Search results
Results from the WOW.Com Content Network
Conceptually, it is the number of half-period zones in the wavefront amplitude, counted from the center to the edge of the aperture, as seen from the observation point (the center of the imaging screen), where a half-period zone is defined so that the wavefront phase changes by when moving from one half-period zone to the next.
For plates with many zones, you can calculate the distance to the focus if you only know the radius of the outermost zone, r N, and its width, Δr N: = In the long focal length limit, the area of each zone is equal, because the width of the zones must decrease farther from the center.
Fresnel zone antennas belong to the category of reflector and lens antennas.Unlike traditional reflector and lens antennas, however, the focusing effect in a Fresnel zone antenna is achieved by controlling the phase shifting property of the surface and allows for flat [1] [6] or arbitrary antenna shapes. [4]
The United States Naval Observatory states "the Equation of Time is the difference apparent solar time minus mean solar time", i.e. if the sun is ahead of the clock the sign is positive, and if the clock is ahead of the sun the sign is negative. [6] [7] The equation of time is shown in the upper graph above for a period of slightly more than a ...
The transition zone between these near and far field regions, extending over the distance from one to two wavelengths from the antenna, [citation needed] is the intermediate region in which both near-field and far-field effects are important. In this region, near-field behavior dies out and ceases to be important, leaving far-field effects as ...
Discover the latest breaking news in the U.S. and around the world — politics, weather, entertainment, lifestyle, finance, sports and much more.
oblique Mercator projection. The oblique Mercator map projection is an adaptation of the standard Mercator projection.The oblique version is sometimes used in national mapping systems.
Local mean time (LMT) is a form of solar time that corrects the variations of local apparent time, forming a uniform time scale at a specific longitude. This measurement of time was used for everyday use during the 19th century before time zones were introduced beginning in the late 19th century; it still has some uses in astronomy and navigation.