Lower frequency bands emerging as valid alternatives to free-space lasercom in terrestrial, aerial, and satellite links

2019 ◽  
Author(s):  
Hamid Hemmati
Keyword(s):  
Free Space ◽  
Frequency Bands ◽  
Satellite Links

scholarly journals Controlling Refraction Using Sub-Wavelength Resonators

2018 ◽  
Vol 8 (10) ◽  
pp. 1942
Author(s):  
Yue Chen ◽  
Robert Lipton
Keyword(s):  
Frequency Dependence ◽  
Free Space ◽  
Near Infrared ◽  
Center Frequency ◽  
Negative Index ◽  
Index Properties ◽  
Frequency Bands ◽  
Transmitted Signal ◽  
Sub Wavelength

We construct metamaterials from sub-wavelength nonmagnetic resonators and consider the refraction of incoming signals traveling from free space into the metamaterial. We show that the direction of the transmitted signal is a function of its center frequency and bandwidth. The directionality of the transmitted signal and its frequency dependence is shown to be explicitly controlled by sub-wavelength resonances that can be calculated from the geometry of the sub-wavelength scatters. We outline how to construct a medium with both positive and negative index properties across different frequency bands in the near infrared and optical regime.

scholarly journals Spectral characteristics of satellite links at ka band in the southern tropical region of India

2017 ◽  
Vol 7 (1.1) ◽  
pp. 631
Author(s):  
Sravya Velaga ◽  
Jagadeesh Korrapati ◽  
Chaithanya Krishna B ◽  
Vandana Matti ◽  
K Ch. Sri Kavya ◽  
...  
Keyword(s):  
High Frequency ◽  
Spectral Characteristics ◽  
Low Frequency ◽  
Radiowave Propagation ◽  
Tropical Region ◽  
Multimedia Services ◽  
System Availability ◽  
Ka Band ◽  
Frequency Bands ◽  
Satellite Links

The objective of this study was to perform a spectral analysis of the Ka band propagation channel. Now a day, because of the expanding interest of the end users for multimedia services which require vast bandwidth, and because of the immersion of low frequency bands, for example, L, S, C bands, and Ku band in close future, satellite media transmission systems are moving to higher frequency bands. In such high frequency bands, the presence of the atmosphere strongly affects radiowave propagation and attenuation effects become so severe that system availability would not be sufficient if systems were designed in a conventional way with a static propagation margin. 

scholarly journals A Dual-Band Base Station Antenna with a Split Ring for Sub-6 GHz Communication

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Bei Huang ◽  
Jie Cao ◽  
Weifeng Lin ◽  
Jun Zhang ◽  
Gary Zhang ◽  
...  
Keyword(s):  
Frequency Band ◽  
Free Space ◽  
Base Station ◽  
Dual Band ◽  
Operating Frequency ◽  
Impedance Bandwidth ◽  
Dual Polarization ◽  
Split Ring ◽  
Average Gain ◽  
Frequency Bands

A dual-band base station antenna is introduced in this paper. The proposed antenna is composed of baluns, bowtie patches, and a split ring. The two pairs of bowtie patches excited by the two orthogonal balun structures can achieve dual polarization. The split ring is used to yield two additional resonances to broaden the impedance bandwidth. In this way, a compact dual-band base station antenna is obtained with the size of 0.41 λc × 0.41 λc × 0.13 λc (λc is the wavelength in the free space at the lowest operating frequency band) and the average gain of 8.2 dBi. Moreover, the operating frequency bands of the proposed antenna cover 2515–2675 MHz, 3400–3600 MHz, and 4800–5000 MHz, which can function as an element for macro- or microcells in sub-6 GHz communications.

scholarly journals Low-altitude frequency-banded equatorial emissions observed below the electron cyclotron frequency

2020 ◽  
Vol 38 (3) ◽  
pp. 765-774
Author(s):  
Mohammed Y. Boudjada ◽  
Patrick H. M. Galopeau ◽  
Sami Sawas ◽  
Valery Denisenko ◽  
Konrad Schwingenschuh ◽  
...  
Keyword(s):  
Equatorial Plane ◽  
Free Space ◽  
Cyclotron Frequency ◽  
Power Level ◽  
Source Region ◽  
Electron Cyclotron ◽  
Frequency Bands ◽  
Electron Cyclotron Frequency ◽  
Electro Magnetic ◽  
In The Beginning

Abstract. The ICE (Instrument Champ Électrique) experiment on board the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite recorded frequency-banded wave emissions below the electron cyclotron frequency, with band spacing ≳ frequency low-hybrid resonance, in the vicinity of the magnetic equatorial plane. Those radiations were observed in the beginning of the year 2010 on the night side of Earth and rarely on the day side. We distinguish two components: one appears as frequency bands continuous in time between a few kilohertz and up to 50 kHz, and the other one is from 50 to 800 kHz. The first component exhibits positive and negative frequency drift rates in the Southern Hemisphere and Northern Hemisphere, at latitudes between 40 and 20∘. The second one displays multiple spaced frequency bands. Such bands mainly occur near the magnetic equatorial plane with a particular enhancement of the power level when the satellite latitude is close to the magnetic equatorial plane. We show in this study the similarities and the discrepancies between the non-free-space DEMETER frequency-banded emissions and the well-known free-space terrestrial kilometric radiation. The hollow cones of the DEMETER frequency-banded wave emissions are oriented towards Earth's ionosphere. We suggest that the source region is localized in regions poleward of the plasmapause where the ratio of the plasma frequency to gyro-frequency is smaller than one.

scholarly journals Radio Propagation Measurements in the Indoor Stairwell Environment at 3.5 and 28 GHz for 5G Wireless Networks

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Ahmed Al-Saman ◽  
Marshed Mohamed ◽  
Michael Cheffena
Keyword(s):  
Wireless Networks ◽  
Free Space ◽  
Path Loss ◽  
Access Point ◽  
Decay Rates ◽  
Radio Propagation ◽  
Cluster Decay ◽  
Delay Spread ◽  
Frequency Bands ◽  
Reference Distance

To cover the high demand for wireless data services for different applications in the wireless networks, different frequency bands below 6 GHz and in millimeter-wave (mm-Wave) above 24 GHz are proposed for the fifth generation (5G) of communication. The communication network is supposed to handle, among others, indoor traffic in normal situations as well as during emergencies. The stairway is one of those areas which has less network traffic during normal conditions but increases significantly during emergencies. This paper presents the radio propagation in an indoor stairway environment based on wideband measurements in the line of sight (LOS) at two candidate frequencies for 5G wireless networks, namely, 3.5 GHz and 28 GHz. The path loss, root mean square (RMS) delay spread, K-factor results, and analysis are provided. The close-in free-space reference distance (CI), floating intercept (FI), and the close-in free-space reference distance with frequency weighting (CIF) path loss models are provided. The channel parameters such as the number of clusters, the ray and cluster arrival rates, and the ray and cluster decay factors are also obtained for both frequencies. The findings of the path loss show that the CI, FI, and CIF models fit the measured data well in both frequencies with the path loss exponent identical to the free-space path loss. Based on clustering results, it is found that the cluster decay rates are identical at both bands. The results from this and previous measurements indicate that at least one access point is required for every two sections of the stairway to support good coverage along the stairwell area in 5G wireless networks. Moreover, for 5G systems utilizing mm-Wave frequency bands, one access point for each stair section might be necessary for increased reliability of the 5G network in stairwell environments.

Synthesis of Electromagnetic Pulses with Different Frequency Bands in Free Space

2020 ◽  
Vol 65 (5) ◽  
pp. 480-494 ◽  
Author(s):  
A. M. Efremov ◽  
V. I. Koshelev ◽  
V. V. Plisko
Keyword(s):  
Free Space ◽  
Electromagnetic Pulses ◽  
Frequency Bands

scholarly journals Novel High-Speed Polarization Source for Decoy-State BB84 Quantum Key Distribution Over Free Space and Satellite Links

2013 ◽  
Vol 31 (9) ◽  
pp. 1399-1408 ◽  
Author(s):  
Zhizhong Yan ◽  
Evan Meyer-Scott ◽  
Jean-Philippe Bourgoin ◽  
Brendon L. Higgins ◽  
Nikolay Gigov ◽  
...  
Keyword(s):  
Free Space ◽  
Quantum Key Distribution ◽  
High Speed ◽  
Key Distribution ◽  
Decoy State ◽  
Satellite Links
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