Experimental investigation of the input-impedance characteristics of an antenna in a rectangular waveguide

1969 ◽  
Vol 5 (21) ◽  
pp. 513 ◽  
Author(s):  
M.J. Al-Hakkak
Keyword(s):  
Experimental Investigation ◽  
Input Impedance ◽  
Rectangular Waveguide ◽  
Impedance Characteristics

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.

scholarly journals Input Impedance Analysis of Wearable Antenna and Experimental Study with Real Human Subjects: Differences between Individual Users

Electronics ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1152
Author(s):  
Dairoku Muramatsu ◽  
Ken Sasaki
Keyword(s):  
Human Body ◽  
Input Impedance ◽  
Human Subjects ◽  
Impedance Analysis ◽  
The Body ◽  
Design Parameters ◽  
Moisture Condition ◽  
Wearable Antenna ◽  
Body Tissues ◽  
Impedance Characteristics

In human body communication (HBC) systems, radio-frequency signals are excited in the human body through a wearable antenna comprised of electrodes that are in contact with the surface of the body. The input impedance characteristics of these antennas are important design parameters for increasing transmission efficiency and reducing signal reflection, similar to other wireless circuits. In this study, we discuss variations of input impedance characteristics of a wearable antenna prototype caused by differences among real human subjects. A realistic human arm model is used for simulations, and the analytical results obtained are compared to measured data obtained from real human subjects, in a range from 1 to 100 MHz. The simulations of input impedance characteristics from antennas worn on the wrists of male and female models with dry and wet skin conditions show that the impedance variation between genders is small. The moisture condition of the skin has little influence on frequencies exceeding several MHz. Measurements with a proto-type wearable antenna and 22 real human subjects reveal that HBC is robust against the variations of individual users from the viewpoint of the voltage standing wave ratio. Moreover, a simplified rectangular prism model is proposed to analyze the thickness of body tissues. Comparisons of measured input impedances indicate that individual differences in impedance are mainly due to differences in the thickness of skin and fat layers. The model also enables us to design the antenna prototype without multiple subject experiments.

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