The receiver shows a measured average responsivity of 4.1 kV/W and a noise equivalent power of 211.4 pW/Hz1/2 over all D-band frequencies. The dc power consumption of the transmitter and the receiver is 76 and 32.5 mW, respectively. The transceiver is tested in both on-chip loopback and air-channel configurations and demonstrates data transmission up to 10 and 2 Gb/s at a distance of 0.03 m, respectively.

We present the fabrication and electromagnetic testing of serpentine waveguide traveling-wave tube amplifier circuits operating in the W-band (75-110 GHz) and D-band (110-170 GHz) frequency ranges. The circuit structures were fabricated in a split-block configuration in a photopolymer material using a commercial digital light processing (DLP) 3D printer and, subsequently, covered with a conducting layer by Au sputtering and Cu electroplating. Two-port S-parameter measurements of the W-band circuit demonstrate a transmission band from ~87-104 GHz, with a 26.7-dB return loss and a 0.55-dB insertion loss measured at 95 GHz. The D-band circuit demonstrates a transmission band from ~139 to 145 GHz, with a 21.5-dB return loss and a 2.4-dB insertion loss measured at 140 GHz.

To address the challenge of highly efficient water splitting into H2, successful fabrication of novel porous three-dimensional Ni-doped CoP3 nanowall arrays on carbon cloth was realized, resulting in an effective self-supported electrode for the electrocatalytic hydrogen-evolution reaction. The synthesized samples exhibit rough, curly, and porous structures, which are beneficial for gaseous transfer and diffusion during the electrocatalytic process. As expected, the obtained Ni-doped CoP3 nanowall arrays with a doping concentration of 7% exhibit the promoted electrocatalytic activity. The achieved overpotentials of 176 mV for the hydrogen-evolution reaction afford a current density of 100 mA cm−2, which indicates that electrocatalytic performance can be dramatically enhanced via Ni doping. The Ni-doped CoP3 electrocatalysts with increasing catalytic activity should have significant potential in the field of water splitting into H2. This study also opens an avenue for further enhancement of electrocatalytic performance through tuning of electronic structure and d-band center by doping.

The mechanism of atomic collisions in excited bands plays an important role in both the atomic dynamics in high bands of optical lattices and the simulation of condensed matter physics. Atoms distributed in an excited band of an optical lattice can collide and decay to other bands through different scattering channels. In the excited bands of a one-dimensional lattice there is no significant difference between the cross sections to different scattering channels, due to the sameness of all of the geometrical couplings. Here, we investigate the collisional scattering channels for atoms in the excited bands of a triangular optical lattice and demonstrate a dominant scattering channel in the experiment. A shortcut method is utilized to load Bose-Einstein condensate of $^{87}\mathrm{Rb}$ atoms into the $\mathrm{\ensuremath{\Gamma}}$ point of the first $D$ band with zero quasimomentum in the triangular optical lattice. After some evolution time, the number of atoms scattering into the $S$ band induced by two-body collisions is around four times the number that scatter into the second most populated band. Our numerical calculation shows that the $ss$ scattering channel is dominant, which is roughly consistent with the experimental measurement. The appearance of dominant scattering channels in a triangular optical lattice is owing to nonorthogonal lattice vectors. This work is helpful for the research on many-body systems and directional enhancement in optical lattices.

In this paper a 140 GHz circularly polarized antenna is studied. The motivation of this work is to propose a suitable antenna configuration to reduce the subsequent manufacturing cost and complexity. The resultant antenna consists of a circular waveguide feed and a dielectric cover which is used to increase antenna directivity. Numerical study shows that the proposed antenna exhibits a 17% relative S11 bandwidth with a maximum gain of 16 dBi. The axial ratio is less than 3 dB ranging from 130 GHz to 155 GHz.

Collagen fibrils are the main structural component of load-bearing tissues such as tendons, ligaments, skin, the cornea of the eye, and the heart. The D-band of collagen fibrils is an axial periodic density modulation that can be easily characterized by tissue-level X-ray scattering. During mechanical testing, D-band strain is often used as a proxy for fibril strain. However, this approach ignores the coupling between strain and molecular tilt. We examine the validity of this approximation using an elastomeric collagen fibril model that includes both the D-band and a molecular tilt field. In the low strain regime, we show that the D-band strain substantially underestimates fibril strain for strongly twisted collagen fibrils -- such as fibrils from skin or corneal tissue., 12 pages, 1 figure

Observationally, the interstellar gas-phase abundance of deuterium (D) is considerably depleted and the missing D atoms are often postulated to have been locked up into carbonaceous solids and polycyclic aromatic hydrocarbon (PAH) molecules. An accurate knowledge of the fractional amount of D (relative to H) tied up in carbon dust and PAHs has important cosmological implications since D originated exclusively from the Big Bang and the present-day D abundance, after accounting for the astration it has experienced during the Galactic evolution, provides essential clues to the primordial nucleosynthesis and the cosmological parameters. To quantitatively explore the extent to which PAHs could possibly accommodate the observed D depletion, we have previously quantum-chemically computed the infrared vibrational spectra of mono-deuterated PAHs and derived the mean intrinsic band strengths of the 3.3 $\mu$m C--H stretch (A$_{3.3}$) and the 4.4 $\mu$m C--D stretch (A$_{4.4}$). Here we extend our previous work to multi-deuterated PAH species of different deuterations, sizes and structures. We find that both the intrinsic band strengths A$_{3.3}$ and A$_{4.4}$ and their ratios A$_{4.4}$/A$_{3.3}$ not only show little variations among PAHs of different deuterations, sizes and structures, they are also closely similar to that of mono-deuterated PAHs. Therefore, a PAH deuteration level (i.e., the fraction of peripheral atoms attached to C atoms in the form of D) of ~2.4% previously estimated from the observed 4.4 $\mu$m to 3.3 $\mu$m band ratio based on the A$_{4.4}$/A$_{3.3}$ ratio of mono-deuterated PAHs is robust., Comment: 36 pages, 17 figures, 6 tables; accepted for publication in The Astrophysical Journal Supplement Series

The Raman spectra of graphene-based matter exhibit a set of defect/disorder-induced bands. The D band, which exhibits a strong dispersion up to similar to 50 cm(-1)/eV, comes from transverse optical phonons around K or K ' in the first Brillouin zone and involves an intervalley double resonance (DR) Raman process. In the present work, resonant Raman scattering (lines ranging from 1.58 to 3.81 eV) is used to study the unusual behavior of the one-phonon Raman band of a carbonaceous material (anthracene-based carbon which is one of the graphitizable carbons) upon its secondary carbonization stage (450 degrees C-1000 degrees C). While the G band appears to be nondispersive, the D band exhibits a change in both position and intensity. Its dispersion progressively rises from similar to 6 cm(-1)/eV to values close to what is usually observed in defected graphene-based systems when anthracene-based carbon becomes almost pure. This evolution appears to be correlated with a release of hydrogen (fixed on the edges of polyaromatic layers) questioning their role in changing the D band resonance conditions.

This article reviews the current state-of-the-art of millimeter-wave (mm-wave) antennas for communication and sensing applications in the D-band between 110 and 170 GHz. The most popular design techniques, including Antenna-on-Board (AoB), slotted waveguides, Antenna-in-Package (AiP) and Antenna-on-Chip (AoC), are described using relevant examples from scientific literature. Potential benefits and limitations of integration technologies, such as specialized packaging, chip post-processing steps and interconnects, are listed as well. The reported performances of all listed designs are compared against each other, taking the antenna size relative to operating frequency into account. This novel comparison indicates that small-scale integrated AiP and AoC designs can achieve competitive performance levels with short and low-loss interconnects.

The first Transmission Hub for Point to multipoint wireless distribution at D-band (141 – 148.5 GHz) is presented. The paper reports the development of the main components of the transmission hub, including MMIC chipset, TWT, Image rejection filter and horn antennas.

In this work, a dual-mode (divide-by-2 and divide-by-3) dynamic frequency divider is presented. A tunable delay gated ring oscillator (TDGRO) topology is proposed for dual-mode operation and bandwidth extension. It uses a 130-nm gate length SiGe BiCMOS technology with the $f_{t}$ and $f_{\mathrm {max}}$ of 250 and 370 GHz, respectively. Verification shows that it works at $W$ -band from 70 to 114 GHz (47.8% bandwidth) for divide-by-2 and works at $D$ -band from 105 to 160 GHz (41.5% bandwidth) for divide-by-3. This divider can be used in integrated phase-locked loops (PLLs) at millimeter-wave frequencies.

A novel front end for high data rate point to point links at D-band (151 – 174.8 GHz) will provide up to 45 Gb/s over 1 km range. The low power signal generation is provided by a low cost Resonant Tunnelling Diode (RTD) oscillator. The RTD oscillator is connected to a Traveling Wave Tube that provides up to 10 W transmission power.

Gap waveguide technology is particularly attractive for the design of passive elements in mm-wave systems. Recently, the so-called zero-gap implementation has proved to be very robust to manufacturing tolerances, while at the same time keeping the low loss associated to the contactless standard gap waveguide. In this paper, a Chebyshev filter working at 145 GHz based on this idea and intended to be used in a wireless communication system is designed and optimized. A conventional milling technique has been used in its fabrication, and good measured results have been obtained in a single-pass process. This work has been partly funded by EU Commission within the H2020 Ultrawave project, Spanish Government under project TEC-2016-79700-C2-2-R, and by Chairs of Excellence project appointment at the Universidad Carlos III de Madrid, Madrid, Spain.

The first Point to MultiPoint wireless system at D-band has been designed and is in advanced development. The European Commission H2020 ULTRAWAVE "Ultra capacity wireless layer beyond 100 GHz based on millimeter wave Traveling Wave Tubes" project aims to respond to the demand of high capacity at level of tens of Gigabit per second, in urban areas, where fiber backhaul is not economically viable and high density small cell architectures are deployed. A transmission hub powered by a novel D-band TWTs will feed a number of terminals arbitrarily allocated in the corresponding area sector. This paper illustrates the main characteristics, advantages and networking aspects and provide a summary of the latest results of the ULTRAWAVE project.

The first isolation of graphene in 2004 opened a new area of 2D Van der Waals materials with one or several elements arranged in one plane with atomic thin thickness, which attracts great attention for the potential in the miniaturization of electronic devices. Various spectacular properties that do not exist in their 3D bulk form also provide opportunities for the design of novel electronic devices. In this thesis, by first principle calculations, I investigate the electronic properties of several typical 2D systems and explore the possibility to tune them for practical application. In chapter 2, I study the ferroelectric field effect on the two-dimensional electron gas at the n-type LAO/STO (001) interface through a ferroelectric substrate BaTiO3 (BTO). In chapter 3, I explore the possibility of making a semiconducting monolayer of MoS2 ferromagnetic by introducing holes into the narrow Mo d band that forms the top of the valence band. In chapter 4, I carry out a systematic study of the structural and electronic properties of single acceptor and double acceptor (V, Nb, Ta, Ti, Zr, Hf) doped MX2 (M = Cr;Mo;W, X = S; Se;Te) monolayers in the single impurity limit. In chapter 5, I study the structural reconstruction at the bare zigzag edge of 2D-Xene (X=Si, Ge, Sn).

This paper reports the design and fabrication of a novel all-metal antenna operating in the millimeter-wave band. Based on the resonant cavity antenna (RCA) concept, the principle of antenna operation is explained, and a parametric study of several key design parameters is provided. A novel impedance matching technique is introduced to broaden the antenna return loss bandwidth. Two gain enhancement methods have been employed to achieve a more directive beam with reduced side lobes and back lobes. The D-band antenna prototypes are produced using i) all-metal printing without any post-processing; ii) dielectric printing with copper metallization applied later. Comparisons of the simulated and measured results amongst the antennas fabricated using the two additive manufacturing techniques are made. Measurement results of the two antenna prototypes show that the proposed design can achieve a 14.2% bandwidth with a maximum gain of 15.5 dBi at 135 GHz. The present work is the first D-band resonant cavity antenna fabricated using two different 3D printing methods.

A robust and wideband differential microstrip line-to-WR6-waveguide transition for mixed multilayer PCBs at D-band is presented. The PCB stack is composed of three standard RF core materials with standard thicknesses. Compared to other inline transitions above 90 GHz, which are designed for single substrates, it can be applied to mixed multilayer circuits. The tapered transition is only 8.0-mm wide and 2.5-mm long, has an insertion loss between 1.2 and 1.8 dB, and a return loss higher than 10 dB for 30-GHz bandwidth around the center frequency of 120 GHz., acceptedVersion

The coupling efficiency between free space waves and surface waves is low, narrowband, or both. Highly efficient broadband (better than 20% fractional bandwidth) coupling from waveguide modes can be achieved through sophisticated transitions whose fabrication can be enabled through additive manufacturing (e.g. selective laser melting). Here, we present alternative metallic transitions designed to couple the fundamental mode of a D-band waveguide to the fundamental transversemagnetic surface mode supported by a periodic metal corrugated grating. Simulations of the coupling process and initial measurements have been undertaken. Work supported by EPSRC [Grant No. EP/S018395/1, Studentship No. 2137478], the Royal Society [Grant No. RSG/R1/180040], and the University of Birmingham [Birmingham Fellowship].

We present the design, manufacturing, and testing of a 37-element array of corrugated feedhorns for Cosmic Microwave Background CMB) measurements between 140 and 170 GHz. The array was designed to be coupled to Kinetic Inductance Detector arrays, either directly (for total power measurements) or through an orthomode transducer (for polarization measurements). We manufactured the array in platelets by chemically etching aluminum plates of 0.3 mm and 0.4 mm thickness. The process is fast, low-cost, scalable, and yields high-performance antennas compared to other techniques in the same frequency range. Room temperature electromagnetic measurements show excellent repeatability with an average cross polarization level about − 20 dB, return loss about − 25 dB, first sidelobes below − 25 dB and far sidelobes below − 35 dB. Our results qualify this process as a valid candidate for state-of-the-art CMB experiments, where large detector arrays with high sensitivity and polarization purity are of paramount importance in the quest for the discovery of CMB polarizationB-modes.

In this paper, a study of quantitative analysis of the defects in chemical vapor deposition (CVD) grown graphene through plasmon-enhanced Raman scattering has been performed. By designing and fabricating three-dimensional hybrid Au nano-particles/single-layer-graphene/Au nano-holes (Au NPs/SLG/Au NHs) structures, the defects induced Raman scattering signals of SLG have been extremely enhanced. The light-graphene interaction between graphene and plasmonic nanostructures heightened the cross-section of the Raman scattering resulting in enhancing Raman signals. In the SERS spectra of graphene, the D band and D′ band which associated with defects-induced double resonance (DR) Raman scattering processes have been clearly observed. A general and empirical formula has been applied to quantify graphene defects nano-crystallite (La) through the relation between the ratio of ID/IG and EL4. Additionally, an empirical formula for quantifying the defects based on the relation between ID’/IG and EL4 was proposed. Besides, the Au NPs/SLG/Au NHs as a SERS substrate has been applied in detecting the fluorescein molecular under low concentration, and it exhibited good SERS performance.