This two-part article presents a review of different techniques of mutual coupling (MC) reduction. MC is a major issue when an array of antennas is densely packed. When the separation between the antennas is <λ
 0 
/2, i.e., half of the free-space wavelength, the antenna parameters suffer from the surface wave, and the space wave coupling effect between the antenna elements. To reduce the MC influence, several techniques have been discussed in the scientific literature. This part of the review paper will discuss strategies: antenna placement and orientation approach, Defected Ground Structures (DGSs), slots/slits-etching approach, protruding ground stub structures, and parasitic elements/structures. This article concludes with feasibility, applications, and comparison of the techniques mentioned above. Simultaneously, the applications and possibilities of the remaining methods are discussed in part two of the article.

A review on different techniques of mutual coupling reduction between elements of any MIMO antenna. Part 1: DGSs and parasitic structures

In this paper, we present a non-standalone dual-band shared aperture antenna array that operates at both the current Dedicated Short Range Communications (DSRC) band (viz. 5.9 GHz) and the future 5G millimeter-wave (mm-wave) band (viz. 28 GHz) allocated for vehicle-to-vehicle (V2V) communications. The design consists of a 2 $\times $ 2 differentially fed patch array operating at 5.9 GHz, co-printed with a 1 $\times $ 2 series fed array operating at 28 GHz on a single layer substrate. In particular, the shared aperture array operates from 5.84-5.94 GHz (DSRC band) with a 100 MHz impedance bandwidth and from 27.75 - 28.47 GHz (5G mm-wave band) with a 720 MHz impedance bandwidth. Gain improvement of ~1.44 dB at 28 GHz is observed as a result of the higher order modes generated by the 5.9 GHz array. The shared aperture array was fabricated and measured showing a gain of ~9.97 dBi at 5.9 GHz and ~12.3 dBi at 28 GHz. The ports of the array are highly isolated with measured isolation >55 dB at the DSRC band and >33 dB at the 5G mm-wave band.

/pdf/low-profile-dual-band-shared-aperture-array-for-vehicle-to-79h887l1xb.pdf

Low Profile Dual-Band Shared Aperture Array for Vehicle-to-Vehicle Communication

In this work, a miniaturized multiple-input-multiple-output (MIMO) antenna with frequency agility is designed and developed for 1.8 GHz, 2.4 GHz, and 3.5 GHz application bands. The prospective antenna element comprised of a modified ground surface and a microstrip-line-fed slotted radiator (SR) loaded with a modified-electric inductive capacitive (m-ELC) meta-resonator. In order to achieve frequency reconfigurability, a PIN diode is integrated between the SR and the m-ELC resonator. The size of the antenna element is 0.19λ0 × 0.18λ0, and the size of the MIMO antenna is 0.39λ0 × 0.36λ0, where λ0 is the smallest resonating frequency. In the proposed MIMO antenna, only four PIN diodes are required to provide frequency reconfigurability, and it does not require an additional impedance matching network. 

Design and performance analysis of a frequency reconfigurable four-element multiple-input-multiple-output antenna

Recent research activities are focused on improving Vehicle-to-Vehicle Communication (V2V) based on the 5G Technology. V2V applications are important because they are expected to reduce the risk of accidents up to 80%, enhance traffic management, mitigate congestion, and optimize fuel consumption. Typical autonomous vehicle applications require a high bandwidth transmission channel, so the 5G communication channel might be a reliable solution to support this technology. The dedicated short-range communications (DSRC), characterized by a frequency bandwidth of 5.9 GHz, were used as vehicular connectivity with bandwidth up to 200 mb/s and limited capacity, and it is here utilized for comparison to 5G. The 5G band can support connected autonomous vehicles with higher data rates and larger bandwidth. The 5G communication channel is suitable for vehicular connectivity since it has a very high bandwidth in the millimeter waves spectrum range. The quality of 5G wireless communication channels between connected vehicles is affected by weather conditions such as rain, snow, fog, dust, and sand. In this paper, the effect of dust and sand on the propagation of millimeter waves is presented. The effect of dust and sand on the communication path loss of DSRC and 5G frequency band is investigated in the case of Urban area and Highway condition. Results show that the attenuation caused by dust and sand depends on the particle size of sand,frequency of propagating wave, and concentration of dust. Finally, a new model of link margin is proposed to estimate the effect of dust and sand on DSRC (5.9 GHz) and 5G (28 GHz-73.5 GHz) communication path loss. 

https://figshare.com/articles/preprint/Impact_of_Dust_and_Sand_on_5G_Communications_for_Connected_Vehicles_Applications/18482000/1/files/33249089.pdf

Impact of Dust and Sand on 5G Communications for Connected Vehicles Applications

Closely-coupled wideband MIMO antenna with isolation improvement using decoupling circuit and hexagonal split-ring resonators

Multiple-input and multiple-output (MIMO) systems utilize multiple antenna elements to improve channel capacity and achieve higher data rates. The successful implementation of MIMO systems requires low mutual coupling between antenna elements to reduce the envelope correlation coefficient (ECC) at the operating frequency. In this paper, we introduce a mutual coupling suppression technique using an open stub meandered (OSM) bandstop filter (BSF) design for MIMO applications. The OSM-BSF is optimized and implemented on the ground plane side of a two-element patch array. The designed filter provides high isolation of 60 dB at 2.4 GHz across a 30% bandwidth. A parametric study of antenna element spacing was carried out, showing at least 40 dB of mutual coupling suppression in the antenna array, irrespective of the antenna element spacing. A two-element antenna array prototype with OSM-BSF was fabricated and tested. Measurements showed that ≥ 57 dB isolation was achieved using OSM-BSF. Besides, the fabricated array provides a low ECC of 0.0093 at 2.42 GHz, while maintaining edge-to-edge spacing as little as $0.19\lambda _{0}$ .

/pdf/mutual-coupling-suppression-in-antenna-arrays-using-1n0sdskd7x.pdf

Mutual Coupling Suppression in Antenna Arrays Using Meandered Open Stub Filtering Technique

The Dedicated Short Range Communications (DSRC) band (5.85-5.925 GHz) allocated for vehicle-to-vehicle (V2V) communication provides limited opportunities for high speed data transfer. Alternatively, high speed communication of at least 1Gbps is possible in the millimeter-wave (mm-wave) bands. To overcome the propagation losses associated with mmwave frequencies, high gain radio architectures are required. In this paper, we present a novel dual-band V2V receiver architecture for both DSRC and 28GHz communications. For each band, we optimized antenna gain and number of elements to maximize range and data rate. For simplicity, free space path loss model was used for link budget estimation. Results show that an antenna array of at least 9×9 element is required to achieve a maximum data rate of 27Mbps at 5.9GHz and a range of 867m. At 28GHz, the same 9×9 dual band array is capable of transmitting high speed signals at a rate of 1Gbps with coverage of 688m.

Range Optimization for DSRC and 5G Millimeter-Wave Vehicle-to-Vehicle Communication Link

This paper presents a 60 GHz millimeter-wave (mm-wave) antenna array using standard printed circuit board (PCB) for 3D Antenna-in-package (AiP) implementation. The array consists of a 4 microstrip patch elements, differentially fed with an open stub matching feed network to enable 3D integration. The $1\times 4$ finite antenna array with ball grid array (BGA) and silicon (Si) interposer operates from 58.46 to 62.14 GHz with 3.6 GHz instantaneous bandwidth, low mutual coupling of about $1\times 4$ array consists of two substrates and one bondply layer with antennas, via-to-open stub matching network, and a differential to single-ended corporate feed network for the measurement. A prototype with a differential to single-ended corporate feed network was fabricated and tested showing a gain of about 10.02 dBi at the operating frequency with $\geq 90$ % radiation efficiency. Such a gain and efficiency make the presented design a leading candidate for 3D AiP applications.

/pdf/a-60-ghz-millimeter-wave-antenna-array-for-3d-antenna-in-2ra1ffrm1x.pdf

A 60 GHz Millimeter-Wave Antenna Array for 3D Antenna-in-Package Applications

The Dedicated Short Range Communications (DSRC) band (5.85-5.925 GHz) allocated for vehicle-to-vehicle (V2V) communication provides limited opportunities for high speed data transfer. Alternatively, FCC plans to allocate millimeter-wave spectrum for 5G V2V communication. In this paper, we present a novel dual-band dual linearly-polarized antenna array for both DSRC and 28 GHz communications. For each band, we optimized antenna gain and number of elements to maximize range and data rate. The designed array has dual linear polarization and is fed with a simple quarter wave transformer. Due to large available connector's size, a Wilkinson power divider is designed to combine adjacent elements. Infinite array simulation show that the array is well matched $(\mathbf{S}_{\mathbf{11}} from 5.85 to 6.48 GHz, and from 17.29 to 29 GHz. The realized gain at both frequency bands is near-theoretical.

Sandhiya Reddy Govindarajulu

Papers

Mutual Coupling Suppression in Antenna Arrays Using Meandered Open Stub Filtering Technique

Low Profile Dual-Band Shared Aperture Array for Vehicle-to-Vehicle Communication

Range Optimization for DSRC and 5G Millimeter-Wave Vehicle-to-Vehicle Communication Link

A 60 GHz Millimeter-Wave Antenna Array for 3D Antenna-in-Package Applications

Dual-Band Antenna Array for 5.9 GHz DSRC and 28 GHz 5G Vehicle to Vehicle communication