A multiple-input–multiple-output dielectric resonator antenna with enhanced isolation is proposed in this letter for the future 5G millimeter (mm)-wave applications. Two rectangular dielectric resonators (DRs) are mounted on a substrate excited by rectangular microstrip-fed slots underneath DRs. Each DR has a metal strip printed on its upper surface moving the strongest part of the coupling field away from the exciting slot to improve the isolation between two antenna elements. The proposed antenna obtains a simulated impedance bandwidth ( S 11 ≤ –10 dB) from 27.25 to 28.59 GHz, which covers the 28 GHz band (27.5–28.35 GHz) allocated by the Federal Communications Commission for the 5G applications. A maximum improvement of 12 dB on the isolation over 27.5–28.35 GHz is achieved. The mechanism of the isolation improvement and the design procedure are given in this letter. A prototype is manufactured and measured as a validation of the proposed decoupling method.

A MIMO Dielectric Resonator Antenna With Improved Isolation for 5G mm-Wave Applications

With the advancement of wireless technologies and sensing methodologies, many studies have shown the success of re-using wireless signals (e.g., WiFi) to sense human activities and thereby realize a set of emerging applications, ranging from intrusion detection, daily activity recognition, gesture recognition to vital signs monitoring and user identification involving even finer-grained motion sensing. These applications arguably can brace various domains for smart home and office environments, including safety protection, well-being monitoring/management, smart healthcare and smart-appliance interaction. The movements of the human body impact the wireless signal propagation (e.g., reflection, diffraction and scattering), which provide great opportunities to capture human motions by analyzing the received wireless signals. Researchers take the advantage of the existing wireless links among mobile/smart devices (e.g., laptops, smartphones, smart thermostats, smart refrigerators and virtual assistance systems) by either extracting the ready-to-use signal measurements or adopting frequency modulated signals to detect the frequency shift. Due to the low-cost and non-intrusive sensing nature, wireless-based human activity sensing has drawn considerable attention and become a prominent research field over the past decade. In this paper, we survey the existing wireless sensing systems in terms of their basic principles, techniques and system structures. Particularly, we describe how the wireless signals could be utilized to facilitate an array of applications including intrusion detection, room occupancy monitoring, daily activity recognition, gesture recognition, vital signs monitoring, user identification and indoor localization. The future research directions and limitations of using wireless signals for human activity sensing are also discussed.

Wireless Sensing for Human Activity: A Survey

This work presents a systematic design of high performance eight element antenna array for a 5G mobile terminal operating at 2.6/3.5 GHz bands. The proposed eight element slot antenna array based on unit monopole slot antenna embedded in the metal casing or ground resonates at fundamental mode at 2.6 GHz. The antenna array is developed from four antennas (open-end slot antenna) etched near to the corner edges of the printed circuited board with supported pairs of vertically mounted slot antennas in middle section of the long edge ground plane. This combination of the antenna elements provided pattern diversity and enabled the smartphone in the reception of the signal in a different direction. The impedance bandwidth based on -10 dB return loss criteria cover from 2.4 GHz to 3.6 GHz includes the two allocated bands of (2400 MHz to 2600 MHz) and (3400 MHz to 3600 MHz) for 5G cellular communication systems. The vital MIMO performance measures as envelope correlation coefficient or ECC is less than 0.2 for any two antenna array meeting the required standard of less than 0.5 alongside the mean effective gain or MEG ratio of any two antenna meeting the required standard of less than 3 dB for power balance and optimal diversity performance. As modern smartphone demand desires slim handsets, the after mentioned compact multiple antenna structure can be easily implemented for the future smartphones as it utilizes the conductive sheet or chassis and the middle vertically mounted antenna do not use the additional space of the chassis or ground. The customer hand or human hand effect on the multiple antenna array to mimic the use of mobile phone customer is also studied. The maximum MIMO Channel capacity based on measured result is 34.25bps/Hz and is about 3 times of 2 × 2 MIMO operations.

Eight Element Multiple-Input Multiple-Output (MIMO) Antenna for 5G Mobile Applications

This paper reports a thorough overview on the last developments concerning the vital sign detection and the human localization employing the multiple-input-multiple-output (MIMO) technology. The wireless motion and vital sign detection represents an outstanding research area aimed at monitoring the health conditions of human subjects and at detecting their presence in different environments with minimal concern. MIMO radars exhibit several interesting advantages over conventional single-input-single-output architectures mainly related to their angle detection capabilities and enhanced signal-to-noise ratio. This paper describes the main features and details the operating principles of MIMO technology. Thereafter, it summarizes the state-of-the-art of the available solutions with the purpose of fueling the research activities on this hot topic.

https://www.mdpi.com/2079-9292/9/9/1497/pdf

A Review on Biomedical MIMO Radars for Vital Sign Detection and Human Localization

In this paper, the concept of cross-correlation Green's functions (CGFs) is used in conjunction with the finite-difference time-domain (FDTD) technique for the calculation of envelope correlation coefficient (ECC) of any arbitrary multiple-input multiple-output (MIMO) antenna system over wide frequency band. Both frequency-domain (FD) and time-domain (TD) postprocessing techniques are proposed for possible application with this FDTD-CGF scheme. The FDTD-CGF-TD scheme utilizes TD signal-processing methods and exhibits significant reduction in ECC computation time as compared with the FDTD-CGF-FD scheme, for high-frequency resolution requirements. The proposed FDTD-CGF-based schemes can be applied for accurate and fast prediction of wideband ECC response, instead of the conventional scattering parameter-based techniques which have several limitations. Numerical examples of the proposed FDTD-CGF techniques are provided for two-element MIMO systems involving thin-wire half-wavelength dipoles in parallel side-by-side as well as orthogonal arrangements. Furthermore, examples of two-element MIMO systems involving multiband LC resonator loaded dipoles and pattern-diversity antennas using parasitic elements are also included. The results obtained from the FDTD-CGF techniques are compared with results from commercial electromagnetic solver Ansys HFSS, to verify the validity of proposed approach.

Application of Cross-correlation Greens Function along with FDTD for Fast Computation of Envelope Correlation Coefficient over Wideband for MIMO Antennas

This paper proposes a method that uses bistatic MultipleInput Multiple-Output (MIMO) radar to locate living-bodies. In this method, directions of living-bodies are estimated by the MUltiple SIgnal Classification (MUSIC) method at the transmitter and receiver, where the Fourier transformed virtual Single-Input Multiple-Output (SIMO) channel matrix is used. Body location is taken as the intersection of the two directions. The proposal uses a single frequency and so has a great advantage over conventional methods that need a wide frequency band. Also, this method can be used in multipath-rich environments such as indoors. An experiment is performed in an indoor environment, and the MIMO channels yielded by various subject numbers and positions are measured. The result indicates that the proposed method can estimate multiple living-body locations with high accuracy, even in multipath environments. key words: MIMO, living-body location, DOA estimation, microwave sensor, array antenna

Estimating Living-Body Location Using Bistatic MIMO Radar in Multi-Path Environment

This paper presents a living body localization method suitable for multi-path environments. The time-variant MIMO channel is measured and the bistatic MIMO radar estimates the target location from Fourier-transformed channel information. Measurements are carried out, and the proposed method is shown to accurately estimate target location.

Localizing living body using bistatic MIMO radar in multi-path environment

Since the evaluation of multiple-input multiple-output (MIMO) antennas requires full information of its complex radiation patterns as well as propagation channels, its design procedures and analyses are cumbersome and complicated in general. In this letter, the accuracy of a closed-form capacity formula for mean MIMO channel capacity is investigated, where the $S$ -parameter of the antenna is needed but the antenna must be lossless. Numerical analyses show that this formula gives mean channel capacity with a good accuracy when the signal-to-noise ratio is sufficiently high.

Accuracy of MIMO Channel Capacity Equation Based Only on $S$ -Parameters of MIMO Antenna

Analysis of the Convergence Condition of Non-canonical LMS Adaptive Algorithm

This paper presents a localization method of multiple living-bodies suitable for multi-path environments. The time-variant Multiple-Input Multiple-Output (MIMO) channel is measured and the bistatic MIMO radar estimates multiple target locations from Fourier-transformed channel information. Measurements are carried out in an indoor environment, and it is shown the proposed method can estimate multiple target locations with fairly good accuracy.

Yoshitaka Tsunekawa

Papers

Estimating Living-Body Location Using Bistatic MIMO Radar in Multi-Path Environment

Localizing living body using bistatic MIMO radar in multi-path environment

Accuracy of MIMO Channel Capacity Equation Based Only on $S$ -Parameters of MIMO Antenna

Analysis of the Convergence Condition of Non-canonical LMS Adaptive Algorithm

Localizing multiple target using bistatic MIMO radar in multi-path environment