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The rhombic antenna was designed in 1931 by Edmond Bruce [1] and Harald Friis, [2] [3] It was mostly commonly used in the high frequency (HF) or shortwave band as a broadband directional antenna. As of 2023, one last remnant pole still stands from the AT&T pole farm which was located in Mercer County, New Jersey
In most antennas, the radiation from the different parts of the antenna interferes at some angles; the radiation pattern of the antenna can be considered an interference pattern. This results in minimum or zero radiation at certain angles where the radio waves from the different parts arrive out of phase , and local maxima of radiation at other ...
The rhombic is a travelling wave antenna, Each segment of the rhombus has a radiation pattern as shown (grey) having two lobes pointed forward at a certain angle. By making the corner angle equal to twice the tilt angle, the main lobes of each of the 4 sides point in the same direction and reinforce each other, increasing the gain.
Antenna directivity is the ratio of maximum radiation intensity (power per unit surface) radiated by the antenna in the maximum direction divided by the intensity radiated by a hypothetical isotropic antenna radiating the same total power as that antenna. For example, a hypothetical antenna which had a radiated pattern of a hemisphere (1/2 ...
Radiant intensity is used to characterize the emission of radiation by an antenna: [2], = (), where E e is the irradiance of the antenna;; r is the distance from the antenna.; Unlike power density, radiant intensity does not depend on distance: because radiant intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is ...
The first experiments using lenses to refract and focus radio waves occurred during the earliest research on radio waves in the 1890s. In 1873 mathematical physicist James Clerk Maxwell in his electromagnetic theory, now called Maxwell's equations, predicted the existence of electromagnetic waves and proposed that light consisted of electromagnetic waves of very short wavelength.
However, that radiation is unpolarized, whereas the antenna is only sensitive to one polarization, reducing it by a factor of 2. To find the total power from black-body radiation accepted by the antenna, we must integrate that quantity times the assumed cross-sectional area A eff of the antenna over all solid angles Ω and over all frequencies f:
Radiation resistance is instead calculated by computing the far-field radiation pattern of the antenna, the power flux (Poynting vector) at each angle, for a given antenna current. [23] This is integrated over a sphere enclosing the antenna to give the total power P r a d {\displaystyle \ P_{\mathsf {rad}}\ } radiated by the antenna.