Enhanced LORAN Receiver (ELR)

Kirk Montgomery – Symmetricom/Advanced Timing Solutions2007 Convention and Technical Symposium - ILA-36Orlando, Florida

2

Beta User Group

8 Units completed Sep 2007. Identified a Beta User Group

USNO Ed Powers NIST Mike Lombardi VOLPE Jim Carroll STANFORD Sherman Lo / Di Qiu CG Academy Capt Hartnett/Greg Johnson Ohio U ? PIG Ben Peterson Symmetricom Kirk Montgomery

Beta User’s Manual

3

Current Features

E-Field & H-Field Antennas E-Field – 8 Chains

–User selectable DC Voltage levels.

H-Field – 4 Chains–Beam forming

–Heading – Antenna

–Azimuth – Strongest Signal

–Bearing – LDC Station

User selects Chains LDC Station

Modes Timing (Stationary) Navigation

User I/O Keyboard/Monitor Ethernet

Internal Rb Steered Uses LDC to recover time

Outputs 1PPS 10Mhz Tracking Data Demodulated LDC Messages NTP IRIG

Inputs 1PPS 10Mhz Reference Station (Timing)

4

Block Diagram

MAIN BOARD

Loran Interface

CH

-0

CH

-1

AnalogBoard

DSP

Ra

w D

ata

PCI BUS

Single BoardComputer

RAM

Antenna

DC Out DC IRIG 1 & 2

IRIG 1 & 2

1PPS 1 & 2

10Mhz 1 & 2

USB 1 & 2

Video

Ethernet

Serial Port

I/F B

us

5

HardwareLoran

Interface Board

Single

Board

Computer

DSP

Power

Supply

Main

Board

Rubidium

Analog Board

6

Time/Frequency Recovery

Raw (decimated) measurements from the Loran Data into the filter were stable. No Corrections Simply a measure of the Loran Time of Arrival from 8290-X (Gillette

WY)

Output from the filter was very stable over the period after the internal clock was locked down

Standard Deviation was ~13nSec over the entire period The TIC measurement was the difference between the

receiver and UTC (Symm) Note the RCVR “thought” it was holding the internal clock at UTC It appears that after the clock stabilized, the rcvr did hold to within

~25nSec of UTC.

7

Time/Frequency Recovery

ELR Time Recovery 180019Z - 191621Z Aug 2007

-100

-80

-60

-40

-20

0

20

40

60

80

100

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Days since start

ns

Raw TOA ELR-UTC UTC-SYMM

8

Rubidium Performance

Open Loop Measured Rb performance against the received signal

3 Cesium Ensemble @ the Transmitting Stations vs Internal Rb Drift estimated @ ~1.468uSec per day (9610-M)

Gillette was ~1.443uSec per day (-20nsec LPA) Short term stability ~20nSec

8290-X Gillette TOAKAS2 Open

30566.2

30566.4

30566.6

30566.8

30567

30567.2

30567.4

30567.6

30567.8

30568

30568.2

30568.4

1

78

15

5

23

2

30

9

38

6

46

3

54

0

61

7

69

4

77

1

84

8

92

5

10

02

10

79

11

56

12

33

13

10

13

87

14

64

15

41

16

18

16

95

17

72

18

49

19

26

20

03

20

80

21

57

22

34

23

11

23

88

24

65

25

42

26

19

26

96

27

73

28

50

29

27

30

04

Samples

uS

ec

Start: 15Aug2007 005601Z Stop 15Aug2007 202347Z1.17uSec/1167min=.00100257 uSec/sec1.443701 uSec per day.

LPA?

9

System Testing

Tracking performance SZC ECD measurements Signal Strength Cross Rate Interference

E-Field & H-Field Antennas Looking at the phasing on the

H-Field Orienting the antenna to the

NORTH (Stationary)

–Rotated the antenna from 0 to 359 degrees in 45 degree steps

–Tracked very well

10

Next Steps

Optimize receiver gain Provide Raw Data (I & Q) over Ethernet User Interface

Web Interface Front Panel Interface

Differential Reference Station Loran Data Channel

Generating & forwarding corrections Decoding the broadcasted corrections Closing the loop (integrity)

1PPS Calibration Tracking Status Alarms

JAMFEST 2007 (5-9 Nov 2007)