navigation signals and antenna measurement in multipath...

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

Heinz 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

Heinz 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


courtesy Greving

Z

Z

X

Y

rear loop antennas atfuselage

Kingair 350

3D-radiation pattern

king3dloop1.dsf 03/02


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°)


courtesy Greving

+5

0

-5

LOC12el 1F

building/reflector

direction of scatterer on the measurement path

TD

Az-pattern


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


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 ...”


Antenna Diagram within Spec?

X

Y

Z

Antenna 1V, tailfinAntenna 2

V, top of fuselage

Antenna 3V, nose


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


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°)


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.


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