Input impedance approximations for small dipole and loop antennas near ground

1970 ◽  
Vol 48 (9) ◽  
pp. 1036-1039 ◽  
Author(s):  
L. E. Vogler
Keyword(s):  
Exact Solution ◽  
Refractive Index ◽  
Input Impedance ◽  
Ground Plane ◽  
Small Dipole ◽  
Loop Antennas ◽  
Approximate Expressions

Approximate expressions for the input impedances of small vertical and horizontal dipole and loop antennas above a conducting ground plane are developed. The formulas give increasingly accurate impedance estimates as [Formula: see text], where N is the refractive index of the ground. A comparison with the exact solution for a specific case, [Formula: see text] and varying antenna heights, is given.

scholarly journals Impedance Matching of Axial Mode Helical Antennas

2021 ◽  
Vol 20 ◽  
pp. 66-69
Author(s):  
Hossein Mardani ◽  
Neil Buchanan ◽  
Robert Cahill ◽  
Vincent Fusco
Keyword(s):  
Input Impedance ◽  
Impedance Matching ◽  
Ground Plane ◽  
Center Frequency ◽  
Design Parameters ◽  
Axial Mode ◽  
Impedance Characteristics ◽  
Measurement Results ◽  
Line Theory ◽  
Helical Antennas

In this paper, we study the input impedance characteristics of axial mode helical antennas to find an effective way for matching it to 50 Ω. The study is done on the important matching parameters such as like wire diameter and helix to the ground plane gap. It is intended that these parameters control the matching without detrimentally affecting the radiation pattern. Using transmission line theory, a simple broadband technique is proposed, which is applicable for perfect matching of antennas with similar design parameters. We provide design curves to help to choose the proper dimensions of the matching section based on the antenna’s unmatched input impedance. Finally, using the proposed technique, a 4-turn axial mode helix is designed at 2.5 GHz center frequency and the measurement results of the manufactured antenna will be included. This parametric study gives a good insight into the input impedance characteristics of axial mode helical antennas and the proposed impedance matching approach provides a simple, useful method for matching these types of antennas.

Load-Supporting Fluid-Filled Cylindrical Membranes

1985 ◽  
Vol 52 (4) ◽  
pp. 913-918 ◽  
Author(s):  
V. Namias
Keyword(s):  
Differential Equation ◽  
Exact Solution ◽  
Analytical Solution ◽  
Boundary Conditions ◽  
Nonlinear Differential Equation ◽  
Entire Range ◽  
Exact Analytical Solution ◽  
Asymptotic Expressions ◽  
Flexible Membranes ◽  
Approximate Expressions

When long cylindrical flexible membranes are filled with a fluid and used to support external weights, the shape they assume and the relevant geometrical and dynamical quantities are governed by a nonlinear differential equation subject to particular boundary conditions. First, a complete and exact analytical solution is obtained for an unloaded membrane. Very accurate approximate expressions are derived directly from the exact solution for the entire range of applied pressures and fluid densities. Next, the nonlinear differential equation is solved exactly under boundary conditions corresponding to the loading of the membrane. Simple asymptotic expressions are also obtained in the limit of large loads.

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