Helical antenner..

Virker forbavsende godt i forbindelse med bevægelig (mobil) kommunikation.. ligner en variant af dens specialiteter, som de tester.

http://en.wikipedia.org/wiki/H...enna

Lavede og brugte sådan en fætter til 2 meterbåndet i 1980'erne, (indre København) og den var fremragende til at holde kontakt med de utallige mobile radioamatører.

Men når det blæste op til storm, så var de med at komme op på taget (4-5 sal) og få 'ålerusen' solidt tøjret :)

Snoet lys

Kan man se snoet lys med det menneskelige øje?

Hm?

Det var da en kringlet(!) måde at forklare cirkulær polarisering :-)

Det er ikke cirkulær polarisering

Det er, som jeg skriver i artiklen, netop ikke cirkulær polarisering, der er tale om.

Orbital angular momentum (OAM) - for at holde os til den engelske beskrivelse - er noget helt andet. Se f.eks. referencerne jeg har givet under DOKUMENTATION.

Re.: Det er ikke cirkulær polarisering

Måske skulle man kalde det for et azimutalt impulsmoment.

En primitiv opfattelse af fotoner som "små kugler" holder ikke.

Den nærmeste primitive opfattelse må være roterende ellipsoider, hvor en roterende hovedakse ikke er sammenfaldende med udbredelsesretningen.
(2 forskellige rotationer).

Meget spændende i forbindelse med sorte huller ! Og man må sige, at mystikken breder sig, når man gør sig den tætte kobling mellem gravitation og elektrodynamik klart - uden at vi endnu har den fulde forståelse.

Produktion af snoet lys

Er blevet opmærksom på en annonce i Scientific American, april 2011 (side 7) fra Hamamatsu med bl.a. følgende tekst:

Hamamatsu's computer-controlled Liquid Crystal on Silicon Spatial Light Modulator (LCOS-SLM) is able to very precisely convert a straight beam of light into a twisted, helix-shaped beam for use in many advanced applications. ....

Usually we think of light as traveling in a straight path, in a train of parallel planes called wavefronts. But light can also be twisted into helix-shaped
wavefronts for many useful new applications.The challenge is how to precisely control the twisting of the light—and do that with equipment that is
flexible and widely usable.

Hamamatsu created an elegantly simple solution. Their Liquid Crystal on
Silicon Spatial Light Modulator (LCOS-SLM) uses a computer to precisely shape the reflective profile of a liquid crystal surface. Applying special phase profiles to that surface will twist the reflected light in precisely controllable ways. Yet the system is compact, cost-efficient and easy to use.

Snobølge nyt...

Institute of Physics (IOP) (2012, March 2). Pasta-shaped radio waves beamed across Venice. ScienceDaily:
http://www.sciencedaily.com/re....htm
"...
"In a three-dimensional perspective, this phase twist looks like a fusilli-pasta-shaped beam. Each of these twisted beams can be independently generated, propagated and detected even in the very same frequency band, behaving as independent communication channels," Tamburini continued.
...
"Within reasonable economic boundaries, one can think about using five orbital angular momentum states, from -5 (counter-clockwise) up to 5 (clockwise), including untwisted waves. In this instance, we can have 11 channels in one frequency band.
..."

2 March 2012, 'Twisted' waves could boost capacity of wi-fi and TV:
http://www.bbc.co.uk/news/scie...1490
CItat: "...
The technique exploits what is called the "orbital angular momentum" of the waves - imparting them with a "twist".
...
[ Hvem kan forklare forskellen? ;-) : ]
The key lies in the distinction between the orbital and spin angular momentum of electromagnetic waves.
..."

Re: Snobølge nyt...

Hvem kan forklare forskellen mellem cirkular polarisation - og elektromagnetisk(f.eks. lys, radiobølger...) orbital angular momentum (OAM).

Hvis det virkelig er rigtigt, betyder det at man bl.a. kan lave nye?:
* bedre optiske mikroskoper
* finde materialer som fungerer ligesom polariserende stoffer a la LCD, men til OAM.
* som de skriver større effektiv udnyttet båndbredde - jeg kan dog ikke se hvordan båndbredde kan bibeholdes for varierende modulation af OAM-kanaler.

Mar 7, 2012, Physicists put a new twist on radio:
http://physicsworld.com/cws/ar...8869
Citat: "...
Physicists have known for many years that a beam of light can be twisted so that its wavefront rotates around its direction of propagation in a spiral shape. The twisting is achieved by controlling the orbital angular momentum of the light. This property is associated with the shape of a light beam's wavefront – the imaginary line or plane joining the points on a wave that have the same phase.

The orbital angular momentum should not be confused with the more familiar spin angular momentum of light, which is associated with a wave's polarization or direction of oscillation.
...
[Jeg kunne godt tænke mig en demonstration med 4 eller 8 OAM-kanaler - to er ikke nok - måske er det i virkeligheden de 2 ortogonale venstre/højre-drejede polarisationskanaler de sender og modtager?: ]
A specially adapted satellite-dish-style antenna on the lighthouse on St George's Island was used to create radio waves with a frequency of 2.4 GHz and an orbital angular momentum of 1 – the latter meaning that the wavefront is rotated 360° in the space of one wavelength. A standard "Yagi" antenna was also used to send waves of the same frequency but without orbital angular momentum across the same stretch of lagoon.
...
[ Det tyder på, at det IKKE er 2 ortogonale venstre/højre-drejede polarisationskanaler?: ]
By varying the distance between the two receiving antennas on the balcony of the Doge's Palace, the researchers were able to tune in to either the twisted or the untwisted beam. This proves, they say, that they were able to transmit two channels simultaneously using just a single frequency.
...
[ Guleroden - hvis det er rigtigt: ]
it means in principle being able to create an infinite number of channels in a given bandwidth, with each channel encoded using a different orbital angular momentum.
..."

1 marts 2012, Encoding many channels on the same frequency through radio vorticity: first experimental test:
http://iopscience.iop.org/1367...icle

Light orbital angular momentum:
http://en.wikipedia.org/wiki/L...ntum

Circular polarization:
http://en.wikipedia.org/wiki/C...tion

Spin (physics):
http://en.wikipedia.org/wiki/S...s%29
Citat: "...
Standard model of particle physics; hence bosons are also called force carriers. These bosons have s=1.
...
Theory predicts the existence of two bosons whose s differs from 1. The force carrier for gravity is the hypothetical graviton; theory suggests that it has s = 2. The Higgs mechanism predicts that elementary particles acquire nonzero rest mass by exchanging hypothetical Higgs bosons with an all-pervasive Higgs field. Theory predicts that the Higgs boson has s = 0. If so, it would be the only elementary particle for which this is the case.
..."

Photon:
http://en.wikipedia.org/wiki/P...oton
Citat: "...
Spin 1
...
The photon is massless,[Note 2] has no electric charge,[12] and is stable. A photon has two possible polarization states and is described by exactly three continuous parameters: the components of its wave vector, which determine its wavelength lambda and its direction of propagation.
...
The photon also carries spin angular momentum that does not depend on its frequency.[17] The magnitude of its spin is \scriptstyle{\sqrt{2} \hbar} and the component measured along its direction of motion, its helicity, must be +-h. These two possible helicities, called right-handed and left-handed, correspond to the two possible circular polarization states of the photon.[18]
..."

Re: Snobølge nyt...

Hvis 4 antenner, er nok til at lave en spin-modtager, og hver af disse 4 antenner er fyldt op, set udfra et informationsmæssigt synspunkt - hvordan kan man så øge mængden af data, mere end 4 gange?

Det minder lidt om manden, der foreslog at sende med forskellig fase. Som sådan ikke nogen dum idé, når der sendes digitalt. Men er den nu så revolutionerende, at der kan fyldes mere i luften?

En af mine gamle idéer fra da jeg var dreng, var at udskifte sinus kurven, med en anden kurveform. Normalt, kan vi beskrive vores modtagne signal, som en integration med en sinus kurve. Vi kan få to signaler, hvis vi også kan integrere med en cosinus kurve. Nu var fidusen så, om vi kunne bruge en helt anden kurve, f.eks. en kurve der består af sinus, som er frekvensmoduleret med en cosinus funktion. Den skal naturligvis passe i fase, for at kunne modtage signalet - så varieres fasen, må det svare til en anden frekvens, Og vi kan ændre "signalets" frekvens udstrækning, ved at ændre amplituden på det signal, som styrer frekvensen.

Jo, vi har masser af parametre der kan justeres, men kan vi reelt få mere ud af luften af den grund?

Re: Snobølge nyt...

Jeg benægter ikke, at vi ud fra et fysisk synspunkt, kan modtage mere fra luften. Kun at vi kan modtage mere end 4 gange så megen information med 4 antanner. Det er muligt med et stort antal informationer i luften, også på samme bølgelængde. F.eks. kan en parabol antenne rettes mod hundreder af forskellige sattelitter. Men skal "elektronisk" kunne vælges mellem disse, så kræves naturligvis et tilsvarende stort antal hoveder. Med et stort antal antenner, er måske muligt at såvel kunne sende, som modtage flere indformationer.

Re: Snobølge nyt...

Hvem kan forklare mig forskellen mellem cirkular polarisation - og elektromagnetisk(f.eks. lys, radiobølger...) orbital angular momentum (OAM)-bølger? - eller henvise til dansk eller engelsk litteratur om det?

Bispørgsmål - er der en relation mellem kvantemekanisk spin og OAM?

Hvis det virkelig er rigtigt, betyder det at man bl.a. kan lave nye?:
* bedre optiske mikroskoper
* finde materialer som fungerer ligesom polariserende stoffer a la LCD-polarisationsfiltre, men til OAM.
* som de skriver i New Journal of Physics-artiklen - større effektiv udnyttet båndbredde - jeg kan dog ikke se hvordan båndbredde kan bibeholdes for varierende modulation af OAM-kanaler.

Nogen burde gå forrest og teste om det virker?

* Hvorfor kan en opklippet og passende bøjet reflektor (se New Journal of Physics-artiklen, "Figure A4. The helicoidal parabolic antenna") have en sådan OAM virkning?

* Er vandret/lodret/venstre/højre-drejede polarisationer ortogonale på OAM-bølger? (måske varierer effekten/fænomenet med afstanden?)

* Kan en yagi/helical-antenne laves om til en OAM-antenne ved at klippe og bøje en cirkulær reflektor? Ligesom parabolreflektoren i New Journal of Physics-artiklen?

* Kan en yagi/helical-antenne laves om til en OAM-antenne uden at pille ved reflektoren?

* Findes der naturlige radiobølge objekt passeringer/reflekteringer, som konverterer en traditionel radiobølge til en eller anden OAM-radiobølge?

* Radar burde i den grad kunne få gavn af OAM-bølger?

* kan man sende og identificere OAM-superpositioner? F.eks. burde man kunne skelne mellem 3-OAM, 5-OAM og 7-OAM, uanset om de reflekteres eller lægges sammen med andre?

* Kan (-1_OAM) + (+1_OAM) ophæve hinanden?

* kan to ens antenner som sender samme OAM-superposition, "lægges" sammen eller vil de interferere anderledes end traditionelle polarisationer?

Benytter "spatial_multiplexing" i virkeligheden OAM?:
http://en.wikipedia.org/wiki/S...xing

Functions of MIMO:
http://en.wikipedia.org/wiki/M...MIMO
Citat: "…
In spatial multiplexing, a high rate signal is split into multiple lower rate streams and each stream is transmitted from a different transmit antenna in the same frequency channel. If these signals arrive at the receiver antenna array with sufficiently different spatial signatures, the receiver can separate these streams into (almost) parallel channels. Spatial multiplexing is a very powerful technique for increasing channel capacity at higher signal-to-noise ratios (SNR). The maximum number of spatial streams is limited by the lesser of the number of antennas at the transmitter or receiver.
…"

-

Akustiske bølger med OAM-lignende egenskab i faststof eller måske også i væske og gas (luft)?:

* Har akustiske bølger (f.eks. lydbølger) også mulighed for "OAM"-lignende-bølger? Bruger flagermus dem (uden at vide det)? Sonar kan i så fald forbedres?

* Kan visse tryk/seismiske/jordskælvsbølger benytte "OAM"-lignende-bølger?

* Det kan anvendes til at afdække mineral og olie/gas-forekomster bedre?

-

Hvad med andre bølgetyper? Findes de også i "OAM"-lignende-bølger?

Kan graviationsbølger f.eks. lettere afdækkes hvis de modtages opløst i OAM-"polariseringer"?

-

Mar 7, 2012, Physicists put a new twist on radio:
http://physicsworld.com/cws/ar...8869
Citat: "...
Physicists have known for many years that a beam of light can be twisted so that its wavefront rotates around its direction of propagation in a spiral shape. The twisting is achieved by controlling the orbital angular momentum of the light. This property is associated with the shape of a light beam's wavefront – the imaginary line or plane joining the points on a wave that have the same phase.

The orbital angular momentum should not be confused with the more familiar spin angular momentum of light, which is associated with a wave's polarization or direction of oscillation.
...
[Jeg kunne godt tænke mig en demonstration med 4 eller 8 OAM-kanaler - to er ikke nok - måske er det i virkeligheden de 2 ortogonale venstre/højre-drejede polarisationskanaler de sender og modtager?: ]
A specially adapted satellite-dish-style antenna on the lighthouse on St George's Island was used to create radio waves with a frequency of 2.4 GHz and an orbital angular momentum of 1 – the latter meaning that the wavefront is rotated 360° in the space of one wavelength. A standard "Yagi" antenna was also used to send waves of the same frequency but without orbital angular momentum across the same stretch of lagoon.
...
[ Det tyder på, at det IKKE er 2 ortogonale venstre/højre-drejede polarisationskanaler?: ]
By varying the distance between the two receiving antennas on the balcony of the Doge's Palace, the researchers were able to tune in to either the twisted or the untwisted beam. This proves, they say, that they were able to transmit two channels simultaneously using just a single frequency.
...
[ En af gulerødderne - hvis det er rigtigt: ]
it means in principle being able to create an infinite number of channels in a given bandwidth, with each channel encoded using a different orbital angular momentum.
..."

1 marts 2012, Encoding many channels on the same frequency through radio vorticity: first experimental test:
http://iopscience.iop.org/1367...icle

-

Light orbital angular momentum:
http://en.wikipedia.org/wiki/L...ntum

Circular polarization:
http://en.wikipedia.org/wiki/C...tion

Spin (physics):
http://en.wikipedia.org/wiki/S...s%29
Citat: "...
Standard model of particle physics; hence bosons are also called force carriers. These bosons have s=1.
...
Theory predicts the existence of two bosons whose s differs from 1. The force carrier for gravity is the hypothetical graviton; theory suggests that it has s = 2. The Higgs mechanism predicts that elementary particles acquire nonzero rest mass by exchanging hypothetical Higgs bosons with an all-pervasive Higgs field. Theory predicts that the Higgs boson has s = 0. If so, it would be the only elementary particle for which this is the case.
..."

Photon:
http://en.wikipedia.org/wiki/P...oton
Citat: "...
Spin 1
...
The photon is massless,[Note 2] has no electric charge,[12] and is stable. A photon has two possible polarization states and is described by exactly three continuous parameters: the components of its wave vector, which determine its wavelength lambda and its direction of propagation.
...
The photon also carries spin angular momentum that does not depend on its frequency.[17] The magnitude of its spin is \scriptstyle{\sqrt{2} \hbar} and the component measured along its direction of motion, its helicity, must be +-h. These two possible helicities, called right-handed and left-handed, correspond to the two possible circular polarization states of the photon.[18]
..."

-

Dette kabeltype burde kunne formidle alle OAM:

http://en.wikipedia.org/wiki/S...Line
Citat: "...
a more general mode has recently been discovered and demonstrated which does not have this limitation. "E-Line" is similar to Goubau-Lines in its use of launching horns to couple to and from a radially symmetric wave propagating in the space around a single conductor but different in that it can operate on insulation-free conductors, including those that are polished and completely unfeatured
...
Contrary to Goubau's assertions, it has been shown both possible and practical to launch a surface wave on an uninsulated conductor without special conditioning and without reducing the wave velocity, while still using launches of practical size. In addition, conductors much larger than those used by Goubau have been shown to be completely adequate.

Of particular practical value, common uninsulated single or multistrand overhead power conductor may be used to support very low attenuation propagation over the *entire* *frequency* *range* from below 200 MHz to above 10 GHz while employing a launch device of only 15-20 cm in diameter. This makes available the worldwide installed base of overhead powerline for very high rate information transport.
...
The effects of line taps, bends, insulators and other impairments normally found on power distribution systems have proven to be predictable and managable.
..."

TESLA'S BIG MISTAKE?
William Beaty
http://www.amasci.com/tesla/tm...html
Citat: "...
Note that this is a SINGLE WIRE transmission line!
...
It turns out that you can send microwave or UHF signals along a *single* wire as long as that wire is coated with a dielectric [Nej, ikke nødvendig - se E-line]. To do this, you start out with a normal coaxial cable. You strip the shield from a central section, then solder on a pair of large, cone-shaped copper horns which attach to the coax shield at either end of the coax cable. The dielectric-coated single wire extends between the ends of the coax. Sort of like this
...
The metal cones act as "wave launchers" or "wave catchers".
..."

A History of Surface-Wave Technology:
http://web.archive.org/web/200....pdf
Citat: "...The single-wire G-line could transmit microwave RF power with less loss than coaxial cable..."

http://www.corridor.biz/
Citat: "...The PowerCorridortm MOBILE system provides extremely cost effective hole filling and coverage extension with greatly simplified permitting and installation - all at CAPEX costs that are a fraction of alternative solutions. The system supports all wireless systems including 2G, 3G and WiFi..."

-

Se hornet til venstre:

PowerCorridor(tm) MOBILE:
http://www.corridor.biz/Techno...html
Citat: "...
Applications of this discovery easily and inexpensively provides very efficient, linear and broadband transport of information-carrying spectrum anywhere in the 50MHz - 20Ghz frequency range using existing infrastrure.
..."


Broadband over Power Lines:
http://www.rac.ca/en/amateur-r...firm
Citat: "... Surfacewave transmission on an insulated single conductor
was first discovered and presented by Goubau 1 in the early 1950's and
known as G-Line 2 after the inventor. The characteristics of surfacewave
propagation, when used with a variety of dielectric types, thickness
and specially prepared conductors, have been taught and available in
reference texts for many years 3. Though not widely utilized in
practice, the mode can exhibit extremely low radiation and transmission
losses from VHF into the microwave regions..."

-

Endnu et par løsninger med lave tab:

Er vist først interessant ved 3GHz eller højere - ukendt tab/længde:

http://www.corridor.biz/images....JPG

-

Mon man kan lave SWR-måler som måler for hver enkelt OAM? ;-) Kunne det anvendes til TDR på E-lines/G-lines? (OAM-TDR ;-) ):

http://en.wikipedia.org/wiki/T...eter
http://en.wikipedia.org/wiki/T...etry

Bedre mikroskoper

Hvis det virkelig er rigtigt, betyder det at man bl.a. kan lave nye?:
bedre optiske mikroskoper