Editorial

3 pages, 176 KiB

Open AccessEditorial

by Manuel García Sánchez

Electronics 2020, 9(2), 251; https://doi.org/10.3390/electronics9020251 - 03 Feb 2020

Cited by 8 | Viewed by 2403

For the last few decades, the millimeter wave (mmWave) frequency band (30–300 GHz) has been seen as a serious candidate to host very high data rate communications [...] Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

Research

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24 pages, 7876 KiB

Open AccessFeature PaperArticle

A Software-Defined Radio for Future Wireless Communication Systems at 60 GHz

by Luis Duarte, Rodolfo Gomes, Carlos Ribeiro and Rafael F. S. Caldeirinha

Electronics 2019, 8(12), 1490; https://doi.org/10.3390/electronics8121490 - 06 Dec 2019

Cited by 15 | Viewed by 6402

Abstract

This paper reports on a complete end-to-end 5G mmWave testbed fully reconfigurable based on a FPGA architecture. The proposed system is composed of a baseband/low-IF processing unit, and a mmWave RF front-end at both TX/RX ends. In particular, the baseband unit design is [...] Read more.

This paper reports on a complete end-to-end 5G mmWave testbed fully reconfigurable based on a FPGA architecture. The proposed system is composed of a baseband/low-IF processing unit, and a mmWave RF front-end at both TX/RX ends. In particular, the baseband unit design is based on a typical agile digital IF architecture, enabling on-the-fly modulations up to 256-QAM. The real-time 5G mmWave testbed, herein presented, adopts OFDM as the transmission scheme waveform, which was assessed OTA by considering the key performance indicators, namely EVM and BER. A detailed overview of system architecture is addressed together with the hardware considerations taken into account for the mmWave testbed development. Following this, it is demonstrated that the proposed testbed enables real-time multi-stream transmissions of UHD video content captured by nine individual cameras, which is in fact one of the killing applications for 5G. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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14 pages, 2075 KiB

Open AccessFeature PaperArticle

Contribution to the Channel Path Loss and Time-Dispersion Characterization in an Office Environment at 26 GHz

by Lorenzo Rubio, Rafael P. Torres, Vicent M. Rodrigo Peñarrocha, Jesús R. Pérez, Herman Fernández, Jose-Maria Molina-Garcia-Pardo and Juan Reig

Electronics 2019, 8(11), 1261; https://doi.org/10.3390/electronics8111261 - 01 Nov 2019

Cited by 8 | Viewed by 2746

Abstract

In this paper, path loss and time-dispersion results of the propagation channel in a typical office environment are reported. The results were derived from a channel measurement campaign carried out at 26 GHz in line-of-sight (LOS) and obstructed-LOS (OLOS) conditions. The parameters of [...] Read more.

In this paper, path loss and time-dispersion results of the propagation channel in a typical office environment are reported. The results were derived from a channel measurement campaign carried out at 26 GHz in line-of-sight (LOS) and obstructed-LOS (OLOS) conditions. The parameters of both the floating-intercept (FI) and close-in (CI) free space reference distance path loss models were derived using the minimum-mean-squared-error (MMSE). The time-dispersion characteristics of the propagation channel were analyzed through the root-mean-squared (rms) delay-spread and the coherence bandwidth. The results reported here provide better knowledge of the propagation channel features and can be also used to design and evaluate the performance of the next fifth-generation (5G) networks in indoor office environments at the potential 26 GHz frequency band. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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23 pages, 9645 KiB

Open AccessFeature PaperArticle

Wideband Performance Comparison between the 40 GHz and 60 GHz Frequency Bands for Indoor Radio Channels

by Miguel Riobó, Rob Hofman, Iñigo Cuiñas, Manuel García Sánchez and Jo Verhaevert

Electronics 2019, 8(11), 1234; https://doi.org/10.3390/electronics8111234 - 29 Oct 2019

Cited by 5 | Viewed by 3440

Abstract

When 5G networks are to be deployed, the usability of millimeter-wave frequency allocations seems to be left out of the debate. However, there is an open question regarding the advantages and disadvantages of the main candidates for this allocation: The use of the [...] Read more.

When 5G networks are to be deployed, the usability of millimeter-wave frequency allocations seems to be left out of the debate. However, there is an open question regarding the advantages and disadvantages of the main candidates for this allocation: The use of the licensed spectrum near 40 GHz or the unlicensed band at 60 GHz. Both bands may be adequate for high performance radio communication systems, and this paper provides insight into such alternatives. A large measurement campaign supplied enough data to analyze and to evaluate the network performance for both frequency bands in different types of indoor environments: Both large rooms and narrow corridors, and both line of sight and obstructed line of sight conditions. As a result of such a campaign and after a deep analysis in terms of wideband parameters, the radio channel usability is analyzed with numerical data regarding its performance. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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17 pages, 2446 KiB

Open AccessFeature PaperArticle

by Enass Hriba and Matthew C. Valenti

Electronics 2019, 8(10), 1187; https://doi.org/10.3390/electronics8101187 - 18 Oct 2019

Cited by 9 | Viewed by 3143

Abstract

In this paper, we provide a comprehensive analysis of macrodiversity for millimeter wave (mmWave) cellular networks. The key issue with mmWave networks is that signals are prone to blocking by objects in the environment, which causes paths to go from line-of-sight (LOS) to [...] Read more.

In this paper, we provide a comprehensive analysis of macrodiversity for millimeter wave (mmWave) cellular networks. The key issue with mmWave networks is that signals are prone to blocking by objects in the environment, which causes paths to go from line-of-sight (LOS) to non-LOS (NLOS). We identify macrodiversity as an important strategy for mitigating blocking, as with macrodiversity the user will attempt to connect with two or more base stations. Diversity is achieved because if the closest base station is blocked, then the next base station might still be unblocked. However, since it is possible for a single blockage to simultaneously block the paths to two base stations, the issue of correlated blocking must be taken into account by the analysis. Our analysis characterizes the macrodiverity gain in the presence of correlated random blocking and interference. To do so, we develop a framework to determine distributions for the LOS probability, Signal to Noise Ratio (SNR), and Signal to Interference and Noise Ratio (SINR) by taking into account correlated blocking. We validate our framework by comparing our analysis, which models blockages using a random point process, with an analysis that uses real-world data to account for blockage. We consider a cellular uplink with both diversity combining and selection combining schemes. We also study the impact of blockage size and blockage density along with the effect of co-channel interference arising from other cells. We show that the assumption of independent blocking can lead to an incorrect evaluation of macrodiversity gain, as the correlation tends to decrease macrodiversity gain. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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11 pages, 3491 KiB

Open AccessFeature PaperArticle

Multi-Backup Beams for Instantaneous Link Recovery in mmWave Communications

by Adel Aldalbahi

Electronics 2019, 8(10), 1145; https://doi.org/10.3390/electronics8101145 - 10 Oct 2019

Cited by 2 | Viewed by 2270

Abstract

In this paper, a novel link recover scheme is proposed for standalone (SA) millimeter wave communications. Once the main beam between the base station (BS) and the mobile station (MS) is blocked, then a bundle-beam is radiated that covers the spatial direction of [...] Read more.

In this paper, a novel link recover scheme is proposed for standalone (SA) millimeter wave communications. Once the main beam between the base station (BS) and the mobile station (MS) is blocked, then a bundle-beam is radiated that covers the spatial direction of the blocked beam. These beams are generated from an analog beamformer design that is composed of parallel adjacent antenna arrays to radiate multiple simultaneous beams, thus creating an analog beamformer of multiple beams. The proposed recovery scheme features instantaneous recovery times, without the need for beam scanning to search for alternative beam directions. Hence, the scheme features reduced recovery times and latencies, as opposed to existing methods. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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14 pages, 9280 KiB

Open AccessArticle

Design of a SIW Variable Phase Shifter for Beam Steering Antenna Systems

by Sara Salem Hesari and Jens Bornemann

Electronics 2019, 8(9), 1013; https://doi.org/10.3390/electronics8091013 - 11 Sep 2019

Cited by 5 | Viewed by 3962

Abstract

This paper proposes a new beam steering antenna system consisting of two variable reflection-type phase shifters, a 3 dB coupler, and a 90° phase transition. The entire structure is designed and fabricated on a single layer of substrate integrated waveguide (SIW), which makes [...] Read more.

This paper proposes a new beam steering antenna system consisting of two variable reflection-type phase shifters, a 3 dB coupler, and a 90° phase transition. The entire structure is designed and fabricated on a single layer of substrate integrated waveguide (SIW), which makes it a low loss and low-profile antenna system. Surface mount tuning varactor diodes are chosen as electrical phase control elements. By changing the biasing voltage of the varactor diodes in the phase shifter circuits, the far-field radiation pattern of the antenna steers from −25° to 25°. The system has a reflection coefficient better than −10 dB for a 2 GHz bandwidth centered at 17 GHz, a directive radiation pattern with a maximum of 10.7 dB gain at the mid-band frequency, and cross polarization better than 20 dB. A prototype is fabricated and measured for design verification. The measured far-field radiation patterns, co and cross polarization, and the reflection coefficient of the antenna system agree with simulated results. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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12 pages, 2213 KiB

Open AccessArticle

Permittivity of Undoped Silicon in the Millimeter Wave Range

by Xiaofan Yang, Xiaoming Liu, Shuo Yu, Lu Gan, Jun Zhou and Yonghu Zeng

Electronics 2019, 8(8), 886; https://doi.org/10.3390/electronics8080886 - 10 Aug 2019

Cited by 20 | Viewed by 7161

Abstract

With the rapid development of millimeter wave technology, it is a fundamental requirement to understand the permittivity of materials in this frequency range. This paper describes the dielectric measurement of undoped silicon in the E-band (60–90 GHz) using a free-space quasi-optical system. This [...] Read more.

With the rapid development of millimeter wave technology, it is a fundamental requirement to understand the permittivity of materials in this frequency range. This paper describes the dielectric measurement of undoped silicon in the E-band (60–90 GHz) using a free-space quasi-optical system. This system is capable of creating local plane wave, which is desirable for dielectric measurement in the millimeter wave range. Details of the design and performance of the quasi-optical system are presented. The principle of dielectric measurement and retrieval process are described incorporating the theories of wave propagation and scattering parameters. Measured results of a sheet of undoped silicon are in agreement with the published results in the literature, within a discrepancy of 1%. It is also observed that silicon has a small temperature coefficient for permittivity. This work is helpful for understanding the dielectric property of silicon in the millimeter wave range. The method is applicable to other electronic materials as well as liquid samples. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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9 pages, 4529 KiB

Open AccessArticle

Design of Broadband W-Band Waveguide Package and Application to Low Noise Amplifier Module

by Jihoon Doo, Woojin Park, Wonseok Choe and Jinho Jeong

Electronics 2019, 8(5), 523; https://doi.org/10.3390/electronics8050523 - 10 May 2019

Cited by 7 | Viewed by 5092

Abstract

In this paper, the broadband millimeter-wave waveguide package, which can cover the entire W-band (75–110 GHz) is presented and applied to build a low noise amplifier module. For this purpose, a broadband waveguide-to-microstrip transition was designed using an extended E-plane probe [...] Read more.

In this paper, the broadband millimeter-wave waveguide package, which can cover the entire W-band (75–110 GHz) is presented and applied to build a low noise amplifier module. For this purpose, a broadband waveguide-to-microstrip transition was designed using an extended E-plane probe in a low-loss and thin dielectric substrate. The end of the probe substrate was firmly fixed on to the waveguide wall in order to minimize the performance degradation caused by the probable bending of the substrate. In addition, we predicted and analyzed in-band resonances by the simulations that are caused by the empty spaces in the waveguide package to accommodate integrated circuits (ICs) and external bias circuits. These resonances are removed by designing an asymmetrical bias space structure with a radiation boundary at an external bias connection plane. The bond-wires, which are used to connect the ICs with the transition, can generate impedance mismatches and limit the bandwidth performance of the waveguide package. Their effect is carefully compensated for by designing the broadband two-section matching circuits in the transition substrate. Finally, the broadband waveguide package is designed using a commercial three-dimensional electromagnetic structure simulator and applied to build a W-band low noise amplifier module. The measurement of the back-to-back connected waveguide-to-microstrip transition including the empty spaces for the ICs and bias circuits showed the insertion loss less than 3.5 dB and return loss higher than 13.3 dB across the entire W-band without any in-band resonances. The measured insertion loss includes the losses of 8.7 mm-long microstrip line and 41.8 mm-long waveguide section. The designed waveguide package was utilized to build the low noise amplifier module that had a measured gain greater than 14.9 dB from 75 GHz to 105 GHz (>12.9 dB at the entire W-band) and noise figure less than 4.4 dB from 93.5 GHz to 94.5 GHz. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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12 pages, 4176 KiB

Open AccessArticle

A High-Efficiency K-band MMIC Linear Amplifier Using Diode Compensation

by Heng Zhu, Wei Chen, Jianhua Huang, Zhiyu Wang and Faxin Yu

Electronics 2019, 8(5), 487; https://doi.org/10.3390/electronics8050487 - 30 Apr 2019

Cited by 4 | Viewed by 3242

Abstract

This paper describes the design and measured performance of a high-efficiency and linearity-enhanced K-band MMIC amplifier fabricated with a 0.15 μm GaAs pHEMT processing technology. The linearization enhancement method utilizing a parallel nonlinear capacitance compensation diode was analyzed and verified. The three-stage MMIC [...] Read more.

This paper describes the design and measured performance of a high-efficiency and linearity-enhanced K-band MMIC amplifier fabricated with a 0.15 μm GaAs pHEMT processing technology. The linearization enhancement method utilizing a parallel nonlinear capacitance compensation diode was analyzed and verified. The three-stage MMIC operating at 20–22 GHz obtained an improved third-order intermodulation ratio (IM3) of 20 dBc at a 27 dBm per carrier output power while demonstrating higher than a 27 dB small signal gain and 1-dB compression point output power of 30 dBm with 33% power added efficiency (PAE). The chip dimension was 2.00 mm × 1.40 mm. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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16 pages, 2386 KiB

Open AccessFeature PaperArticle

Multi-User Linear Equalizer and Precoder Scheme for Hybrid Sub-Connected Wideband Systems

by Daniel Castanheira, Sara Teodoro, Ricardo Simões, Adão Silva and Atilio Gameiro

Electronics 2019, 8(4), 436; https://doi.org/10.3390/electronics8040436 - 16 Apr 2019

Cited by 6 | Viewed by 2454

Abstract

Millimeter waves and massive multiple-input multiple output (MIMO) are two promising key technologies to achieve the high demands of data rate for the future mobile communication generation. Due to hardware limitations, these systems employ hybrid analog–digital architectures. Nonetheless, most of the works developed [...] Read more.

Millimeter waves and massive multiple-input multiple output (MIMO) are two promising key technologies to achieve the high demands of data rate for the future mobile communication generation. Due to hardware limitations, these systems employ hybrid analog–digital architectures. Nonetheless, most of the works developed for hybrid architectures focus on narrowband channels, and it is expected that millimeter waves be wideband. Moreover, it is more feasible to have a sub-connected architecture than a fully connected one, due to the hardware constraints. Therefore, the aim of this paper is to design a sub-connected hybrid analog–digital multi-user linear equalizer combined with an analog precoder to efficiently remove the multi-user interference. We consider low complexity user terminals employing pure analog precoders, computed with the knowledge of a quantized version of the average angles of departure of each cluster. At the base station, the hybrid multi-user linear equalizer is optimized by using the bit-error-rate (BER) as a metric over all the subcarriers. The analog domain hardware constraints, together with the assumption of a flat analog equalizer over the subcarriers, considerably increase the complexity of the corresponding optimization problem. To simplify the problem at hand, the merit function is first upper bounded, and by leveraging the specific properties of the resulting problem, we show that the analog equalizer may be computed iteratively over the radio frequency (RF) chains by assigning the users in an interleaved fashion to the RF chains. The proposed hybrid sub-connected scheme is compared with a fully connected counterpart. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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13 pages, 4543 KiB

Open AccessArticle

Beam Scanning Capabilities of a 3D-Printed Perforated Dielectric Transmitarray

by Andrea Massaccesi, Gianluca Dassano and Paola Pirinoli

Electronics 2019, 8(4), 379; https://doi.org/10.3390/electronics8040379 - 28 Mar 2019

Cited by 21 | Viewed by 4028

Abstract

In this paper, the design of a beam scanning, 3D-printed dielectric Transmitarray (TA) working in Ka-band is discussed. Thanks to the use of an innovative three-layer dielectric unit-cell that exploits tapered sections to enhance the bandwidth, a 50 × 50 elements transmitarray with [...] Read more.

In this paper, the design of a beam scanning, 3D-printed dielectric Transmitarray (TA) working in Ka-band is discussed. Thanks to the use of an innovative three-layer dielectric unit-cell that exploits tapered sections to enhance the bandwidth, a 50 × 50 elements transmitarray with improved scanning capabilities and wideband behavior has been designed and experimentally validated. The measured radiation performances over a scanning coverage of ±27

^{\circ}

shown a variation of the gain lower than 2.9 dB and a 1-dB bandwidth in any case higher than 23%. The promising results suggest that the proposed TA technology is a valid alternative to realize a passive multibeam antenna, with the additional advantage that it can be easily manufactured using 3D-printing techniques. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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9 pages, 4637 KiB

Open AccessArticle

3D Printing Using a 60 GHz Millimeter Wave Segmented Parabolic Reflective Curved Antenna

by Benxiao Cai, Lingling Sun and Yuchao Lei

Electronics 2019, 8(2), 203; https://doi.org/10.3390/electronics8020203 - 11 Feb 2019

Cited by 1 | Viewed by 3466

Abstract

This paper proposes a segmented parabolic curved antenna, which can be used in the base station of a 60 GHz millimeter wave communication system, with an oblique Yagi antenna as a feed. By analyzing the reflection and multi-path interference cancellation phenomenon when the [...] Read more.

This paper proposes a segmented parabolic curved antenna, which can be used in the base station of a 60 GHz millimeter wave communication system, with an oblique Yagi antenna as a feed. By analyzing the reflection and multi-path interference cancellation phenomenon when the main lobe of the Yagi antenna is reflected, the problem of main lobe splitting is solved. 3D printing technology relying on PLA (polylactic acid) granule raw materials was used to make the coaxial connector bracket and segmented parabolic surface. The reflective surface was vacuum coated (via aluminum evaporation) with low-loss aluminum. The manufacturing method is environmentally friendly and the structure was printed with 0.1 mm accuracy based on large-scale commercial applications at a low cost. The experimental results show that the reflector antenna proposed in this paper achieves a high gain of nearly 20 dBi in 57–64 GHz frequency band and ensures that the main lobe does not split. Full article

(This article belongs to the Special Issue Millimeter-Wave (mmWave) Communications)

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