Search results
Results from the WOW.Com Content Network
A typical parabolic antenna consists of a metal parabolic reflector with a small feed antenna suspended in front of the reflector at its focus, pointed back toward the reflector. [ 2 ] [ 3 ] The reflector is a metallic surface formed into a paraboloid of revolution and usually truncated in a circular rim that forms the diameter of the antenna ...
The half-power beamwidth of the main beam is 2 × Ψ 0. Preferably, when using amplitude comparison methods for direction finding, the main lobe should approximate to a Gaussian characteristic. Although the figure also shows the presence of sidelobes, these are not a major concern when antennas are used in a DF array.
The half-power point is the angle off boresight at which the antenna gain first falls to half power (approximately −3 dB) [a] from the peak. The angle between the −3 dB points is known as the half-power beam width (or simply beam width). [4] Beamwidth is usually but not always expressed in degrees and for the horizontal plane.
The beam solid angle can be approximated for antennas with one narrow major lobe and very negligible minor lobes by simply multiplying the half-power beamwidths (in radians) in two perpendicular planes. The half-power beamwidth is simply the angle in which the radiation intensity is at least half of the peak radiation intensity.
A helical antenna is an antenna consisting of one or more conducting wires wound in the form of a helix.A helical antenna made of one helical wire, the most common type, is called monofilar, while antennas with two or four wires in a helix are called bifilar, or quadrifilar, respectively.
A type of antenna that combines a horn with a parabolic reflector is known as a Hogg-horn, or horn-reflector antenna, invented by Alfred C. Beck and Harald T. Friis in 1941 [20] and further developed by David C. Hogg at Bell Labs in 1961. [21] It is also referred to as the "sugar scoop" due to its characteristic shape.
The most widely used high gain antenna at microwave frequencies and above. Consists of a dish-shaped metal parabolic reflector with a feed antenna at the focus. It can have some of the highest gains of any antenna type, up to 60 dBi, but the dish must be large compared to a wavelength.
Two Yagi–Uda antennas on a single mast. The top one includes a corner reflector and three stacked Yagis fed in phase in order to increase gain in the horizontal direction (by cancelling power radiated toward the ground or sky). The lower antenna is oriented for vertical polarization, with a much lower resonant frequency.