Microwave Communications_b (1)

MICROWAVE

MICROWAVE

COMMUNICATION

COMMUNICATION

“God chose the weak

“God chose the weak

things of the world to

things of the world to

shame the strong.”

shame the strong.”

1 Cor. 1:27

What is

What is

Microwave

Microwave



 _{Microwave CommunicationsMicrowave Communications}



 _{s sim!l" a high radio fre#uenc" link s!eci$call"s sim!l" a high radio fre#uenc" link s!eci$call"}

designed to !rovide signal connection %etween

designed to !rovide signal connection %etween

two s!eci$c !oints.

two s!eci$c !oints.



 _{&lso coined as 'ine(of()ight or '*)&lso coined as 'ine(of()ight or '*)}

communications+ ,adio 'ink+ -oint(to(-oint

communications+ ,adio 'ink+ -oint(to(-oint

communications.

communications.

2 2

Classi$cation of

Classi$cation of

Microwave

Microwave

  _{atureature}   _&nalog&nalog   _{/igital/igital} 

 _{/istance 0 re#uenc"/istance 0 re#uenc"}



 _{)hort aul)hort aul}



 _{used for short distance microwave transmission usuall" atused for short distance microwave transmission usuall" at}

lower ca!acit" ranging from 34 k%!s u! to 2M%!s

lower ca!acit" ranging from 34 k%!s u! to 2M%!s



 _{Medium aulMedium aul}



 _{'ong aul'ong aul}



 _{used for long distance0multi(ho! microwave transmission.used for long distance0multi(ho! microwave transmission.}

5sed for %ack%one route a!!lications at 64 M%!s to 32

5sed for %ack%one route a!!lications at 64 M%!s to 32

M%!s ca!acit"

M%!s ca!acit"



 _{Ca!acit" 0 8andwidthCa!acit" 0 8andwidth}



 _{'ight 9arrow 8and'ight 9arrow 8and}



 _{Medium 9arrow 8andMedium 9arrow 8and}



 _{'arge 9Wide 8and'arge 9Wide 8and}

3 3

&dvantages of Microwave )"stem

electrical si<e.

 _{& 1= %andwidth !rovides more fre#uenc" range at}

microwave fre#uencies than that of .

 _{Microwave signals travel !redominantl" %" '*).}

 _{;here is much less %ackground noise at microwave}

fre#uencies than at ,.

 _{Microwave s"stems do not re#uire a right(of(wa"}

ac#uisition %etween stations.

 _{ewer re!eaters are necessar" for am!li$cation.}  _{5nderground facilities are minimi<ed.}

 _{ncreased relia%ilit" and less maintenance.}

/isadvantage of Microwave )"stem

 _{More di>cult to anal"<e electronic circuits}

 _{Conventional com!onents 9resistors+ inductors+ and}

ca!acitors cannot %e used at microwave fre#uencies.

 _{;here are !h"sical limitations in creating resonant circuits}

at microwave fre#uencies.

 _{Conventional semi(conductor devices do not work !ro!erl"}

at microwave fre#uencies %ecause of

 _{nherent inductances and ca!acitances of the terminal}

leads and

 _{;ransit time}

 _{or am!li$cation+ vacuum tu%es are used such as kl"strons+}

magnetrons and traveling wave tu%es 9;W;.

 _{/istance of o!eration is limited %" line of sight 9'*).}  _{Microwave signals are easil" re?ected and0or diverted}

%ecause of the ver" short wavelength.

 _{&tmos!heric conditions such as rain0fog can attenuate and}

a%sor% the microwave signal es!eciall" at 2 G< and u!.

Terrestrial Microwave

 _{;"!es *f Microwave )tations}

 _{;erminals @ are !oints in the s"stem where the %ase%and}

signals either originate or terminate

 _{,e!eaters @ are !oints in the s"stem where the %ase%and}

signals ma"%e recon$gured or sim!l" re!eated or am!li$ed.

 _{Passive Microwave repeaters @ a device that re(}

radiates microwave energ" without additional electronic !ower.

 _{%ack to %ack}  _{%ill%oard t"!e}

 _{Active Microwave repeater – a receiver and a}

transmitter !laced %ack to %ack or in tandem with the s"stem. t receives the signal+ am!li$es and resha!es it+ then retransmits the signal to the neAt station.

 ;he B(Curve

 _{& numerical $gure that considers the non(ideal condition of}

the atmos!here refraction that causes the ra" %eam to %e %ent toward the earth or awa" from the earth.

o e r  r  k = = Radius Earth True Radius Earth Effective where: r _o = 6370 km 1 = k  ∞ = k  3 4 = k  1 < k 

B(Curve Conditions

 _{;he microwave %eam is %ent awa"}

from the arth

 _{)tandard Condition}

 _{;he $ctitious earth radius a!!ears}

to the microwave %eams to %e longer than the true earth radius.

 _{)u!er(standard Condition.}  _{;his condition results in an}

eDective ?attening of the

e#uivalent earthEs curvature.

 _{n$nit" Condition 9lat arth}

Condition

 _{;his condition results to <ero}

curvature 9as if the earth is ?at and the microwave %eam follows the curvature of the earth.

8

1

Dective arth ,adius

e

r 

r 

04665

.

0

1

−

=

r _e = effective earth radius

r _o = true earth radius (6370 km) N_ = urface !efractivit" (300) S   H  o S 

 N 

e

 N 

=

arth 8ulge and Curvature

 _{;he num%er of feet or meters an o%stacle is}

raised higher in elevation 9into the !ath owing to earth curvature or earth %ulge.

 K  d  d  h 5 . 1 2 1

=

h = dista%ce i% feet from hori,o%ta' refere%ce 'i%e d_- = dista%ce i% statute mi'es from o%e e%d

d₂ = dista%ce from the other e%d of the .ath

 K  d  d  h 75 . 12 2 1

=

h = dista%ce i% meters from hori,o%ta' refere%ce 'i%e d_- = dista%ce i% ki'ometers from o%e e%d

d₂ = dista%ce from the other e%d of the .ath

/u!leA ;ransmission

re#uenc" -lanning

Frequenc Pat! "en#t! 26 G< 1 miles 1F G< 1 miles 1. G< 2 miles F G< 6 miles

/ata )heets

-3

1reue%c" of #.eratio%

ominal *ut!ut -ower

resnel Hone

=

1_- = radius of the first 1res%e' ,o%e i% feet d_- = dista%ce i% statute mi'es from o%e e%d d₂ = dista%ce from the other e%d of the .ath  = tota' dista%ce i% statute mi'es

GHz   DF  d  d   F ₁

=

1_- = radius of the first 1res%e' ,o%e i% meters d_- = dista%ce i% ki'ometers from o%e e%d d₂ = dista%ce from the other e%d of the .ath  = tota' dista%ce i% ki'ometers

$st _{Fresnel %one}

"ine&o'&(i#!t )*+ o' $st _{Fresnel %one}

&ntenna Gain

(

)

472

.

10

fD

G

=

η 

 

 

 



 

 

=

λ 

π 

η 

D

G

 = *.erture fficie%c"(+etwee% 05 a%d 08)  = *%te%%a iameter i% meters

 = ave'e%th

where:

 = *.erture fficie%c"(+etwee% 05 a%d 08)  = *%te%%a iameter i% meters

f = freue%c" i% /,

&ntenna &rchitecture

)*,

)*+

$*.

-

'ink &nal"sis

ormulas

1. Dective sotro!icall" ,adiated -ower 9,- the amount of !ower that would have to %e emitted %" an isotro!ic antenna to !roduce the !eak !ower densit" o%served in the direction of maAimum antenna gain.

,- I -

 J G

 @ ;''

where:

-_t I , !ower out!ut 9d8m

G_ant I transmit antenna gain 9d8

 ;'' I total transmission line loss at transmitter 9taken from s!ecs+ in d8

2. &ntenna Gain ormula

G

 I K 9Ld0

where:

K I antenna efficienc"

9t"!ical value I .

&ntenna Gain ormula

G

 I 2 log f

 J 2 log d

 J 17.F

where:

f I fre#uenc" in G<

d I diameter of antenna in meters

N ;he gain of an antenna increases or decreases !ro!ortional to the s#uare of its diameter. 9f its diameter changes %" a factor of 2+ its gain changes %" a factor of 4 I 3 d8

6. sotro!ic ,eceive 'evel 9,'

,' I ,- @ )'

where:

,- I Dective sotro!icall" ,adiated -ower in d8m

4. ree )!ace 'oss 9)'



₄

π

_D



 λ





₄

π

_fD





_C





₄

π

_fD





_C



4

π

fD

C

ree )!ace 'oss 9)'

)' I 2 log 94

π

0C J 2 log f J 2 log /

_{When the fre#uenc" is given in M< and}

distance in km+

 )' I 62.4 J 2 log f _9M< J 2 log / _9km

_{When the fre#uenc" is given in M< and}

distance in miles+

ree )!ace 'oss 9)'



_{When the fre#uenc" is given in G< and}

distance in km+



)' I O2.4 J 2 log f

 J 2 log /



_{When the fre#uenc" is given in G< and}

distance in miles+

. ,eceived )ignal 'evel

. ,eceived )ignal 'evel

9,)' @ unfaded

9,)' @ unfaded

,)' I ,' J G

,)' I ,' J G

 @ ;''

 @ ;''

,)' I

-,)' I -_tt J G J G_{ant9;Aant9;A} @ ;'' @ ;''_9;A9;A @ )' J G @ )' J G_{ant9,Aant9,A} @ @

 ;''  ;''_9,A9,A

where:

where:

,' I in d8m

,' I in d8m

G

G

 I receive antenna gain 9d8

 I receive antenna gain 9d8

 ;''

3. ,eceiver ;hreshold 9C0

3. ,eceiver ;hreshold 9C0

the minimum wide%and carrier !ower 9C

the minimum wide%and carrier !ower 9Cminmin at at

the in!ut to a receiver that will !rovide a

the in!ut to a receiver that will !rovide a

usa%le %ase%and out!utP sometimes called

usa%le %ase%and out!utP sometimes called

receiver sensitivit" receiver sensitivit" C0 C0_9d89d8 I ,)' I ,)'_{9d8m9d8m} ( -n ( -n_{9d8m9d8m} where: where:

-n I thermal noise threshold of the

-n I thermal noise threshold of the

receiving s"stem

7. ;hermal oise

7. ;hermal oise

;hreshold 9-n

;hreshold 9-n

-n

-n9d%:9d%: I 174 J 1 log 8 J  I 174 J 1 log 8 J 

where:

where:

 I receiver noise $gure

 I receiver noise $gure

8 I 8andwidth 9hert<

F. ade Margin 9M

e#uation considers the non(ideal and less !redicta%le characteristics of radio wave !ro!agation such as multi- path loss and terrain sensitivity 

Usin# 0arnett&Vi#nant Equation1

M I ,)' @ ,eceiver ;hreshold -ower 'evel

M I 6 log / J 1 log 93&8f @ 1 log 91 @, @ 7 where:

6 log / I multi(!ath eDect

1 log 93&8f I terrain sensitivit"

0arnett&Vi#nant Equation

A @ roughness factor 0 @ factor to convert a worst month !ro%a%ilit" to an annual !ro%a%ilit" A Values

4 smooth terrain+ over water+ or ?at desert

1 average terrain

.2 mountains+ ver" rough or ver" dr" terrain

B Values

. hot humid areas

.2 average inland areas+ normal+ interior

tem!erature or su%(arctic areas

.12 mountainous or ver" dr" %ut non(re?ective areas

)"stem Gain

( t is the diDerence %etween the nominal out!ut !ower of a transmitter and the minimum in!ut !ower re#uired %" a receiver.

( t must %e greater than or e#ual to the sum of all gains and losses incurred %" a signal as it !ro!agates from a transmitter to a receiver.

( t re!resents the net loss of a radio s"stem.

G₎ I -_t ( C_min

-_t ( C_min R 'osses @ Gains where:

G₎ @ )"stem Gain 9d8

-_t @ transmitter out!ut !ower 9d8m

C_min @ minimum receiver in!ut !ower for a given #ualit" o%Qective 9d8m

G

 I M J )' J '

 J '

 @ &

 ( &

Gains

&t @ transmit antenna gain 9d8

&_r @ receive antenna gain 9d8 'osses

)' @ free s!ace !ath loss %etween antennas

'f  @ waveguide feeder loss %etween

distri%ution network and antenna '_% @ %ranching and cou!ling losses

M @ ade Margin for a given relia%ilit" o%Qective

)am!le -ro%lems

1. or a carrier fre#uenc" of 3 G< and a distance of  km+ determine the free(s!ace !ath loss.

)olution:

4

π

fD

C

4

π

6 ! 10

_{#50 ! 10}

_#

3 ! 10

2. &n M '*) microwave link o!erates at 3.1 G<. ;he transmitter out!ut !ower is 1 watt.  ;he !ath length is 64 kmP the antennas at each end have a 6(d8 gain and the transmission line losses at each end are 6 d8. ind the received signal level 9,)'.

)olution: -art 1

Given: f I 3.1 G< -_t I 1 watt I 6 d8m / I 64 km

G_ant9;A I G_ant9,A I 6 d8

 ;''

 ;''

,e#Ed: ,)'

)olEn:

)olution: -art 2

)olving for )':

)' I 2 log

I 2 log

)' I 16F. F d8

70-4

π

fD

C

4

π

6.15 ! 10

_{#34 ! 10}

_#

3 ! 10

'ink 8udget

MICROWAVE COMMUNICATION MICROWAVE COMMUNICATION

'B 85/G;



_{s %asicall" the summar" of all !ossi%le}

losses and gains that a signal ma"

encounter along a microwave !ath.



_{*nce the !ath for a microwave link has}

%een determined+ it is necessar" to

ensure that the received signal !ower is

su>cient for the re#uired signal(to

noise ratio.

 ;ransmitter *ut!ut -ower

 _{taken from the data sheet 9s!eci$cations of the microwave radio}

e#ui!ment.

  _{;his is the amount of microwave carrier out!ut !ower+ usuall" eA!ressed}

Antenna Gain



_{Tx Antenna Gain}

 _{taken from the s!eci$cations of the !ara%olic dish.}   _{;he amount of increase in the signal densit" when it}

undergoes the !rocess of %eing focused into a !encil %eam.

  _{;his amount of gain+ usuall" eA!ressed in d8 9over} isotro!ic



_{Rx Antenna Gain}

 _{taken from the s!eci$cations of the !ara%olic dish.}   _{;his amount of gain+ usuall" eA!ressed in d8 9over}

isotro!ic

  _{;he amount of increase in the signal densit" when} it undergoes the !rocess of %eing focused %ack into the waveguide.

Types of Gain



Received Signal Level (RSL)

 _{com!uted from a formula.}

  _{;his is the amount of in!ut signal into the}

receiver from the waveguide.

 t is the sum of all losses and gains on the

transmitter out!ut.



Receiver Threshold Power

 _{taken from s!ecs of radio e#ui!ment.}

  _{;his is the minimum amount of microwave}

carrier in!ut !ower+ usuall" eA!ressed in d8m which the receiver can still accuratel" detect and discriminate information carried. 9C0

 ;"!es of 'osses

TYPES OF LOSSES



_{ree )!ace 'oss 0 -ath}

&ttenuation 9)' 0 -&

 _{Com!uted from a formula. ;his amount of}

loss+ eA!ressed in d8+ is how much the

signal densit" reduces as it travels in free s!ace.



 ;otal ;ransmission 'oss

 _{losses due to the transmission medium used in}

ree()!ace 'oss 9)'



_{where / is measured in kilometersP}



_{where / is measured in statute milesP}



_{where / is measured in nautical milesP}

 MHz  km dB  D F   FSL ₌

₃₂

_.

₄₅

₂₀

_log

₂₀

_log

₃₆

_.

₅₈

₂₀

_log

₂₀

_log

 D

F 

 FSL

=

37

.

80

+

20

log

+

20

log

ote! f 1 is stated i% iahert, add 60 to the va'ue of the co%sta%t term

Transmission Losses

 _{W&SG5/ '*))}

  _{;aken from the s!ecs of the waveguide used. ;his is the amount of}

loss+ usuall" eA!ressed in d8 !er unit length 9d80ft or d80m of signal as it travels in the waveguide.

 _{C*C;*, '*))}

 _{taken from s!ecs 9. d8}

 _{C*5-'G '*))}

 _{taken form s!ecs 9coaA to waveguide to air}

 _{T8,/ '*))}

 _{taken from s!ecs+ a.k.a circulator loss 91d8}

 _{,&/*M '*))}

 ;ransmission 'osses

#NN;#! &#

#<&N/ &#

>?! &# !*#$ &#

ade Margins

Para-eter Function Value Unit Tpe 2escription Microwave ,adio

*ut!ut -ower Given d8 Saria%le ;aken from ,adio )!eci$cation Connector 'oss )u%tracted d8 ;"!ical ;aken from Waveguide )!eci$cations Waveguide 'oss )u%tracted d8 Saria%le ;aken from Waveguide )!eci$cations Connector 'oss )u%tracted d8 ;"!ical ;aken from Waveguide )!eci$cations &ntenna Gain &dded d8 Saria%le ;aken from &ntenna )!eci$cations ree )!ace 'oss )u%tracted d8 Saria%le Com!uted from ormula

&ntenna Gain &dded d8 Saria%le ;aken from &ntenna )!eci$cations Connector 'oss )u%tracted d8 ;"!ical ;aken from Waveguide )!eci$cations Waveguide 'oss )u%tracted d8 Saria%le ;aken from Waveguide )!eci$cations Connector 'oss )u%tracted d8 ;"!ical ;aken from Waveguide )!eci$cations

-ower n!ut to

,eceiver 9,)' Com!uted d8 Saria%le Com!uted from ormula Minimum ,eceiver

 ;hreshold Given d8 Saria%le ;aken from ,adio )!eci$cation  ;hermal ade

Atmospheric Absorption Loss (AAL)

a. *UTG &8)*,-;* '*))

( attenuation due to the a%sor!tion

of radio fre#uenc" energ" %" oA"gen

molecules in the atmos!here.

%. W&;, S&-*, '*))

( attenuation due to the a%sor!tion

of radio fre#uenc" energ" %" water

va!or in the atmos!here.

Miscellaneous Path Loss (MPL)

a. /,&C;* '*)))

( /e$ned as the modulation or redistri%ution of 

energ" within a wave front when it !asses near the edge of an o!a#ue o%Qect.

( !ath is %locked %" an o%struction

i. /'- @ Difraction Loss due to Path

ii. /') - Difraction Loss due to Shielding %. ,'C;* '*)) 9,'

T!"R LSS"S

a. ,& '*)))

( attenuation due to the eDects of rain

%. C'5;;, '*)))

( attenuation due to trees and %uildings in the front of the antenna

c. &;& M)&'GM;

( human factor error. ;his loss comes from the condition of the antenna when %eing installed.  ;he value of this loss is assumed never to go

a%ove .2d8 !er antenna or . d8 for the link.

#"T PAT! LSS

 _{$i%%erence between the transmitter output}

ading and

ade Margin

ading



_{Sariations in signal loss which can %e}

caused %" natural weather

distur%ances+ such as rainfall+ snowfall+

fog+ hail and eAtremel" cold air over a

warm earth.



_{Can also %e caused %" man(made}

distur%ances+ such as irrigation+ or from

multi!le transmission !aths+ irregular

ade Margin

 _{is the diDerence %etween the ,)' and the}

receiver threshold or sensitivit".

 _{is the additional loss added to the normal !ath}

loss to accommodate the eDects of tem!orar" fading+ that considers the non(ideal and less !redicta%le characteristics of radio(wave

'AT"GR"S  A$#G



_{'&; &/G}

 _{non(fre#uenc" de!endent fading occurring}

during atmos!heric variations like heav" rain and ducting and aging or !artial failure of

e#ui!ment.

 _{R"*+"#', S"L"'T-" A$#G}

 _{due to multi!aths formed %" atmos!here+}

'+#T"RM"AS+R"S

 _{'&; &/G}

 _{Link Overbuilding (Antenna,mproved receiver per!ormance,po"er#}  _{$esite or shorten distance bet"een sites (multihops#}

 _{Path Diversity}   _{)'C;S &/G}  _{Space Diversity}   _{%re&uency Diversity}   _'&ualiers  _{"*+PM"#T R"LA.LT,}

 _{)ot *standby Arrangement}   _{Diversity Arrangement} 

/iversit"

 _{-roviding se!arate !ath to transmit redundant}

information

 _{re#uenc" diversit"}

 _{5ses two diDerent fre#uencies to transmit the} same information.

 _{)!ace diversit"}

 _{)ame fre#uenc" is used+ %ut two receive antennas} se!arated verticall" on the same tower receive the information over two diDerent !h"sical !aths

 ;he method of transmission ma" %e due

to:

a. ,V5CT

 %. )-&C

c. -&;

d. ;M

-&; /S,);T

 _{Method of signal rerouting or simultaneous}

transmission of same information on diDerent !aths. -aths should %e at least 1 kms a!art.

)-&C /S,);T



 _{;he receiver acce!ts signals from 2 or}

more antennas that are verticall" s!aced

a!art %" man" wavelength 92 or

more



_{/e!ending u!on the design+ the diversit"}

com%iner either selects or adds the

signal. f signals are to %e added+ then

the" should %e %rought in !hase.



 _{;he lower of the two antennas must %e}

high enough for relia%le '*)

communication.

)!ace /iversit"

)!ace /iversit" Main

eatures



_{o additional fre#uenc" assignment is}

re#uired.



_{-rovides !ath redundanc" %ut not}

e#ui!ment redundanc".



_{More eA!ensive than fre#uenc"}

diversit" due to additional antennas

and waveguides.

)-&C /S,);T *,M5'&

Antenna (eparation

For-ula I-prove-ent Factor

where: ) I se!aration 9m , I eDective earth radius 9m  I wavelength 9m ' I !ath length 9m 5_sd! I 5nd! l)/ Where:

 l)/I s!ace diversit" im!rovement

factor 9,atio

 ) I vertical se!aration %et 2 antennas 9m

  I fre#uenc" 9G<  / I -ath length 9m

 M I fade margin+ smaller vase 9d8  L  R S = 3λ   D S   f   SD  FM  10 2 23 10 10 23 . 1 × × × × = −

,V5CT /S,);T



_modulates

₂

_diDerent

_,

_carrier

fre#uencies

with

the

same



intelligence+ then transmits %oth ,

signals to a given destination.



_the

_carrier

_fre#uencies

_are

₂₍₆₌

se!arated+ since the fre#uenc" %and

allocations are limited.

re#uenc" /iversit"

mprovement actor o%

re/uenc0 $iversit0

l

 I

l/ I im!rovement factor 9ratio /f I re#uenc" )e!aration 9Mh< M I ade Margin

 I fre#uenc" 9Gh<P 92 f  11 / I -ath length 9kmP 96 /  7

 ;ime 5navaila%ilit"

 ;ime availa%ilit" 9 A_v  is commonl" in the range

from .OO to .OOOOO or OO= to OO.OOO= of the time.

 5navaila%ilit" 9+_nav is Qust contrar" to the

a%ove de$nition.

v nav

A

,eferences

 _{,adio )"stem /esign for ;elecommunication+}

 ;hird dition

 _{,oger '. reeman}

 _{Co!"right X 27 Yohn Wile" Z )ons+ nc.}

 _{Microwave ;ransmission etworks}

 _{arve" 'eh!amer}

 _{Co!"right X 24 McGraw(ill Com!anies+ nc.}

 _{undamentals of Microwave Communication}

 _{Mann" ;. ,ule}

 _{Microwave ngineering /esign Consideration}