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Topic: Far-field region


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In the News (Sun 18 Aug 19)

  
 Near and far field - Wikipedia, the free encyclopedia
In telecommunication, far-field region is the region outside the near-field region where the angular field distribution is essentially independent of distance from the source.
In the study of diffraction and antenna design, the near field is that part of the radiated field that is within a quarter of a wavelength of the diffracting edge or antenna.
In the study of diffraction and antenna design, the near field is that part of the radiated field that is within a small number of wavelengths of the diffracting edge or antenna.
en.wikipedia.org /wiki/Near-field_region   (280 words)

  
 Region
Shumen (region) Shumen is a region in northeastern Bulgaria.
Ruse (region) Ruse is a region of northern Ruse.
Razgrad (region) Razgrad is a region of northern Bulgaria.
www.brainyencyclopedia.com /topics/region.html   (2663 words)

  
 An Integrated Near-field EMC Measurement System
3. The region furthest from the radiating object is the Fraunhofer or far-field region.
The transition distance (R) for the far-field region is generally a distance where the phase curvature of the phase front is 22.5 degrees or:
1. The region nearest the radiating object is the reactive or evanescent near-field region.
www.nearfield.com /amta/amta94_EMI.htm   (1330 words)

  
 Intermediate-field region - Wikipedia, the free encyclopedia
Intermediate-field region: For an antenna, the transition region--lying between the near-field region and the far-field region--in which the field strength of an electromagnetic wave is dependent upon the inverse distance, inverse square of the distance, and the inverse cube of the distance from the antenna.
Note: For an antenna that is small compared to the wavelength in question, the intermediate-field region is considered to exist at all distances between 0.1 wavelength and 1.0 wavelength from the antenna.
en.wikipedia.org /wiki/Intermediate-field_region   (111 words)

  
 Method and apparatus for automatically monitoring objects - Patent 4112421
the near-field regions 58, the far-field regions 60 and the overlap regions 66.
The dual range detection established via the near-field region and the far-field region of each of the signpost units 12 allows the vehicle units 16 to be constructed to identifiably distinguish between signals received within the near-field region and signals received within the far-field region via the strength or power level of the received signal.
TABLE I ______________________________________ Intersections: 48-34; Identified via an overlap 52-34; 56-34; 50-36; 54-36; region 66 formed by the 48-38; 52-38; 56-38; 50-40; overlapping portions of the 54-40; 48-42; 52-42; 56-42; far-field regions 60 of one 50-44; 54-44; 48-46; 52-46; of the signpost units 12A and 56-46; and one of the signpost units 128.
www.freepatentsonline.com /4112421.html   (7939 words)

  
 Depth of field - Encyclopedia.WorldSearch
In photolithography depth of field is taken to the extreme, as the variations in physical distance across a semiconductor chip may be a few micrometers.
This region is greater behind the point of focus than it is in front, as the angle of the light rays change more rapidly; they approach being parallel with increasing distance.
In film and photography, the depth of field is the distance in front of and behind the subject which appears to be in focus.
encyclopedia.worldsearch.com /depth_of_field.htm   (1195 words)

  
 Method and apparatus for automatically monitoring objects - Patent 4112421
the near-field regions 58, the far-field regions 60 and the overlap regions 66.
The dual range detection established via the near-field region and the far-field region of each of the signpost units 12 allows the vehicle units 16 to be constructed to identifiably distinguish between signals received within the near-field region and signals received within the far-field region via the strength or power level of the received signal.
TABLE I ______________________________________ Intersections: 48-34; Identified via an overlap 52-34; 56-34; 50-36; 54-36; region 66 formed by the 48-38; 52-38; 56-38; 50-40; overlapping portions of the 54-40; 48-42; 52-42; 56-42; far-field regions 60 of one 50-44; 54-44; 48-46; 52-46; of the signpost units 12A and 56-46; and one of the signpost units 128.
www.freepatentsonline.com /4112421.html   (7939 words)

  
 Intermediate-field region - Wikipedia, the free encyclopedia
Intermediate-field region: For an antenna, the transition region--lying between the near-field region and the far-field region--in which the field strength of an electromagnetic wave is dependent upon the inverse distance, inverse square of the distance, and the inverse cube of the distance from the antenna.
Note: For an antenna that is small compared to the wavelength in question, the intermediate-field region is considered to exist at all distances between 0.1 wavelength and 1.0 wavelength from the antenna.
www.wikipedia.org /wiki/Intermediate-field_region   (111 words)

  
 Wave-Guide: Glossary Containing EMF/EMR Terminology
That region of the field of an antenna where the angular field distribution is essentially independent of the distance from the antenna.
A field vector that is equal to the magnetic flux density divided by the permeability of the medium.
Fields that are nonuniform over volumes comparable to the human body may occur due to highly directional sources, standing-waves, re-radiating sources or in the near field.
www.wave-guide.org /library/glossary.html   (7522 words)

  
 Method for monitoring the location of monitored objects - Patent 4209787
In the overlap region, the reference signpost selector 126 is constructed to select the new signpost code as the reference signpost code (this choice dictated to a large extent on the particular logic system) and this selected, reference signpost code is entered into the vehicle location code register 134 via the signal path 129.
In the overlap region, one of the signpost codes from one of the signpost units 12 forming the particular overlap region will be entered into the last signpost register 114 and the signpost code of the other signpost unit 12 forming the particular overlap region will be entered into the new signpost register 112.
In the transition regions and in the overlap regions, the vehicle unit 14 receives in an alternating manner the signpost codes transmitted via the signpost units 12 cooperating to form the particular transition region and the particular overlap region, as described in my co-pending application (referred to before) with respect to overlap regions.
www.freepatentsonline.com /4209787.html   (4547 words)

  
 Untitled Normal Page
In a conventional RF system, the receiving antenna is located in the far-field region of the transmitting antenna.
In the near-field region, the phase relation and the relative orientation between the electric and magnetic fields are not constant with position.
In this region, the field strength decays with distance as 1/r, where r is the distance from the transmitting antenna.
www.ittc.ku.edu /~rvc/projects/wirelan/nearf.htm   (1345 words)

  
 Plane wave - Wikipedia, the free encyclopedia
For example, a localized source such as an antenna produces a field that is approximately a plane wave in its far-field region.
For the vector wave equation of electromagnetism, a is the vector for the electric or magnetic field (and is orthogonal to k, for an isotropic medium).
By extension, the term is also used to describe waves that are approximately plane waves in a localized region of space.
en.wikipedia.org /wiki/Plane_wave   (281 words)

  
 Interpreting Antenna Performance Parameters for EMC Applications - Part 2
The strict IEEE definition is "That portion of the near field region of an antenna between the far field and the reactive portion of the near field region, wherein the angular field distribution is dependent upon distance from the antenna." Appreciable radial (non-radiating) fields may exist in the radiating near field region.
The strict IEEE definition is "That region of the field of an antenna where the angular field distribution is essentially independent of the distance from a specified point in the antenna region." The far field region is sometimes termed the Fraunhoffer region in analogy with Fraunhoffer diffraction.
The far field region of an antenna is the region surrounding an antenna which is sufficiently far from the antenna such that only the radiating field components are significant.
www.djmelectronics.com /articles/antenna_parameters_p2.html   (3904 words)

  
 Re: TEM vs E and M
The 1/r terms are the only ones that survive into the far field region, where both the E and H fields depend only on the amplitude and phase of the current in the filament.
Bill - You are pretty accurate with your description of the near and far field region, and it is explained in books like "Antennas and radiowave propagation" by R.E.Collin, which treat the near and far fields produced by a short current filament.
Collin also says that the outgoing power is carried exclusively in the 1/r field components, which are of course continuous up to the surface of the antenna but not so intense as the other terms in the near field region...
www.antennex.com /atheory3/_atheory3/00000022.htm   (237 words)

  
 CSS Antenna... Technical Notes
Far-field region: "That region of the field of an antenna where the angular field distribution is essentially independent of the distance from a specified point in the antenna region".
Antenna polarization: "In a specified direction from an antenna and at a point in its far field, is the polarization of the (locally) plane wave which is used to represent the radiated wave at that point".
The radiation pattern is measured in the far field.
www.cssantenna.com /technotes/notes.html   (1677 words)

  
 TFCBooks -- Tesla Site Glossary
It is characterized by a variation of the electric and magnetic fields in the far-field region associated with a radiating antenna.
In the far zone, field components (E and H) lie transverse to the direction of the propagation, and the shape of the field pattern is independent of the radius at which it is taken.
Faraday rotation The orientation of the electric field vector of an electromagnetic wave propagating parallel to a magnetic field embedded in a plasma rotates as the wave propagates.
www.tfcbooks.com /mainpage/glossary.htm   (12184 words)

  
 Near field effect should dominate the region
Near field effect should be the actual dominate radiative effect - which would indicate that a coil placed near any sort of tuned circuit will lose much of its power to that tuned circuit.
The near field effect is a big part of why crystal sets can work as well as they do.
And it isn't limited to being close to the set, theory indicates that near field effects occur within a quarter wavelength of the tank circuit.
www.midnightscience.com /_web/000017c7.htm   (246 words)

  
 -MRS-
The STM tip is illuminated with a focused laser radiation and the light scattered from the tip-sample region is detected by means of a PIN photodiode and filtered from the background by dithering the tip-sample voltage and using a lock-in amplifier tuned at the dithering frequency.
Two major probable contributions to it could be the laser field enhancement at the tip considered as a metallic nanostructure (similar to the enhancement in surface enhanced Raman experiments) and a pure quantum origin mechanism arising from the overlap of the wave functions of the tip and sample.
When a magnetic field pulse is applied, the time to switch the film magnetization changes from greater than 10 ns to less than 500 ps as the pulse amplitude is increased from the coercive field to 10 mT and beyond.
www.mrs.org /meetings/spring99/abstractbook/AbstractBookAA.html   (7353 words)

  
 GO 326 Eifel volcanism
The blue region (near map bottom) is the Niedermendiger lava flow, which formed between 100,000 to 150,000 years ago.
The Eifel volcanic region is closely associated with the Rhine Graben, a continental rift zone of Cenozoic age--see handout maps.
The Eifel volcanic field is located in western Germany, near the Rhine River--see handout maps.
academic.emporia.edu /aberjame/tectonic/eifel/eifel.htm   (882 words)

  
 Near Field Test Facility Design
There is a one-to-one correspondence between energy at a given spatial frequency in the near field and at a specific angle in the far field.
The patterns produced by a near field range are often of higher quality and therefore different than patterns measured in a far-field range.
The number of rays is determined by the far field radiation symmetry of the antenna under test.
www.nearfield.com /amta/amta85_ds-2.htm   (3978 words)

  
 Homepage of Jianming Shi
The near-field region is defined as the region away from the sample that is less than the wavelength of the incident light.
This slow decay is due to the Drude material having very low loss over the higher frequencies, so that the fields which penetrate into the sphere will resonate for a long time before finally decaying or escaping from the sphere to radiate into the far zone.
This has been the traditional resolution limit for light collection in the far-field that is when the collection optics is further away from the sample than the wavelength of the incident light.
www.people.virginia.edu /~js4hx/ResearchInterests.htm   (1318 words)

  
 Nat' Academies Press, Twenty-First Symposium on Naval Hydrodynamics (1997)
It is shone that in the very near region to the foil tip where no fluctuation of position are measurable the axial fluctuations are important but they are decreasing for more distant positions downstream the tip for which the wandering is noticeable.
In the very near region, the roll-up of the vortex is initiated and a rapid change of its local intensity (circulation) occurs.
These velocity profiles are characterized by an inner region where the velocities increase linearly as for a solid body rotation, an outer region where they decrease as for a potential vortex, and an intermediate region which assures a smooth transition between the previous ones.
www.nap.edu /books/0309058791/html/865.html   (9027 words)

  
 Electromagnetic Radiation: Field Memo
Ratio of the electric field (E) to the magnetic field (H), in the far-field this is the characteristic impedance of free space, 377 Ohms.
Since both the E field and the H field components of electromagnetic waves are absorbed by living tissue, and since the relationship between E and H is complicated in the near-field, we must measure both E and H when evaluating near-field hazards.
The area near this coupling activity is exactly where compliance officers have to deal with electromagnetic fields, as in the case of RF heat sealers.
www.osha.gov /SLTC/radiofrequencyradiation/electromagnetic_fieldmemo/electromagnetic.html   (8300 words)

  
 Re: True Antenna Efficiency
The antenna fields also induce currents in nearby structures; wires, guys, trees, walls, support structures, all of which may be within the radian sphere or near-near field region.<><><> Then we have energy which escapes from the radian sphere.
But there are other sources of dissipation; the antenna induces currents in the ground or earth which heats the soil in the near field region.
This heating is over and above the propagation loss of the ground, which is taken care of in standard "radiation field over earth" simulations.
www.antennex.com /storage/atheory3/_atheory3/00000063.htm   (329 words)

  
 Re: TEM vs E and M
The 1/r terms are the only ones that survive into the far field region, where both the E and H fields depend only on the amplitude and phase of the current in the filament.
Bill - You are pretty accurate with your description of the near and far field region, and it is explained in books like "Antennas and radiowave propagation" by R.E.Collin, which treat the near and far fields produced by a short current filament.
Collin also says that the outgoing power is carried exclusively in the 1/r field components, which are of course continuous up to the surface of the antenna but not so intense as the other terms in the near field region...
www.antennex.com /atheory3/_atheory3/00000022.htm   (237 words)

  
 Interpreting Antenna Performance Parameters for EMC Applications - Part 2
The strict IEEE definition is "That portion of the near field region of an antenna between the far field and the reactive portion of the near field region, wherein the angular field distribution is dependent upon distance from the antenna." Appreciable radial (non-radiating) fields may exist in the radiating near field region.
The strict IEEE definition is "That region of the field of an antenna where the angular field distribution is essentially independent of the distance from a specified point in the antenna region." The far field region is sometimes termed the Fraunhoffer region in analogy with Fraunhoffer diffraction.
The far field region of an antenna is the region surrounding an antenna which is sufficiently far from the antenna such that only the radiating field components are significant.
www.djmelectronics.com /articles/emc-antenna-parameters-p2.html   (3904 words)

  
 Intermediate-field region -- Facts, Info, and Encyclopedia article
Note: For an antenna that is small compared to the (The distance (measured in the direction of propagation) between two points in the same phase in consecutive cycles of a wave) wavelength in question, the intermediate-field region is considered to exist at all distances between 0.1 wavelength and 1.0 wavelength from the antenna.
Intermediate-field region -- Facts, Info, and Encyclopedia article
Synonyms: intermediate field, intermediate zone, (A passage that connects a topic to one that follows) transition zone.
www.absoluteastronomy.com /encyclopedia/i/in/intermediate-field_region.htm   (106 words)

  
 Focus detection system for an optical disk drive using photo sensor elements in the far field of information pits - Patent 4998235
In detail, the light power distribution is symmetric about the optical axis of the far field in the case that the depth or height of the pit is n.lambda./4 (n:integral number,.lambda.:wavelength of the light beam) or the information structure is made of marks the reflective index of which is different from that of ground.
In the far field area, those diffraction beams, overlapping one another, produce bright and dark interference stripes the period of which is a function of the focus error.
3c show far field patterns respectively when the distance between the recording layer 10b and the principal plane of the objective lens 3 is shorter or longer than the focal length of the objective lens 3.
www.freepatentsonline.com /4998235.html   (4828 words)

  
 NAB99 CFA Paper
It should also be commented that the Barnis CFA is situated in a region of dry desert, which introduces attenuation on the ground wave thus resulting in what may be expected as a different radiation characteristic pattern than Tanta in the extreme far field.
In the far field, the E and H fields are in time-phase, and the ratio E/H, often called the wave impedance Z
Secondly, the E and H fields in the far field, which produce the radiated power, are much weaker than the reactive field components located in the near field.
www.antennex.com /preview/cfa/nab99cfa.htm   (2858 words)

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