Search results
Results from the WOW.Com Content Network
So the element has a node of the current standing wave at both top and bottom, it is equivalent to an end-fed vertical dipole antenna (so some sources do not call this antenna a monopole [65]). The resonant frequencies can be calculated by a derivation similar to that in the previous section, but it is easier to note that a standing wave has a ...
Paradoxically, every antenna of any type, shorter than ~ 1 / 10 wave in its longest dimension is approximately isotropic, but no real antenna can ever be exactly isotropic. An antenna that is exactly isotropic is only a mathematical model , used as the base of comparison to calculate either the directivity or gain of real antennas.
The length of a whip antenna is determined by the wavelength of the radio waves it is used with. Their length varies from compact electrically short antennas 1 / 10 wavelength long, up to 5 / 8 wavelength to improve directivity. The most common type is the quarter-wave whip, which is approximately 1 / 4 wavelength long.
Mode conversion occurs when a wave encounters an interface between materials of different impedances and the incident angle is not normal to the interface. [1] Thus, for example, if a longitudinal wave from a fluid (e.g., water or air) strikes a solid (e.g., steel plate), it is usually refracted and reflected as a function of the angle of incidence, but if some of the energy causes particle ...
The difference between EIRP and ERP is that ERP compares the actual antenna to a half-wave dipole antenna, while EIRP compares it to a theoretical isotropic antenna. Since a half-wave dipole antenna has a gain of 1.64 (or 2.15 dB) compared to an isotropic radiator, if ERP and EIRP are expressed in watts their relation is = If they are expressed ...
The first technique developed was the far-field range, where the antenna under test (AUT) is placed in the far-field of a range antenna. Due to the size required to create a far-field range for large antennas, near-field techniques were developed, which allow the measurement of the field on a distance close to the antenna (typically 3 to 10 ...
Typical feeder loops are 1 / 8 to 1 / 5 the size of the antenna's main loop, which gives transform ratios of 64:1 to 25:1, respectively. Adjusting the proximity and angle of the feeder loop to the main loop, and distorting the feeder's shape, both make small-to-moderate changes to the transform ratio, and allows for fine ...
2.4 GHz helical antenna radiation pattern (NEC simulation) The Numerical Electromagnetics Code, or NEC, is a popular antenna modeling computer program for wire and surface antennas. It was originally written in FORTRAN during the 1970s by Gerald Burke and Andrew Poggio of the Lawrence Livermore National Laboratory. The code was made publicly ...