Millimeter-wave Research Articles

Propagation Characteristics of Modulated EHF Signal in the Wake Region of Plasma Sheath

A large number of studies have confirmed that the wake region may be a more ideal antenna installation area for the reentry vehicle communication problem, but many practical issues such as how to choose the modulation mode, carrier frequency, and antenna orientation are still pending. Based on numerical simulations, the characteristics of tail channels and the bit error rate (BER) of extremely high-frequency (EHF) communication in the wake region of the plasma sheath of hypersonic vehicle are studied. It is found that, with an increase in the angle between the tail channel and the tail of the vehicle, the attenuation of the EHF signals decreases and the phase shift fluctuates more severely. In order to obtain better communication performance, 2PSK with a carrier frequency of 140 GHz or 225 GHz, or 4QAM (QPSK) modulation with a carrier frequency of 140 GHz, and the tail channel with an angle between 50° and 60° to the tail of the vehicle can be selected. This study reveals the propagation characteristics and BER performance of EHF signals in the wake region of plasma sheath, which can provide a valuable reference for the design of the hypersonic vehicle communication system.

Numerical modeling on the bit error rate of EHF communication in time-varying hypersonic plasma sheath

Plasma sheaths enveloping hypersonic vehicles could yield a communication blackout. Many previous studies have shown that the electromagnetic wave in an extremely high frequency (EHF) band could penetrate a hypersonic plasma sheath effectively. In other words, the EHF communication could be a potential solution to the communication blackout problem. Nevertheless, most of those works used to concern only the EHF signal attenuation. In addition, those works normally treated plasma sheaths as a static plasma layer. However, plasma sheaths always keep evolving. In the present study, the modulated EHF signal propagation in a time-varying plasma sheath was investigated numerically. The plasma sheath was obtained with a hypersonic hydrodynamical model that has been utilized in previous studies. The EHF signal propagation was modeled based on theories of geometrical optics. The frequencies studied are 94, 140, and 225 GHz. The investigation revealed that not only signal attenuation but also the phase shifts for carrier waves vary with time. Their impact on the bit error rate (BER) of the EHF communication system was studied numerically. The modulation modes concerned in the present study are 2ASK, 2PSK, 4QAM, and Non-Coherent demodulation 2FSK (NC-2FSK). According to the study, the BER keeps varying with time. This study also showed that the BER is impacted by the carrier frequency, modulation mode, and the demodulation method. According to the comparison and the analysis, the suggested modulation modes are 2PSK and 4QAM at the carrier frequency of 140 GHz, which could lead to smaller and more stable BER for the EHF communication system utilized by hypersonic vehicles.

Optimization of system’s parameters for wavelength conversion of E-band signals

Current and future wireless communication systems are designed to achieve the user’s demands such as high data rate and high speed with low latency and simultaneously to save bandwidth and spectrum. In 5G and 6G networks, a high speed of transmitting and switching is required for internet of things (IoT) applications with higher capacity. To achieve these requirements a semiconductor optical amplifier (SOA) is considered as a wavelength converter to transmit a signal with an orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM). It exploits the subcarrier’s power in conventional OFDM block in order to send additional bits beside the normally transmitted bits. In this paper, we optimized the SOA’s parameters to have efficient wavelength conversion process. These parameters are included the injection current (IC) of SOA, power of pump and probe signals. A 7 Gbps OFDM-SPM signal with a millimeter waves (MMW) carrier of 80 GHz is considered for signal switching. The simulation results investigated and analyzed the performance of the designed system in terms of error vector magnitude (EVM), bit error rate (BER) and optical signal-to-noise ratio (OSNR). The optimum value of IC is 0.6 A while probe power is 9.45 and 8.9 dBm for pump power. The simulation is executed by virtual photonic integrated (VPI) software.

Cylindrical Dielectric Lens Antenna for 5G Mobile Base Station

Abstract A wide range new technologies such as millimetre wave, massive MIMO technology, multi beam base station antenna are required in the fifth-generation (5G) mobile system. For multi beam base station application, a dielectric lens antenna is selected due to capabilities of achieving excellent radiation patterns in a wide angular range by applying the lens shaping method. A cylindrical structure is suitable for a lens antenna installation on the base station pole. In this paper, a cylindrical dielectric lens antenna is proposed and multi beam radiation patterns are investigated through the calculations by an electromagnetic simulator (FEKO) at the operating frequency of 28 GHz. As a result, good multi beam radiation patterns are achieved in the scanning angle from 0°to 30° with total gain reduction around 5dBi and antenna efficiency of about 95.9%.

ATOMIUM: ALMA tracing the origins of molecules in dust forming oxygen rich M-type stars

This overview paper presentsATOMIUM, a Large Programme in Cycle 6 with the Atacama Large Millimeter/submillimeter Array (ALMA). The goal ofATOMIUMis to understand the dynamics and the gas phase and dust formation chemistry in the winds of evolved asymptotic giant branch (AGB) and red supergiant (RSG) stars. A more general aim is to identify chemical processes applicable to other astrophysical environments. Seventeen oxygen-rich AGB and RSG stars spanning a range in (circum)stellar parameters and evolutionary phases were observed in a homogeneous observing strategy allowing for an unambiguous comparison. Data were obtained between 213.83 and 269.71 GHz at high (∼0″​​.025–0″​​.050), medium (∼0″​​.13–0″​​.24), and low (∼1″) angular resolution. The sensitivity per ∼1.3 km s−1channel was 1.5–5 mJy beam−1, and the line-free channels were used to image the millimetre wave continuum. Our primary molecules for studying the gas dynamics and dust formation are CO, SiO, AlO, AlOH, TiO, TiO2, and HCN; secondary molecules include SO, SO2, SiS, CS, H2O, and NaCl. The scientific motivation, survey design, sample properties, data reduction, and an overview of the data products are described. In addition, we highlight one scientific result – the wind kinematics of theATOMIUMsources. Our analysis suggests that theATOMIUMsources often have a slow wind acceleration, and a fraction of the gas reaches a velocity which can be up to a factor of two times larger than previously reported terminal velocities assuming isotropic expansion. Moreover, the wind kinematic profiles establish that the radial velocity described by the momentum equation for a spherical wind structure cannot capture the complexity of the velocity field. In fifteen sources, some molecular transitions other than12COv = 0J = 2 − 1 reach a higher outflow velocity, with a spatial emission zone that is often greater than 30 stellar radii, but much less than the extent of CO. We propose that a binary interaction with a (sub)stellar companion may (partly) explain the non-monotonic behaviour of the projected velocity field. TheATOMIUMdata hence provide a crucial benchmark for the wind dynamics of evolved stars in single and binary star models.

Attenuation of millimetre wave radio signal at worst hour rainfall rate in a tropical region: A case study, Nigeria

The classical sub-6 GHz spectrum currently being used by wireless networks cannot support the requirement of 5G and higher upcoming mobile communication networks due to its limited bandwidth. Millimeter Wave (MMW) radio systems operating at 30 to 300GHz band provides higher bandwidth, frequency reuse and communications security but suffers greatly from atmospheric, environmental and rain attenuation. The attenuation of millimeter wave radio signal at worst hour rainfall rate was therefore investigated. The data was collected from the Tropospheric Data Acquisition network (TRODAN), the International Institute for Tropical Agriculture (IITA) and the Federal University of Technology, Akure. The rainfall rates were measured at 5 and 1-minutes integration time and the Lavergnat and Gole model was used for the conversion of the measured 5 minute to equivalent 1-minute values. The results revealed that throughout the study period, about 66.67% of the sites recorded the worst rainfall events at the 15 hours Local Time (LT). The range of rainfall rate at 0.01% exceedance was 1.18 to 62 mm/hr while at 0.001% it ranged from 51.50 to 116 mm/hr. The specific attenuation at the threshold frequency of 200 GHz at the 0.01% exceedance ranged from 1.638 to 6.175 dB/km. The clear signal band frequency threshold was 60 GHz and the path attenuation ranged from 15.34 dB to 20.43 dB. These results suggest the inclusion of the estimated attenuation values by radio propagation engineers in designs for this region.

Performance Analysis at different millimetre wave frequencies for indoor shopping complex and outdoor UAV applications towards 5G

This paper provides descriptions and implementations of NYUSIM, a novel framework for simulation of networks and applications for the three essential characteristics of channel design, spatial consistency, human blockage, and outdoor-to-indoor penetration. This paper also introduces NYUSIM 2.0, an enhanced channel simulator that can simulate spatially consistent channel parameters according to the NYUSIM 2.0 drop-dependent simulator. The 5 G Network Analysis special interest community introduced a parabolic model for outdoor-indoor penetration failure to model the excess route failure due to penetration through buildings and enforced in NYUSIM 2.0. It is a powerful measuring-based channel emulator for the fifth generation and beyond the configuration and measurement of the mm-Wave communication network.

Millimetre Observations of Maser-Emitting Planetary Nebulae

Observations in the millimetre bands of maser-emitting planetary nebulae (PNe) are crucial to study their circumstellar molecular gas at the beginning of the PN phase. Maser-emitting PNe are in the earliest phases of PN formation; therefore, these sources are key objects to study the molecular content during the early evolution of PNe. These circumstellar envelopes are active sites for the formation of molecules. We present preliminary results of millimetre observations with the IRAM 30 m telescope towards one PN (IRAS 17393−2727) of a sample of five maser-emitting PNe, where we detect 12CO and 13CO lines in both J=1→0 and J=2→1 transitions.

A Filterless Generation of Optical Millimeter Wave Signal Based on Frequency 16-Tupling Using Cascaded Polarization Modulators

Millimeter wave (MMW) frequencies are becoming vital as they bolster a large number of applications requiring higher data rates. In this paper, we have demonstrated a frequency multiplication technique based on external modulation for a 160 GHz MMW signal generation. The proposed scheme which uses a four-stage cascaded structure of polarization modulators proves to be a lucrative solution since the selected modulation index of 2.826 is phenomenally low. A precise choice of phase shifts between the cascaded stages ensures two eighth-order peaks spaced 160 GHz apart. This technique renders Radio Frequency Spurious Suppression Ratio and Optical Sideband Suppression Ratio of 45 and 65 dB, respectively. Simulation results are verified from a mathematical standpoint. The requirement of a Radio Frequency Local Oscillator with a higher frequency has been eliminated by a higher value of frequency multiplication factor.

Multi-Pass Free Electron Laser Assisted Spectral and Imaging Applications in the Terahertz/Far-IR Range Using the Future Superconducting Electron Source BriXSinO

Free-Electron Lasers are a rapidly growing field for advanced science and applications, and worldwide facilities for intense field generation, characterization and usage are becoming increasingly popular due to their peculiarities, including extremely bright, coherent, wide band tunable ultra-short pulses which are not achievable with other techniques up to now. In this review we give a thorough survey of the latest advances in the Free-Electron Laser-based field generation and detection methodologies and then present the main characteristics of a future THz/IR source, named TerRa@BriXSinO, based on a superconducting linear accelerator. The foreseen source is strongly monochromatic, with a bandwidth of 1% or smaller, highly coherent both transversally and longitudinally, with extreme versatility and high frequency tunability. After introducing the most recent and novel FEL-assisted scientific investigations, including fundamental explorations into complex systems and time-dependent interactions and material dynamics, we present our vision on the potential use of the TerRa facility and analyze some possible applications, ranging from non-linear physics under extreme conditions to polarization sensitive imaging and metamaterial-based sensing.

The effect of modulation frequency for frequency domain diffuse optic tomography (FDDOT)

In this study, it was illustrated that extremely high frequency (EHF) Ka-band (26.5–40 GHz) modulated frequency domain diffuse optic tomography biomedical optic imaging modality is superior to the generally accepted 100 MHz modulation frequency case. The effect of modulation frequency was shown with reconstructed images for two different modulation frequency simulation cases. Ka EHF-band frequency range covers 26.5–40 GHz. In this simulation study 33 GHz modulation frequency was selected. Forward model problem photon fluencies were generated for 30 equally separated sequential phase delays. Each phase delay has different photon fluence distributions inside the imaging geometry. 3.1 cm grid sizes were set in the x, y, z cartesian grid coordinate system with 31 × 31 × 31 xyz grid elements. To test the advantage of EHF-band modulation frequecy, inverse problem solution algorithm was done and inclusion images were reconstructed for each modulation frequency simulation case. Original inclusion was embedded inside the imaging geometry at (15–16, 15–16, 15–16) x, y, z coordinate system in the three-dimensional (3D) cubic spatial form. Homogeneuous tissue background photon absorption, scattering, and anisotropy coefficients were selected as µa = 0.1 cm−1, µs = 100 cm−1, and g = 0.9. Four sources and four detectors were placed on the back-reflection geometry. Forward model problem was built between sources, voxels, and detectors. Forward model problem photon fluencies were generated based on the diffusion equation approximation of the radiative transport equation formula in the frequency domain. Original inclusion was reconstructed by simply applying mathematical pseudoinverse problem solution function. It was observed that, reconstructed inclusion image at the 33 GHz Ka-band modulation frequency simulation case is superior to the reconstructed inclusion image at the 100 MHz modulation frequency simualtion case. Since there are too many frequency selection opportunities, the best Ka-band frequency was selected to demonstrate here. Thus, 33 GHz and 100 MHz modulation frequencies were tested against each other. These two different electronic modulation frequencies were tested and compared with each other.

Generalized 3-D Spatial Scattering Modulation

Three-dimensional (3-D) massive multiple-input-and-multiple-output (MIMO) systems, which explore degrees of freedom in both the vertical and the horizontal dimensions, are a promising technology to enhance spectral efficiency in the next-generation communication systems. As an emerging modulation technology with millimetre wave (mm-wave) communication in massive MIMO systems with limited radio-frequency (RF) chains, the spatial scattering modulation (SSM) makes use of beamspace domain resources to further improve the spectral efficiency. However, most published works on the SSM only focus on two-dimensional (2-D) MIMO systems. In this paper, we generalize the SSM system to 3-D space. First, we design a novel generalized 3-D SSM system by considering both vertical and horizontal angles to determine scattering paths, which are selected to convey information bits. Then, we propose a whitening filter based optimal detection algorithm to detect the received symbols with correlated noise, where the correlation is generated by the combination of the received signals from the large-scale planar receiving antenna array. Next, we design a 2-D fast Fourier transform (FFT) based transceiving approach to improve the hardware friendliness. After that, we propose a low-complexity detector based on the linear minimum mean square error (MMSE) detection algorithm. Moreover, we derive the union upper bound on average bit error probability (ABEP) in a closed form and the asymptotic performance expression for the generalized 3-D SSM system. Finally, we analyse the impact of transmission environment on the ABEP performance. Numerical results show that the generalized 3-D SSM system outperforms the conventional 2-D SSM system, which reduces the ABEP by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10\times $ </tex-math></inline-formula> with the same signal-to-noise ratio (SNR) level under the typical indoor environment.

Electromagnetic Characterization of Breast Tissue Phantoms in D-Band Regime

The potential of higher band millimeter waves to characterize different types of breast tissues based on the dielectric contrast between normal and malignant tissues has been reported. Low–cost phantom samples of normal and malignant tissues have been prepared using naturally occurring components, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i.e.</i> , agar, water, olive oil, and pectin. A waveguide probe-based calibration technique was used to extract the complex permittivities of the two-component (water–agar) and three-component (water-oil–agar) phantoms. The two-component phantoms were used to study the change in the dielectric properties of phantom with change in agar concentration. Water, agar, and varying proportions of oil were used to develop three-component phantom mixtures to mimic the dielectric properties of fat, fibrous and malignant breast tissues. Finally, the reflection and transmission properties of tissue-mimicking phantoms were tested using the waveguide probe calibration-based measurement setup. The difference in the S parameters between the three types of phantoms demonstrates the potential utility of D band-based data acquisition setups for tumor margin assessment applications <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">.</b>

Double-Layered metamaterial resonator operating at millimetre wave for detection of dengue virus

In this paper, a metamaterial-based resonator is proposed for the detection of dengue infection. The replaceable top layer can measure the dielectric characteristics of blood samples to detect the dengue virus. The sensor observed a shift in the resonant frequency towards higher frequencies with the reduction in the blood's permittivity. The sensor showed a 0.325 GHz shift in resonance per unit change in the dielectric permittivity. To corroborate the sensor’s practical sensing capability, a sensor prototype was fabricated and validated with alcohol-aqueous solutions. The sensor exhibited shifting of resonance towards lower frequencies with the addition of water contents in methylated alcohol. With the enhanced sensitivity and repeatable measuring capability, the results suggested that this sensor can be applied with real-time applications on the Internet of Medical Things (IoMT) for early remote detection of the dengue outbreak.

A novel miniaturized, multiband, AMC-integrated CPW-fed antenna operating at millimetric wave frequencies suitable for IoT applications

PurposePlanar periodic metallic arrays behave as artificial magnetic conductor (AMC) surfaces when placed on a grounded dielectric substrate, and they introduce a zero-degree reflection phase shift to incident waves. The antenna designers have new challenges while designing the AMC structure. The steps followed in designing the structure are as follows: 1) Designing the antenna, aimed to operate at millimetric wave frequencies, (2) Designing the AMC at desired frequencies, (3) Integrating the antenna design and AMC to resonate at millimetric wave frequencies and (4) Validate the output parameters of the antenna to be suitable for Internet of Things (IoT) applications.Design/methodology/approachThe antenna is integrated with artificial material known as high impedance surface (HIS) for performance enhancement. A miniaturized, multiband, enhanced gain, AMC-integrated CPW-fed antenna is proposed and aimed to operate at millimetric wave frequencies, which is most suitable for IoT applications. The developed antenna operates at an extremely high range (30–300 GHz), i.e. from 40 to 60 GHz with the return loss values at lesser than −20 dB, and gain is greater than 10. The antenna is developed and simulated by using HFSS software.FindingsAn extensive research study has been carried out to develop a low profile, high gain and optimized antenna. The first two steps are separately designing the antenna and the AMC unit cell at the desired frequencies. The third step is finding the antenna or AMC radiating parts responsible for each resonant frequency by analysing the surface current distribution. CPW fed along with AMC integration has made the antenna feasible to achieve the extremely high frequency (EHF) range, i.e. 40–60 GHz, which is highly adoptable in IoT applications.Originality/valueThe result represented that the developed antenna is resonating at EHF rank with high gain and good imped matching when it is being compared with the previous models and has only CPW fed without having AMC structure integration. It is evident that the antenna which has only CPW fed has resonated at lower frequency than EHF range and justified output characteristics. But when it is embedded with the AMC structure, it resonates at the EHF range, which makes the antenna highly suitable for IoT applications, with more accuracy and high data rate possibility.

Physical and materials aspects of photonic crystals for microwaves and millimetre waves

Abstract Experimental and numerical results on photonic crystals are presented for the frequency range 26–60 GHz. The material used is alumina where two techniques have been applied for fabricating the photonic crystals: manual assembly of alumina rods and rapid prototyping. The observed positions of the fundamental and higher photonic band gaps are in excellent agreement with the calculated results. A new type of defect in the 3D woodpile structure, is created by inserting interstitial rods. As a new 2D structure a square parquet lattice is investigated. The concept of a negative index of refraction is adressed including a model calculation and an experimental demonstration by the transmission through a slab of a 2D photonic crystal.

Resonance Frequency Tuning of a 200 GHz Band Absorber by an External Magnetic Field

The effect of the external magnetic field on the millimeter‐wave absorption of rhodium‐substituted epsilon iron oxide, ε‐Rh0.13Fe1.87O3 (1) and ε‐Rh0.19Fe1.81O3 (2) nanomagnets, is investigated. Terahertz time‐domain spectroscopy (THz‐TDS) shows that 1 and 2 display a zero‐field ferromagnetic resonance (the so‐called natural resonance) at 201 GHz with a linewidth of 20 GHz and at 210 GHz with a linewidth of 30 GHz, respectively. The ferromagnetic resonance is measured under an external magnetic field (H ex). Applying +3.5 kOe parallel to the remnant magnetization and −3.5 kOe antiparallel to the remnant magnetization shifts the resonance frequency at 201 GHz in 1 by +6 and −4 GHz and that in 2 by +4 and −4 GHz, respectively. Simulations of the ferromagnetic resonance using the Landau−Lifshitz−Gilbert model reproduce the magnetic field‐induced shifts of the resonance frequencies. The 220 GHz band millimeter wave is the highest frequency with a high transparency for “atmospheric windows” and is expected to be a carrier frequency for sixth‐generation mobile communication systems (6 G) or 7 G. This study may help realize applications for millimeter‐wave isolators, circulators, or shutters.

Imaging of a High-Power Millimeter Wave Beam Using a Millimeter Wave-Induced Gas Breakdown Initiated by a Metal-Dielectric Screen

A semiquantitative technique for imaging of high-power millimeter wave (MMW) beam using visible light from the plasma of an MMW-induced gas breakdown, which was initiated by a metal-dielectric (MD) screen, is discussed. The design of the gas breakdown sensor for imaging of the wave beam is presented. A plane MD screen was placed in a shallow airtight chamber with a transparent window of a thin mylar film. The chamber was filled with gas at a near atmospheric pressure. An MMW-induced breakdown in air, nitrogen, helium, and krypton, initiated by an MD screen, has been experimentally studied. In the experiments, a high-power 250-GHz pulsed gyrotron served as the source of MMWs. In a chamber filled with noble gases, bulk plasma was formed at an MMW intensity above the gas breakdown threshold. A single-pulse wave beam was imaged using a profile of the flux density of light from the breakdown plasma in helium and krypton. It was shown that using the presented technique, one can determine the position of the intensity maxima and the beam profile of an MMW beam in the range from one to two threshold intensities of an MMW-induced gas breakdown initiated by an MD screen.

Modeling of SHF/EHF Radio-Wave Scattering for Curved Surfaces With Voxel Cone Tracing

Efficient and accurate radio propagation modeling is essential for optimization of both radio sensing and communication systems. However, highly accurate full-wave methods remain inefficient at high frequencies, as unit of computation has to be made much smaller than the wavelength. On the other hand, ray-based approaches offer the desired speed, but the surface element (typically, a triangle) must be made much larger than the wavelength, thus making it difficult to represent complex curved surfaces of common objects, such as cars or unmanned aerial vehicles. As a result, for super high frequency (SHF)/extremely high frequency (EHF) bands, it is challenging to select a method that is both fast and capable of capturing curved surfaces correctly. To address this issue, we present a method that offers a reasonable tradeoff between speed and accuracy for radio propagation modeling in the bands of interest. Specifically, we combine efficient voxel scene representation targeting a cone tracing algorithm with a statistical scattering model. To confirm the validity of our approach, we report the dependence of reflected power on the distance for basic primitives, such as cone and sphere, for which closed-form radar cross-section solutions are known. We demonstrate that the proposed approach is superior compared to the conventional ray-tracing solutions, while posing no restrictions for efficient voxel cone tracing implementations.

A Multispectral Single‐Layer Frequency Selective Surface Absorber for Infrared and Millimeter Wave Selective Bi‐Stealth

AbstractThe multispectral electromagnetic (EM) absorber based on the frequency selective surface (FSS) has been applied with interest in the field of stealth technology due to its ability to avoid detectors or guided weapons at multiple wavelengths simultaneously. The multispectral absorption performance is generally accomplished by stacking different types of FSS absorbers in multiple layers. Herein, a thin and flexible multispectral single‐layer FSS (MSLF) absorber is presented using a micro‐holed, macroscale FSS combined with an infrared (IR) absorbing ground. The FSSs are simplified to MSLF by changing the absorbing layered microstructure to a transmitting microstructure. Dual‐band millimeter waves (MMWs) are absorbed by the macroscale resonance cavity, while the target IR waves are absorbed by the IR absorbing ground after penetrating the micro‐hole array pattern. Thermal emission is reduced significantly due to its low emissivity at IR bands other than the target IR. It is confirmed analytically and experimentally that patterns of various sizes do not exhibit functional crosstalk. The demonstrated multispectral absorption and low thermal emission make this a very promising material for IR−MMW selective bi‐stealth. Furthermore, the proposed structure can be applied to existing macroscale patterns in order to increase their applicability by providing additional selectivity without any functional interference.