# Chapter 13: Interference¶

## Example 13.1, Page 350¶

In [1]:
#Variable Declaration
EIRP1=34     #desired carrier EIRP from satellite(dB)
G1=44    # ground station receiving antenna gain(dB)
G2=24.47 #Gain in desired direction(dB)
EIRP2=34  #EIRP by interfering satellite(dB)
PD=4      #Polarization discrimination(dB)

#Calculation

CIR=EIRP1-EIRP2+G1-G2+PD  #Carrier to Interference ratio(dB)

#Result

print "The Carrier to interfernce ratio at the ground receiving antenna is",CIR,"dB"

The Carrier to interfernce ratio at the ground receiving antenna is 23.53 dB


## Example 13.2, Page 350¶

In [2]:
#Variable Decalration

PA=24   #Transmit power by station A(dBW)
G1=54   #Antenna Gain(dB)
PC=30   #Transmit power by station C(dBW)
G2=24.47#off-axis gain in the S1 direction(dB)
PD=4      #Polarization discrimination(dB)

#Calculation

CIR=PA-PC+G1-G2+PD   #Carrier to Interference ratio(dB)

#Result

print "The Carrier to interfernce ratio on uplink is",CIR,"dB"

The Carrier to interfernce ratio on uplink is 27.53 dB


## Example 13.3, Page 351¶

In [3]:
import math
#Variable Declaration

CIR1=27.53   #Carrier to interference ratio from Example 13.1(dB)
CIR2=23.53   #Carrier to interference ratio from Example 13.2(dB)

#Calculation

ICRu=10**(-CIR1/10)  #Interferece to carrier ratio for uplink
ICRd=10**(-CIR2/10)  #Interferece to carrier ratio for downlink

ICRant=ICRu+ICRd   #Overall Interferece to carrier ratio
CIRant=-10*math.log10(ICRant)#Overall Carrier to interference ratio (dB)
CIRant=round(CIRant,2)
#Result

print "The overall carrier to interference ratio is",CIRant,"dB"

The overall carrier to interference ratio is 22.07 dB


## Example 13.4, Page 352¶

In [4]:
import math
#Variable Declaration

SSi=4 #Initial satellite spacing(degrees)
SSl=2 #Later Satellite spacing(degrees)

#Calculation

IIR=(29-25*math.log10(SSl))-(29-25*math.log10(SSi))  #Increase in Interference(dB)
IIR=round(IIR,1)
#Result


The degradation in downlink C/I is 7.5 dB


## Example 13.5, Page 356¶

In [5]:
#Variable Declaration

f=4.2  #modualating frequency(MHz)
m=2.571 #Modulation index
QIF1=4.2   #Quality Impairment factor(a)
QIF2=4.5  #Quality Impairment factor(b)

#Calculation

Dv=2*m*f  #Peak to peak deviation(MHz)

PR1=12.5-20*math.log10(Dv/12)-QIF1+1.1*QIF1**2 #Protection ratio for case(a)
PR1=round(PR1,1)
PR2=12.5-20*math.log10(Dv/12)-QIF2+1.1*QIF2**2 #Protection ratio for case(b)
PR2=round(PR2,1)
#Results

print "The protection ratio for quality impairment factor of 4.2 is",PR1,"dB"

print "The protection ratio for quality impairment factor of 4.5 is",PR2,"dB"

The protection ratio for quality impairment factor of 4.2 is 22.6 dB
The protection ratio for quality impairment factor of 4.5 is 25.2 dB


## Example 13.6, Page 363¶

In [6]:
#Variable Decalration
GE=25    #Receiving gain of earth station(dB)
GE1=25   #Transmit gain of E1 in the direction of S(dB)
GS=9     #receive gain of S in the direction of E1(dB)
GS1=9   #Transmit gain of satellite S1 in the direction of E(dB)
GTE=48  #Transmit gain of E(dB)
GTS=19  #Transmit gain of S(dB)
US=-60    #Maximum power spectral density(dBJ)
US1=1   #Maximum power spectral density(uJ)
UE1=10  #Maximum power spectral density transmitted by earth station(uJ)
UE=-50  #Maximum power spectral density transmitted by earth station(dBJ)
k=-228.6
#Calculation

URS=UE+GTE+GRS-LU#Received power spectral density at satellite S(dB)
URE=US+GTS+GRE-LD#Received power spectral density at satellite E(dB)
y=URE-URS    #Transmission gain for network R(dB)

I1=US+GS1+GE-LD  #Interference received by earth station(dB)

delTS=I2-k   #Noise temperature at satellite receiver input(dBK)

delTSE=y+delTS  #Noise Temperature rise(dBKelvin)
delTSE=10**(delTSE/10)  #Noise Temperature rise(Kelvin)
delT=delTSE+delTE  #Equivalent noise temperature rise
delT=round(delT,2)

print URE,URS
#Results

print "The transmission gain is",y,"dB"
print "The interference levels I1 an I2 are",I1,I2,"dBJ respectively"
print "The equivalent temperature rise overall is",delT,"Kelvin"

-189 -183
The transmission gain is -6 dB
The interference levels I1 an I2 are -222 -216 dBJ respectively
The equivalent temperature rise overall is 9.14 Kelvin