A Review on Coexistence Issues of Broadband Millimeter-Wave Communications

<div>With higher frequencies and broader spectrum than conventional frequency bands, the millimeter-wave (mmWave) band is suitable for next-generation wireless networks featuring short-distance high-rate communications. As a newcomer, mmWaves are expected to have the backward compatibility with existing services and collaborate with other technologies in order to enhance system performances. Therefore, the coexistence issues become an essential topic for next-generation wireless communications. In this paper, we systematically review the coexistence issues of broadband mmWave communications and their corresponding solutions proposed in the literature, helping shed light on the insights of the mmWave design. Particularly, the works surveyed in this paper can be classified into four categories: coexistence with microwave communications, coexistence with fixed services, coexistence with non-orthogonal multiple access (NOMA), and other coexistence issues. Results of numerical evaluations inspired by the literature are presented for a deeper analysis. We also point out some challenges and future directions for each category as a roadmap to further investigate the coexistence issues of broadband mmWave communications.</div>

A Review on Coexistence Issues of Broadband Millimeter-Wave Communications

<div>With higher frequencies and broader spectrum than conventional frequency bands, the millimeter-wave (mmWave) band is suitable for next-generation wireless networks featuring short-distance high-rate communications. As a newcomer, mmWaves are expected to have the backward compatibility with existing services and collaborate with other technologies in order to enhance system performances. Therefore, the coexistence issues become an essential topic for next-generation wireless communications. In this paper, we systematically review the coexistence issues of broadband mmWave communications and their corresponding solutions proposed in the literature, helping shed light on the insights of the mmWave design. Particularly, the works surveyed in this paper can be classified into four categories: coexistence with microwave communications, coexistence with fixed services, coexistence with non-orthogonal multiple access (NOMA), and other coexistence issues. Results of numerical evaluations inspired by the literature are presented for a deeper analysis. We also point out some challenges and future directions for each category as a roadmap to further investigate the coexistence issues of broadband mmWave communications.</div>

High Gain Cavity Backed SIW Array Antenna for Microwave Communications

A high gain 4-element Cavity Backed Substrate Integrated Waveguide (CBSIW) based antenna is proposed in this paper. The combination of low loss SIW cavities with quarter wave transformer based transmission line power divider can enhance the gain and power efficiency of the CBSIW antenna. A bow-tie shaped slot is located on rectangular shaped SIW cavity with optimum dimensions to form each element. The feed network is constructed with two quarter wave T-junction power dividers connected back-to-back to accomplish the impedance matching and optimum power distribution to the elements. The proposed CBSIW antenna exhibits a high gain of 21.9dBi with 82% of efficiency on low cost FR4 epoxy substrate. The measured results agree with simulated results obtained from commercial HFSS full-wave electromagnetic solver.

Giant nonreciprocity of surface acoustic waves enabled by the magnetoelastic interaction

Nonreciprocity, the defining characteristic of isolators, circulators, and a wealth of other applications in radio/microwave communications technologies, is generally difficult to achieve as most physical systems incorporate symmetries that prevent the effect. In particular, acoustic waves are an important medium for information transport, but they are inherently symmetric in time. In this work, we report giant nonreciprocity in the transmission of surface acoustic waves (SAWs) on lithium niobate substrate coated with ferromagnet/insulator/ferromagnet (FeGaB/Al2O3/FeGaB) multilayer structure. We exploit this structure with a unique asymmetric band diagram and expand on magnetoelastic coupling theory to show how the magnetic bands couple with acoustic waves only in a single direction. We measure 48.4-dB (power ratio of 1:69,200) isolation that outperforms current state-of-the-art microwave isolator devices in a previously unidentified acoustic wave system that facilitates unprecedented size, weight, and power reduction. In addition, these results offer a promising platform to study nonreciprocal SAW devices.

Effects of Rising Temperature on Microwave Communications in Ducting Environment over the Southern Region of Pakistan in the Northern Arabian Sea

The propagation of microwave (MW) of frequencies above 300 MHz is affected by the existence and properties of the atmospheric duct. Atmospheric ducts exist in many areas of the world ocean, including the Arabian Sea. Located in the Hadley Cell and monsoon region, different seasons bring air masses of different properties into the area under investigation, which has a significant impact on the formation and strength of the atmospheric duct. In this paper, we have done the modeling to analyze the patterns of electromagnetic ducting, which is significant in the southern region of Pakistan in the Arabian Sea. To analyze the real-time scenario, data were collected from three different areas off the southern coast of Pakistan in the northern Arabian Sea to observe the electromagnetic wave's effect on the evaporation ducts. Our analysis results reveal that rising temperature plays a significant role where ducts occur above 30% in the summer months and less than 7% in the spring, autumn, and winter months. It is due to an increase in temperature, especially in summer and autumn months, where humidity gradients play an essential role in creating a higher frequency of duct. The same observations were simulated to view the time analysis of pressure, humidity, and potential temperature in this region, depending upon the refractive index.

Cavity Backed Circular Half Mode SIW Array for Microwave Communications

A two element array of circular shaped cavity backed substrate integrated waveguide (SIW) based antenna is proposed in this work. The elements are backed by a dielectric cavity of FR4 epoxy and fed by SIW slot coupling mechanism. Keeping the advantages of the conventional waveguides, the bandwidth of the radiation can be increased by choosing proper dimensions to the slots and circular patches. The two element array configuration in the design contributed to the comfortable uplift of the gain. The impedance matching is achieved by inserting a two arm power divider with pre-calculated dimensions. The accurate formulation of the electromagnetic problem of analyzing the SIW antenna is achieved by using integral equation based methods which can be solved numerically. The designed top layer of the antenna is analyzed with well known Method of Moments (MoM) and the results are compared. The functioning of the antenna is compared in terms of Return losses, radiation pattern and gain. The antenna exhibits 72% of bandwidth with peak gain of 4.2dB in the range of 4.4GHz to9.9GHz with the resonating frequency of 7.54GHz and well suited for C-band microwave communication applications.

“The Lucky Start Toward Today’s Cosmology”? Serendipity, the “Big Bang” Theory, and the Science of Radio Noise in Cold War America

The discovery of cosmic microwave background radiation—an inflection point in postwar cosmology—has not lacked chroniclers, but few have drawn deeply upon the available archival record. Many accounts emphasize the serendipitous manner in which the radiation was detected. This article redefines the relative contributions of luck, skill, and circumstance to the discovery by thickening the contexts in which it occurred. In its emphasis upon the material conditions of scientific enquiry, the development of technical expertise, and the permeability of disciplinary boundaries, the article situates the discovery in the sort of explanatory context more familiar from histories of Cold War nuclear and electronics research, where funds flowed freely across a broad front of institutions and subject fields, underwriting innovation and exchange, and incentivizing the instrumentalization of basic knowledge to address real world problems—in this case, microwave radio noise. It was not research to resolve the “big-bang”/“steady-state” controversy that pulled the radiation within range of detection, but a protean technoscientific program to improve signal-to-noise ratios. The accumulation of proficiency in microwave communications at Bell Laboratories, where the radiation was detected, was as significant to the breakthrough as the expertise in theoretical astrophysics available at Princeton, where the Bell Labs measurements were linked to the “big bang.” Princeton physicists, led by Robert Dicke, had already embarked on their own independent effort to detect the radiation, but evidence suggests they may not have succeeded absent the instrumental contributions made by Bell Labs.

Performance Analysis of Single and Multiple Channel FSO System under Turbulent Conditions Using Various Models

Telecommunications occupying the major part of research across the world, has become a part and parcel of present day human’s life. As a part of research many new technologies emerged among which free space optics was found to be highly efficient and a competent technology. So, replacing the present microwave communications, in future free space optics provides many advantages like higher bandwidth, higher data rate (capable of sending up to 1.25 Gbps of data, voice, and video communications simultaneously through the air), low bit error rate and license free long-range communications etc. As a known fact that every coin has two sides, free space optics besides providing the above advantages also suffers from many range limiting factors like fog, beam dispersion, atmospheric absorption, rain attenuation, snow, terrestrial scintillation amongst which rain, scintillation and fog are popular in tropical regions like India. In this paper the effect of rain on FSO link is analysed in 1/1 and 4/4 channel cases and the results were analysed.