Relations between radiation characteristics of small antennas located in free space and close to lossy phantom

2006 ◽  
Author(s):  
V. Tavakol ◽  
P.-S. Kildal
Keyword(s):  
Free Space ◽  
Radiation Characteristics ◽  
Small Antennas

Introducing the new wideband small plate antennas with engraved voids to form new geometries based on CRLH MTM-TLs for wireless applications

2014 ◽  
Vol 6 (6) ◽  
pp. 629-637 ◽  
Author(s):  
Mohammad Alibakhshi
Keyword(s):  
Transmission Line ◽  
Free Space ◽  
Model Parameters ◽  
Transmission Line Model ◽  
Physical Size ◽  
Wireless Applications ◽  
Small Antennas ◽  
Left Handed ◽  
Unit Cells ◽  
Operational Frequency

In this paper, four new wideband small antennas based on the composite right/left-handed transmission line (CRLH-TL) structures are designed, tooled, and made. The proposed antennas are introduced with best in size, bandwidth, and radiation patterns. The physical size and the operational frequency of the antennas depend on size of the unit cells and the equivalent transmission line model parameters of the CRLH-TLs, including series inductance, series capacitance, shunt inductance, and shunt capacitance. To define characteristics of the antennas, the engraved J- and I-formed voids on the radiation patches are used. The physical sizes of the CRLH antennas are 0.45λ0 × 0.175λ0 × 0.02λ0, 0.428λ0 × 0.179λ0 × 0.041λ0, 0. 564λ0 × 0.175λ0 × 0.02λ0, and 0.556λ0 × 0.179λ0 × 0.041λ0 in terms of free-space wavelengths at the 7.5, 7.7, 7.5, and 7.7 GHz, respectively. These metamaterial antennas can be used for frequency bands from 7.5–16.8 GHz, 7.7–18.6 GHz, 7.25–17.8 GHz, and 7.8–19.85 GHz for VSWR < 2, which correspond to 74.4, 82.88, 84.23, and 87.16% practical bandwidths, respectively. Also, the ranges of the measured gains and radiation efficiencies of the recommended antennas are 0.1 dBi < G < 2.1 dBi and 20% < eff < 44.3%, and 0.8 dBi < G < 2.35 dBi and 23% < eff < 48.2%, for J-shaped antennas, whereas 0.1.15 dBi < G < 3.11 dBi and 30.24% < eff < 58.6%, and 1.2 dBi < G < 3.4 dBi and 32.4% < eff < 68.1% for I-shaped antennas, respectively.

scholarly journals Magnetic Pendulum Arrays for Efficient ULF Transmission

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Srinivas Prasad M N ◽  
Rustu Umut Tok ◽  
Foad Fereidoony ◽  
Yuanxun Ethan Wang ◽  
Rui Zhu ◽  
...  
Keyword(s):  
Quality Factor ◽  
Free Space ◽  
Low Frequency ◽  
Transmission Efficiency ◽  
Experimental Results ◽  
Proof Of Concept ◽  
Electrically Small Antennas ◽  
Fundamental Limits ◽  
Small Antennas ◽  
Order Of Magnitude

Abstract The frequencies lying between 300 Hz to 3 kHz have been designated as Ultra Low Frequency (ULF) with corresponding wavelengths from 1000 Km to 100 Km. Although ULF has very low bandwidth it is very reliable, penetrating and difficult to jam which makes it a great choice for communication in underwater and underground environments. Small and portable ULF antennas within a diameter of 1 meter would operate under an electrical length on the order of 10−4 to 10−6 wavelengths in free space, making them very inefficient because of fundamental limits on radiation from electrically small antennas. To overcome this problem, Mechanical Antennas or ‘Mechtennas’ for Ultra Low Frequency Communications have been proposed recently. For efficient generation of ULF radiation, we propose a portable electromechanical system called a Magnetic Pendulum Array (MPA). A proof of concept demonstration of the system at 1.03 kHz is presented. The theory and experimental results demonstrate that such a system can achieve a significantly higher quality factor than conventional coils and thus order of magnitude higher transmission efficiency. The concept can be easily scaled to the ULF range of frequencies.

scholarly journals A Low Profile Ultrawide Band Monopole Antenna for Wearable Applications

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Srinivas Doddipalli ◽  
Ashwin Kothari ◽  
Paritosh Peshwe
Keyword(s):  
Free Space ◽  
Specific Absorption Rate ◽  
Monopole Antenna ◽  
Human Tissues ◽  
Radiation Characteristics ◽  
Wide Bandwidth ◽  
Overall Design ◽  
Antenna Performance ◽  
Low Profile ◽  
The Impact

A low profile pentagonal shaped monopole antenna is designed and presented for wearable applications. The main objective of this paper is to design a miniaturized ultrawide band monopole planar antenna which can work efficiently in free space but also on the surface of the human body. The impact of human tissues on antenna performance is explained using the proposed pentagonal monopole antenna. The antenna is designed with a pentagonal radiator and a matched feed line of 50 ohm and square slots are integrated on defected ground of FR4 substrate with a size of 15 mm × 25 mm to achieve ultrawide band (UWB) performance in free space and human proximity. This overall design will enhance the antenna performance with wide bandwidth ranging from 2.9 GHz to 11 GHz. Specific absorption rate (SAR) of the proposed antenna on dispersive phantom model is also measured to observe the exposure of electromagnetic energy on human tissues. The simulated and measured results of the proposed antenna exhibit wide bandwidth and radiation characteristics in both free space and human proximity.

scholarly journals On the Effects of Balun on Small Antennas Performance for Animal Health- Monitoring and Tracking

2021 ◽  
Vol 10 (2) ◽  
pp. 39-43
Author(s):  
A. Alemaryeen ◽  
S. Noghanian
Keyword(s):  
Health Monitoring ◽  
Free Space ◽  
Animal Health ◽  
Antenna Design ◽  
Impedance Match ◽  
Wildlife Health ◽  
Small Antennas ◽  
Flexible Loop ◽  
Measurement Results ◽  
Bandwidth Characteristic

This paper presents the performance evaluation of a sleeve Balun integration in the design of a flexible loop antenna for wildlife health monitoring and tracking applications. To verify the design concept, an experimental antenna is designed, fabricated, and measured in free-space and muscle mimicking phantom. Moreover, investigations are carried out for wearable and implanted antennas in planar and conformal arrangements. In free-space, the antenna is operating within the industrial, scientific, and medical ISM 5.8 GHz band. Balun integration in the antenna design efficiently chokes the currents excited on the outer surface of the feeding cable and provides a good impedance match between antenna and feed line, as demonstrated by simulation and measurement results. On the other hand, in phantom, the antenna has a wide bandwidth characteristic that covers the most used frequency bands for in-body devices. Balun integration, in this case, showed a negligible effect on antenna’s matching properties for two studied implantation depths; 2.5 cm and 5 cm.  The proposed study offers a promising guideline in the design and realization of wearable and implanted antennas.

EFFECT OF ION SHEATH ON RADIATION IN A MAGNETOIONIC MEDIUM: I. SOURCE CURRENT PARALLEL TO THE MAGNETOSTATIC FIELD

1966 ◽  
Vol 44 (7) ◽  
pp. 1401-1418
Author(s):  
S. R. Seshadri ◽  
K. L. Bhatnagar
Keyword(s):  
Point Source ◽  
Electric Current ◽  
Finite Length ◽  
Current Distribution ◽  
Radiation Resistance ◽  
Free Space ◽  
Sheath Thickness ◽  
Radiation Characteristics ◽  
Magnetostatic Field ◽  
Source Current

The radiation characteristics of an axially oriented point source of electric current and a filament of finite length with a triangular current distribution are treated for the case in which these sources are situated at the center of an infinite cylindrical column of free space and surrounded by a homogeneous, loss-free magnetoionic medium. The direction of the magnetostatic field is assumed to be parallel to the axis of the free-space column which is an idealization for the geometry of the ion sheath formed around the antenna in the ionosphere. The dependence of the radiation resistance of these sources on the frequency and the ion-sheath thickness is examined. It is found that, within the framework of the classical magnetoionic theory, the radiation resistance of even a point source of electric current remains finite for all frequencies, provided the ion-sheath effects are included. Also the radiation resistance of a finite-length filament with a triangular current distribution is found to be insensitive to the changes in the thickness of the ion sheath. This result is in conformity with the experimental observations, which indicate no data variations correlated with the changes in the thickness of the ion sheath.

RADIATION FROM A PHASED LINE SOURCE IN A MAGNETOIONIC MEDIUM

1965 ◽  
Vol 43 (9) ◽  
pp. 1636-1648
Author(s):  
H. S. Tuan ◽  
S. R. Seshadri
Keyword(s):  
Electric Current ◽  
Current Distribution ◽  
Free Space ◽  
Line Source ◽  
Propagation Constant ◽  
Electron Plasma ◽  
Radiation Characteristics ◽  
Magnetostatic Field ◽  
Phase Constant ◽  
Special Case

The radiation characteristics of a phased line source of electric current immersed in a magnetoionic medium are analyzed. The line source is assumed to be parallel to the direction of the external magnetostatic field and the phase constant for the current distribution is assumed to be given by k0/β, where k0 is the propagation constant of free space and β is a dimensionless phase parameter. In general, it is found that two modes are excited. The frequency ranges of propagation of these so-called ordinary and extraordinary modes are examined by means of a construction in the Ω2–R2 parameter space for the case [Formula: see text], where Ω = ω/ωp, R = ωc/ωp, and ω, ωp and ωc are the source, the electron plasma, and the gyromagnetic frequency respectively. The dispersion relations and the frequency spectrum are evaluated. It is found that β = 1 is a special case for which only one mode is excited.

Measurement of free-space impedances of small antennas in reverberation chambers

2001 ◽  
Vol 32 (2) ◽  
pp. 112-115 ◽  
Author(s):  
Per-Simon Kildal ◽  
Charlie Carlsson ◽  
Jian Yang
Keyword(s):  
Free Space ◽  
Small Antennas ◽  
Reverberation Chambers

scholarly journals A Wideband Reflector-Backed Antenna for Applications in GPR

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
A. Raza ◽  
W. Lin ◽  
M. K. Ishfaq ◽  
M. Inam ◽  
F. Masud ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Patch Antenna ◽  
Free Space ◽  
Periodic Array ◽  
Radiation Characteristics ◽  
Wide Bandwidth ◽  
Reflective Surface ◽  
Compact Size ◽  
Ground Penetrating ◽  
Peak Gain

A resistively loaded wideband slotted patch antenna with optimized performance on lower frequencies is proposed for ground-penetrating radar (GPR) applications. The proposed design is backed by an optimized reflector composed of a periodic array of square loop elements, which enhances the antenna’s gain and directivity. The antenna shows good radiation characteristics and ease of integration with the GPR systems. The proposed structure features a compact size and wide bandwidth covering from 0.6 to 4.6 GHz. The peak gain of 7 dBi is achieved. The fabricated prototype of the antenna along with an integrated optimized reflective surface has overall dimensions of 18 × 22 × 5 cm3. The measured results validate the antenna’s performance in both free space and sandy medium, which enlighten its use for GPR applications.

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