Transcript PowerPoint 簡報

TWSTFT using DPN signals
Yi-Jiun Huang and Wen-Hung Tseng
National Time and Frequency Standard Lab.,
Chunghwa Telecommunication Laboratories (TL), Taiwan
APMP 2012
November 26, 2012
Wellington, New Zealand
Telecommunication Laboratories
Outline
1.
2.
3.
4.
Introduce DPN TWSTFT signal and system
DPN TWSTFT system @ 2010 and 2012
Time link result and TDEV comparison
Summary and discussion
Telecommunication Laboratories
Dual Pseudorandom Noise (DPN) Signal
Lower tone at 66.4 MHz
Chip rate: 127.75 kcps
BW: 200 kHz
0
-10
Signal Power (dBm)
-20
Upper tone at 86.4 MHz
20 MHz
-30
-40
-50
-60
-70
-80
-90
60
65
70
Telecommunication Laboratories
75
80
Frequency (MHz)
85
90
DPN TWSTFT System
Conventional Modem does not support TX/RX function for DPN
Hardware:
1. Arbitrary waveform generator
2. A/D sampler
Software: (especially at RX)
1. Signal acquisition  tracking
2. Group delay estimation, i.e. τ = - dφ/dω
(Use GPU for accelerating correlation and convolution)
Arbitrary
Waveform Generator
Communication
Channel
A/D
Sampler, 64Msps
Sample Stream
Software
PC with GPU
Telecommunication Laboratories
DPN TWSTFT System (Receiver)
LO, 11.3 GHz
Down Converter
LNB
Band Pass Filter
UTC (TL)
A/D
NCO, higher tone
Phase
Detector
Group
Delay
Detector
I
F
F
T
FFT
FFT
Phase
Detector
I
F
F
T
Pseudorandom Code
FFT
NCO, lower tone
Telecommunication Laboratories
DPN TWSTFT System @ 2010
UTC(TL)
UTC(NICT)
IS-8
AWG
A/D
66.4 MHz
86.4MHz
AWG
A/D
66.4 MHz
Wideband BPF 20MHz
Telecommunication Laboratories
86.4MHz
Time Link Result @ 2010
-28
Conventional TW (1 h)
DPN (5-minute average)
GPS PPP(5 minutes)
Time Difference (ns)
-30
-32
-34
-36
-38
-40
-42
17 days
-44
55515
55517
55519
55521
55523
MJD
Telecommunication Laboratories
55525
55527
55529
55531
Time Link Result @ 2010
6
Conventional TW (1h)
DPN (5-minute average)
GPS PPP(5 minutes)
5
4
3
2
1
0
55520
2 days
55520.5
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55521
MJD
55521.5
55522
8
Time Deviation (ps)
TDEV Comparison @ 2010
100
PPP: 15ps@300s
PPP
10
10
DPN: 9.9ps@300s
DPN
2
10
3
10
4
Averaging Time (s)
Telecommunication Laboratories
10
5
Modification of DPN system @ 2012
To improve short term resolution:
1. Increase band separation (not occupied bandwidth)
2. Use narrow BPF to avoid in-band noise thus get high signalto-noise ratio
Unfortunately, observations: 300 (real time)  15 @5min
Telecommunication Laboratories
DPN TWSTFT System @ 2012
UTC(TL)
UTC(NICT)
GE-23
54.175MHz
AWG
A/D
54.175 MHz
AWG
85.875MHz
Wideband BPF 32MHz
Telecommunication Laboratories
A/D
85.875MHz
Narrowband BPF 4MHz
TDEV Comparison @ 2012
Time Deviation (s)
1.0E-08
1.0E-09
DPN: 14.9ps@300s
1.0E-10
DPN
GPS PPP
TWSTFT
1.0E-11
1.0E+02
1.0E+03
PPP: 12.3ps@300s
Telecommunication Laboratories
1.0E+04
1.0E+05
Averaging Time (s)
1.0E+06
1.0E+07
Comparison
DPN TWSTFT
Experiment
@2010
@2012
future
Observation
300 obs @ 5min
15 obs @5min
300 obs @5min
Real-time
observation?
Yes
No
Yes
Separation
20 MHz
31.2 MHz
20 MHz
Single
bandwidth /
code rate
200 kHz /
127.75 kcps
200 kHz /
127.75 kcps
200 kHz /
127.75 kcps
Band Pass Filter
20MHz@NICT,
TL
4MHz x 2 @NICT 2MHz x 2 @NICT,
32MHz@TL
TL
TDEV @ 300 s
9.9 ps
14.9 ps
Telecommunication Laboratories
< 10 ps(expected)
13
Summary and Discussion
1. We appreciate NICT colleagues for their great deals of
system development and equipment
2. DPN saves more bandwidth (200kHz x 2) than conventional
TWSTFT (2.5 MHz)
3. DPN provides the same resolution (10 ps level) as GPS PPP
and DPN can be perform in real-time
4. DPN TWSTFT has been conducted between NICT and TL
(baseline more than 2000km) for 9 months, and it agreed
with Cirt. T. Only a fixed offset existed due to no calibration
5. Software-based receiver can be more flexible than the
conventional one, e.g. decoding algorithm can be modified
Telecommunication Laboratories
Summary and Discussion
1. We appreciate NICT colleagues for their great deals of
system development and equipment
2. DPN saves more bandwidth (200kHz x 2) than conventional
TWSTFT (2.5 MHz)
3. DPN provides the same resolution (10 ps level) as GPS PPP
and DPN can be perform in real-time
4. DPN TWSTFT has been conducted between NICT and TL
(baseline more than 2000km) for 9 months, and it agreed
with Cirt. T. Only a fixed offset existed due to no calibration
5. Software-based receiver can be more flexible than the
conventional one, e.g. decoding algorithm can be modified
Telecommunication Laboratories
Thank you for your listening!!