augstas stabilitātes gps pieskaņojamās atbalsta frekvences ģeneratora moduļa izstrāde un...
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Informatīvais seminārs, R ī ga, 2012. g ada 2 9 .maijs. par projekta 2010/0283/2DP/2.1.1.1.0/10/APIA/VIAA/084 “Daudzfunkcionāla signālu laika analizatora eksperimentāla izstrāde" tekošajiem rezultātiem. - PowerPoint PPT PresentationTRANSCRIPT
Augstas stabilitātes GPS pieskaņojamās atbalsta frekvences ģeneratora moduļa izstrāde un izpēte
Projekta zinātniskais vadītājs Dr.hab.sc.comp. Jurijs Artjuhs
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par projekta 2010/0283/2DP/2.1.1.1.0/10/APIA/VIAA/084 “Daudzfunkcionāla signālu laika analizatora eksperimentāla izstrāde" tekošajiem rezultātiem
Elektronikas unDatorzinātņuInstitūts
InstituteofElectronics andComputerScience
Elektronikas unDatorzinātņuInstitūts
InstituteofElectronics andComputerScience
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
Referents Armands Mezeriņš
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Subject and objectives of research
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The performance of Frequency Standard directly definesaccuracy of the Time Analyser
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
Research Objectives:
• Comparative analysis of available high-stability clock oscillators • Design and investigation of Frequency Standard module
Time Analyser
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State-of-the-art
Commonly used built-in clock oscillators:
• Temperature Compensated Crystal Oscillators (Stability: 1 ppm - over operating temperature range)
• Oven Controlled Crystal Oscillators (Stability: 10 ppb)
• Rubidium Oscillators (Stability: 0.05 ppb)
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
Main drawbacks:
• Noticeable long-term instability • Aging •Requires regular calibration against a traceable reference with a high long-term accuracy
Currently GPS disciplining the clock oscillators allows considerable reducing these drawback
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GPS Disciplined Oscillator Basics
Space based navigation system (such as NAVSTAR GPS) provides 3D position, velocity, precise time (traceable to UTC) and high accuracy frequency worldwide.
GPS disciplining technique uses the signals obtained from a GPS receiver as a time and frequency reference to synchronize, calibrate or control a frequency source.
In a simple GPS Disciplined Oscillator the voltage controlled oscillator VCO (10 MHz) signal is divided to a lower frequency prior to phase comparison with 1PPS derived from GPS receiver. A microcontroller monitors the phase difference, and software changes the control voltage applied to the VCO to held phase difference within an appropriate range.
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
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Commercially available GPS Disciplined Oscillators
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
www.trimble.com www.jackson-labs.com www.conwin.com
Trimble Mini-T GPS Disciplined Clock board ULN-2550 GPSDO FTS375 Disciplined Reference
Trimble Thunderbolt E GPS Disciplined Clock Fury GPS Disciplined Frequency Standard FTS500 XenithTBR
GPS-12R Portable GPS Rubidium Frequency Standard
www.spectracomcorp.com
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Frequency stability of some commercial GPS Disciplined Oscillators
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
• Allan Deviation σ(τ) is a stability metric which shows the RMS frequency change we can expect over a τ second interval.
• Frequency deviations measured at 10 MHz relative to an atomic frequency standard.
• A stability of 1 × 10-13 or less after one day of averagingindicates a device of very high quality.
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GPS Disciplined Oscillator Module Design
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
The module consists of :
• FTS375-010.0M hybrid circuit – 10MHz CMOS and 10MHz phase-lock loop circuit synchronized with GPS signal• PIC18F24K20 microcontroller unit - provide initial setup and monitoring functions;• MAX202 transceiver circuit for RS232 to TTL level conversion
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Experimental estimation of the module stability
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
10-2
10-1
100
101
102
103
10-11
10-10
10-9
Averaging Time tau, seconds
Alla
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FREQUENCY STABILITY
GPS Disciplined State
Unlocked State (Holdover)
10-2
10-1
100
101
102
10-12
10-11
10-10
10-9
Averaging Time tau, seconds
Alla
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FREQUENCY STABILITY
Pendulum GPS-12R Rubidium Frequency Standard
GPS Disciplined Frequency Reference module
Trimble Thunderbolt GPS Disciplined Clock
Locked versus unlocked state of GPSDO module
GPSDO module versus Trimble Thunderbolt E GPS Clock
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GPS receiver data using NS3Kview software
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
Navigation window – current time, clock drift, longitude, latitude and altitude or elevation
Satellite Azimuth & Elevation Window – azimuth and elevation for each satellite that is in view
NMEA Command Monitor Window - all NMEA data sentences received from the GPS receiver
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Summary
Informatīvais seminārs, Rīga, 2012. gada 29.maijs
GPSDO is self calibrating reference with an excellent long-term stability.
Application of GPS Disciplined Oscillator Module as time-base in analyzer provides possibility for accurate and stable long-term measurements (frequency stability is in the range from 4·10-11 at 300s to 10-13 at 1 day).
For short-term measurements GPS disciplining may be turned off (time intervals less than 300 seconds) .
Timing data from GPS receiver and synchronization with UTC may provide time tagging of measured events in real time scale.