Ben-Hassine, Seif

Chabory, Alexandre

Douvenot, Rémi

Morlaas, Christophe

English

Archive Ouverte en Sciences de l'Information et de la Communication

Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Analysis of an IQ Receiver Model by means of Laboratory Measurements
for Conventional VOR
Seif Ben-Hassine, Alexandre Chabory, Christophe Morlaas, Rémi Douvenot
ENAC, TELECOM-EMA, Université de Toulouse, Toulouse, France
Funded by
December 6, 2019
EMWT 2019, Toulouse, France
1/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
VOR system
VOR gives an aircraft its bearing (azimuth) with respect to a ground beacon
VHF frequency band (108-118 MHz), horizontal polarization
Two components : a reference signal (REF) and a variable azimuth-dependent signal (VAR)
Two types of VOR station : Conventional VOR and Doppler VOR
Building restricted areas
Multipath yields bearing errors in the VOR
system
Surrounding objects can be a potential major
contributor to this error and particularly wind
turbines
ICAO recommendations exist but the applied
rules differs between countries
600 m 5 km 15 km
radial
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Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Introduction
ENAC-EMA contribution
Static VOR error accuracy has been given in [Morlaas et al., ITAES 2008]
In [Morlaas et al., Eucap 2010], a hybridization of parabolic equation with physical optics has been
proposed, called VERSO for VOR Error SimulatOR
Improvements of this method have been discussed in [Claudepierre et al., Eucap 2015]
Confrontation with in-flight measurements at Boulogne-sur-Mer in [Claudepierre et al., Eucap 2016]
In [Ben-Hassine et al., EuCAP 2019], a digital IQ receiver model including filtering and demodulation
responses, has been developed⇒ Take into account the variations in time of multipath in the bearing
error
Previous study : measurements of VOR signals
Measurements have been performed in [Bredemeyer, FCS 2015] to analyze the effect of multipath on
Doppler VOR signal
Objectives
Develop a tools to assess the impact of wind turbines on bearing in dynamic context
Analyze the response of digital IQ receiver model for a conventional VOR signal by means of
VHF measurement for one canonical multipath
Baseband IQ measurement in complex realistic scenarios
⇒ Compare the digital IQ receiver model with a calibration receiver
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Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Plan
1 Introduction
2 VOR Receiver Model
3 Confrontation from VHF measurements
4 Confrontation from baseband IQ measurements
5 Conclusion
4/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
VOR Receiver Model
Objective
Present the digital VOR receiver model
Proposed model
Developed model based on I/Q signals
Signal generator
Generate I/Q channels from time series of multipath parameters
Digital IQ receiver model
Envelope detector
VAR channel
REF channel
Azimuth estimation
Envelope
Detector
Band Pass Filter
30 Hz
High Pass Filter
9960 Hz
FM
Demodulator
Phase
comparatorIQ signal
Generator
Azimuth
Information
Decimation
I
Q
Decimation
Digital IQ
Receiver Model
Signals
Generator
Direct
+
Multipaths
Noise LF VAR
LF REF
5/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
VOR Receiver Model
Envelope
Detector
Band Pass Filter
30 Hz
High Pass Filter
9960 Hz
FM
Demodulator
Phase
comparatorIQ signal
Generator
Azimuth
Information
Decimation
I
Q
Decimation
Digital IQ
Receiver Model
Signals
Generator
Direct
+
Multipaths
Noise LF VAR
LF REF
Figure 2 – Block diagram of the VOR receiver
Used model parameters
IQ sampling frequency = 25 kHz
Decimation rate = 210
Filtering parameters
Type Fpass (Hz) Fstop (Hz) Rpass (dB) Rstop (dB)
Band pass filter
30 Hz
Butterworth [29,31] [24,36] 0.1 30
Low pass filter
DC
Butterworth 1 2 0.1 20
High pass filter
9960 Hz
Kaiser 8000 7000 ∅ 60
Table 1 – jjj
6/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Plan
1 Introduction
2 VOR Receiver Model
3 Confrontation from VHF measurements
4 Confrontation from baseband IQ measurements
5 Conclusion
7/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Problematic with in-flight measurements (1)
Figure 3 – Wind farm located at 5 km from the VORC
station in Boulogne-sur-Mer
Figure 4 – Relief from the VOR station to the wind turbines
Parameters
Antenna of the Boulogne-sur-Mer VORC (113.8 MHz)
9 windturbines on 3 radials
Mast : ground diameter = 7.5 m, top diameter = 2 m, height = 98 m
Nacelle : 4 m× 11 m× 4 m
Blades : length = 35.5 m
Ground with relief
8/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Problematic with in-flight measurements (2)
100 150 200 250 300 350
Time (s)
−1.5
−1.0
−0.5
0.0
0.5
1.0
1.5
E 
 o
  V
OR
 (°
)
Odunayia model
Receive   esponse
Measu ement
3604.4
103.9
9083.9
114.9
14946.6
118.5
20920.0
120.8
26944.0
120.1
32956.8
121.1
Distance to VOR (m)
Speed(m/s)
Figure 5 – Measured and simulated bearing error on radial ϕ = 78◦
Analysis
Good agreement for the error maximal value
Differences between simulations-measurements
Residual error without wind turbines (other
scatterers, noise)
Time variation of multipath
Atmospheric effects
Deficiencies in the configuration characteristics
⇒Measurement parameters must be controlled to improve the analysis of our receiver behaviour
9/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Description (1)
Objective
Compare the digital IQ receiver model with a calibration receiver by processing a VHF signal for one
canonical multipath in controlled environment
Measurement campaign
Generation of baseband VOR signals (direct + multipath)
VHF AM modulation
Combination/Splitting of VHF signals
Analog to IQ digital converter
Receiver processing
R&S EVS300
Digital IQ receiver
VHF AM
Modulator
Calibration
receiver
Power
Combiner
Baseband VOR
signal generator
I
Q
Power
Splitter
IQ
Detector
Digital IQ
receiver model
VHF AM
Modulator
Direct signal generator
Multipath generator
LO sync
Baseband VOR
signal generator
Comparison
LO sync
Figure 6 – Block diagram of measurement campaign
10/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Description (2)
VHF AM
Modulator
Calibration
receiver
Power
Combiner
Baseband VOR
signal generator
I
Q
Power
Splitter
IQ
Detector
Digital IQ
receiver model
VHF AM
Modulator
Direct signal generator
Multipath generator
LO sync
Baseband VOR
signal generator
Comparison
LO sync
Generation of baseband VOR signals
HP 8904A generator
Generate the baseband VOR
signals (direct + multipath)
Synchronized LF phases
11/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Description (3)
VHF AM
Modulator
Calibration
receiver
Power
Combiner
Baseband VOR
signal generator
I
Q
Power
Splitter
IQ
Detector
Digital IQ
receiver model
VHF AM
Modulator
Direct signal generator
Multipath generator
LO sync
Baseband VOR
signal generator
Comparison
LO sync
VHF AM modulation
Rohde & Schwarz SMA100
Generate an amplitude-modulated
VHF signals
Synchronized RF phases
12/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Description (4)
VHF AM
Modulator
Calibration
receiver
Power
Combiner
Baseband VOR
signal generator
I
Q
Power
Splitter
IQ
Detector
Digital IQ
receiver model
VHF AM
Modulator
Direct signal generator
Multipath generator
LO sync
Baseband VOR
signal generator
Comparison
LO sync
Combination/Splitting of VHF signals
Power splitter/combiner ZFSC-2-5
Combine the direct signal and the
multipath
Divide the signals towards the two
type of receivers
13/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Description (5)
VHF AM
Modulator
Calibration
receiver
Power
Combiner
Baseband VOR
signal generator
I
Q
Power
Splitter
IQ
Detector
Digital IQ
receiver model
VHF AM
Modulator
Direct signal generator
Multipath generator
LO sync
Baseband VOR
signal generator
Comparison
LO sync
Analog to IQ digital converter
TNT-SDR dongle type Nooelec
R820T2
Recover the baseband VOR signal
Analog to IQ digital converter
Save IQ binary data
14/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Description (6)
VHF AM
Modulator
Calibration
receiver
Power
Combiner
Baseband VOR
signal generator
I
Q
Power
Splitter
IQ
Detector
Digital IQ
receiver model
VHF AM
Modulator
Direct signal generator
Multipath generator
LO sync
Baseband VOR
signal generator
Comparison
LO sync
Calibration receiver
Rohde & Schwarz EVS300
ILS/VOR analyzer
Measure the azimuth information
via RF input
⇒ to compare with digital IQ
receiver model
15/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Description (7)
VHF AM
Modulator
Calibration
receiver
Power
Combiner
Baseband VOR
signal generator
I
Q
Power
Splitter
IQ
Detector
Digital IQ
receiver model
VHF AM
Modulator
Direct signal generator
Multipath generator
LO sync
Baseband VOR
signal generator
Comparison
LO sync
VHF phase
constant
VHF phase
variable
Measurement process
The parameters of the IQ receiver model are fixed
Band pass filter 30 Hz
High pass filter 9960 Hz
Low pass DC filter
Set an azimuth difference between direct and multipath at a value of 90◦
⇒maximize the conventional VOR error
Manual variation of the RF phase shift between the direct signal and the multipath
⇒ generate variations on the bearing error
16/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from VHF measurement : Results
Confrontation result
CVOR frequency = 113 MHz
Recording time = 6 mn
VHF direct signal
Power = -50 dBm
Azimuth = 0◦
Phase = 0◦
VHF multipath signal
Power = -70 dBm
Azimuth = 270◦
Variable phase in [−90◦, 90◦] by
hand random turning
Analysis
Relative similarity between the
behaviours of digital and calibration
receiver
Delay between the two responses
0 50 100 150 200 250 300 350
Time (s)
)8
)7
)6
)5
)4
)3
)2
)1
0
Er
ro
r (
()
VOR error : Azimuth dir = 0(, Azimuth mul = 270(
VERSO receiver
VERSO receiver + smoothi g filter
EVS300
Figure 7 – Receivers responses
17/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Plan
1 Introduction
2 VOR Receiver Model
3 Confrontation from VHF measurements
4 Confrontation from baseband IQ measurements
5 Conclusion
18/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from baseband IQ measurement : Description
Objective
Compare the digital IQ receiver model with a calibration receiver by processing a baseband IQ signal in
complex scenario
Measurement campaign
Generation of baseband IQ signal in a complex scenarios computed with a multipath times series
simulator
Transmission of IQ data by means of standard sound card to R&S EVS300 receiver via its LF input
Receiver processing by ; static model (Odunaiya), digital IQ receiver model and R&S EVS300
IQ signals
Generator
I
Q
IQ
Sound Card
Digital IQ
receiver model
Multipath times series
Simulator
Multipath
times series
Static model
(Odunaiya)
I
Q
R&S
EVS300
Figure 8 – Block diagram of measurement campaign
19/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Multipath times series simulator
2-rays model
Planar dielectric ground
Physical optics
Planar dielectric ground
Parabolic equation
Dielectric ground with relief
Input/output
Input
VOR station position and radiation pattern
Positions and characteristics of the wind turbines
Relief
Aircraft trajectory
Space sampling step of trajectory
Aircraft speed
Output
Time series of multipath parameters : amplitude
an, phase θn and azimuth ϕn (relative to
Magnetic North)
20/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from baseband IQ measurement : Configuration
Configuration
CVOR station
F= 113.8 MHz
P= 50 W
1 wind turbine is placed at 1 km from
the VOR
Simplified model
Based on ENERCON E82 size
Mast : ground diameter= 7 m, top
diameter= 3 m, height= 90 m
Nacelle : 3 m× 3 m× 3 m
Blades : length= 10 m
VOR Receiver
Straight trajectory of 15 km
Departure= [500,0,1000] m
Speed= 180 km/h
Space step= λ5 ≃ 0.526 m
Motionless for the first 5 s
VOR
Wind turbine
Receiver
500 m
15 k
m
1 k
m
1
km
x
z
y
Figure 9 – Configuration
21/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from baseband IQ measurement : Results (1)
VOR
Wind turbine
Receiver
500 m
15 k
m
1 k
m
1
km
x
z
y
Figure 10 – Configuration Figure 11 – Receivers responses
Analysis
Good agreement between receiver model and calibration device
22/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from baseband IQ measurement : Results (2)
VOR
Wind turbine
Receiver
500 m
15 k
m
1 k
m
1
km
x
z
y
Figure 12 – Configuration Figure 13 – Receivers responses
Analysis
Good agreement between receiver model and calibration device
When the multipath varies slowly⇒ digital and calibration receiver response = static model response
23/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from baseband IQ measurement : Results (3)
VOR
Wind turbine
Receiver
500 m
15 k
m
1 k
m
1
km
x
z
y
Figure 14 – Configuration Figure 15 – Receivers responses
Analysis
Good agreement between receiver model and calibration device
When the multipath varies slowly⇒ digital and calibration receiver response = static model response
When the multipath varies quickly⇒ digital and calibration receiver response 6= static model response
⇒ It is due to the dynamic effects of multipath
24/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Confrontation from baseband IQ measurement : Results (4)
VOR
Wind turbine
Receiver
500 m
15 k
m
1 k
m
1
km
x
z
y
Figure 16 – Configuration Figure 17 – Receivers responses
Analysis
Good agreement between receiver model and calibration device
When the multipath varies slowly⇒ digital and calibration receiver response = static model response
When the multipath varies quickly⇒ digital and calibration receiver response 6= static model response
⇒ It is due to the dynamic effects of multipath
Digital and calibration receiver response is shifted with respect to 0◦ between 5 s and 150 s⇒ It is due
to the group delay of receivers25/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Dynamic effects of multipath
Geometric criterion for dynamic sensitivity of VOR receiver
[Ben-Hassine et al., EuCAP 2020] : "Validity Domain of the Odunaiya Expression for Computing
the Conventional VOR Multpath Error"
Doppler frequency of multipath depends on the speed of the aircraft and its position with respect to the
VOR station and wind turbine
When the Doppler frequency δfmult is not included in one of the two filter bandwidths of receiver
(W30,WDC )⇒ no multipath error
Odunaiya model is considered invalid (red area) when
|δfmult | >
min(W30,WDC)
2
(1)
Figure 18 – Validity domain of the Odunaiya expression (in blue)
26/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Plan
1 Introduction
2 VOR Receiver Model
3 Confrontation from VHF measurements
4 Confrontation from baseband IQ measurements
5 Conclusion
27/28
Introduction VOR Receiver Model Confrontation from VHF measurements Confrontation from baseband IQ measurements Conclusion
Conclusion
Conclusion
Analysis of the digital IQ receiver model behaviour
Comparison with a calibration receiver (R&S EVS300) from laboratory measurements by processing a
VHF conventional signal for one canonical multipath
Baseband IQ conventional signal in complex realistic scenarios
Good agreement between results
⇒ Good confidence in the parameters of the digital IQ receiver model
Future works
Validation with a Doppler VOR multipath
Confrontation with other types of receivers (R&S EB200)
28/28


Analysis of an IQ Receiver Model by Means of Laboratory Measurements for Conventional VOR

https://hal-enac.archives-ouvertes.fr/hal-02458584/file/presentation_EMWT2019_Mesures.pdf

Analysis of an IQ Receiver Model by Means of Laboratory Measurements for Conventional VOR

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