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Navigation Signals and Antenna Measurementin Multipath Environment
Heinz Wipf – skyguide – El Eng HTL
IEEE AP-Society Washington and Northern VA ChaptersUniversity of Maryland 17.04.2012
page 2Heinz Wipf, 13.02.2012
Outline
+ Introduction
+ Instrument Landing System - ILS
+ LLZ Orbit: Effects and Causes
+ Measurements and Computational Electromagnetics
+ Straight-In-Approach in Comparison
+ Specifications in Question
+ Other Solutions
+ Conclusions
3
ILS - Basic Layout
Surface-of-Pos
Surface-of-Pos
Localizer
LLZ,
Glide Path
GP
Glide Path Angle
nom 3°
Line-of-Position
GS
LOC
DDM
4
ILS-Categories
Runway Visual Range Decision Height
• CAT I: 800m 60m
• CAT II: 400m 30m
• CAT III: 200m 0m
5
Photo Thales
Typical LLZ Antenna Configuration 13 Elements
2 m
24.2 m
1136
6
LLZ – Antenna Diagrams 25 Elements L=45m Course & Clearance
-60
-50
-40
-30
-20
-10
0
-180 -160 -140 -120 -100 -80 -60 -40 -20 0 20 40 60 80 100 120 140 160 180
AZ in deg
Dire
ctiv
ity in
dB
crs_CSBcrs_SBOclr_CSB
page 7Heinz Wipf, 13.02.2012
Flight Inspection Results
courtesy FII
tangent to orbit 10° yaw angle
LOC 2F CATIII
orbit
course
clearance
reflector/scatterer
orbitcase.dsf 04/02
10°20°
30°
page 8Heinz Wipf, 13.02.2012
X
Y
Z
Antenna 4loops at fuselage
page 9Heinz Wipf, 13.02.2012
courtesy Greving
Z
Z
X
Y
rear loop antennas atfuselage
Kingair 350
3D-radiation pattern
king3dloop1.dsf 03/02
page 10Heinz Wipf, 13.02.2012
Computational Electromagnetics
courtesy Greving
-25
-20
-15
-10
-5
0
5
10
15
20
25
-25 -20 -15 -10 -5 0 5 10 15 20 25
dB freespace
dB fr
eesp
ace
EMFieldCompmeasureCCWmeasureCW
page 11
Calculation vs. Measurements
courtesy FCSI
delta / m
DD
M/
A
-500 -250 0 250 500
160
170
180
190
200
210
220
230
240
250
260
3D-pattern, yaw angle = 10°
LOC: SN400 (21/7) x/y: 0/0building (x/y): 1950m / -430mrot. angle: 6°length / height: 50m / 50m
3D-pattern, yaw angle = 0°
kingddmorbit.dsf 04/02
DDM on orbit flight in the clearance region(Radius 11km, Elevation 1.1°)
page 12Heinz Wipf, 13.02.2012
courtesy Greving
+5
0
-5
LOC12el 1F
building/reflector
direction of scatterer on the measurement path
TD
Az-pattern
page 13Heinz Wipf, 13.02.2012
courtesy Greving
Straight-In-Approaches?
Distance to LOC / m
DD
M/µ
A
2800 2900 3000 3100 3200-100
-50
0
50
100
150
200
King Air 3D diagram (30° rotated)omni direct. atenna in free spaceKing Air 3D diagram (0° rotated)dipole in free space
LOC (x/y): 0 / 0 (12ele-1F)THR (x/y): 3000 / 0Centerline: x-axesbuilding (x/y): 3025 / -200(length: 50m, height: 10m)building 47° rotated
11.4.02DDM2
page 14Heinz Wipf, 17.04.2012
RTCA
“.. frequency range 108 –112 MHz, the horizontal
component of the radiated signal in the forward and
rearward directions shall not be down more then
10 dB when compared to the max radiation from a
standard horizontal dipole antenna resonant at 113
MHz and mounted 10 inch above a ...”
page 15Heinz Wipf, 13.02.2012
Antenna Diagram within Spec?
X
Y
Z
Antenna 1V, tailfinAntenna 2
V, top of fuselage
Antenna 3V, nose
page 16Heinz Wipf, 13.02.2012
Other Antenna Type
better Mounting Locations?
courtesy Greving
Z
X
Y
V-dipole on top of fuselageKingair 350
3D-radiation pattern
kingvd3d.dsf 03/02
page 19Heinz Wipf, 13.02.2012
Distance to LOC / m
DD
M/µ
A
2800 2900 3000 3100 3200-100
-50
0
50
100
150
200
omni direct. atenna in free space
dipole in free space
3D-diagram:V-dipole above Kingair 350
12.4.02DDM3
LOC (x/y): 0 / 0 (12ele-1F)THR (x/y): 3000 / 0Centerline: x-axesbuilding (x/y): 3025 / -200(length: 10m, height: 50m)building 47° rotated
omni
Kingair, 0°
dipole
DDM LOC on GP for different antennas kingvgp2.dsf 04/02
V-dipole Kingair top (yaw 0°)
page 22Heinz Wipf, 13.02.2012
courtesy Greving
Conclusions
• Antennas once mounted on an aircraft differ from specified free-space pattern.
• Given certain typical flight inspection procedures and aircraft attitudes together
with multipath, 3d aircraft antenna diagram
care must be taken to avoid erroneous results.
• RTCA/DOC-195 spec may not suffice to embrace flight inspection applications.
page 23Heinz Wipf, 13.02.2012