eDME Architecture Development and Flight-Test ... - IEEE Xplore

eDME Architecture Development and Flight-Test Evaluation

Ohio University - Avionics Engineering – DASC October 2012

1

DME CONOPS within NextGen 4 Pillars of APNT CONOPS: Concept Of Operations for NextGen Alternative Positioning, Navigation, and Timing, FAA, March 1, 2012

Backup

Evolutionary improvements

Legacy DME

Modified procedures

Revolutionary improvements

Enhanced DME

Land safely

1. Safe recovery (landing) of aircraft flying in Instrument Meteorological Conditions (IMC) under Instrument Flight Rule (IFR) operations, 2. Strategic modification of flight trajectories to avoid areas of interference and manage demand within the interference area, 3. Continued dispatch of air carrier operations to deny an economic target for an intentional jammer,

Alternate

4. Flight operations continue without a significant increase in workload for Continue either the pilot or the Air Navigation procedures as usual Service Provider (ANSP) during an interference event.

Ohio University - Avionics Engineering – DASC October 2012

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PBN and ADS-B Surveillance Performance in Support of TBO From: “Concept Of Operations for NextGen Alternative Positioning, Navigation, and Timing,” Appendix G, FAA, March 1 2012

Flight Operation Taxi-out Takeoff Climb to Cleanup Departure / Climb

Cruise HD airspace Top of Descent Arrival Approach Taxi –in

HD airspace HD airspace LNAV RNP (AR)

Navigation Surveillance ( 

  ( 

  Accuracy* Containment NACp NIC Separation  -  - Visual Visual Visual 92.6 m (8) 1111 m (6) Visual Visual Visual 92.6 m (8) 1111 m (6)   3 nm    1 nm 2 nm 3 nm 92.6 m (8) 1111 m (6)   3 nm   10 nm 20 nm 20 nm 4 nm 8 nm 10 nm 5 nm < 308 m (7) < 1852 m (5) 2 nm 4 nm 3 nm   2 nm 1 nm 2 nm 4 nm 5 nm < 308 m (7) < 1852 m (5) 1 nm 2 nm 3 nm  <  1 nm 2 nm 3 nm < 308 m (7) < 1852 m (5)   3 nm  <    3 nm   > 1 MHz, e.g. 10 MHz) - TDMA to mitigate near-far • Superior multipath mitigation and ranging accuracy

Precise 3&5 #""" &.,""#6& 8. 5 $'%&"&%%$ Multipath bounding Æ assured ranging

Data broadcast

Remain legacy compliant Broadcast of alternative modulation signal

DME-Next

•

Synchronized beat signal broadcast – – – –

•

Transponders time & frequency sync passive ranging -> unlimited capacity Precise time '+,"0."# distribution Improved multipath performance

Carrier phase tracking –

Ultra precise displacement measurement (mm/s)

Ohio University - Avionics Engineering – DASC October 2012

DME-Sync

;  %'=., " #"9",+%, #"

DME Architecture Development Cost-Benefit DME-AltMod Alternate modulation

DME-Sync D ME S DME-Next

Synchronized transponders Precise time

Transponder beat signal, carrier phase, data broadcast No transponder synchronization

DME/N-Recap Upgraded transponder & interrogator performance, improved coverage

legacy DME/N

>"0.,"3) "&" Ohio University - Avionics Engineering – DASC October 2012

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Unique Architecture Elements

amplitude

DME Carrier Phase

Combination of 1-way and 2-way ranging

time

Increased Capacity

Improved Accuracy

Significant reduction of interrogation rate

Range smoothing Precise Velocity

Enhanced Integrity Multipath bound

Ohio University - Avionics Engineering – DASC October 2012

13

Flight Test Setup GROUND

AIR DME transponder GPS/IMU/Rb

10 MHz

PPS

RF data recorder GPS

PPS

10 MHz

CW @ 1107 MHz

RF data recorder

RF signal gen. 1 ms CW cal. burst

CW @ 1107 MHz

Freq spectrum

RF signal gen. DME pulses

Rb oscillator

Real-time quality monitoring

Ohio University - Avionics Engineering – DASC October 2012

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DME carrier phase Pulses are NOT phase coherent amplitude

(There is no fixed relationship between pulse phase and pulse envelope) But the carrier phase is continuous between pulses time

DME carrier phase provides ultra-precise (mm-level) displacement

measurements. This enables: Averaging of the pulse-measurement noise and multipath Æ Accuracy ++ Bounding of multipath Æ assured ranging Æ Integrity ++ precise velocity Æ accurate intent for ADS-B (tight) integration with inertials of a wide variety of performance classes

(Navigation grade, Tactical grade, Sub-Tactical) Successfully flight-"&"3 @$%J ",&2K . , 35,  Ohio University - Avionics Engineering – DASC October 2012

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Measured DME carrier phase performance DME carrier phase - GPS/IMU/Rb truth 0.15

0.03

#

0.026

± #Q

0.05 DME carrier phase - GPS/IMU/Rb truth

0.024 100 0.022 80 0.02

0.1

DME slant displacement error [m]

0.028

60 40

± 92.6m &"#

0.018

20 56.5

57

0

57.5

58

58.5

0

-0.05

59 -0.1

-20 -40

0

10

-60

-100

20 30 40 50 Horizontal distance towards transponder [km]

60

10

-80

Antennna Gain [dB]

DME slant displacement error [m]

DME slant displacement error [m]

0.032

5 V&"#W6&

0

10

20 30 40 50 0 Horizontal distance towards transponder [km] -5

60

-10

April 5, 2012: Ohio University Baron-58, Thales 415SE low-power DME transponder, custom -15 0 10 20 30 40 50 60 RF data collection setup and custom GPS/IMU/Rb truth Horizontal distance towardssystem transponder [km] Ohio University - Avionics Engineering – DASC October 2012

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Transponder Antenna Pattern 3000 50 30 20 15 12 10

8 7

6

5

4

3

2.4o

2500

Only high-performance DME measurements in main beam of transponder antenna

altitude [m]

2000

dB Systems 510A antenna gain

1500 10 dB

10

0 dB 1000

-10 dB

5

-20 dB -30 dB 500

-5 0

-10 -15 -20 -25 -30

0

10

0

10

20

30

40

50

60

10

Antennna Gain [dB]

Antenna Gain [dB]

0

0

10

20

30

40

50

elevation angle [ o]

60

70

80

90

0 -10 -20 -30

20 30 40 50 Horizontal distance towards transponder [km]

Ohio University - Avionics Engineering – DASC October 2012

60

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Measured DME pulse range performance 4

2.2

PDF of DME pulse range error

x 10

2 1.8 1.6

# occurances

1.4 1.2 1 0.8 0.6 0.4 0.2 0 -150

-100

-50 0 50 DME pulse range error [m]

100

150

• Transponder is “squittering” at 2700 ppps • Post-processing of RF recording of each transmitted (ground) and received (air) pulse , use classic half-amplitude method to determine TOT and TOA • 2700 ppps Æ .#%,," "3%"-way pulse pair range measurements per second • Total " &.,""  &X (mean of all range measurements) • (Note: approximately 9 dB additional insertion loss in setup due to bad contact) Ohio University - Avionics Engineering – DASC October 2012

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“Simulating” legacy DME/N performance • Assume noise and multipath statistics of 2-way ranging are identical to 1-way ranging • Interrogation rate of legacy DME/N ranges from 5 to 30 ppps, here ppps is used • Assume 1 sec smoothing 50 40

500

Apply a 1-sec moving average 0

DME/N ranging error [m]

Randomly select 15 ppps from 2700 ppps measurements

30

± 

20 10 0 -10 -20 -30 -40

-500 10

20 30 40 50 60 Slant range towards transponder [km]

-50 10

40 50 20 30 Slant range towards transponder [km]

Ohio University - Avionics Engineering – DASC October 2012

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“Simulating” eDME beat signal • Assume 500 ppps beat signal with pseudo-random pulse timing • Assume 100 sec smoothing using carrier (Carrier-Smoothed Pseudorange) 50

Randomly select 500 ppps from 2700 ppps measurements Apply a -sec moving average

eDME pseudoranging error [m]

40 30

± 

20 10 0 -10 -20 -30 -40 -50 10

40 50 20 30 Slant range towards transponder [km]

Ohio University - Avionics Engineering – DASC October 2012

60

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DME-Next: Combine 1-way & 2-way ranging • Two-way range (using legacy interrogation – reply): – Absolute range, but – Limited capacity

• One-way range (using “beat” signal broadcasted by transponders): – Synchronize with occasional 2-way ranging to solve for unknown Tx clock offset – Low interrogation rate (e.g. 1 Hz) Æ high capacity – Transponders only require stable frequency (  -1, 10-11 s/s) Carrier phase displacement x xx x x x xx x x x x x 2-way range xx x x* x x x x x x x x*x x x x xx xx x x x x 1-way range x x x* x x xx x * xx Multipath bound Carrier-smoothed 2-way range 1-way range Tx clock offset 1-way range Rx clock offset Solve Tx and Rx clock offset by occasional 2-way ranging

Solve for change in Rx clock offset by carrier phase precise velocity

Ohio University - Avionics Engineering – DASC October 2012

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DME 2-Way Ranging Measurement Error True range

Troposphere delay

A = Air = Interrogator G = Ground = Transponder

Interrogator clock drift during Time of Flight

Error in reply delay Multipath measured by transponder

Noise transponder

Multipath measured by interrogator

Noise interrogator

Uncompensated interrogator delays (cable, filter, etc) Remaining error terms (Example: Bias introduced by squaring for half-amplitude TOA)

Ohio University - Avionics Engineering – DASC October 2012

22

DME Carrier Phase Measurement Error True range

Troposphere delay

A = Air = Interrogator G = Ground = Transponder

Remaining errors, such as antenna phase patterns Multipath

Interrogator clock Error

Interrogator clock drift. Solve for by DME carrier phase precise velocity

Transponder clock Error

Transponder clock drift. Assumed small (