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The spectrum monitoring
Mr.Zhao ZhengEngineer of Beijing Monitoring Station
State Radio Monitoring Center
+8610-60271116
Radio Monitoring and Spectrum Management Training
(China,23-31,May,2005)
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General introduction
DF method and location
Siting of monitoring stations
Typical Procedure for Dealing withInterference Complaints
Contents
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General Introduction
Brief introduction
Types of monitoring stations
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Spectrum management
Spectrum monitoring
Eyeandear
Spectrum monitoring function
Efficiency ofusing spectrum
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The goals of monitoring
General
support the management
Specially
resolution of EMC problemensuring an acceptable quality of radio and TV
providing valuable monitoring data
providing valuable monitoring information
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Tasks of the monitoring service
From radio regulation (RR)
On national basis
Assigned to the radio inspectionCooperation with other bodies
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Tasks from RR
Monitoring emissions for compliance with frequencyassignment
Frequency band observations and frequency channel
occupancy measurementsInvestigating cases of interference
Identifying and stopping unauthorized emissions
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Tasks on national basis
Assistance on special occasions
Radio coverage measurements
Radio compatibility and EMC studies
Technical and scientific studies
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Tasks assigned to the radio inspection
Inspecting radio equipment on site
Measuring radio equipment
Processing cases EMC
Market surveillance activities
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Cooperation with other bodies
Police and court
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Measurement tasks
Frequency Frequency counter
Field strength spectrum analyzer
Bandwidth spectrum analyzer
Modulation vector analyzer
Spectrum occupancy automatic receiver
Direction finding DFer
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Type of monitoring station
Frequency band
HF, V/UHF station
Different application
fixed, mobile, portable
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Fixed monitoring station
Central element of the monitoring system
Advantages:
without limitation of workspace
setup of antenna
power supply
Disadvantage:
limited by environment
coverage
C Fi d i i i
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Common Fixed monitoring station
block diagram
Spec-022
GPSreceiver
Video recordersand other
peripheralequipment
Frequencystandard to
equipment VLF/HF - VHF/UHFDF and measuring
receivers
L
A
N
RFdistribution
and
antennaswitching
DFantenna
switching
DatarecordersConsole
Console
Console
Printers
Database
Uninterruptablepower supply
Enginegenerator
110/220 V50/60 HzRouter
Wide area network
DF: direction finding
GPS: global positioning system
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ExampleDF system
Antenna array
triangle array (cross-loop element))
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Picture of antenna array
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ExampleDF system interface
DF techniquecorrelative interferometer
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Examplelistening system
Log antenna
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Pictures of listening site
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Listening interface
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Mobile monitoring station
Advantagesflexibility
expanded coverage
Disadvantageslimited by workspace
setup antennapower supply
living condition
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What is the first important thing for mobile
monitoring station?
GPS system
ensure the location
know the bearing
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Division by differenttransportation
Vehicle station
Airborne stationMarinetime station
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Vehicles
General consideration
Antennas for vehicle monitoring station
Requirements to be fulfilled by thevehicle
Power supply
Examples of a vehicle concept
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General consideration
what functions the vehicle is to be used for
general-purpose or specialized
What manner it is to be used in
(where and how long)
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Antennas for vehicle monitoring station
The size and the number
Distorting effectcalibration
Directional antenna
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Requirements to be fulfilled by the vehicle
Communication system
Sufficient leg room
Windows
SafetyConvenient seat location
Interior light
Thermal insulation
WeightPowerful built-in generating set
Speed
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Spec-023
Telescopic mast
Air conditioning
system
Onboard Diesel
generator
19" cabinet
equipment
Operat
or
table
Interior of a mobile monitoring station
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Power supply
Equipment type Power consumption(W)
Spectrum analyser (26GHz, portable) 210
Oscilloscope (400MHz, portable) 120Signal generator (100kHz-2GHz) 200
DF (20MHz-3GHz) 140
HF receiver 150Industrial personal computer (PC) with colour display monitor 200
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Power supply
Batteries and secondary cells
Alternators coupled to the engine-InvertersGenerating sets
Mains supply
Diesel engine preferred
E amples of a ehicle concept
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Examples of a vehicle concept
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The vehicle example
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Rear view
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Interior View 1
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Interior View 2
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Brief introduction of this example
Frequency band :HF and V/UHF bands.DF method:
Watson-Watt method on HFcorrelative interferometer on V/UHF
ITU measurement
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Airborne monitoring stations
advantage1. Quick exploration of broad geographical areas
2. obtaining several lines of bearing from different locations
3. Better opportunity to perform measurements due to line of sight4. Rapid location of emergency beacons, interferers and Earth stations
which sometimes cannot be detected from ground
5. All means of measurement of aeronautical flight aid transmissions
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Airborne monitoring stations
Disadvantage1.Cost of flight
2.Limitations in weight, power, size, cooling
3.Limited by weather, winds4.Limited flight time due to fuel limitations
5.Requires accurate azimuth and depression angle, fast DF capability andantenna tracking
6. Frequency compensation for relative velocity may be needed
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Maritime monitoring stations
Advantagethe area surrounding the marine vessel is generally very quiet
from a radio frequency point of view
Disadvantage Corrosive atmosphere
Multipath due to sea state reflection
Antenna mounting
Radio frequency ducting over warm bodies ofwater
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Portable monitoring station
advantage
more flexibility than mobiles
one person can carry
Disadvantage
less functions
less accuracy
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DF and Location
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Contents
DFGeneral principle of DF
Main DFers features
DF methods
Bearing related topicsDF features due to frequency difference
DF antenna
Location
Location overview
Cross-bearing location
Single station location
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General Principle of DF
Concept of radio DF
Concept of azimuth
The basic architecture of DF system
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The process to determine the line of bearing(LOB) of any source of electromagnetic radiationby means of the propagation properties of radiowaves.
Normally, direction is expressed by azimuth.
Concept of Radio DF
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Direction Finder
Reference direction radiation source
Concept of Azimuth
Azimuth: the clockwiseangle from the line
( the radiation source tothe direction finder) toa reference direction.
Geographicalnorth ;geomagnetic north;or the heading ofvehicle in mobile DF.
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The Basic Architecture of DF System
Antenna
system
Inputswitching
networkReceiver Terminal
devices
receive the signalfrom the radiationsource.
transmit the signal withoutdistortion. includeimpedance convertor,distribution, etc.
signal processing.Such as amplify,demodulate, etc.
get and display theazimuth.
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Main DF Engineering Features
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Accuracy
Concept:
DF error=Vm-Vreal
within 1to 3.
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Sensitivity
Concept:Emin ensure the accuracy within certain range
Importance:extending the coverage of DFer
under good receiving conditions
sufficiently reliable DF
under less favourable receiving conditions.
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Response time
Concept:Tmin to finish one DF task
Duration of signal > response time
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Immunity to distorted wavefronts
(coherent interference)
obstacle
transmitterwhat produce distortedwavefronts?
reflection by obstacles and
diffraction by edges.
multi-path reception.
Result:There are interferences andthe original plane wavefrontis distorted.
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Depending on its diameter D, a DF antenna detects only a smallpart of the wavefront.
D/
narrow-apertureDF antennas
medium aperture
DF antennas
Wide-apertureDF antennas
D/
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Narrow/wide aperture DF antenna
bearing with wide-aperture DF antenna
bearing with narrow-aperture DF antenna
nominal bearing
Narrow- /w ide-aper ture
DF ant enna s
undistortedwave front
distorted
wave front
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Immunity to co-channel interference
Concept:
non-coherent ,co-channel interference.
Erroneous bearings
should be recognized and identified.
Individual bearings
should be taken of all the signals.
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DF methods
Rotating DF method
Non-rotating DF method Amplitude-comparison DF method
Phase-comparison DF method
Combination of amplitude and phase DF method
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Rotating antenna DF method
receiver
90
0
270
Bearing indicator
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Advantages
High sensitivity due to the directivity ofthe antenna
Simple and inexpensive realizationResolution of multi-wavefronts
Same antenna can be used for direction
finding and monitoring
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Disadvantages
Probability of intercept is reciprocal ofthe directivity
in case of short-duration signals
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Non-rotatingDF methods
Phase-comparisonDF methods
Amplitude-comparisonDF methods
Dopplers
interferometers
Wullenwebers
Watson-Watts
Combination of amplitudeand phase DF methods
Correlation
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Amplitude-comparison DF methods
Watson-Watt DF method
Wullenweber DF method
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Watson-Watt DF method
CosKUmSin
N-S
E-W
NSU = CosKUmCos
EWU
CosKUmSin=
Cos
Sinarctg
U
Uarctg
NS
EW=
: Azimuth
: Elevation
Can not get the Elevation
A 1 2
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Accuracy
(without site influence)
1 to 2
Sensitivity Med-High
NOTEPerformance based on antenna selection
Response time < 1 ms
Immunity against
distorted wavefronts
(coherent interference)
Limited, as no wide aperture antenna arrays possible
Immunity against co-channel interference
(non-coherent
interference)
Separation possible using analogues CRT displaytechniques. Operator interpretation of CRT used in
resolving interference pattern.
Digital signal processing cannot algorithmically
separate time coincident co-channel signals. Histogram
techniques may be employed for non-time coincident
signals
Adcock/Watson-Watt DF systems
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A B
O
120
C
D
Antennas:ACB (arc) Time delay network
Antennas:ADB (line)
AD BD
-+
Incomingwave
+ radiation
pattern
- radiation
pattern
Wullenweber DF method
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Wullenweber direction finder
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Advantages: High accuracy High sensitivity
Strong immunity to co-channel interference
Disadvantages: Long response time
Complicated structure
Wullenweber DF method
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Phase-comparison DF methods
Doppler/pseudo-Doppler
Phase interferometer
D l / d D l
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Doppler/pseudo-Doppler
f
f
1
12
2
3
34
4 1
Incoming
wave
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Accuracy HF/VHF/UHF: 1,VHF: 0.1(D/>4)
Sensitivity High
Response time HF: approx 100ms; VHF/UHF: approx 10ms
Immunity against distorted
wavefronts
(coherent interference)
D/>1, wide-aperture DF antennas
Immunity against co-channelinterference
(non-coherent interference)
Limited, only measure the strongest signal
HF skywave capability With across circle antennas, the signal with
elevation up to 90 can be measured (sensitivity
reduce), SSL function
Doppler/pseudo-Doppler DF system
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L = d sin t = Lc
t = L = 2f d sin c c
f = c , = 2 c d sin c
2 d sin d
N
Phase interferometer
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a = d sin cos t = a/c (distance/speed) = (d sin cos )/c = * t = (2 d / ) sin cos 2d sin cos
1 2d
a
P1
P2
P3
Considering elevation angle
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Accuracy (without siteinfluence)
1
Sensitivity High
Response time 10 ms 1 ms*
*NOTE
Successful systems, which use antenna switchingto a pair of coherent measurement channels, are common.
Response time is most rapid when one receiver is used for
each antenna, and all measurements are made in parallel.
Immunity against distorted
wavefronts
(coherent interference)
High when using wide aperture antenna arrays
Immunity against co-channel
interference (non-coherent
interference)
Separation possible using histogram techniques for non-time
coincident signals; for time coincident signals only the
signal that is stronger by 3 to 5 dB can be evaluated
Phase interferometer system
Combination of amplitude and
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Combination of amplitude and
phase DF methods
Correlation/Super-resolution
C l ti / l ti
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Correlation/super-resolution
Antenna array 1
2
3
A,
Referencechannel
1
2
9
3
8
4
7
5
6
MemoryA ref,ref
Incoming wave (azimuth:,elevation:)
,
DF converter
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Sensitivity High
Accuracy (without siteinfluence)
1
Response time for HF 100 msfor VHF/UHF 10 ms
NOTESystem processing times will be lengthened if only one or
two parallel receiver channels are used
Immunity against
distorted wavefronts
(coherent interference)
High when using wide aperture antenna arrays
Immunity against co-
channel interference(non-coherent
interference)
Separation possible using histogram techniques for non-time
coincident signals; for time coincident signals in the vectorcorrelation system, only the signal that is stronger by 3 to 5 dB can
be evaluated; the SR-DF system separates multiple signals
Correlative interferometer/Super-resolution-DF (SR-DF)
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Bearing related topics
Display of bearings
Sources and expression of bearing errors
Classification of bearingsCalibration and correction
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Display of Bearings
Display of results of a single channel DFer:Parameters indicated: numeric DF value
azimuth in polar coordinates elevation as bar graph (combined with
azimuth display)
DF quality
level Histogram of DF values
Waterfall (DF values versus time)
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Sources and expression
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bearing errors
instrumenterror
Environmenterror
Propagationerror
Operationerror
Maximumerror
Averagingerror
Statisticprobability error
Averaging squareroot error
error sources
error expression
Sources and expressionof bearing error:
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Classification of bearings
Class Bearing
error
(degrees)
Observational characteristics
Signal
strength
Bearing
indication
Fading Interference Bearing
swing
(degrees)
Duration of
observation
A 2 Verygood
or good
definite negligible negligible
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Classification of bearings
Class Bearing
error
(degrees)
Observational characteristics
Signal
strength
Bearing
indication
Fading Interference Bearing
swing
(degrees)
Duration of
observation
A 1 Verygood
or good
definite negligible negligible
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Calibration and Correction
Because oferrors due
to thedirectionfinder site
andequipment
To check the impact of thesite and re-radiation fromnearby structures, forest etc
on direction findersperformance
To check ifthe DFer
works well andis in goodconditionsafter being
installed at thesite
Calibration of mobile
Direction finders
Calibration of fixed
Direction finders
Instrument Calibration
Site Calibration
To eliminate the influenceof the vehicle on the DFer
DF features due to
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DF features due tofrequency difference
DF below 30MHz
DF above 30MHz
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DF Below 30MHz
Different propagation modes
DFers are remote from the area of interest
Measurements are relatively unstable
Susceptible to errors induced by reflectionsfrom the ionosphere
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DF above 30MHz
DFers are in the vicinity of the area ofinterest
Measurements are reliable DF measurements can be made difficult
due to the presence of interference and
the reflections suffered by waves.
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DF antenna
Antenna parameters
DF antennas in common use
A t t
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Mainly includes:
Radiation Pattern
Directivity
Efficiency and Gain
Impedance characteristic
Antenna PolarizationBandwidth
Antenna parameters
DF t i
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HF rangefixedarrays of monopoles or crossed-loop elementsmobileeither loops or ferrite elements
VHF/UHF rangemostly arrays of dipoles or fans
DF antennas in common use
E l 1 HF l t
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Example 1: HF cross loop antenna
Array of 7 or more crossloop antennas installedalong an 81 mequilateral triangle.
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Example 2: V/UHF dipole antenna
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UHF1 sub band antenna (160 - 500MHz)
h = 55 cm
O = 100.8 cm
VHF sub band antenna (20 - 160
MHz)h = 180 cm
O = 295.6 cm
UHF2 Sub band antenna (500 MHz
- 1350 MHz)
h =22 cm
O = 36 cm
Example 2: V/UHF dipole antenna
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Location
Location overview
Cross-bearing locationSingle station location
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Location Overview
Location method
Cross-bearing Location(In V/UHF or HF band)
Single Station Location(Only in HF band)
More accurate butneeds at least twodirection finders
Only need onedirectionfinder
C b i l ti th d
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Cross-bearing location method
Using two or more direction finders indifferent geo-positions;
test and get two or more azimuths ofthe interference at the same time;
According to the azimuths, along thearc of the great circleconnect interference with the
receiving point on an electronic map.
the point of intersection is thelocation of the radiation source .
Station B
Station C
Station A
Locationarea
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Cross-bearing Location Principle
Basic principle of triangulationusing two direction finders
DFer1: A
DFer2: B
Emitter: E
The reference direction: X axis
Azimuth from DFer1: 1
Azimuth from DFer2: 2
Ye-Y1=(Xe-X1) tg1
Ye-Y2=(Xe-X1) tg(180-2)X
Y
A(X1,Y1) B(X2,Y2)
E(Xe,Ye)
1 2
0
Bearingerrors arenot taken
into account.
C b i L i P i i l
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Cross-bearing Location Principle
DFer
Bearing
Uncertainty onbearing due to
errors
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Cross-bearing Location Principle
DFer1 DFer2
Bearing
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Location calculation
Location calculation
Triangulation method
Large circles,spherical triangles method
LongdistancesWhen a direction finder is very far from atransmitter, the bearing line cannot beconsidered as a straight line but an arc.
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Cross-bearing Location Systems
Most common and economical way ofcross-bearing location is a remote-controlled
direction finding system.
ll d
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Remote-controlled DF Systems
Monitoring center
Remote
DF station
Remote
DF station
Remote
DF station
l l
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Location calculation
dependent on the quality of bearings
Bearings should be analyzed at both DF stationsand monitoring station.
L i l l i
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Location calculation
DF stations analysis what mainly consist in?
Classifying the bearings
Eliminating aberrant shootingsCalculating the mean value and the
variance of shootings
L ti l l ti
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Location calculation
What mainly consist in mobile station?
Determining the bearings to be used for
the location calculationCalculating the position
Calculating the uncertainty ellipse
L ti l l ti t
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Location calculation steps
Determining bearing
made reliable for each
DFer
Eliminat ing off-center
shootings
Location
calculation
Uncertanty ellipse
calculation
Elementary bearings
Azimuth, elevation, typi cal deviation
Technical measurements
Frequency, modulation, bandwidth
Ellipce
charactristics
Qualitynotation
Bearing processing by
the monitoring center
Bearing by
the direction-finder
Bearing made
reliable by DFer
Bearing geograophically
consistent
Lattitude,
longitude
The computer program TRIANGULATION, that generally
follows these steps, is available in the ITU.
Eliminating non convergent bearings
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Eliminating non-convergent bearings
DFer 1
DFer 2
DFer 3DFer 4
Areas of uncertainty on each
intersection on bearing from
DFer 1
Uncertainty on
bearing
Bearing
E l ti th l ti i t
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Evaluating the location point
The optimum point is searched applying the leastsquares method.
...)/()/()/( 3232
221
21 vdvdvdSp
Pis any one point
d1, d2, d3,... the angular variations to be applied toeach bearing to intersect P
v1, v2, v3,... the variances of the various bearings.
The optimum point is the point minimizing Sp,
SSL Principle
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SSL Principle
DF.
= Geographical Azimuth = Elevation AngleD = Distance
h = Virtual Reflection Height
DF.
h
DNorth
Li i i f SSL h i
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Limitation of SSL technique
Multi-hops propagation
The reflection may take place from
layers of different heights.
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Siting of MonitoringStations
G l id ti
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General considerations
Frequency ranges and geographicalareas;
International or domestic ;Whether special installations required;
On-site field strengths;
Administrative considerations;Land costs;
Desirable minimum site
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Desirable minimum site
criteria for a stationLocation;Protected from obstacles;
Electromagnetically protected.
Additi l d i bl it
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Additional desirable site
criteria with DFerGeneral considerations:Obstacles
Terrain deviationSoil requirement
Underground pipes etc.
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Additional desirable site criteria with
DFers (below 30MHz)
Obstacles: see table 1Terrain: flat ground with watertable near the surface
Additional desirable site criteria with
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DFers (below 30MHz)
Guiding rules:
Terrain:
no more than 1% within 100m area (HF)
slopes can be steeper within larger areaObstacles: 2-3 degrees
Ground: clear within 200m area
Cables: 1-2m deep (30m range),0.5m deep(30-250m)
Additional desirable site criteria with
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DFers (above 30MHz)
For VHF/UHF DFers requirements in Table1
may be reduced
In smaller zones: fixed and mobile radios
should be restricted
In larger zones:high power ISM equipmentand major obstacles should be restricted
Protection from strong
t ansmitte fields
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transmitter fields
General consideration
To protect monitoring capability
Protection from strongt ansmitte fields(2)
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transmitter fields(2)
How to evaluate?
Harmonics as well as fundamental
Two or more transmitters(other range)Experiential way of evaluating
Protection from strongtransmitter fields(3)
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transmitter fields(3)
License applications
Strong signal area:
avoid active antennas
Protection from local computer
systems
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systems
Computer systems may causeinterference
Computer emissions may be hard toidentify
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Recommendations:
Shielded cables
computer system installed apartmonitoring offices close to the antennas
avoid or minimize interference in the planningstage
Land requirements
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Land requirements
Largely mission dependent
The use of adjacent property
legal aspects related to operationalsafety and public safety
Other considerations
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Other considerations
Road access
Fencing
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Typical Procedure for Dealing
with Interference Complaints
St
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Steps
Complaint report received
Preliminary diagnosis
Localization by mobile means
Measurement of emissions
Measurement evaluation and actions
Final check-up
Interference Report
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Interference Report
Details of the following are required:
Information of party experiencing the interference;
Data about the interfered-with device;
Data about the following of the interference
1.occurrence
2.description
3.suspected source
Preliminary diagnosis
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Preliminary diagnosis
Preliminary diagnosis are performed withthe help of the following:
Fixed and remotely controlled measurement
equipmentDirection-finding
Frequency assignment databases
Switching off the transmitter of the suspectedoperator (if possible)
l b b l
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Localization by Mobile Means
A complementary means
Could be very time-consuming
M f i i
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Measurements of emissions
Once the source has been localized and identified,
Measure the technical characteristics todetermine the nature of the interference;
equipments and their settings should berecorded for use in the next step.
Measurement Evaluation and
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Necessary Action
Measurement results compared withassignment and standards
Actions:1.Taken out of operation
2.Modification or system rectification
3.AcceptedFine or other penalty may take place
Measurement Evaluation and
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Necessary Action
Actions should
Conform to the law;Be reasonable;
Final check-up
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Final check up
Check if remedial actions has been taken
Using fixed or remotely controlled equipment
On-site inspection
Asking the interfered party
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