Electromagnetic Characteristics of Yagi-Uda Antenna at HF/VHF/UHF

2018 ◽  
Vol 3 (2) ◽  
pp. 7-11
Author(s):  
Raji A. Abimbola
Keyword(s):  
Electric Field ◽  
Method Of Moments ◽  
Current Distribution ◽  
High Frequency ◽  
Very High Frequency ◽  
Radiation Characteristics ◽  
Radiation Beam ◽  
Field Patterns ◽  
Electromagnetic Characteristics ◽  
Very High

In this paper, the radiation characteristics of Yagi-Uda antenna operating at High Frequency (HF), Very High Frequency (VHF) and Ultra High Frequency (UHF) are examined. Upon employing method of moments, the current distribution on the antenna emerges from the solution of matrix equation. It is found that the angular distribution of electric field intensity generated in free space by the antenna, obtained by evaluating the integral of associated current distribution, is characterized by patterns with significant portion of radiation beam in the main lobe in the direction of Yagi axis. This is accompanied by relatively small undesirable radiation in the minor lobe, and which persist over those communication frequencies. It is observed also that the current distribution that generates the radiated electric field patterns is relatively consistent over the same range of frequency.

Influence of select discharge parameters on electric field transients triggered in collisionless very high frequency capacitive discharges

2019 ◽  
Vol 26 (10) ◽  
pp. 103508 ◽  
Author(s):  
Sarveshwar Sharma ◽  
Nishant Sirse ◽  
Abhijit Sen ◽  
Miles M. Turner ◽  
Albert R. Ellingboe
Keyword(s):  
Electric Field ◽  
High Frequency ◽  
Very High Frequency ◽  
Discharge Parameters ◽  
Capacitive Discharges ◽  
Very High

Kinetic theory of very high-frequency and high-pressure continuous atomic discharges

1995 ◽  
Vol 54 (3) ◽  
pp. 309-332
Author(s):  
N. Peyraud-Cuenca ◽  
P. Faucher
Keyword(s):  
High Pressure ◽  
Electric Field ◽  
High Frequency ◽  
Electron Distribution Function ◽  
Very High Frequency ◽  
High Frequency Electric Field ◽  
Analytical Approaches ◽  
Very High ◽  
Stationary Electron ◽  
Good Agreement

We derive the analytical solution of the Boltzmann equation for the stationary electron distribution function that is reached in a plasma generated on the application of a uniform very high-frequency electric field in an atomic gas. The theory includes all excitation transitions: ionization and electronic transitions. The analytic solution is also extended to continuous discharges with low electric field or high pressure in the gas. Then the electron rate coefficient for excitation of the first state (which is the most significant) is calculated analytically. We apply the results to the modelling of very high-frequency argon discharges and to high-pressure continuous discharges in argon and in sodium. The results are compared with numerical results of Ferreira and co-workers for argon and of LaVerne for sodium: in both cases we find good agreement between numerical and analytical approaches.

scholarly journals Flexible Magnetic Polymer Composite Substrate with Ba1.5Sr1.5Z Hexaferrite Particles of VHF/Low UHF Patch Antennas for UAVs and Medical Implant Devices

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1021
Author(s):  
Sang-Eui Lee ◽  
Seong Pil Choi ◽  
Kyung-Sub Oh ◽  
Jaehwan Kim ◽  
Sang Min Lee ◽  
...  
Keyword(s):  
Unmanned Aerial Vehicles ◽  
Medical Devices ◽  
High Frequency ◽  
Zero Order ◽  
Patch Antennas ◽  
Very High Frequency ◽  
Order Analysis ◽  
Composite Substrate ◽  
Electromagnetic Characteristics ◽  
Very High

Our goal is to fabricate flexible magnetic polymer composites as antenna substrates for very high frequency (VHF)/low ultra high frequency (UHF) antennas for unmanned aerial vehicles (UAVs) and medical devices. Magnetodielectric materials, which have permeability (μ) similar to permittivity (ε), have attracted great attention, because they facilitate miniaturization of microwave devices while keeping or enhancing electromagnetic characteristics. Mechanically millled Ba1.5Sr1.5Co2Fe24O41 (Ba1.5Sr1.5Z) hexaferrite particles were used to increase permeability in the interesting frequency band. The microwave properties of Ba1.5Sr1.5Z composites were predicted and measured. Hansen’s zero-order analysis of antenna bandwidth and electromagnetic field simulation showed that the hexaferrite-based flexible composite could enhance a bandwidth and achieve the miniaturization of antennas as well. The magnetic antenna substrates can be a good solution to integrate antennas into the UAVs whose dimensions are comparable to or larger than communication wavelength.

Experimental Investigation of very High Frequency Slot Antenna on M-60A-1 Tank

1977 ◽  
Author(s):  
D. V. Campbell ◽  
William Kennebeck ◽  
A. Zanella ◽  
Paul Sexton
Keyword(s):  
Experimental Investigation ◽  
High Frequency ◽  
Slot Antenna ◽  
Very High Frequency ◽  
Very High

A collision feedback based multiple access control protocol for very high frequency data exchange system in E-navigation

2021 ◽  
pp. 1-16
Author(s):  
Xu Hu ◽  
Bin Lin ◽  
Ping Wang ◽  
Hongguang Lyu ◽  
Tie-Shan Li
Keyword(s):  
Access Control ◽  
High Frequency ◽  
Multiple Access ◽  
Data Exchange ◽  
High Frequency Data ◽  
Frequency Data ◽  
Exchange System ◽  
Very High Frequency ◽  
Time Division ◽  
Very High

Abstract The very high frequency data exchange system (VDES) is promising in promoting electronic navigation (E-navigation) and improving navigation safety. The multiple access control (MAC) protocol is crucial to the transmission performance of VDES. The self-organising time division multiple access (SOTDMA) protocol, as the only access mode given by current recommendations, leads to a high rate of transmission collisions in the traditional automatic identification system (AIS), especially with heavy traffic loads. This paper proposes a novel feedback based time division multiple access (FBTDMA) protocol to address the problems caused by SOTDMA, such that collision of transmissions can be avoided in information transmission among vessels. Simulation results demonstrate that the proposed FBTDMA outperforms the traditional SOTDMA in terms of channel utilisation and throughput, and significantly reduces the transmission collision rate. The study is expected to provide insights into VDES standardisation and E-navigation modernisation.

scholarly journals Measurement of Electrical Properties of Superconducting YBCO Thin Films in the VHF Range

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3360
Author(s):  
Yakir Dahan ◽  
Eldad Holdengreber ◽  
Elichai Glassner ◽  
Oz Sorkin ◽  
Shmuel E. Schacham ◽  
...  
Keyword(s):  
Thin Films ◽  
Theoretical Model ◽  
Quality Factor ◽  
High Frequency ◽  
Unit Length ◽  
Superconducting Thin Films ◽  
Electrical Parameters ◽  
Very High Frequency ◽  
Production Constraints ◽  
Very High

A new measurement technique of electrical parameters of superconducting thin films at the Very High Frequency (VHF) range is described, based on resonators with microstrip (MS) structures. The design of an optimal resonator was achieved, based on a thorough theoretical analysis, which is required for derivation of the exact configuration of the MS. A theoretical model is presented, from which an expression for the attenuation of a MS line can be derived. Accordingly, simulations were performed, and an optimal resonator for the VHF range was designed and implemented. Production constraints of YBa2Cu3O7 (YBCO) limited the diameter of the sapphire substrate to 3″. Therefore, a meander configuration was formed to fit the long λ/4 MS line on the wafer. By measuring the complex input reflection coefficients of a λ/4 resonator, we extracted the quality factor, which is mainly affected by the dielectric and conductor attenuations. The experimental results are well fitted by the theoretical model. The dielectric attenuation was calculated using the quasi-static analysis of the MS line. An identical copper resonator was produced and measured to compare the properties of the YBCO resonator in reference to the copper one. A quality factor of ~6·105 was calculated for the YBCO resonator, three orders of magnitude larger than that of the copper resonator. The attenuation per unit length of the YBCO layer was smaller by more than five orders of magnitude than that of the copper.

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