# Chapter No.2 : Appendix B Noise figure calculations for link budgets¶

## Example no B.1 Page no. 613¶

In [11]:
# To determine SNR at the detector output stage

# Given data
SNRin=20#                                         # SNR at the receiver antenna input terminal in dB
F=6#                                              # Noise figure in dB

# SNR at the detector output stage
SNRout=SNRin-F#                                  # SNR at the detector output stage in dB

# Displaying the result in command window
print '\n SNR at the detector output stage = %0.0f dB'%(SNRout)#

 SNR at the detector output stage = 14 dB


## Example no B.2 Page no. 613¶

In [12]:
from __future__ import division
from math import log10
#To compute noise figure of mobile receiver system

#Given data
F1=3#                                       #Coaxial cable loss in dB
F1=10**(F1/10)#                              #Coaxial cable loss
F2=6#                                       #Noise figure of phone in dB
F2=10**(F2/10)#                              #Noise figure of phone

Fsys=F1+((F2-1)/0.5)#                       #Noise figure of mobile receiver system
Fsys=10*log10(Fsys)#                        #Noise figure of mobile receiver system in dB

# Displaying the result in command window
print '\n Noise figure of mobile receiver system = %0.0f dB'%(Fsys)

 Noise figure of mobile receiver system = 9 dB


## Example no B.3 Page no. 614¶

In [13]:
from __future__ import division
from math import log10
# To determine average output thermal noise power

# Given data
T0=300#                                                                   # Ambient room temperature in K
Fsys=8#                                                                   # Noise figure of the system
Tant=290#                                                                 # Effective temperature of antenna in K
K=1.38*10**-23#                                                            # Boltzmann's constant in J/K
B=30000#                                                                  # Effective bandwidth in Hz

Te=(Fsys-1)*T0#                                                           # Effective noise temperature in K
Ttotal=Tant+Te#                                                           # Overall system noise temperature in K

# To determine average output thermal noise power
Pn=(1+(Ttotal/T0))*K*T0*B#                                                # Average output thermal noise power in W
Pn=10*log10(Pn/(10**-3))#                                                  # Average output thermal noise power in dBm

# Displaying the result in command window
print '\n Average output thermal noise power = %0.1f dBm'%(Pn)#

 Average output thermal noise power = -119.5 dBm


## Example no B.4 Page no. 614¶

In [1]:
# To determine average signal strength at the antenna terminal

# Given data
Pn=-119.5#                                                           # Average output thermal noise power in dBm
SNR=30#                                                              # SNR at the receiver output in dB

# To determine average signal strength at the antenna terminal to provide 30dB SNR
Ps=SNR+Pn#                                                           # Average signal strength at the antenna terminal

# Displaying the result in command window
print '\n Average signal strength at the antenna terminal to provide 30dB SNR = %0.1f dBm'%(Ps)#

 Average signal strength at the antenna terminal to provide 30dB SNR = -89.5 dBm


## Example no B.5 Page no. 615¶

In [2]:
# To determine average signal strength at the antenna terminal

# Given data
Pn=-104.5#                                                           # Average output thermal noise power in dBm
SNR=36#                                                              # SNR at the receiver output in dB

# To determine average signal strength at the antenna terminal to provide 36dB SNR
Ps=SNR+Pn#                                                           # Average signal strength at the antenna terminal

# Displaying the result in command window
print '\n Average signal strength at the antenna terminal to provide 30dB SNR = %0.1f dBm'%(Ps)#

 Average signal strength at the antenna terminal to provide 30dB SNR = -68.5 dBm


## Example no B.6 Page no. 615¶

In [16]:
from __future__ import division
from math import log10
#To compute noise figure of mobile receiver system

#Given data
F1=5#                                       #Coaxial cable loss in dB
F1=10**(F1/10)#                              #Coaxial cable loss
F2=8#                                       #Noise figure of phone in dB
F2=10**(F2/10)#                              #Noise figure of phone

Fsys=F1+((F2-1)/0.5)#                       #Noise figure of mobile receiver system
Fsys=10*log10(Fsys)#                        #Noise figure of mobile receiver system in dB

# Displaying the result in command window
print '\n Noise figure of mobile receiver system = %0.0f dB'%(Fsys)

 Noise figure of mobile receiver system = 11 dB


## Example no B.7 Page no. 615¶

In [3]:
# To determine SNR at the detector output stage

# Given data
SNRin=30#                                         # SNR at the receiver antenna input terminal in dB
F=6#                                              # Noise figure in dB

# SNR at the detector output stage
SNRout=SNRin-F#                                  # SNR at the detector output stage in dB

# Displaying the result in command window
print '\n SNR at the detector output stage = %0.0f dB'%(SNRout)#

 SNR at the detector output stage = 24 dB