enhanced loran receiver (elr) kirk montgomery – symmetricom/advanced timing solutions 2007...
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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)