Microwave communication is kind of Line of Sight communication (LOS) and Transmitting power without obstacle.
Radio Microwave Link determines below parameters:
Principle of Link budget is path length with signal level and Receive signal level determines Fading margin.
Factor for calculating Fading margin is Free-Space loss:
Receiver Signal Level = EIRP – Lfs+ Grx – Lrx
EIRP (Effective Isotropic Radiated Power) is the measured radiated power of an antenna in a specific direction. It is also called Equivalent Isotropic Radiated Power. It is the output power when a signal is concentrated into a smaller area by the Antenna. The EIRP can take into account the losses in transmission line, connectors and includes the gain of the antenna. It is represented in dB. Enter the transmitted power, cable loss and antenna gain to calculate the EIRP (Effective Isotropic Radiated Power).
EIRP = Ptx – Ltx + Gtx
Where is:
Where is:
We receive
F radius of Fresnel Zone is the most important to calculate the antenna height to make sure to transmit signal radio frequency without obstacle.
Fresnel Zone calculation depends on:
Radius of First Fresnel Zone
F = 12.75x[(d1xd2)/(f xD)]1/2
Where is
f : transmitting frequency GHz
d1 and d2distance compare with obstacle point between both stations Km
D distance between both stations Km F is Radius of First Fresnel Zone m
Radius of First Fresnel Zone without obstacle between both stations
F = 17.3x(D/4f)1/2
Where is:
F Radius of First Fresnel Zone m
D distance between both stations Km
f transmitting frequency GHz
Microwave Antenna height is bigger than Radius of First Fresnel Zone plus obstacle between both stations
Radius of First Fresnel Zone(m)+Obstruction Height(m) ≤ Microwave Antenna Height(m)
Also read Fresnel Zone in Digital Microwave Communication
- Flat Fading Margin (FFM) or System Operating Margin (SOM): relate to Transmitting Power, Type of Antenna Disk Lenght Coaxial and distance. It is calcaulated to ensure if tramsitting power is enough.
- Free Space Loss (FSL) : determines transmitting power in space
- Fresnel Zone Clearance (FZC) : Height antenna
- Antenna Bearing, Antenna down tilt and Antenna down tilt coverage radius :
Calculation of Link Budget and Fresnel Zone Clearance
1. Link Budge
Factor for calculating Fading margin is Free-Space loss:
Receiver Signal Level = EIRP – Lfs+ Grx – Lrx
EIRP (Effective Isotropic Radiated Power) is the measured radiated power of an antenna in a specific direction. It is also called Equivalent Isotropic Radiated Power. It is the output power when a signal is concentrated into a smaller area by the Antenna. The EIRP can take into account the losses in transmission line, connectors and includes the gain of the antenna. It is represented in dB. Enter the transmitted power, cable loss and antenna gain to calculate the EIRP (Effective Isotropic Radiated Power).
EIRP = Ptx – Ltx + Gtx
Where is:
- Ptx: transmitter output power
- Lfs: free space path loss (dB)
- Gtx: transmitter antenna gain
- Grx: receiver antenna gain
- Ltx: transmitter feeder loss
- Lrx: receiver feeder loss
Free space path loss calculation
Lfs = 32.4 + 20*log10 F + 20* log10 D
Where is:
- Lfs= free space loss in dB
- F = frequency (MHz)
- D = path length, in kilometers (Km)
Flat Fade Margin
Flat fade margin = Receive signal level – Receiver sensibility threshold
2. Fresnel Zone Clearance
Fresnel Zone calculation depends on:
- Transmitting frequency
- The distance covered
- If Radius of First Fresnel Zone has obstacle between both stations
Radius of First Fresnel Zone
F = 12.75x[(d1xd2)/(f xD)]1/2
Where is
f : transmitting frequency GHz
d1 and d2distance compare with obstacle point between both stations Km
D distance between both stations Km F is Radius of First Fresnel Zone m
Radius of First Fresnel Zone without obstacle between both stations
F = 17.3x(D/4f)1/2
Where is:
F Radius of First Fresnel Zone m
D distance between both stations Km
f transmitting frequency GHz
3. Microwave Antenna height
Microwave Antenna height is bigger than Radius of First Fresnel Zone plus obstacle between both stations
Radius of First Fresnel Zone(m)+Obstruction Height(m) ≤ Microwave Antenna Height(m)
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| Fresnel Zone |
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