Microwave link operaton

MW link operration:

Microwave link will only work when, 

RSL >= Rx

RSL= Receiver Signal Level
Rx= Receiver Sensitivity Threshold

-Here we ignore the path fading phenomenon that may add additional loss to the radio signal and cause the strength of the received signal to fall.

RSL: 

RSL= TX power- TX cable loss + TX antenna gain-free space loss +RX antenna gain-RX cable loss.

Assuming identical antenna and cables at both ends:

RSL= TX power- 2x Cable loss+ 2x Antenna gain-Free space loss.

 AGC (Automatic Gain Control):

AGC is a system by means of which the overall gain of a radio receiver is varied automatically with the changing strength of the received signal, to keep the output substantially constant.

Some Units:

-AGC= Volts
-RSL(RX Power) = dBm
-TX power= dBm
-Cable Loss= dB
-Antenna Gain= dBi

Conversions:
Watts to dB:
dB=10 log P in Watts ; P = Power

Relation Between dB and dBm:
dBm = dB + 30

RX Threshold:

Rx sensitivity = -174 + 10 log BW + NF + SNR

-NF= Noise Figure(8 dB for 15GHz Link) 

-SNR=Signal to Noise Ratio(10 Minimum)
-BW= Bandwidth (No of PCM’s)

For 15 GHz Link with 4E1 capacity the sensitivity would be

                                                          = -174 + 10 log (8.2x10^6) + 8 +10

                                                          = -86dBm