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A6-1PPSOEM 1PPS Timing Modulen Compact form factorn License availablen Very fast lock to GPSSTOP PRESS Now available as a complete instrumentThis is a PCB level product to control an OCXO or Rubidium oscillator from an external 1PPS.The A6-1PPS uses a 3 state Kalman filter algorithm to measure & correct the frequency offset of theoscillator with respect to the 1PPS input. Time-tagged 1PPS to 200ps resolution &
A6-1PPSA locking module for timingThis module is designed to lock a 10MHz stable oscillator, either OCXO or rubidium, to the 1PPS time marksignal generated from a GPS receiver. The module can be programmed for a wide range of controlled oscillatorparameters, and GPS receivers. The controlled oscillator can be either on or off the board. A stable 1PPS timemark is generated from the controlled oscillator. This can be adjusted to any offset from the GPS 1PPS in 1ns steps.The control algorithm used is designed to give optimum control results and the fastest possible acquisitionfrom switch on.Design strategyThis module is designed to lock a 10MHz stable oscillator, eitheran OCXO or a rubidium, to the 1PPS time mark signal generated froma GPS receiver.There are a number of challenging problems involved in this, asthe data rate by definition is only one measurement per second. Inorder to get sufficient frequency resolution to correct the oscillator, avery long averaging time would be required.Because the 1PPS time mark is a fast rise time logic signal, theonly measurement that is feasible is to time tag the incoming1PPS edge relative to a local clock driven by the controlledoscillator. By calculating the rate of change of the arrival time overa suitable averaging period, the frequency offset of the controlledoscillator can be calculated. An alternative strategy would be to setthe time of the first 1PPS arrival as the zero phase of a phase detectorwith a range of +/- 0.5s. This is equivalent to +/- Pi radians. A phaselock loop would then provide a very slow control of the oscillator.In both systems the timing accuracy and resolution of theincoming 1PPS is important. Modern GPS receivers provide a 1PPSoutput jitter of between 1us RMS for a navigation receiver, to lessthan 7ns RMS for a special timing receiver operating in position holdmode. It is desirable that the timing resolution of the module shouldbe better than this, as otherwise quantization noise would enterthe averaging process and degrade the performance of the system.It would only be possible to compensate for this by increasing theaveraging time. A suitable specification for time resolution is +/- 1ns.To achieve this directly would need a 1GHz clock. A much moresuitable method is an analog time interval expander. This device hasbeen used in many designs of frequency counter starting with theRacal 1992. The principle is that an error pulse is generated whichhas a width equal to the time between the incoming edge to betimed, and the next clock pulse. For example, with a 100ns clock,the error pulse will have a width of between 0 and 100ns. This errorpulse is then used to charge a capacitor or integrator. The capacitoror integrator is then discharges at a much slower rate, say 1/1000of the rate. The resulting stretched pulse is then measured using theavailable clock pulses. The improvement in resolution equals the ratioof the discharge to charge rate. For the example above the resolutionwill be 100ps.The next thing to consider is the choice of the controlalgorithm. This must provide an appropriate control bandwidth sothe short term stability of the controlled oscillator (Allen variance)is optimised over a wide range. The ideal bandwidth will varyconsiderably between a low cost OCXO, and a rubidium.One option is to use a simple phase lock loop. This would bea type 2 second order loop ( ie with an integrator in the loop filter)with a zero to give suitable phase margins for optimum dynamicperformance. However one problem with a phase lock loop is that itmust reduce the initial phase error to zero by changing the frequencyof the VCO. With the very long loop time constant necessary toremove the effect of the GPS time jitter, the eventual settling of theloop could take several days. It is also difficult to extract measures ofperformance from the loop, for example it is difficult to estimate thecurrent frequency error of the VCO. It was felt that a frequencycontrol loop would settle quicker. For a frequency standard we donot mind operating with a fixed phase offset, and there is no need toreduce this to zero.Tel +44 (0)1803 862062Fax +44 (0)1803 867962Email sales@quartzlock.comwww.quartzlock.com15
Page 1 and 2: instrumentsQuartzlock FOR EFTF &
Page 3 and 4: IndexOven Controlled Crystal Oscill
Page 5 and 6: E10-MRX Sub Miniature Atomic Clock
Page 7 and 8: A3-60SCSC Cut Oven-controlledQuartz
Page 9 and 10: A5-8Typical Characteristics *No of
Page 11 and 12: E5000SpecificationNo of Outputs 12N
Page 13: E5-XSpecificationsNo of outputs 6No
Page 17 and 18: A6-1PPSa particular time, and provi
Page 19 and 20: A6-1PPSSpecificationFrequencyInput
Page 21 and 22: A6-CPSTechnical DescriptionThis mod
Page 23 and 24: A6-CPSSpecificationReference InputF
Page 25 and 26: A6-ANFTechnical DescriptionThis mod
Page 27 and 28: A6-ANFA6-ANF Typical Stability, Pha
Page 29 and 30: A7-MXFeatures• Broadband 50kHz-65
Page 31 and 32: A7-MXMeasurement ErrorInput referre
Page 33 and 34: TypicalTypicalNarrowbandNarrowbandP
Page 35 and 36: A7-MXOperational DescriptionThere a
Page 37 and 38: A7-MXA7-MX Block DiagramFigure 1Fig
Page 39 and 40: E8-X / E8-X OEMSpecificationOutputs
Page 41 and 42: E8-Y / E8-Y OEMSpecificationOutputs
Page 43 and 44: E8000SpecificationE8000 VERY LOW NO
Page 45 and 46: E8010SpecificationOutputs a) Sinewa
Page 47 and 48: E10-MRXSpecificationOutputsHarmonic
Page 49 and 50: E10-LNSpecificationOutputs See opti
Page 51 and 52: A10-LPROStandard SpecificationOutpu
Page 53 and 54: A10-YSpecificationsOutput(100MHz UL
Page 55 and 56: E10-MROSpecificationOutputOptional
Page 57 and 58: E10-GPSSpecificationAccuracyShort T
Page 59 and 60: A10-M (A10-MX)SpecificationOutputAd
Page 61 and 62: A1000SpecificationOutputs See optio
Page 63 and 64: E1000SpecificationMagnetic FieldOut
Page 65 and 66:
E10-PSpecificationsOutputHarmonicsA
Page 67 and 68:
E10-XSpecificationsOutputHarmonicsA
Page 69 and 70:
E10-Y4 & E10-Y8SpecificationMagneti
Page 71 and 72:
CH1-75ASpecificationFrequency Outpu
Page 73 and 74:
CH1-75ACH1-75A Active Hydrogen Mase
Page 75 and 76:
CH1-76ASpecificationFrequency Outpu
Page 77 and 78:
CH1-76AAtomic Clock ComparisonsAs f
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Product Family TreeProductsFrequenc
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