Multiple antenna technologies have attracted much research interest for several decades and have gradually made their way into mainstream communication systems. Two main benefits are adaptive beamforming gains and spatial multiplexing, leading to high data rates per user and per cell, especially when large antenna arrays are adopted. Since multiple antenna technology has become a key component of the fifth-generation (5G) networks, it is time for the research community to look for new multiple antenna technologies to meet the immensely higher data rate, reliability, and traffic demands in the beyond 5G era. Radically new approaches are required to achieve orders-of-magnitude improvements in these metrics. There will be large technical challenges, many of which are yet to be identified. In this paper, we survey three new multiple antenna technologies that can play key roles in beyond 5G networks: cell-free massive MIMO, beamspace massive MIMO, and intelligent reflecting surfaces. For each of these technologies, we present the fundamental motivation, key characteristics, recent technical progresses, and provide our perspectives for future research directions. The paper is not meant to be a survey/tutorial of a mature subject, but rather serve as a catalyst to encourage more research and experiments in these multiple antenna technologies.

/pdf/prospective-multiple-antenna-technologies-for-beyond-5g-m5fvfgltfg.pdf

Prospective Multiple Antenna Technologies for Beyond 5G

For the first time to the best of our knowledge, this paper provides an overview of millimeter-wave (mmWave) 5G antennas for cellular handsets. Practical design considerations and solutions related to the integration of mmWave phased-array antennas with beam switching capabilities are investigated in detail. To experimentally examine the proposed methodologies, two types of mesh-grid phased-array antennas featuring reconfigurable horizontal and vertical polarizations are designed, fabricated, and measured at the 60 GHz spectrum. Afterward the antennas are integrated with the rest of the 60 GHz RF and digital architecture to create integrated mmWave antenna modules and implemented within fully operating cellular handsets under plausible user scenarios. The effectiveness, current limitations, and required future research areas regarding the presented mmWave 5G antenna design technologies are studied using mmWave 5G system benchmarks.

Millimeter-Wave 5G Antennas for Smartphones: Overview and Experimental Demonstration

Metamaterials are materials typically engineered with novel or artificial structures to produce electromagnetic properties that are unusual or difficult to obtain in nature. Because of their promise to provide engineerable permittivity, permeability, and index of refraction, metamaterials have drawn broad interest and have led to possible utilization in many electromagnetic applications from the microwave to optical regime, especially for the radiated-wave devices. This paper presents a detailed review upon the most recent research efforts associated with those metamaterial-based small antennas. They are discussed and classified in several different categories such as the antennas based on dispersion engineering, metaresonators, and metamaterial loadings. Some practical difficulties or limitations for the development of metamaterial-based small antennas are pointed out and the possible approaches to resolve these problems are also illustrated. A wide variety of antenna examples are included to facilitate the understanding for general readers.

Metamaterial-Based Antennas

With the development of the Internet of Things (IoT), the demand for thin and wearable electronic devices is growing quickly The essential part of the IoT is communication between devices, which requires radio-frequency (RF) antennas Metals are widely used for antennas; however, their bulkiness limits the fabrication of thin, lightweight, and flexible antennas Recently, nanomaterials such as graphene, carbon nanotubes, and conductive polymers came into play However, poor conductivity limits their use We show RF devices for wireless communication based on metallic two-dimensional (2D) titanium carbide (MXene) prepared by a single-step spray coating We fabricated a ~100-nm-thick translucent MXene antenna with a reflection coefficient of less than −10 dB By increasing the antenna thickness to 8 μm, we achieved a reflection coefficient of −65 dB We also fabricated a 1-μm-thick MXene RF identification device tag reaching a reading distance of 8 m at 860 MHz Our finding shows that 2D titanium carbide MXene operates below the skin depth of copper or other metals as well as offers an opportunity to produce transparent antennas Being the most conductive, as well as water-dispersible, among solution-processed 2D materials, MXenes open new avenues for manufacturing various classes of RF and other portable, flexible, and wearable electronic devices

https://advances.sciencemag.org/content/advances/4/9/eaau0920.full.pdf

2D titanium carbide (MXene) for wireless communication

An investigation into the design of compact patch antennas loaded with complementary split-ring resonators (CSRRs) and reactive impedance surface (RIS) is presented in this study. The CSRR is incorporated on the patch as a shunt LC resonator providing a low resonance frequency and the RIS is realized using the two-dimensional metallic patches printed on a metal-grounded substrate. Both the meta-resonator (CSRR) and the meta-surface (RIS) are able to miniaturize the antenna size. By changing the configuration of the CSRRs, multi-band operation with varied polarization states can be obtained. An equivalent circuit has been developed for the CSRR-loaded patch antennas to illustrate their working principles. Six antennas with different features are designed and compared, including a circularly-polarized antenna, which validate their versatility for practical applications. These antennas are fabricated and tested. The measured results are in good agreement with the simulation.

Design and Characterization of Miniaturized Patch Antennas Loaded With Complementary Split-Ring Resonators

The design is presented of aperture-coupled microstrip line-fed patch antennas (ACMPAs) and 4times4 planar arrays on Ferro A6-S low-temperature cofired ceramic (LTCC) substrate operating in the 60-GHz frequency band. In addition to the traditional ACMPA design, air cavities processed inside the LTCC substrate are used to improve the bandwidth and gain of the antennas. The arrays are excited through the microstrip-line feed networks using quarter-wave matched T-junctions and using Wilkinson power dividers. The results show that ACMPAs and arrays can be fabricated with a standard LTCC process even for the millimeter-wave region. Good agreement is achieved between simulations and measurements. The measured S-parameters indicate impedance bandwidths of 9.5% and 5.8% for the array elements with and without an embedded cavity. The measured maximum gains for the 16-element patch arrays (with and without cavity) are 18.2 and 15.7 dBi, respectively.

60-GHz Patch Antennas and Arrays on LTCC With Embedded-Cavity Substrates

The new services available through smart devices require very high cellular network capacity. The capacity requirement is expected to increase exponentially with the forthcoming 5G networks. The only available spectrum for truly wideband communication (>1 GHz) is at millimeter wavelengths. The high free space loss can be overcome by using the directive and beam-steerable antennas. This paper describes a design and the measurement results for a lens antenna system for $E$ -band having 2-D beam-steering capability. Continuous beam-switching range of about $\pm 4 {^{\circ }} \times \pm 17^{\circ }$ is demonstrated with the lens having the maximum measured directivity of 36.7 dB. Link budget calculation for backhaul application using the presented lens antenna system is presented and compared with the measurement results of the implemented demo system.

2-D Beam-Steerable Integrated Lens Antenna System for 5G $E$ -Band Access and Backhaul

The relatively high dielectric constant of the low-temperature cofired ceramic (LTCC) substrate materials can reduce the antenna gain and increase the mutual coupling in antenna arrays due to the increased surface-wave power. We present a design of a uniplanar-compact electromagnetic band-gap (UC-EBG) structure on the Ferro A6-S LTCC tape system operating in the 60-GHz frequency band. The UC-EBG design is used with an aperture-coupled microstrip-line-fed patch antenna (ACMPA) and with a 16-element array to increase the antenna gain. The UC-EBG is also used to reduce the mutual coupling between antennas in the E- and H-planes. The performance of the antennas with and without UC-EBG are evaluated with the probe-station and radiation-pattern measurements. In addition, the reflection from the UC-EBG surface is measured using a WR-15 waveguide excitation. Good agreement is achieved between the simulations and the measurements. An increase of up to 4.5 and 2.3 dBi is achieved in the gain for a single element and for a 16-element array, respectively. A reduction of up to 11.8 dB is observed in the E-plane coupling between two patches. The presented design is suitable for electromagnetic shielding, reduction of coupling in integrated LTCC modules, and providing high gain antennas for low-cost millimeter-wave applications.

UC-EBG on LTCC for 60-GHz Frequency Band Antenna Applications

A reader module at 60 GHz for high data-rate short-range backscattering-based communications is presented. The reader consists of a CMOS-based oscillator, amplifiers, and a mixer on a low-temperature co-fired ceramic (LTCC) substrate. The filter, power splitter, and antennas are directly patterned on the LTCC. All millimeter-wave components are contained within the module and the only interfaces to the module are the IF and bias lines. Transmit power of the module is +11.6-dBm effective isotropic radiated power with an IF bandwidth of 400 MHz. The LTCC module measures 13×24 mm2 and has a dc power consumption of 130 mW. Reception of a 20-MHz square wave from a tag 5 cm apart from the reader is demonstrated; the suggested millimeter-wave identification concept enables a 102- 103-fold data-rate increase in comparison to the present near-field communication technique, with similar size, range, and power consumption of the reader.

60-GHz Millimeter-Wave Identification Reader on 90-nm CMOS and LTCC

This paper presents the design, manufacturing, and characterization of a wide-band cavity-backed aperture-coupled patch antenna and a 16-element antenna array on multilayer printed circuit board (PCB) targeted for D-band applications Microstrip line and grounded coplanar waveguide (GCPW) transmission lines are also designed and tested to investigate line losses at D-band The test structures are manufactured using printed circuit board technology with semi-additive processing (mSAP) of conductors on a multilayered substrate The measurement results indicate an insertion loss of 19 dB/cm for the microstrip line and 18 dB/cm for the coplanar waveguide at 150 GHz The measured maximum gains for single antenna and 16-element array are respectively 7 dBi and 14 dBi at 143 GHz The measured antenna input matching bandwidth is 20 GHz The results show the viability of advanced printed circuit technology for D-band transmission lines, antennas, and antenna arrays

/pdf/patch-antenna-and-antenna-array-on-multilayer-high-frequency-4sady68etx.pdf

Antti Lamminen

Papers

60-GHz Patch Antennas and Arrays on LTCC With Embedded-Cavity Substrates

2-D Beam-Steerable Integrated Lens Antenna System for 5G $E$ -Band Access and Backhaul

UC-EBG on LTCC for 60-GHz Frequency Band Antenna Applications

60-GHz Millimeter-Wave Identification Reader on 90-nm CMOS and LTCC

Patch Antenna and Antenna Array on Multilayer High-Frequency PCB for D-Band