Antenna Guide

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WiFi ; ; ; (socrates.. @.. awmn.net) (2002-2007: Athens Wireles s Metropolitan Network)

; ; ;

ISM 2,4 5GHz.

, - , AWMN (Athens Wireless Metropolitan Network).

. , , - .

> ; > > : / > > > Waveguides, Yagi Panel > Omni, Sector: > Sectorized Omni > > > > , gain dB > Side/back Lobes, F/B Ratio > > (Impedance) > > (Efficiency) > > > > > > > > > & >

; ( ) WiFi .

. . .

; . . ( , / , dB, , IEEE WiFi) .

... , [email protected], (wireless_surfer)!

/ . , , [. 1].

. 1:

. , , , . " " " HERTZ" [. 2]. WLAN, 2,4GHz 5GHz.

. 2: 2,45GHz ( =122mm)

H (transponder) . , , .

/ , . , (maximum power rating), . , (reciprocity). , . . , . . [q2] . [. 3].

.

.

. 3: Point to Point Point to Multipoint

, . (Point to point ) , (Point to Multipoint: Access Points, Hot Spots) . [. 4].

. 4: . , -,

. omni sector ( ). . I .

Grid

Offset

Prime Focus

. feeder. () .

feeder feeder. (feeder) , , (waveguide horn), yagi. ( ) , Cassegrain ,

feeder [. 5].

feeder

. (grid). . offset cassegrain[. 5] .

. 5 . .

feeder

prime focus ( ). feeder . offset . cassegrain -. feeder ( ). (spillover) feeder ( cassengrain)

. , microwave absorbers. . .

backfire

waveguide

Yagi

Panel

WLAN . Yagi Panels. (waveguides) backfire 15dBi. To . ( ). Yagi Yagi-Uda , Hidetsugu Yagi Shintaro Uda. . [. 6] Yagi 7 Yagi , , .

. 6: .

(driving

element)

. . WiFi . yagi

( ). . panel . . - .

Omni

Sector

Sectorized Omni

( , , ). Herz ( ). ( ) , . omni sector. omni. 360 . omni. omni

( ). - . omni sector. 180. omni downtilt . downtilt . omni ( 360) sector ( , downtilt) sector (sectorized omni: ). .1.

(client capacity). , . 802.11b Access Point sector 120 1, 6, 11 , omni. gain / . sector downtilt/uptilt . . sector , Access Point . . sector , , . . /sector , . downtime Access Point.

2.

3.

4.

5.

, , . : , , , , ( ), ( ), ( ). [q1] . WiFi 2401-2483 MHz (802.11b, 802.11g) 5470-5725 MHz (802.11a). ( ) . ( radiation pattern - aperture), [. 7].

(vertical/elevation E-Plane) (horizontal/azimuth H-Plane) , [. 8].

. 7: 3d . Sector (), Grid parabolic ( ), Panel ( ).

. 8: 3d- 2d ( & ).

(. , f/b ratio, , ), , . . [. 8], 360 (. gain) .

. 8:

, gain , . . [. 9]

. 9

, , . ,

. . , . ( ) , .

[q3] . ( rf ). (directional) . (omnidirectional) . omni o [. 10].

. 10: dBi omni .

. . (gain), dBi (deciBel over isotrop) dBd (deciBel over dipole). dBi gain , gain isotropic dipole antenna ( , , ). dBd dBi Hertz. 2dB 65% .

dBd dBi 1.76 dBd. gain 30 dBd 28.24 dBi. gain (mainlobe mainbeam) . [. 11] , gain . (= beamwidth) , (-3dB) [. 11]. , , . . . .

. 11: .

Side back Lobs, Front to Back Ratio [q4] .

.

"front-to-back" (F/B ratio). dB ( , 0 ) 180 . F/B ratio, . ( ). 10-15 dB . , . , . [q5] , . (E-Plane) ( [. 12]).

. 12:

-Plane , . , ( , ) [. 1 3].

. 13: ) , ) , )

( , , / ). . , . . 1,4,6 .1 1 2 3 4 5 6 7 8 / / / / 2 0 45 90 -0dB -3dB -20dB -0dB -20dB -0dB -3db -3dB

3 5 ( ) ( ).

. ( ), . (helix antennas, cross yagi) . , ( V H ), . . . . , . . (impedance) [q6] ( RF ) (impedance) ohms. , , , . . VSWR (voltage-standing-wave-ratio) . VSWR ( 2:1, 3:1, 10: 1). tranmission line 50 Ohm. VSWR ( ) . VSWR 1.5:1 37.5 75 Ohms. VSWR 2.5:1 . 1:1 . 1.5:1

. VSWR VSWR [. 14]. VSWR .

. 14: VSWR

50 100 Watt. WiFi . . (Efficiency) . 40 () 70 () . . , . . [q8] . , , , . ,

.

gain, 80 ( 35cm ). . . . 2,4GHz panel 19dBi 40 ( 5GHz 10 . ), 2,5 . yagi 19dBi , 15 . . 24dBi 60 , 100 40 .

[q9] . . . . [q7] . ( ) . offset downtilt , downtilt.

, . ( ) . . . . . prime focus offset. .

EIRP 20dB 100mW . EIRP 1999/5/EC CEPT

Rec 70.03 . (, ) (). EIRP : EIRP = (gain) + , . RF , . gain . ( 01 1996) CE certification 89/336/CE.

( 01- 2006) Restriction of Hazardous Substances Directive (RoHS) 2002/95/EC 6 (, , , Cr6+, PBB PBDE) . . . . . . . . . 200. . (lighting arrestors). . [. 15].

. 15: -50083-11 ( ). (gass lighting arrestor).

' , .

. (. ) . . . & . . . ( ) .

. . . . , . . . , , , .

Further Reading IEEE Standard Definitions of Terms for Antennas, IEEE Std 145-1983. Dr. Steven R. Best, Antenna Performance and Design Considerations for Optimum Coverage in Wireless Communication Systems . ., /II : , -, , 1999-2002, www.antennas.duth.gr. . ., I/II : , , -, , 2001-2002, [email protected] Joseph H. Reisert, Antenna Selection and Specification Made Easy http://www.astronwireless.com/antsel.html Joseph H. Reisert, Understanding and Using Antenna Radiation Patterns http://www.astronwireless.com/radiation_patterns.html Joseph H. Reisert, Antenna Polarization Application Note http://www.astronwireless.com/polarization.html Interpreting Antenna Performance Parameters for EMC Applications http://www.djmelectronics.com/articles/emc-antenna-parameters-p1.html www.wikipedia.org (antenna:radio) www.wikipedia.org (Restriction of Hazardous Substances Directive) http://www.microwaves101.com/encyclopedia/ (microwave encyclopedia) Cellular antennas & The mysteries of the Gain? (By David Benchoam) http://www.benelec.com.au/technical/cellular_antennas.htm