MICROWAVE PATH PROFILE 18 GHz
MICROWAVE PATH PROFILE
18 GHz | 12 km Link
[OVERVIEW]
This diagram shows a realistic point-to-point microwave (MW) backhaul link between two telecom towers.
The link is designed using line-of-sight (LOS), Fresnel zone clearance, obstacle clearance, and Earth curvature calculation.
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[SITE A DETAILS]
Site Name: Site A
Ground Elevation: 102 m AMSL
Tower Height: 30 m
Antenna Center Height:
= 102 m + 30 m
= 132 m AMSL
Equipment at Site A:
- MW dish antenna
- Tower structure
- Outdoor radio unit
- Indoor transmission equipment in shelter
- Power and grounding system
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[SITE B DETAILS]
Site Name: Site B
Ground Elevation: 118 m AMSL
Tower Height: 25 m
Antenna Center Height:
= 118 m + 25 m
= 143 m AMSL
Equipment at Site B:
- MW dish antenna
- Tower structure
- Outdoor radio unit
- Indoor transmission equipment in shelter
- Power and grounding system
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[LINK DETAILS]
Link Type: Point-to-Point Microwave Link
Frequency: 18 GHz
Total Path Distance: 12 km
Transmission Type: LOS Microwave Backhaul
Typical Use:
- BTS to BTS connectivity
- BTS to hub site
- Transmission backhaul
- Data and voice transport
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[LINE OF SIGHT (LOS)]
The straight blue line between Site A and Site B is the LOS path.
This is the direct signal path that the microwave radio follows.
LOS midpoint height:
= (132 m + 143 m) / 2
= 137.5 m AMSL
Meaning:
- Signal travels directly from one antenna to the other
- No major obstruction should block this path
- Good alignment is required for stable performance
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[FIRST FRESNEL ZONE]
First Fresnel Zone Radius Formula:
F1 = 17.3 × sqrt((d1 × d2) / (f × d))
Where:
- d1 = distance from Site A to obstacle = 6 km
- d2 = distance from obstacle to Site B = 6 km
- d = total path distance = 12 km
- f = frequency = 18 GHz
Calculation:
F1 = 17.3 × sqrt((6 × 6) / (18 × 12))
F1 = 17.3 × sqrt(36 / 216)
F1 = 17.3 × sqrt(0.1667)
F1 ≈ 17.3 × 0.408
F1 ≈ 7.06 m
Result:
First Fresnel Zone Radius = 7.06 m
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[REQUIRED FRESNEL CLEARANCE]
For safe MW design, at least 60% of the first Fresnel zone should be clear.
Calculation:
Required Clearance = 0.6 × 7.06
Required Clearance = 4.24 m
Result:
60% Fresnel Clearance = 4.24 m
Meaning:
- Obstacles should stay below this safe clearance zone
- Better clearance means better signal reliability
- Poor Fresnel clearance can cause fading and signal loss
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[OBSTACLE DETAILS]
Highest Obstacle Elevation: 128 m AMSL
Obstacle Location: Midpoint of path
Meaning:
- This is the highest point between both sites
- It can be a hill, building, tree cluster, or terrain rise
- It must stay below the required clearance zone
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[EARTH CURVATURE]
Earth bulge must be considered in real path profile design.
Formula:
hb = (d1 × d2) / (12.75 × K)
Where:
- d1 = 6 km
- d2 = 6 km
- K = 4/3 standard Earth radius factor
Calculation:
hb = (6 × 6) / (12.75 × 4/3)
hb = 36 / 17
hb ≈ 2.12 m
Result:
Earth Curvature Effect at Midpoint = 2.12 m
Meaning:
- Due to Earth curvature, the ground appears to rise in the middle of the path
- This reduces the effective link clearance
- It must be included in MW path design
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[TOTAL REQUIRED CLEARANCE HEIGHT]
Minimum required LOS height over obstacle point:
Required path height
= Obstacle Height + Earth Curvature + 60% Fresnel Clearance
= 128 + 2.12 + 4.24
= 134.36 m AMSL
Result:
Minimum required signal path height at obstacle point = 134.36 m AMSL
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[ACTUAL MIDPOINT PATH HEIGHT]
Actual LOS midpoint height:
= 137.5 m AMSL
Clearance above obstacle:
= 137.5 - 128
= 9.5 m
Clearance above obstacle and Earth curvature:
= 137.5 - 128 - 2.12
= 7.38 m
Spare clearance after 60% Fresnel requirement:
= 7.38 - 4.24
= 3.14 m
Result:
Extra Safe Clearance Margin = 3.14 m
Meaning:
- The path is clear
- The design passes the basic path profile check
- The link should work properly if alignment and link budget are also correct
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[FINAL DESIGN STATUS]
Path Status: PASS
Reason:
- Direct LOS is available
- Fresnel zone clearance requirement is met
- Earth curvature is included
- Obstacle does not block the safe signal area
- Extra margin is available
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[FIELD ENGINEERING INTERPRETATION]
This profile shows that:
- Site A and Site B can be connected by MW radio
- 18 GHz is possible over 12 km in this example
- Proper antenna height selection is very important
- Even with a midpoint obstacle, the path is still workable
- A safe margin of 3.14 m remains after all major checks
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[WHAT THE DIAGRAM LABELS MEAN]
MICROWAVE PATH PROFILE
= Overall name of the path design drawing
18 GHz | 12 km Link
= Operating frequency and total link distance
LOS (Line of Sight)
= Direct MW radio path between both antennas
First Fresnel Zone: 7.06 m
= Radius of first Fresnel zone at critical point
60% Clearance: 4.24 m
= Minimum recommended safe Fresnel clearance
Highest Obstacle: 128 m AMSL
= Highest terrain/object elevation along path
Earth Curvature: 2.12 m
= Midpoint Earth bulge effect
Clearance Margin: 3.1 m
= Remaining safe design margin after calculations
Distance: 12 km
= Total separation between both towers
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[PRACTICAL SITE COMPONENTS NOTED IN THIS TYPE OF DESIGN]
Typical MW link installation includes:
- MW dish antenna
- ODU / radio unit
- IF or Ethernet cable route
- IDU / modem
- Router or transmission equipment
- DC power system
- Rectifier and battery backup
- Earthing / grounding
- Aviation light if required
- Tower ladder and mounting bracket
- Waveguide or feeder arrangement depending on system
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[IMPORTANT REAL-WORLD CHECKS BEFORE FINAL DEPLOYMENT]
This drawing is a planning example.
Before real deployment, engineers should also check:
- Exact GPS coordinates
- Actual terrain survey
- Clutter data
- Rain fade calculation
- Link budget
- Antenna gain
- Radio TX power
- Receiver sensitivity
- Modulation level
- Availability target (99.9%, 99.99%, etc.)
- Wind loading
- Tower strength
- Lightning protection
- Alignment azimuth and elevation
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[SIMPLE SUMMARY]
This diagram explains a 12 km, 18 GHz MW link between two telecom towers.
Site A:
- Ground elevation = 102 m AMSL
- Tower height = 30 m
- Antenna height = 132 m AMSL
Site B:
- Ground elevation = 118 m AMSL
- Tower height = 25 m
- Antenna height = 143 m AMSL
Path calculations:
- First Fresnel Zone = 7.06 m
- 60% Fresnel Clearance = 4.24 m
- Highest obstacle = 128 m AMSL
- Earth curvature = 2.12 m
- Actual midpoint LOS height = 137.5 m AMSL
- Extra clearance margin = 3.14 m
Conclusion:
This MW path profile is technically clear and suitable as a basic telecom microwave link example.
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[SHORT CAPTION]
Realistic 18 GHz microwave path profile over 12 km showing LOS, Fresnel zone, Earth curvature, obstacle clearance, tower heights, and safe clearance margin between Site A and Site B.
