Mm-wave Frequencies Research Articles

On the Physical Layer Security of Untrusted Millimeter Wave Relaying Networks: A Stochastic Geometry Approach

The physical layer security (PLS) of millimeter wave (mmWave) communication systems is investigated, where the secure source-to-destination communication is assisted by an untrusted relay selected from a group of them and there are also several passive eavesdroppers (Eves) in the network. In the considered system model, while the distributions of the untrusted relays and Eves follow a homogeneous Poisson Point Process (PPP). To maximize the instantaneous secrecy rate, a novel joint relay selection and power allocation (JRP) method is developed where the destination and source aim for jamming the reception of both the untrusted relays and passive Eves. New expressions of the optimal power allocation (OPA) are derived for both non-colluding Eves (NCE) and colluding Eves (CE). Subsequently, by considering the impact of potential blockages, new closed-form equations are derived for analyzing the system’s ergodic secrecy rate (ESR) and secrecy outage probability (SOP) for transmission over fading mmWave channels. Finally, numerical examples are provided for demonstrating the superiority of our proposed JRP method over the relevant benchmarks found in the literature. Interestingly, the ESR increases with the density of untrusted relays for both the NCE and CE scenarios, which is a benefit of the improved probability of selecting a relay with a stronger second-hop channel. Furthermore, in the low transmit power regime, employing relatively low mmWave frequencies achieves better ESR, while in the high transmit power regime, high mmWave frequencies provide higher ESR.

Recent Developments of Butler Matrix From Components Design Evolution to System Integration for 5G Beamforming Applications: A Survey

Beamforming networks for multiple beam antennas are believed to be in the vanguard of technological developments in mmWave for 5G wireless applications. The basic idea of beamforming technique is the application of multiple antenna elements radiating the same signal at an identical phase and wavelength, into one strong signal pointed to a specific direction. For low cost and power consumption, radio frequency beamforming networks (RF-BFNs) such as Blass matrices, Butler matrices, and Nolen matrices will play a critical role in achieving the ever-increasing demands in wireless technology. Therefore, this study aims to present a comprehensive survey and developments of RF-BFNs with (particular focus in Butler matrices). From the fundamental perspectives of the beamforming techniques and progress over time, component evolution includes branch-line coupler (BLC), Phase shifter (PS), and Crossovers to complete system Butler matrix (BM) integration. Different design techniques to improve bandwidth, size reduction, multi-band, and other performance characteristics are discussed extensively. Furthermore, the paper also discusses different geometry of Butler matrices in open microstrip transmission lines, substrate integrated waveguide (SIW) and gap waveguide (GWG) technologies highlighting key developments and research challenges from single band to dual-band operations.We expect this paper to provide more profound insights into the designs processes and suggest suitable ways to facilitate further developments of RF-beamforming networks at mmWave and sub-mmWave frequency ranges.

Uncertainty Estimation via Monte Carlo Dropout in CNN-Based mmWave MIMO Localization

Recently, there has been much interest in the use of convolutional neural networks (CNN) for mobile user localization in massive multiple-input multiple-output (MIMO) systems operating at millimeter wave (mmWave) frequencies. However, current CNN-based approaches cannot predict the confidence interval bounds for the localization accuracy. While the Bayesian neural network (BNN) method can be employed to estimate the model uncertainty, it entails a high computational cost. In this letter, the Monte Carlo (MC) dropout based method is proposed as a low-complexity approximation to BNN inference for capturing the uncertainty in a CNN-based mmWave MIMO outdoor localization system, without sacrificing accuracy. The proposed method is evaluated by means of simulations using a ray-tracing model of urban propagation at 28GHz. Results show that the localization uncertainty region can be properly determined and that their shape depends on the maximum power received at the user.

Glass Package for Radar MMICs Above 150 GHz

This work presents a novel sensor packaging and a novel transition concept for radar applications above 150 GHz based on glass material. By using laser induced deep etching (LIDE) technology, glass vias and cavities are fabricated without degrading the mechanical stability of glass, as micro-cracks are completely avoided. Especially at high millimeter wave (mm-wave) frequencies, precise structuring on low dielectric loss materials and a high integration density are essential for low loss transitions. In this paper, an ultra compact FMCW radar monolithic microwave integrated circuit (MMIC) at 160 GHz is used to demonstrate this packaging technology. In addition, the high frequency signal is guided by a low loss transition to a deposed antenna via a dielectric waveguide (DWG) providing the antenna front end with mechanical flexibility. Thus, using plated through glass vias (TGVs) and a circulating solder ring, the package is hermetically sealed. The optical transparent glass package has a size of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${5.8}\,\rm {mm}\times {4.4}\,\rm {mm}\times {0.9}\,\rm {mm}$</tex-math></inline-formula> . A minimum measured insertion loss of 2.85 dB at 162 GHz from chip to DWG is achieved. The complete radar system with a range resolution of 12 mm is demonstrated via radar measurement.

A Survey on Millimeter-Wave Beamforming Enabled UAV Communications and Networking

Unmanned aerial vehicles (UAVs) have found widespread commercial, civilian, and military applications. Wireless communication has always been one of the core technologies for UAV. However, the communication capacity is becoming a bottleneck for UAV to support more challenging application scenarios. The heavily-occupied sub-6 GHz frequency band is not sufficient to meet the ultra high-data-traffic requirements. The utilization of the millimeter-wave (mmWave) frequency bands is a promising direction for UAV communications, where large antenna arrays can be packed in a small area on the UAV to perform three-dimensional (3D) beamforming. On the other hand, UAVs serving as aerial access points or relays can significantly enhance the coverage and quality of service of the terrestrial mmWave cellular networks. In this paper, we provide a comprehensive survey on mmWave beamforming enabled UAV communications and networking. The technical potential of and challenges for mmWave-UAV communications are presented first. Then, we provide an overview on relevant mmWave antenna structures and channel modeling. Subsequently, the technologies and solutions for UAV-connected mmWave cellular networks and mmWave-UAV ad hoc networks are reviewed, respectively. Finally, we present open issues and promising directions for future research in mmWave beamforming enabled UAV communications and networking.

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

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

Design and Characterization of 10-Elements MIMO Antenna With Improved Isolation and Radiation Characteristics for mm-Wave 5G Applications

A ten-elements MIMO antenna with improved isolation and reduction of X-polar radiation (XPR) in millimeter (mm) wave region is presented. The individual antenna element consists of stub loaded coplanar waveguide (CPW) structure with elliptical shaped radiator. Defected ground structure (DGS) has been incorporated by engraving partial elliptical shaped slots at the coplanar ground to reduce the mutual coupling effect between the adjacent antenna pairs of the MIMO. The backside of the substrate has a metallic plane with defects which is not connected to the coplanar ground of the antenna. This defected metal structure (DMS) acts as a reflector to improve the radiation characteristics by lowering of XPR as well as improving the co-pol to X-pol isolation. The proposed MIMO structure has a fractional bandwidth of 23.52% (22.5GHz-28.5 GHz) which entails the mm-wave 5G frequency spectrum n258 (24.25-27.5 GHz). The isolation| characteristics of the proposed MIMO antenna are below -35 dB over the operating bandwidth for any pair of adjacent antenna elements which imply significantly improved isolation between the adjacent antenna elements with highly compact layout area of 3.4λ × 8.5λ, where λ is wavelength corresponding to the mid-point of the bandwidth. The inter-element spacing of the MIMO structure is 0.44 λ. The main attractive feature offered by this structure is reduction of XPR in the operating frequency range thus improving the co-pol to X-pol isolation up to 20 dB and 28 dB in the boresight direction in both the XZ and YZ planes respectively. Furthermore, the co-pol to X-pol isolation is maintained above 15 dB almost throughout the elevation angular region -180° to 180° thereby negating the hindrance imposed by surface waves in mm-wave region. The diversity performances in terms of Envelope Correlation Coefficient (ECC), Diversity Gain (DG) and Channel Capacity Loss (CCL) are obtained as 0.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> , 10 dB and 0.005 bps/Hz respectively which are within the acceptable limits. Mean effective gain (MEG) values with respect to the excited port 2 and port 3 is identical and approximately -3dB thus indicating the mean value of these two ports to be almost 1 dB. The multiplexing efficiency of the proposed MIMO antenna is satisfactory over the bandwidth. The group delay is investigated and found to be almost constant with a variation of 1.2 ns thus indicating linear phase characteristic of the antenna. The proposed structure is compared with other mm-wave MIMO antennas and found to be advantageous with respect to the number of antenna elements, compactness, low mutual coupling, co-pol to X-pol isolation, and ECC. A prototype of the proposed 10-elements MIMO is fabricated, and the measured results resemble with the simulated results.

Wireless Backhaul in 5G and Beyond: Issues, Challenges and Opportunities

With the introduction of new technologies such as unmanned aerial vehicles (UAVs), high altitude platforms (HAPS), millimeter wave (mmWave) frequencies, massive multiple-input multiple-output (MIMO), and beamforming, wireless backhaul is expected to be an integral part of the 5G networks. While this concept is nothing new, it was shortcoming in terms of performance compared to the fiber backhauling. However, with these new technologies, fiber is no longer the foremost technology for backhauling. With the projected densification of networks, wireless backhaul has become mandatory to use. There are still challenges to be tackled if wireless backhaul is to be used efficiently. Resource allocation, deployment, scheduling, power management and energy efficiency are some of these problems. Wireless backhaul also acts as an enabler for new technologies and improves some of the existing ones significantly. To name a few, rural connectivity, satellite communication, and mobile edge computing are some concepts for which wireless backhauling acts as an enabler. Small cell usage with wireless backhaul presents different security challenges. Governing bodies of cellular networks have standardization efforts going on especially for the integrated access and backhaul (IAB) concept, and this is briefly mentioned. Finally, wireless backhaul is also projected to be an important part of the beyond 5G networks, and newly developed concepts such as cell-free networking, ultra-massive MIMO, and extremely dense network show this trend as well. In this survey, we present the aforementioned issues, challenges, opportunities, and applications of wireless backhaul in 5G, while briefly mentioning concepts related to wireless backhaul beyond 5G alongside with security and standardization issues.

Beamforming Performance Analysis of Millimeter-Wave 5G Wireless Networks

With the rapid growth in the number of mobile devices and user connectivity, the demand for higher system capacity and improved quality-of-service is required. As the demand for high-speed wireless communication grows, numerous modulation techniques in the frequency, temporal, and spatial domains, such as orthogonal frequency division multiplexing (OFDM), time division multiple access (TDMA), space division multiple access (SDMA), and multiple-input multiple-output (MIMO), are being developed. Along with those approaches, electromagnetic waves’ orbital angular momentum (OAM) is attracting attention because it has the potential to boost the wireless communication capacity. Antenna electromagnetic radiation can be described by a sum of Eigen functions with unique eigenvalues, as is well known. In order to address such issues, the millimeter-wave (mmWave) communication is proposed which is considered as one of the potential technology for 5G wireless networks. The intrinsic feature of all electromagnetic waves is OAM. The OAM beams’ unique qualities have led to a slew of new uses. Broadband OAM generators, on the other hand, have gotten very little attention, especially in the mmWave frequency band. The use of OAM in conjunction with mmWave can reduce the beam power loss, enhance the received signal quality, and hence increase the system capacity. The transmitter and receiver antennas must be coaxial and parallel to achieve precise mode detection. The proposed mmWave integrated with OAM system model is discussed in this study. The channel model is created using the channel transition characteristics. The simulation results demonstrate that the proposed system model is a good way to boost the system capacity.

Design Methodology of Multiband Printed Antennas for Future Generations of Mobile Handsets

The present paper introduces a design methodology to extend the operation of a microstrip patch antenna to operate efficiently at multiple higher-order resonances. This method depends on the geometrical modification of the antenna structure by adding well-designed inductively-loaded and capacitively-coupled elements to the primary patch so that it can efficiently radiate at the desired higher frequency bands. It is explained quantitatively how to use the geometrical parameters of the inductively and capacitively coupled elements for accurate tuning of the multiple resonant frequencies of the antenna. The proposed method is applied to modify a primary hexagonal patch antenna (designed to principally radiate at 28 GHz as its first-order resonance) so as to operate at additional higher frequency bands around 43, 52, and 57 GHz. Also, an alternative design is provided for a quad-band printed antenna of composite patch structure that operates in the same millimetric-wave (mm-wave) bands, 28, 43, 52, and 57 GHz with high radiation efficiency, excellent impedance matching, and satisfactory values of the antenna gain. The corresponding frequency bands are, respectively, (27.7-28.3 GHz), (42.7-43.3 GHz), (51.2-53.0 GHz), and (55.7-57.5 GHz). The dimensions of the area occupied by the primary patch and the parasitic elements are 5.2 &#x00D7; 3.3 mm².&#x2013; The two antennas are fabricated for experimental assessment of their performance including the impedance matching and radiation patterns. It is shown that the experimental measurements come in agreement with the simulation results over all the four operational mm-wave frequency bands. One of the advantages of the proposed method is that it can be applied to patch antennas of arbitrary shapes and is not restricted to hexagonal patch antennas. Furthermore, this method is not restricted by extending the operation of the antenna to radiate at four frequency bands. It is capable of adding any desired number of frequency bands so that the antenna can operate at five or, even, more bands.

Broadband Millimeter-Wave Dielectric Properties of Liquid Crystal Polymer Materials

Liquid crystal polymers (LCPs) are a class of thermoplastic polymers widely used for packaging radio frequency (RF), microwave, and low millimeter (mm)-wave integrated circuits operating at frequencies as high as 77 GHz. Because of their relatively low cost and attractive electrical, thermal, and mechanical properties, LCPs are of potential interest as a packaging material for advanced circuits operating at high mm-wave frequencies, &#x007E;100&#x2013;300 GHz. To potentially use LCPs at these frequencies will require a quantitative knowledge of the materials&#x2019; dielectric properties across a broad frequency band. Here, we present nondestructive measurements of the dielectric constant, <i>Dk</i>, and dissipation factor, <i>Df</i>, on six commercially made LCP materials now used for packaging RF/microwave circuits. Measurements using phase-sensitive transmission from 140 to 220 GHz show values of <i>Dk</i> ranging between 2.0 and 4.5, with four materials essentially nondispersive but two showing significant dispersion in this band. <i>Df</i> values were in the range 0.01&#x2013;0.06, substantially higher than that has been reported for many LCP materials at RF/microwave frequencies. The results are useful to model accurately the performance of packaged mm-wave circuits.

Methodology for Measuring the Frequency Dependence of Multipath Channels Across the Millimeter-Wave Spectrum

Millimeter-wave (mmWave) communications promise Gigabit/s data rates thanks to the availability of large swaths of bandwidth between 10–100 GHz. Although cellular operators prefer the lower portions of the spectrum due to popular belief that propagation there is more favorable, the measurement campaigns to confirm this – conducted by ten organizations thus far – report conflicting results. Yet it is not clear whether the conflict can be attributed to the channel itself – measured in different environments and at different center frequencies – or to the differences in the organizations’ channel sounders and sounding techniques. In this paper, we propose a methodology to measure mmWave frequency dependence, using the 26.5–40 GHz band as an example. The methodology emphasizes calibration of the equipment so that the measurement results represent the channel alone (and not the channel coupled with the channel sounder). Our results confirm that free-space propagation is indeed frequency invariant – a well understood phenomena but to our knowledge reported nowhere else at mmWave to date. More interestingly, we found that specular paths – the strongest after the line-of-sight path and so pivotal to maintaining connectivity during blockage – are the least invariant compared to weaker diffracted and diffuse paths.

Analysis and Design of High-Harmonic-Rejection Multi-Ratio mm-Wave Frequency Multipliers

Frequency multipliers are key components for high-quality millimeter-wave signal generations. However, the harmonic spurs generated by the frequency multipliers significantly affect the system performance. As a result, a high harmonic rejection is required in the frequency multiplier design. In this article, we present a multi-ratio (MR) frequency multiplier that exhibits x5 and x7 switchable multiplication ratios. Three processes of frequency multiplication, harmonic generation, harmonic amplification, and harmonic selection, are analyzed, and the corresponding techniques for harmonic suppression are introduced. The harmonic spurs can be suppressed by these three techniques: high-efficiency harmonic generation, injection locking, and tunable fourth-order resonator. First, the high-efficiency harmonic generation is realized by chopping the drain current, which enables a harmonic-rich spectrum to be generated, and the shape of the spectrum can be controlled by the biasing voltage. The second technique, injection locking, can suppress the harmonic spurs by its frequency-modulation (FM) and amplitude-modulation (AM) nature. The third technique, the tunable fourth-order resonator, can select the desired harmonic and suppress others. An MR injection-locked frequency multiplier was implemented in a 65-nm CMOS process as the proof-of-concept design. The multiplier operates from 22.4 to 40.6 GHz, and the measured harmonic rejection ratio is 57.7 dBc at 28 GHz and 51.7 dBc at 39 GHz with 10.0-mW power consumption.

State of the Art Sub-Terahertz Switching Solutions

In this paper the state of the art in RF switches for mm-wave frequency range is summarized and evaluated. Several leading technologies is presented from typical semiconductor devices based on transistors and diodes on Si, SiGe or III-V semiconductor substrates to more unconventional solutions such as microelectromechanical or phase-change material switches. The most important parameters and characteristics for those technologies are gathered and compiled for comparison. Besides different technologies, also various switch topologies of mm-wave switches are presented, assessed and compared. Furthermore, new emerging technological solutions approaching mm-wave range involving two-dimensional materials are also presented. Their evaluation is focused on proposed designs and current results for experimentally evaluated prototypes. Although the performance of these devices are currently not competitive with more traditional approaches, some reported results near the mm-wave range makes them a promising solution for future mm-wave switches and an interesting topic for further research and development.

Extra Wide Band MIMO Antenna with High Isolation and Low Correlation at 38 GHz mm-Wave Frequency Band for 5G Applications

A compact wide-band Multiple Input Multiple Output (MIMO) antenna having highest isolation and least correlation for millimeter-wave 5G communications is proposed in this paper. Firstly, a single antenna was designed and simulated to be working at 38 GHz, a potential target band for 5G applications. It consists of a 5-shaped radiating patch, with partial ground plane. Its length is adjusted and a wide bandwidth is obtained. Then, the two antenna elements are closely positioned with edge-to-edge spacing of 1 mm (0.55 λ, with λ is the free space wavelength at resonance). Thanks to the technique of spatial diversity, a high degree of isolation is attained; more than 25 dB in the whole bandwidth. Moreover, correlation value is under 0.0002 in the working band. The prototype antennas are fabricated and measured. The result indicates that this antenna shows a reflection coefficient under -10 dB over a range of frequencies from 32.3 to 54.6 GHz (BW=22.3 GHz, 58.68% fractional bandwidth). The antenna presents a high realized gain of 7.12 dBi and radiation efficiency of about 82.46% at the desired frequency. Due to these results, our antenna may be regarded a suitable candidate for mm-wave 5G MIMO applications.

Radar Cross Section Analysis of Two Wind Turbines via a Novel Millimeter-Wave Technique and Scale Model Measurements

A novel, low cost, highly accurate, millimeter-wave RCS characterization method is developed and presented in this paper. In order to develop and verify the validity of the proposed method, full scale models and scale models of the horizontal-axis wind turbine (HAWT) and Crossflow turbines have been simulated and compared for a case study. The RCS of a scaled Crossflow turbine model was then experimentally verified using the novel method presented at frequencies of 76-81GHz. The proposed method utilizes the AWR1843BOOST evaluation board and DCA1000EVM real-time high-speed data capture card from Texas Instruments. To the best of the authors’ knowledge, this is the first RCS analysis of a scaled model performed at the mm-wave frequencies of 76-81GHz. This novel method is quick, simple, and fully automated, while maintaining high accuracy. Additionally, this has been achieved at a low cost using commercially available off the shelf parts. Good agreement was observed between the simulated and experimental results. Comparing the RCS data of the two turbines, it appears that the Crossflow turbine geometry offers a lower RCS and Doppler spectrum contamination as compared with a traditional horizontal axis wind turbine structure. These results are necessary and useful in allaying the increasing concerns regarding wind turbine radar interference, which have appeared as a result of the widespread adoption of wind power generation in recent years.

Sub-6 GHz and mm-Wave 5G Vehicle-to-Everything (5G-V2X) MIMO Antenna Array

A multi-beam and multi-polarized Multiple-Input Multiple-Output (MIMO) antenna system, which operates at Sub-6 GHz and mm-wave frequency bands is realized for 5G Vehicle-to-Everything (5G-V2X) application. Since the vehicle needs to communicate in different scenarios with the others, e.g. vehicles, passengers, control units, and mobile networks, in the surrounding area, an antenna with 360° coverage area is required. In this paper, an eight-element MIMO antenna is designed and implemented for this purpose. Four elements are distributed evenly in a circular substrate placed in the azimuth plane. Meanwhile, the other four elements are printed on two orthogonal substrates which are fixed perpendicularly to the circular substrate. Each radiating component is a tapered slot antenna integrated with a dipole to operate at both microwave and mm-wave bands. The simulated and measured results demonstrate capability of the proposed design in covering the whole surrounding area (360° coverage in azimuth plane). The antenna achieves a realized gain of more than 9 dBi at the mm-wave range and 4 dBi at the microwave range.

Performance and User Association Optimization for UAV Relay-Assisted mm-Wave Massive MIMO Systems

Unmanned aerial vehicle (UAV) relaying is deemed as a promising solution to enhance the achievable rate and widespread connectivity in millimeter-Wave (mm-Wave) systems for tomorrow’s 6G wireless networks. In this paper, we study both the performance and user association optimization for the UAV relay-assisted mm-Wave massive multiple-input multiple-output (MIMO) communication system, where multiple base stations (BSs) serve their respective users with the help of one beamforming UAV relay. Both the beamforming and the UAV relay have essential impact on the achievable sum-rate of the system. Thus, a multi-user hybrid beamforming scheme is designed to mitigate the inter-user interference issues and achieve a better trade-off between performance and complexity in UAV-enabled communications. Also, to exploit UAV relay based architecture in serving different ground BS-user pairs, we propose a UAV relay-assisted multi-BS mm-Wave massive MIMO system with hybrid beamforming architecture, which prevent sudden link disconnections caused by high path loss and line-of-sight (LoS) blockage in mm-Wave frequency band. Then, we formulate a user association problem with multiple constraints so that the sumrate of the overall UAV relay-assisted mm-Wave massive MIMO system is maximized. Simulation results are provided to show the effectiveness of the proposed UAV relay-enabled architecture.

An N-Way Single-Inductor High-Pass Power Divider for 5G Applications

This letter reports on the analysis and the design of a novel N-way single-inductor power divider (PD), which allows for a compact size regardless of the number of ports. Moreover, the reported topology simplifies the interconnection of the isolation resistors, making the design of PDs with more than four ports straightforward and systematic. Finally, a 4-way silicon prototype has been fabricated employing the IHP SG13S BiCMOS technology to validate the concept. The chip is meant for mmWave frequencies and is devoted to 5G applications. It occupies an area of 0.005 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and provides a minimum loss of 1 dB, as well as phase and amplitude errors lower than 0.4 dB and 2°, respectively, in the band of interest. To the best of our knowledge, this design results in the smallest silicon area occupation, halving the size with respect to the state-of-the-art PDs. Comparable physical dimensions to the presented 4-way PD can only be achieved with 2-way designs.

5G SIW-Based Phased Antenna Array With Cosecant-Squared Shaped Pattern

In this article, a concept of a phased antenna array based on substrate integrated waveguide (SIW) technology for 5G base stations is proposed. The array has a cosecant radiation pattern in the vertical plane for uniform illumination in a sector area. The array itself consists of 16 SIW traveling wave subarrays of 12 slot-coupled microstrip patch antennas associated with a pair of reflection-canceling vias and phasing elements to get the tapered distribution both in amplitude and phase for the cosecant-shaped radiation pattern. The array is designed to be operational at 28 GHz with a bandwidth of more than 10%, a candidate mm-wave frequency band for 5G. The phased antenna array supports wide-angle scanning of +/−60° in azimuth and exhibits good active impedance properties. The array design is successfully verified experimentally.