3.4 Antenna System

Site Engineering InstructionsANTENNA SYSTEM
NOKIA NODE-B SITE
ANTENNA LINE
ANTENNA SYSTEM PRODUCTS
* © NOKIA COMPANY CONFIDENTIAL Implementation training v01 Working guidelines (Antenna Line).ppt / 12-12-2003/ ORu
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Antenna Installation
CS72191.14 DT-kit for A, F & Euro panel
CS72196 Clamp 50-115mm for A, F & Euro panel
Combines the advantages of being able to adjust the downtilt angle without affecting the radiation pattern
Downtilt is adjusted using a rotary knob on the bottom of the antenna
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Increase coverage
BTS RX w/o MHA
BTS RX with MHA
MHA (Mast Head Amplifier)
MHA amplifies Rx signal.
Practically always Rx coverage is limited without MHA, due to the antenna feeder loss. MHA compensates for this loss by amplifying Rx signal. By this way we get
- better sensitivity for the BTS
- better up-link signal
- balanced link
- coverage increase
- lower mobile output power: less interference in the network, more battery life
Note! In UltraSite BTS the MHA also does the front end receiver amplification, thus there is not necessarily any Rx gain in BTS. This is a reason why Ultra MHA has high gain (32…33 dB). This kind of system has very sensitivity and can not be affected by any level of feeder loss. The benefit can be even 1.0 dB better system sensitivity than with Talk MHA installed in UltraBTS, in long antenna lines.
All the other Nokia MHAs (Talk, WCDMA) have low 12dB gain. High or low gain MHA has been selected program by program. According to Friiz Law the more gain on top of mast the better the BTS sensitivity. On the other hand high gain MHA is a bit more expensive to build up as the LNA has to be done with 2 serial FETs.
Due to longer antenna lines MHAs are recommended at least in rural, sub-urban and road site.
WCDMA Bias T
Compact easy to install package containing two MHAs
Compensates for feeder and combiner losses in up-link direction
Reduces transmission power level of mobile station
Fully integrated tested and type approved according to 3GPP requirements
Reduces inter-cell and intra-cell interference
2 MHAs mounted back-to-back
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Nokia WCDMA Dual Mast Head Amplifier
Noise Figure is the max at room temp, max over operating temp is 1.9dB
Sheet1
Gain
Weight
Nokia Mast Head Amplifier block diagram
RXin FILTER
RXout FILTER
Current Sense, Bypass & Alarm Control Circuit
In case of MHA failure the signal is routed through the by-pass path, thus allowing the cell to operate (with degraded performance)
Feeds the power to MHA through feeder line
Handles MHA and VSWR alarms
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WCDMA Bias-T
BTS port
ANT port
DC block
Alarm out
Voltage Standing Wave Ratio (VSWR) measurement is integrated in the WCDMA BiasT.
At the moment VSWR monitoring can be performed on TX antenna line only.
Pure Rx diversity antenna can not be monitored now - "Comparing RSSI (received signal strenght indication) Value" will do it in later software releases
The fixed VSWR thresholds are as follows:
VSWR 2.6 or lower: antenna operation OK
VSWR greater than 2.6: indicates antenna fault
An alarm is generated in case of antenna fault when VSWR threshold exceeded. -> alarm raised in the O&M system and the affected TRXs turned off.
VSWR is designed to detect major faults in antenna line, not to be a high accuracy measurement feature
- Note a big RL difference between the antenna line with MHA (e.g.15 dB) and without MHA (e.g. 20 dB)!
- 'Call drop rate' and 'Handover success rate' are still good referencies to make sure antenna line is OK
Lightning protection (MHA + BiasT)
large conducting areas
BiasT
BTS
Feeder
LNA
/4
Jumper
Jumper
/4
This is meant to be a brief sketch of the way a BTS equipped with MHA’s is protected from lightning strikes. As can be seen it is a multi stage protection. Beginning on the antenna port with a large conductive area (>25mm2) grounded quarter wave stub. This is followed by a gas-tube protector on the BTS side of the MHA. Because of the slow reaction from the gas tube arrester a so called transorber (or power zener) is mounted in parallel with it to ensure that no high voltage spikes will reach the LNA board. This protection is tested as a primary protection and can sustain both the short but intense 8/20 micro s. pulse (with 20 kA) as well as the long 10/350 micro s. pulse test (2 kA).
A similar solution is implemented in the Bias Tee to protect the BTS and power supply from induced lightning pulses on the feeder cable. This is also designed and tested as a primary protection with both 8/20 and 10/350 micro s. pulses.
The secondary, or BTS side of the Bias Tee, is galvanically isolated from the primary side by a tubular distributed or “mechanical” capacitor with insulation made from thick PTFE. This design gives a very reliable and ruggedized capacitor, which can withstand thousands of volts. The distributed design also makes it possible to get perfect RF-coupling with less than two Pico Farads of capacitance and thereby very god blocking of any voltages spikes. But a shorted quarter wave stub is still fitted to even further guarantee that no unacceptable voltage spikes will reach the BTS. This last stub however is not of the same large area as the primary one.
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MHA Installation
Mounting bracket on a pole
(40-110 mm diameter)
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MHA Installation with special bracket
Also wall installation is supported by the monting bracket. The bolts have to be provided by installation teams.
Nokia MHAs are always installed vertically.
* © NOKIA MHA. v.1.0. JPe 27.5.2002
MHA Reliability
MTBF is
a design comparison done in favourable conditions (at 25°C)
typically Nokia MHAs have very high MTBF value (>400kh)
Field Returns
- installation quality
- mechanical/operator issues
- NFF units
Field MTBF have been proven to be 2-4 times the calculated figure
Nokia has delivered approximately 250 000 MHAs
some big projects experienced < 10 faulty units off 10.000 installed in 2 years !
Nokia Validation:
All electrical figures compatibility fully tested
Environmental tests
Other tests done in co-operation with vendors:
Vibration, chock tests, lightning, max.power handling, etc.
-> for operation, storage and transportation
System and Type Approval tests
EMC
Taking a reference bearing
Left...left...-10 Degree
OK let’s tilt down 6’
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Improved Network Performance
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Mechanical Tilt
Electrical Tilt
Network planning is more difficult because of the altered radiation pattern
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Mechanical Downtilt
Antenna physically tilted so that mainbeam energy focused towards the ground
Reduction in field strength in main direction but no change +/- 90º leading to deformation of radiation pattern
Accurate network planning is assured
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Electrical Downtilt
Antenna remains physically upright
The phase of the signals going to the dipoles is changed causing electrical tilt
Radiation pattern is not altered
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Antenna Installation
Electrical Downtilt adjustment (Kathrein)
Mechanical Downtilt adjustment (Kathrein)
Use glued/engraved scale provided with downtilt kit to adjust antenna to correct angle of tilt
Confirm always with angle meter!
If scale doesn’t exist use angle meter to adjust antenna to correct angle of tilt
Item Description
The antennas can be either vertically polarised or cross polarised and directional or omni-directional antenna.
The jumper cable is a flexible low loss cable (1/2"), which is used at the ends of the feeder. It protects the connectors from the forces caused by the feeder cable.
7/16 connector are made of silver plated brass or a special grade of copper. All connectors are IP68-classified.
The grounding kit ensures that the Antenna line is DC grounded as a protection against lightning.
The RF-feeder is corrugated coaxial cable. It can be of different sizes, i.e. 1/2”, 7/8” and 1 5/8”, depending on the length of the mast and the desired attenuation.
Cable clamps are made of stainless steel and plastic and they are easy and quick to install. Design of the clamps prevents over tightening of a feeder cable.
A compact EMP protector protects the BTS against lightning and over voltage that may occur down the antenna line.
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For outdoor and indoor general arrangements of feeder cable is AVA5-50 (7/8”), AVA7-50 (1 5/8”) and jumper RF 1/2”, RFF 1/2”.
Note:The photo shows the “Antenna system” at outdoor site in Singapore.
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ANTENNA INSTALLATION SOLUTION
1 SECTOR (X+0+0)
X= TRANSMISSION UNIT
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Single, Macro
Approved connector types have to be used
Used connectors have to be suitable for used cable type
All cables have to be labeled on both end of the cable
Proper tools have to be used during antenna line installation
All cables have to be fixed properly
INDOOR
OUTDOOR
EMP
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Approved connector types have to be used
Used connectors have to be suitable for used cable type
Proper tools have to be used during antenna line installation
INDOOR
OUTDOOR
Bias-T
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Example calculation:
3G cellular network, feeder run is 36 m. Attenuation limit is 3 dB. Which cable should be used?
0.1 + 0.1 + 0.68 + 36m X 0.0553 = 3 dB
-> 7/8" feeder cable
Antenna feeder connector loss ( 2 connectors ) 0.10 dB
Antenna feeder attenuation RF 7/8“ 5.53 dB 100m
RF 1 5/8“ 3.36 dB 100m
EMP Protector loss 0.10 dB
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Feeder Attenuation
900 MHz 1800 MHz 2000 MHz
RFF 3/8”-50 13.9 dB/100m 20.5 dB/100m 21.8 dB/100m
RFF 1/2”-50 10.6 dB/100m 15.6 dB/100m 16.7 dB/100m
RF 1/2”-50 6.88 dB/100m 10.1 dB/100m 10.7 dB/100m
RF 7/8”-50 3.53 dB/100m 5.04 dB/100m 5.53 dB/100m AVA !!
RF 1 1/4”-50 2.74 dB/100m 4.12 dB/100m 4.39 dB/100m
RF 1 5/8”-50 2.11 dB/100m 3.05 dB/100m 3.36 dB/100m AVA !!
3 db is general attenuation limit for antenna line. Network planning team specify exact attenuation limit and used feeder on each site.
NOTE: Given values are for NK Cables feeder cables except 7/8” and 15/8” are for Andrew AVA cable type, other manufacturers’ may have different values, check the proper values before implementation from manufacturer’s data sheets
Important to make short feeder runs:
Feeders from 3/8" to 7/8" and their wiring work is:
+ low cost
- high loss
Feeders from 1 1/4" to 1 5/8" and their wiring work is:
- high cost
+ low loss
3 dB is default value in radio network planners planning tool, but can be also less or more.
Verify that antenna support are installed and in right location.
Hoist the antenna up to the antenna support.
Note: when hoisting antenna in foul weather conditions, it is necessary to control antenna
movement to avoid damage. Use ropes etc.
Install the antennas on the antenna support exactly vertical or with a specified offset.
Use the data specified in the site installation documentation to set the antenna heading, height, vertical and horizontal separation.
Connect one end of the antenna jumpers to the antennas, leaving the opposite ends open.
Note: the open ends should be protected from moisture.
6. Clamp the jumpers to the antenna support.
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Antenna Hardware Type and Torque Specifications
All outdoor fastening hardware must be marine grade stainless steel or acid-proof i.e. nuts / bolts / flat washers / spring washers.
Use material provided by antenna manufacturer.
Follow antenna manufacturer installation instructions.
* These hardware torques are normally limited to pole mounts.
All Antenna
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Dissimilar Metals Electrolysis Reaction
Contact between metals from the opposite group can generate severe corrosion of the conductor from the anodic section. Care must be exercised when terminating one conductor to another. Where possible commercially available transition sections/joints should be used.
Attention must be given to the following:
Use only copper to copper connections where possible.
Ensure that bare copper is not allowed to be placed in contact with zinc or steel of a tower. In such cases tin plated copper may be used. Alternatively, stainless steel section may be placed between the copper and zinc or iron surfaces.
Ensure correct fixing of screws, nuts and washers. Copper or stainless steel screws and washers must be used against bare copper surfaces.
If possible, use anti-corrosive compound on the surfaces between dissimilar metals. This prevents oxidation over long periods.
Electrolytic Table for Various Common Metals
NOTE: Any stainless steel hardware used must be marine grade or acid-proof.
METAL
GROUP
(
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Feeder bending radius
Feeder bending radius guidelines should always be followed to avoid damaging the feeder which causes more cable loss (see antenna and feeder installation document)
NOT allowed:
NOT OK
NOT OK
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Feeder bending radius
NOTE: Given values are for NK Cables feeder cables, other manufacturers’ may have different values, check the proper values before implementation from manufacturer’s data sheets
FEEDER TYPE MINIMUM SINGLE MINIMUM REPEATED
BENDING RADIUS BENDING RADIUS
RF 1 1/4”-50 200 mm 350 mm
RF 1 5/8”-50 250 mm 500 mm
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Follow feeder manufacturer installation instructions.
NOTE: Given values are for NK Cables feeder cables, other manufacturers’ may have different values, check the proper values before implementation from manufacturer’s data sheets
1/4” Superflex
3/8” Superflex
1/2” Superflex
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RF 3/8” superflex
Support Distance Spacing
RFF 1/2” superflex
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On site Feeder and jumper cable installation
For outdoor and indoor general arrangements of feeder jumper cable RF1/2”,RRF 1/2”, RFF 3/8”.
Note:The photo shows the “Jumper installation” at outdoor site in Singapore.
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CHECK the condition of the standard cutting tools from Spinner
Check the condition of the connector package against water
Check the connector installation instructions: correct measure / number of wave tops
Wind the cable tool in the marked direction of the arrow. Do not press the tool more than needed
Use correct torque in all connections
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Feeder cable installation
CRITICAL: DO NOT GO OVER maximum pulling force limit as the jacket may break.
AVOID: jerky pulling to control the forces.
USE: smooth and even pulling.
TAKE CARE OF sharp edges, rough surfaces, extra torsions, bend radius.
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Feeder type for different length
3db is general attenuation limit. The calculation above is based on the normal installation with 1.5m RFF 1/2" jumper for antenna and 3m or 4m RFF 1/2" jumper for BTS.
0 m < length < 8 m -RF 1/2"
9 m < length < 35 m -RF 7/8"
36 m < length < 50 m -RF 1-5/8"
length > 50m add MHA RF 1-5/8"
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TAKE CARE OF sharp edges !
Recommended clamp distance for cables 1/2” to 1 5/8” is 1000 mm
Clamps FIXED TOO TIGHT cause rising of the return loss
Take care of NOT TO DROP plastic cushions
Cables shall be terminated by the resistive load (or source) impedance equal to the characteristic impedance, which generally is 50
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Incorrect
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The distance clamps for jumper cables is about 500mm
It is vitally important that the internal and external jumper cables have to be supported securely. For the 1.5m jumper, minimum 2 (two) points of support are to be used, and for the 3m jumpers, minimum 4 (four) points.
1.5m jumper, used
2 securing points
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Jumpers Cables have to be installaed as straight as possible.
Avoid additional bendings.
All cables have to be fixed properly.
Prefabricated jumpers have to be used always when possible.
On existing sites most practical solution should be used.
Think about future.
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Jumper Connection
Proper tools have to be used.
All connections have to be tightened with correct torque, including unit securing screws.
SMA connector 1-1.2Nm
N connector 1-1.7Nm
7/16” connector 25Nm
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How loose RF-connector influences to performance:
It seems that also 7/16 connector is very sensitive to fixing torque. When you loosen the connector, at first you'll get intermodulation problems, then you loose return loss values. Very easily you'll get 6...12dB return loss values, when you loosen slightly the connector (fixing torque 5...10Nm). However most of the power is still passing the loose connector, but you get VSWR alarms and insertion loss increases easily 1..2dB.
Further, think about if you have 1,5m jumper cable with both ends loose connector. The signal reflects on the both end of jumper and the result is 3rd stage reflections. Depending the frequency and cable length (=depending of the phase of reflection), you'll get very very easily VSWR problems.
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Jumper Cables have to be installed as straight as possible.
Think about future.
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Jumper Cables have to be installed as straight as possible.
Think about future.
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Check the cable ends before installation
Protect the drum/cable ends after cutting; preferably by heat shrinkable rubber cap
Grounding kits: sealing class IP 67. Ground wire connector to be checked after careful pressing.
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Option: 1
This is “normal” site in perfect installation method.
*All Feeder or jumper cable should be tidy inside the “cable trunking” when the Feeder cable need to be laid on the floor.
Option: 2
This is “critical” site in perfect installation method.
*All Feeder or jumper cable should be tidy inside the “cable trunking” when the Feeder cable need to be laid on the floor.
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Option: 1
*When using shorter jumper
( 2, 3 meter ), installation will be difficult. Over bending is possible when using RF7/8” or RF 1 5/8” feeder cables when installing cable tidy to “cable trunking”.
Shorter jumper
Longer jumper
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Site Grounding and Lightning System
Please observe that the ground connection in this document must under no circumstances be regarded as protective ground.
This ground connection is used for lightning protection equipment .
Protective ground has to be installed as described in the local electrical regulations.
Note:The photo shows the “Ground system” at outdoor site in Singapore.
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Site Ground Bar
If vertical rise of the RF cable is greater than 40m for every step then center earth kit is required to be installed
Ground kit
If MHA used install only the grounding kit
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Feeder grounding kit positions
The grounding kit must always be positioned on the straight part of feeder cable and never on a bend or curve in the cable.
Grounding kit's earthing cable can be cut or extended to make grounding cable connection to busbar as straight as possible.
Acceptable
installation
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Screw connection grounding system
An electrical screw connection consists of a cable lug, which has to be secured to a surface. A bolt, washer, locking ring and sometimes a nut are used. These items must be arranged in the following order:
Bolt.
Nut.
When doing up screw connections, it is important to use the correct tightening moment. The correct tightening moments for common bolt sizes are given in the table below.
The earth impedance for a typical BTS site should be less or equal than 10 Ohm.
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All EMPs have to be connected to EMP grounding busbar
EMP manufacturer material have to be used
Feeders have to be grounded before the feeder entry
All feeder grounding kits have to be connected to feeder entry grounding busbar
Feeder grounding kit manufacturer material have to be used
Used cable lugs have to be suitable for used grounding cable
Proper tools have to be used during grounding cable installation
EMP GROUNDING BUSBAR
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Feeders have to be grounded after antenna jumper connection
All feeder grounding kits have to be connected to feeder grounding busbar
Used cable lugs have to be suitable for use with grounding cable
FEEDER GROUNDING BUSBAR
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Feeders have to be grounded approx. 500-1000mm before horizontal bending
All feeder grounding kits have to be connected to feeder grounding busbar
Used cable lugs have to be suitable for used grounding cable
FEEDER GROUNDING BUSBAR
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Jumper to BTS
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To Grounding Busbar
To BTS
To Antenna
Plastic Insulator
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RF connector position
Connector body must not be in contact with cable ladder. Position connectors between the ladder rungs or insulate the ladder rung with rubber sheeting.
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Weather Proofing
All outdoor antenna line connections, grounding kits and wall entries have to be weather proofed.
Connections where weather proofing is needed:
Feeder to feeder
Feeder to EMP and combiner (if located outdoor)
Grounding kits have to be sealed according to manufacturer instructions.
Wall feed through have to be properly sealed.
Ensure that all connectors are on correct torque before sealing!
WEATHER PROOFING NEEDED
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Feeder to Feeder connection
1. CONNECTION TO BE TAPED USING APPROVED TYPE OF INSULATION TAPE
2. CONNECTION TO BE TAPED USING APPROVED TYPE OF SELF AMALGAMATING TAPE
2. TWO STRETCH WRAPPED WRAPS OF SELF AMALGAMATING TAPE (STRETCH 30%, OVERLAPPING 50%)
20
50
50
20
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Feeder to Antenna, Combiner or MHA connection
50
20
CABLE TIE
3. THREE WRAPS OF INSULATION TAPE (OVERLAPPING 50%)
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Feeder to EMP connection
50
20
CABLE TIE
1. ONE WRAP OF INSULATION TAPE (OVERLAPPING 50%)
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TWO WRAPS OF SELF AMALGAMATING TAPE (OVERLAPPING 50%)
20
50
100
20
THREE WRAPS OF INSULATION TAPE (OVERLAPPING 50%)
* Use this method if grounding kit is not supplied with weather proofing tapes or taping instructions
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Follow the instructions given in work instructions.
Fill up the return loss and insertion loss values to the site folder.
Print return loss measurements to A4 paper, sign and attach to site folder.
Three (3) antenna lines per one A4.
Attach measurements to site folder also on electrical format (CD-ROM).
RETURN LOSS
RETURN LOSS
RETURN LOSS
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The commissioning of the antenna system composes of Return Loss measurements on both transmit and receive feeder for all sectors. Also antenna line attenuation and length have to be measured and filled to site folder for Node-B commissioning purposes.
2 separate measurements per feeder has to be done for antenna line with MHA
- Measurement 1: Feeder, Jumpers, and Antenna
- Measurement 2: Feeder, Jumpers, MHA and Antenna

The Return Loss must be less than what is specified in Nokia UltraSite WCDMA Antenna System User Manual at any point between the markers.
Antenna System Return Loss limits without MHA
Antenna System Return Loss limits with MHA
METAL
GROUP
Weight6 kg
Connectors7-16 female
SealingIP 65
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3.4 Antenna System

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