Radwin 2000 - About the Fresnel Zone

RADWIN2000UserManual Release2.8.30 27‐3
Availability
Availability
TheServiceAvailabilitycalculationisbasedontheVigantsBarnettmethodwhichpredictsthe
downtimeprobabilitybasedonaclimatefactor(Cfactor).
AntennaHeight
Therecommendedantennaheightrequiredforlineofsightiscalculatedasthesumthe
Fresnelzoneheightandtheboresightheight.SeeAbouttheFresnelZonebelow.Usingthe
notationofFigure27‐1below,splittingExpectedRangeintod
1
+d
2
,theFresnelzoneheight
atdistanced
1
fromthelefthandantenna,isgivenby
Forthemostconservativesetting,wetakethemid‐pointbetweentheantennas,setting
whichgives
simplifyingto .
Theboresightclearanceheightiscalculatedas:
where .
AbouttheFresnelZone
TheFresnelzone(pronounced"frA‐nel",withasilent“s”)isanellipticallyshapedconicalzone
ofelectromagneticenergythatpropagatesfromthetransmittingantennatothereceiving
antenna.Itisalwa yswidestinthemiddle ofthepathbetweenthetwoantennas.
Availability
16–10
7–
 Cfactor frequency
GHz
 RequiredRange
KM

3

10
ExpectedFadeM inarg–
10
------------------------------------------------------------

=
0.6
300
frequency
GHz
-----------------------------------
d
1
d
2

d
1
d
2
+
-----------------------------------------------------------
d
1
d
2
ExpectedRange
2
-----------------------------------------
==
0.6
300
frequency
GHz
-----------------------------------
ExpectedRange
2
-----------------------------------------
2

ExpectedRange
2
-----------------------------------------
ExpectedRange
2
-----------------------------------------
+
--------------------------------------------------------------------------------------------
0.52
ExpectedRange
frequency
GHz
-----------------------------------------
R
2
Mean
ExpectedRange
2
-----------------------------------------
2
+ R
Mean
–
R
Mean
6367.4425Km=