Millimeter-wave Frequency Band Research Articles

Ray tracing simulation and experimental validation for millimeter-wave massive MIMO systems

Abstract Accurate channel characterization is extremely helpful in channel estimation, channel coding, and many other parts of communication system design and can effectively reduce overhead. Ray tracing (RT) shows accurate channel reconstruction for specific maps, but the multipath propagation in indoor scenes is far more complex than in outdoor scenes leading to a challenge for RT. This work presents and validates an RT tool for a massive multiple-input multiple-output (MIMO) system in the millimeter-wave frequency bands with the associated channel beamforming algorithm and provides ideas for channel estimation algorithm in subsequent MIMO systems. The impact of the order of interactions, e.g. reflections and diffractions on the channel impulse response reconstruction are analyzed in the RT simulation. The comparison between RT simulated and measured results shows a reasonable level of agreement. The presented RT tool that can provide complete and accurate channel information is of high value for the design of reliable communication systems.

Energy-Efficient Joint User Association, Backhaul Bandwidth Allocation, and Power Allocation in Cell-Free mmWave UAV Networks

In this article, we propose a cell-free network architecture for an unmanned aerial vehicle (UAV) base station (BS), i.e., UBS, incorporating high-altitude platform stations (HAPSs) as central processing units (CPUs). The goal is to guarantee the quality of service (QoS) of user equipment (UE), reduce energy consumption, extend communication time, and facilitate rescue operations. The millimeter-wave (mmWave) frequency band is deployed in access and backhaul links to satisfy UE QoS requirements and high backhaul demands. The proposed framework jointly optimizes user association, backhaul bandwidth allocation, and power allocation to maximize energy efficiency while meeting QoS requirements. The optimization problem, modeled as non-convex mixed-integer nonlinear fractional programming, is solved through a three-stage iterative algorithm. This includes (1) optimizing power allocation based on Dinkelbach transformation and a successive convex approximation (SCA) method, (2) clustering UBSs using the Lagrangian method, and (3) deriving a closed-form bandwidth allocation factor. The proposed algorithm significantly outperforms many traditional algorithms in performance while maintaining low computational complexity.

Antenna-in-Package of Lateral Cross-Dipole Elements for Endfire Dual-Polarized Radiation at Dual Millimeter-Wave Frequency Bands for 5G FR2 User Equipment Applications

Antenna-in-Package of Lateral Cross-Dipole Elements for Endfire Dual-Polarized Radiation at Dual Millimeter-Wave Frequency Bands for 5G FR2 User Equipment Applications

Dielectric Resonator Antenna Mode Excitation using Substrate Integrated Waveguide Feed with L-Slot

In this study, a substrate integrated waveguide dielectric resonator antenna excited by an L-slot is proposed, and the design is operated within the frequency range of 24.25 to 29.5 GHz bandwidth for 5G-NR applications. Rogers 5880 is used as a substrate with a permittivity of 2.2; in contrast, the dielectric resonator antenna has a permittivity of 10. The antenna demonstrates a simulated impedance bandwidth of 25.2 to 30.5 GHz, and a high gain of 8.7 dBi is observed due to the excitation of the DRA higher-order TE113 mode, whereas the design exhibits over 98% radiation efficiency, attributed to minimal copper losses at resonant frequencies. These results highlight the antenna's suitability for broadband, high-efficiency, high-gain applications in the millimeter-wave 5G-NR frequency bands.

Negative Group Delay Medium for Millimeter-Wave Applications

ABSTRACT In this paper, a novel structure with negative group delay (NGD) in the millimetre-wave frequency band is proposed. The frequency band covered by this structure is equal to 26.5–28.5 GHz. In the proposed NGD structure (NGDS), using two different parts (Part 1 and Part 2), a transmission-zero (TZ) and a transmission-pole (TP) are created near the centre frequency of 27.5 GHz. By doing this, in the frequency range of 26.5–28.5 GHz, the group delay characteristic is less than −1 ns for both simulated and measured results. The dimensions of the proposed NGD medium are equal to 27.2 mm3 or 0.041 λg 3 at the central frequency of 27.5 GHz.

Design and Fabrication of High-Gain Dual Linearly Polarized Patch antenna at 28 GHz

Abstract Extensive research on millimeter-wave frequency bands is currently in rapid development throughout the world, specifically at an operating frequency of 28 GHz, and Malaysia is no exception. The most conventional patch antennas covered a limited polarization feature of single polarization of radiated beam signals. In order to meet the high demands of network users with a higher data rate, the radiated beam signal coverage should be as wide as possible to ensure the stability and consistency of the received signals for the users. This leads to the development of the dual polarization feature of single-layer antenna design. In this work, a dual element (70 x 70 mm2) patch antenna at 28 GHz has been designed using CST Studio Suite and fabricated using Rogers RT5880. The antenna has been oriented to the right (+45°) and to the left (-45°) from the normal plane to realize a dual linear polarization state. The simulation and measurement results show that the reflection coefficient obtained for all antennas is less than -10 dB. The simulated and measured radiation patterns of the antennas are also shown in this paper. It is observed that the proposed antenna achieves a dual-polarized state with a higher gain of 11.16 dBi, compared to 4.97 dBi for a single patch. This dual-polarized antenna can be applied in various applications, particularly for MIMO and 5G mobile communication networks.

Analysis of 3D Printed Dielectric Resonator Antenna Arrays for Millimeter-Wave 5G Applications

This paper explores the potential use of fused deposition modeling (FDM) technology for manufacturing microwave and millimeter-wave dielectric resonator antennas (DRAs) for 5G and beyond communication systems. DRAs operating at microwave and millimeter-wave (mmWave) frequency bands were simulated, fabricated, and analyzed in terms of manufacturing quality and radio frequency (RF) performance. Samples were manufactured using a 3D printer and PREPERM® ABS1000 filament, which offers a stable dielectric constant (εr = 10 ± 0.35) and low losses (tan δ = 0.003) over wide frequency and temperature ranges. Surface profile tests and microscope measurements revealed discrepancies in the dimensions in the xy-plane and along the z-axis, consistent with the observed shift in resonant frequency. Despite these variations, reasonably good agreement between RF-simulated and measured results was achieved, and the DRA array successfully covered the intended mmWave band. However, challenges in achieving high precision may restrict applications at higher mmWave bands. Nevertheless, compared with conventional methods, FDM techniques offer a highly accessible and flexible solution with a wide range of materials for home and micro-manufacturing of mmWave DRAs for modern 5G systems.

23.5–27.5 GHz Band Doherty Power Amplifier Integrated Circuit Using 28 nm Bulk CMOS Process Based on Dynamic Power Dividing Network

This paper presents a Doherty power amplifier (DPA) integrated circuit (IC) designed to have enhanced gain, efficiency, and AM-AM characteristics through a dynamic power dividing technique, which can control the power dividing ratio according to the input power. Since this multi-purpose dynamic power dividing network also provides the phase offset and impedance matching at the interstage network needed for appropriate DPA operation, the active IC area could be reduced. To verify the proposed technique and its analysis, the DPA was implemented with a 28 nm bulk CMOS process for the fifth-generation (5G) new radio (NR) millimeter-wave frequency band of 23.5–27.5 GHz. The measured results showed a gain of 20.3–21.9 dB, saturated output power of 14.0–15.2 dBm, power added efficiency (PAE) of 22.8–26.7% at the peak power, and PAE of 14.6–17.6% at the 6 dB output power back-off (OBO).

A low-profile dual-band millimeter wave patch antenna for high-speed wearable and biomedical applications

This paper presents a low-profile, dual-band patch antenna designed for the mmWave frequency range. The antenna, fed by a microstrip line, is fabricated on a thin, flexible substrate (Rogers 3003) with dimensions of 12 × 3 × 0.25 mm³. The radiating patch includes two circular slots, enabling dual-band operation at 28 GHz and 38 GHz. Key performance metrics, including realized gain, efficiency, and radiation patterns, are analyzed across these frequency bands, with measured results compared to simulations performed using CST Microwave Studio. Furthermore, the antenna's parameters are evaluated in a bent configuration, demonstrating its suitability for wearable applications. The study also assesses the antenna's impact on human tissues, calculating average SAR values of 0.914 W/Kg and 1.140 W/Kg at 28 GHz, and 0.720 W/Kg and 1.360 W/Kg at 38 GHz, for 1/10 gm tissue. Furthermore, the link margin is calculated to verify effective wireless communication over distances up to 80 m. This antenna effectively covers key millimeter-wave frequency bands, making it ideal for high-speed 5 G and biomedical applications.

Miniaturized tri-band integrated microwave and millimeter-wave MIMO antenna loaded with metamaterial for 5G IoT applications

This study presents a revolutionary tri-band combined microwave (MW) and millimeter wave (MMW) multiple-input-multiple-output (MIMO) antenna. The antenna is built on a Rogers RT-5880 substrate with dimensions of 32 × 32 × 1.6 mm³. This integration increased the isolation from 18 dB to 27 dB in the MW band and 28 dB–40 dB in the MMW band. The effective bandwidths for the MW and MMW bands were initially 3.3–3.7 GHz, 5.45–9.2 GHz, and 24–28 GHz, respectively. The MTM increased these bandwidths to 2.6–4.1 GHz, 5.3–11.3 GHz for the MW band, and 22.5–29.3 GHz for the MMW band. In addition, the realized gain increased significantly, from 1.5 dBi, 3.5 dBi, and 6.5 dBi to 4.5 dBi, 6.1 dBi, and 11 dBi at 3.5 GHz, 6.9 GHz, and 28 GHz. The antenna's overall efficiency increased by 10–12 % across all operational bandwidths. The suggested antenna has excellent diversity performance, with an envelope correlation coefficient of less than 0.0002, a diversity gain greater than 9.998, and a channel capacity loss of less than 0.12 bits/s/Hz. The proposed antenna addresses the increasing demand for IoT devices by efficiently supporting both MW and MMW frequency bands, offering high performance in wireless communication and modern infrastructures. The proposed design not only improves connectivity and efficiency in IoT devices but also supports the Sustainable Development Goals (SDGs) by contributing to the development of smart city infrastructure (SDG 11) and fostering innovation and sustainable industrial practices (SDG 9), thereby promoting sustainable development and industrial innovation.

Beam steerable MIMO antenna based on conformal passive reflective metasurface for 5G millimeter wave applications

A conformal reflective metasurface fed by a dual-band multiple-input multiple-output (MIMO) antenna is proposed for low-cost beam steering applications in 5G Millimeter-wave frequency bands. The beam steering is accomplished by selecting a specific port of MIMO antenna. Each MIMO port is associated with a beam that points in a different direction due to a conformal reflective metasurface. This novel conformal metasurface antenna design has the advantages of higher gain, lower cost, a simpler feeding source, and a lower profile when compared to traditional reflective metasurfaces using bulky horn antennas and phased arrays with complex feeding networks and phase shifters for beam steering. The proposed beam steering antenna consists of a compact five-element dual-band MIMO and a 32×32\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$32 \ imes 32$$\\end{document} unit-cell conformal dual-band reflective metasurface placed at the top of the MIMO antenna to obtain the beam steering capability as well as gain enhancement. The proposed reflective metasurface has a stable response under oblique incidence angles of up to 600\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$60^0$$\\end{document} at 24 GHz and 38 GHz and its symmetric, single-layer structure, ensures polarization insensitivity and stable response under conformal conditions. The presented MIMO antenna design is not only compact but also offers a wideband response effectively covering the desired 5G mm-wave frequency bands. The overall size of the MIMO antenna alone is 70 ×\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ imes$$\\end{document} 12 mm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {mm}^2$$\\end{document} with a maximum gain of 5.4 and 7.2 dB. It is further improved up to 13.1 and 14.2 dB at 24 and 38 GHz respectively, with a beam steering range of ś400\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$40^0$$\\end{document} by using a conformal reflective metasurface. Unlike the existing beam steering strategies, the suggested method is not only cost-effective but also increases the overall directivity and gain of the source MIMO antenna. The measured results agree with the simulated results, making it a potential candidate in the 5G and beyond beam steering applications.

Advanced Metamaterial-Integrated Dipole Array Antenna for Enhanced Gain in 5G Millimeter-Wave Bands

A metamaterial-based non-uniform dipole array antenna is presented for high gain 5G millimeter-wave applications with a wideband characteristic. Initially, a non-uniform dipole array is designed on a 0.202 mm thick Rogers RO4003C substrate, offering a wide operating bandwidth ranging from 23.1 GHz to 44.8 GHz. The dipole array antenna emits unidirectional end-fire radiation with a maximum gain of 8.1 dBi and an average gain of 6.7 dBi. Subsequently, to achieve high gain performance, a 5 × 7 metamaterial structure is designed in the direction of the antenna radiation. The implemented metamaterial structure is optimized for the operating frequency, enhancing the directivity of the antenna radiation and resulting in a gain increment of more than 3 dBi compared to the dipole array alone. The developed metamaterial-integrated dipole array antenna offers an operating bandwidth (S11 < −10 dB) of more than 21 GHz (63.92%), ranging from 23.1 GHz to 44.8 GHz, covering the most commonly used 5G millimeter-wave frequency bands (n257, n258, n259, n260, and n261). Furthermore, the presented antenna yields a stable high gain with a peak gain of 11.21 dBi and a good radiation efficiency of more than 64%. The proposed antenna is an excellent option for millimeter-wave 5G systems due to its overall properties, particularly its high gain and end-fire radiation characteristics, combined with a wide operating bandwidth.

Multilayer-laminated optically transparent 300-GHz-band transmissive beamforming metasurface for wireless communication.

A 300-GHz-band transmission-type multilayer metasurface beamformer based on a Jerusalem cross geometry is presented. A metamaterial cell with a continuous 2π phase variation for the radius change was designed and used in the fabrication of a reference device and three types of beamforming devices. The beamforming metasurface devices achieved steering angles of θ = 18°, θ = 30°, and θ = 38°, which were in good agreement with simulated results. A broadband operation in a 40 GHz band, from 280 GHz to 320 GHz was evaluated, showing only minor frequency dependence of the beamforming angles. The design and fabrication methodology can be applied to various types of metasurface devices, such as circular and fan lenses, beamformers, polarization switches, and so on for millimeter-wave frequency bands that are considered to be used in future 6 G wireless network systems.

Characteristic mode based self isolated MIMO antenna design for millimeter wave 5G communications

The paper introduces a self-isolated quad-port multi input multi output antenna system designed for fifth-generation wireless communication. The reported antenna structure possesses an overall dimension of 12.4 × 12.4 × 0.508 mm3 and is derived from a single-element antenna, featuring a circular patch accompanied by a sectoral slot. To achieve the desired frequency band, an additional circular patch is purposefully placed over the main radiator. The development of each design stage in the antenna structure is investigated using the theory of characteristic mode. This configured multi-element antenna structure achieves a broad operational bandwidth spanning 4.5 GHz, encompassing frequencies from 26.1 GHz to 30.6 GHz, rendering the antenna well-suited for deployment in the millimeter-wave frequency bands of n257, n258, and n261 respectively. A total gain of 6.27 dBi is achieved with port isolation of −24 dB. Furthermore, the antenna undergoes validation for diversity metrics, including envelope correlation coefficient, diversity gain, channel capacity loss, total active reflection coefficient, and mean effective gain. The antenna is fabricated and experimentally validated with the simulated counterpart. Later, a comparative analysis has been conducted which revealed that the proposed antenna demonstrates > 80 % increase in compactness compared to existing antenna designs documented in the literature.

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.

Ultra-broad band plasma–graphene absorber at millimeter-wave frequency bands

This paper introduces a new absorber that can effectively absorb millimeter wave frequencies. The design involves stacking foam, plasma, and laminated graphene sheets on a perfect electric conductor substrate. The absorber can generate a wideband effect on electromagnetic waves by combining graphene layers and a plasma medium. The absorption and bandwidth of the plasma slab depend on various parameters like plasma frequency, collisional rate, and thickness. By tuning the plasma frequency ωp (rad/s), average collision frequency υp(Hz), Fermi energy of graphene sheets, and thickness of the foam and plasma layers, the benefit of wideband and good absorption considering reflection amplitude lower than −15 dB, an ultra-bandwidth from 32 to 150 GHz can be achieved. This structure has multiple layers that have bandgap and band-stop regions. These regions are associated with the cavities of dielectric slabs that have graphene sheets. These regions are identified as coupled Fabry–Pérot resonances, which can induce multiple interference effects in multi-reflection for the incident electromagnetic waves, resulting in high-level absorption. Understanding and controlling these resonances is crucial for optimizing the performance of such systems. An equivalent circuit model has been used to predict the absorber's performance. The proposed absorber has a symmetrical structure that reacts similarly to transverse-electric and transverse-magnetic waves. The frequency range of the absorber has been studied to determine the effects of the graphene sheets' relaxation time and voltage biasing. The absorber offers advantages such as being thin, having a wide bandwidth, and being insensitive to polarization.

Multi-band passive detection and imaging system for concealed weapon with dual assessment method

Technological advancements in the millimeter-wave (MMW) and terahertz (THz) frequency bands have seen rapid progress, especially in the field of concealed weapon detection. The capability to detect concealed objects under clothing without causing harm to individuals is of utmost importance. Because of this reason, the concept of the variable target ranges in a passive MMW/THz imaging system with the infrared band has been studied in detail. An imaging system, called multi-band passive detection and imaging system (MIS) in this study, with variable target ranges, was designed and tested. A passive MMW/THz imaging system is developed specifically for concealed weapon detection, with a primary focus on variable target ranges. In addition to this, an infrared imaging system has been incorporated into the concept of concealed weapon detection. To integrate these two imaging systems, image fusion techniques have been employed as a conjunction between them. Detailed analyses have been conducted to assess the concealed weapon detection capabilities of this integrated system. The image fusion results, combining infrared and passive MMW/THz bands, have been tested at variable target ranges, and the fused images have been compared in terms of structural similarity index (SSIM) and contrast levels (CL). The SSIM alone is an inadequate method in the concept of concealed weapon detection. The CL method, used with SSIM, eliminates the shortcoming of the SSIM alone. The outcomes of these tests demonstrate that MIS enhances the detectability of concealed weapons with the use of SSIM and CL together. As a result, this study lays a solid foundation for the future detection of concealed objects beneath clothing. The dual assessment method proposed in this study will enable the development of new methods that will increase the detection of specific objects under the clothes in the future.

A novel SIGGW dual post band-pass filter for 5G millimeter-wave band applications with a transmission zero

Integration of planar circuits been considered a credible technique for low-cost mass production of microwave and millimeter-wave circuits and systems. For the first time, in this research a dual-post band-pass filter is designed and simulated in a three-layer substrate integrated gap groove waveguide (SIGGW) for 5G millimeter-wave frequency band applications. The filter includes 12 posts (6 times 2). Also, the structure facilitates to use resonant posts and so we can design the posts to add a transmission zero in lower rejection band. The design theory algorithm and its limitations are investigated based on the circuit model of filter. The results shows that FBW of 5% and a lower band transmission zero for the proposed 12 posts filter. Also, the results are verified by simulation using CST. According to the results, the proposed filter is a good option for Ka-band applications and can be used as the building block for suppressing the LO leakage that is commonly used for up-converting the 5G signal to Ka band.

A symmetric T-H shape wideband negative index metamaterial for 28-GHz millimeter-wave applications

One of the leading candidates for the next fifth generation of (5G) and body-centric wireless communications is millimeter-wave frequencies. In this study, a wideband tunable metamaterial (MTM) consisting of T-H shaped symmetric resonator is presented for body-centric applications operating in the millimeter-wave frequency band centered at 28 GHz. The characteristics of the proposed MTM are examined through wave propagation in both Z and X directions. It has a wide operating frequency range of 5.6 GHz for waves travelling along the Z-axis, with DNG characteristics at 26.2 GHz resonance frequency. However, it represents a negative epsilon metamaterial (ENG) range during X-axis wave propagation in the 25–29.4 GHz frequency range. The metamaterial is constructed on a Rogers (RT-5880) substrate and has a compact size, with overall dimensions of 0.420 λo × 0.420 λo. A proposed Y-shaped antenna is developed with a compact size of 1.36 λo × 1.82 λoto cover the 5G at 28 GHz. The single-Y-shaped antenna consists of aradiating patch, Rogers substrate, full ground plane, air bandgap (ABG), and array of DNG MTM.Thus, the array of MTM has been applied to validate the effect in the overall antenna performance such as gain which has been increased from 5.5 dBi to 8.5 dBi. The experimental, simulated results, and equivalent circuit model using Advanced Design Software (ADS) for validation functions showed that the completed results are comparable. The proposed mm-wave metamaterial is expected to be a good candidate for modern 5G wireless communication system components, especially to enhance the antenna gain and isolation. The proposed antenna loaded with MTM is a suitable contender for the upcoming 5G mm wave mobile handheld devices.

Loop-Type Field Probe to Measure Human Body Exposure to 5G Millimeter-Wave Base Stations

This paper proposes a field probe to measure the power density (PD) at a millimeter-wave (mmWave) frequency band. The proposed probe is composed of a loop antenna in which one end is terminated with a load resistor. Such a structure enables the simultaneous measurement of electric (E)- and magnetic (H)-fields: the E-field is measured at a gap where the load resistor is placed, and the H-field is measured through the loop antenna. The simultaneous measurement makes it possible to measure PD for an incident wave even in the near field region where the E- and H-fields have different phases from each other. The proposed probe is fabricated and evaluated for its PD measurement performance. The measurement results show that the probe measures PD with an error less than 1.3 dB. Owing to the near field measurement, the proposed probe is useful in measuring the human body exposure to electromagnetic fields (EMFs) that are generated by 5G mmWave base stations.