Novus NR2310D-ROG User manual

USERS GUIDE
NR2310D-R/O/G
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NR2310D-R/O/G
10MHz Rubidium Frequency Reference, GNSS-Locked, Low
Noise, 10-Channel w/RS232, Display
(Ethernet, SNMP –Optional)
All information provided herein is theproperty of Novus Power Products
LLC. The information included may be reproduced without the permission or prior
approval of Novus Power Products LLC for the purpose of operating the equipment.

USERS GUIDE
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Contents
Contents ...........................................................................................................................2
Safety................................................................................................................................4
Mounting ..........................................................................................................................5
Summary...........................................................................................................................6
The GNSS-Locked Reference..........................................................................................7
The Time Base..............................................................................................................8
The GNSS Receiver .....................................................................................................9
Stability Selection Types............................................................................................12
Dual-Time Base Frequency Verification (option) .....................................................19
External PPS Locking ................................................................................................19
The unit may be configured to lock to an external PPS signal. The signal must
conform to 3.3 V CMOS into a 1000 Ohm load. Rise time must be less than 10ns and
the pulse width must be greater than 10 ms...................................................................19
GNSS Antenna (recommended)-HS1,HS2 ....................................................................20
GNSS Antenna (recommended)-HS3,HS4 ....................................................................21
PPS .................................................................................................................................22
PPS source..................................................................................................................23
PPS Cabling................................................................................................................24
Cable Delays...............................................................................................................27
Pulse Width ................................................................................................................28
PPS Holdover .............................................................................................................29
NMEA - RS232..............................................................................................................29
Base Unit Block Diagram...............................................................................................32
Phase Noise Performance...............................................................................................33
Controls and indicators...................................................................................................34
Channel Status- Front panel LED’s ...........................................................................34
Oven- LED front Panel...............................................................................................34
Digital Display (Optional)..........................................................................................34
Time/Date/Lock Status...............................................................................................35
GNSS/GPS Status.......................................................................................................35
Channel Status............................................................................................................36
Alert Threshold...........................................................................................................37
Latch Channel Value..................................................................................................40
Save Configuration.....................................................................................................40
Fault Status.................................................................................................................41
Rubidium Status –Lock State....................................................................................42

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UTC Mode..................................................................................................................43
GMT offset.................................................................................................................43
RS232 NMEA / Alert –DB9 Male (Optional) .........................................................44
Rear Panel - Outputs.......................................................................................................45
Channel 1 through 10 output connectors –BNC or SMA .........................................45
PPS –SMA (with GPS locking option) .....................................................................45
Alert –BNC-SMA......................................................Error! Bookmark not defined.
Power In......................................................................................................................45
Functional Description (Base NR2310D-ROG) ............................................................46
Outputs .......................................................................................................................46
Built-in Test....................................................................................................................46
Power Supplies...........................................................................................................47
Redundant power........................................................................................................47
Specifications .................................................................................................................48
Technical Specifications.............................................................................................48
Environmental and Mechanical..................................................................................51
LIMITED HARDWARE WARRANTY .......................................................................52

USERS GUIDE
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Safety
This product has been designed and manufactured to recognized safety
standards and rules. The product is a sophisticated electronic instrument that
should be installed and operated by highly trained professionals.
Installation of this equipment should comply with all local electrical codes.
Utilization of this equipment in a manner inconsistent with the operating
instructions can be dangerous.
There are no user serviceable parts within the unit. Removal of the cover to
access interior parts will expose the user to dangerous voltages.
The unit may be powered from more than one power source. Care must be
taken to be certain all power sources are removed before installation or during
removal of the equipment.
The unit must be operated with a secure earth ground to the chassis. The
electrical path for earth ground is through the power connector. The power
switching device that controls power to the equipment must never interrupt the
chassis ground connection.
The equipment contains complex electronic components that can be damaged
by electrostatic discharge. Observe all recognize standards for the handling of
complex electronic devices to avoid high voltage discharge to the equipment.
Be certain the equipment chassis and operator are at equipotential before
handling the equipment.

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Mounting
The equipment is meant to operate in a horizontal - top up configuration.
The equipment is meant to mounted into a 19 inch standard NEMA cabinet.
The unit occupies a single “1RU”. Mounting spaces above and below the
equipment may be used as required.
Please observe the operating temperature range for the equipment. If mounted
into a closed rack, be certain that the total heat load in the cabinet does not
result in an interior operating temperature that exceeds the equipment
maximum rated temperature.
If cooling must be used, care should be given to prevent cooling mechanical
vibration from the coupling into the equipment. Mechanical shock and vibration
may introduce noise into the electronic signals inside the equipment that may
degrade the performance of the equipment. For applications where there is
significant shock and vibration, Novus offers equipment with interior
mechanical design features to minimize the effects of vibration and shock on
the equipment performance.

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Summary
The NR2310D-R/O/G is a high-performance ten channel, 10 MHz, GNSS-
locked Rubidium frequency reference. The core time base is a Rubidium
source that is disciplined with the timing information from the GNSS. The
Rubidium source is followed by a low noise OCXO locked to the Rubidium. The
ten channels provide a 13 dBm sine output that is transient, and fault
protected. The unit also provides a single channel PPS output and a RS232
port. The RS232 port provides NMEA 0183 data as well as proprietary data
streams for instrument status and control. The unit features a front panel
display for equipment status and control. An optional Ethernet port allows
remote access and control via SNMP. There are four levels of optional
reference control for improved Allan Deviation performance and PPS accuracy
and jitter. The platform also supports redundant power sources AC or DC. The
unit may optionally be configured to lock to an external PPS signal.

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The GNSS-Locked Reference
Novus offers four levels of GNSS locked reference performance:
HS1 digital loop using basic radio
HS2 digital loop, basic radio, adding picosecond timing
HS3 digital loop, advanced radio, picosecond timing and thermal stabilization,
Allan Deviation
HS4 digital loop, advanced radio, picosecond timing, thermal stabilization,
Allan Deviation, and vibration isolation.
Novus offers a range of locked reference performance options. Timing
information from the GNSS is very much a function of the receiver used, the
processing of the received timing information and how the timing source - be it
an OCXO, a Rubidium or some other device - is controlled. Environmental
factors such as temperature, shock and vibration all impact the overall system.
Over the years, Novus has invested heavily in the design of locked references
and can offer four levels of GNSS locking performance. Each level of
performance is discussed to allow the system designer to determine the level
of performance required versus system cost constraints.
Method Option
GNSS Locked
PLL
Pulse
Stabilization
Temperature
Control
ADEV (1s) ADEV (100s) ADEV (1ks) ADEV(100ks)
Analog Loop PLL Standard
3.00E-10 5.00E-10 8.00E-12
HS1
3.00E-12 2.00E-11 5.00E-12 5.00E-12
HS2
3.00E-12 1.00E-11 4.00E-12 9.00E-13
HS3
3.00E-12 7.00E-12 4.00E-12 7.00E-14
Digital Loop PLL

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The Time Base
The heart of the system is the reference. Novus offers OCXO and Rubidium
based references. Because of the relatively poor phase noise performance of
Rubidium, many of our customers select a Rubidium with a clean-up OCXO to
achieve high stability and low phase noise. Following is a plot of the phase
noise of a Rubidium reference and a Rubidium reference followed by a clean-
up OCXO.
Our Rubidium references offer a stability of < ±1 ppb/year compared to a
typical OCXO ±50 ppb/year. The Rubidium source consists of a voltage-
controlled crystal oscillator (VCXO) which is locked to a highly stable atomic
transition in the ground state of the 85Rb isotope.
Novus uses several vendors for the OCXO. The OCXO selected is based on
required phase noise, stability, and cost. There are other secondary
considerations such as size, power consumption, etc.
In addition to standard OCXO devices, Novus also uses double oven OCXOs
as an alternative to a single oven OCXO. As can be imagined, a double oven
OCXO offers improved temperature stability and is frequently a lower cost
alternative to a Rubidium source.

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A TCXO reference might be considered for a low-cost application. It offers an
aging stability that is on the order of ±1000 ppb/year. Phase noise is typically
not as good as that of an OCXO - but it is lower cost and consumes much less
power.
The GNSS Receiver
Disciplining a reference, a 10 MHz timing signal to a master reference with all
the noise due to atmospheric conditions, multipath and doppler effects is a
tremendous challenge.
There are likely hundreds of GNSS receivers available with a range of
functionality. Novus uses a few that are selected to meet the needs of our
reference and PPS (pulse per second) sources. PPS stability and accuracy
varies with each radio and cost rises with performance.
A significant part of the problem is the PPS being generated by the radio. No
two radio designs are the same and the algorithms that generate the PPS vary
widely. Following are two histograms for two different radios and their PPS
performance. One is Gaussian and the other is not. Also, the spectral content
of the PPS can vary greatly - often with low frequency content that adds to the
close-in phase noise of the reference.
Stability/Year Temperature Adev@1 sec
ppb ppb/ 0 to 70C Seconds
TCXO <+-1000 <+-1000 1.00E-09
OCXO <+-50 <+-10 1.00E-10
Double OCXO <+-10 <+-0.2 5.00E-12
Rubidium <+-1 <+-0.1 5.00E-11
Timing Sources Comparison

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Depending upon the locking algorithm, the radio PPS variation can contribute
directly to phase noise and uncertainty.
Novus uses two types GNSS receivers depending upon the stability options
installed in the unit.

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RADIO RECEIVER COMPARISON
Standard Advanced
Channels 26 184
Supported Channels
GPS L1C/A (1575.42 Mhz) x x
L2C(1227.60 MHz) x
GLONASS L1OF(1602MHz) x x
L20F(1246 MHz) x
Galileo E1-B/C(1575.42) x x
E5-b(1207.140MHz) x
BeiDou B1l(1561.098MHz) x
B2l(1207.140Mhz) x
Sensitvity
GPS
Tracking -161 -167
Hot Start -161 -157
Cold Start -147 -148
Reacqusition -161 -160
Glonass
Tracking -157 -167
Hot Start -157 -157
Cold Start -143 -148
Reacqusition -157 -160

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Stability Selection Types
Standard GNSS-Locked Reference –Analog Loop
In the case of a basic reference, which is acceptable for many applications, the
OCXO is controlled using a loop as indicated below:
The standard loop does an outstanding job of controlling an OCXO.
Components such as GaAs mixers provide excellent phase measurement
performance, but close-in phase noise is difficult due to the size of the filtering
components required and attendant leakage currents which are limited by the
mixer drive currents.

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Typical Allan Deviation performance for a standard loop is:
Basic Digital Locking Loop (HS1)
Though the analog loop is acceptable for many applications, the devices within
the loop present barriers that are difficult to overcome. Achieving very long
time constants requires larger and larger capacitors which present leakage
current issues. A digital platform allows time constants that are unconstrained
by a device and more flexibility to handle control loop performance.

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The HS1 improves Allan Deviation by an order of magnitude and close-in
phase noise by 10 dB.

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Advanced GNSS-Locked Reference (HS2)
Our most advanced designs address long time constants digitally. High
performance picosecond measurement techniques provide greater timing
resolution. Advanced algorithms coupled with precise analog designs that are
thermally controlled, and vibration-isolated allow Allan Deviation performance
approaching E-14. Performance over a standard loop is improved by almost
two orders of magnitude.

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Our algorithms process the radio information to achieve a more stable
reference. The curve below is a plot of timing jitter after processing:
The standard deviation improved from 17 ns to approximately 400
picoseconds. The most advanced loop reports calculated Allan Deviation on
real time basis locally on a display and/or a selected comm port.

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Allan Deviation can also be set up as an alert so that if there is a defined
variation from the baseline Allan Deviation, an error will be reported. This level
of monitoring will quickly detect a reference variation far in advance of a
complete failure, avoiding system outages. No one in the industry - that we are
aware of - provides this level of monitoring.
Thermally Isolated Reference (HS3)

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Thermally and Vibration Isolated Reference (HS4)
To further enhance performance Novus offers thermal and vibration-isolation.
The thermally isolated unit adds a thermal plate held at a fixed temperature
and an additional case around the reference to provide insulation.
The vibration option adds vibration isolators to attenuate shock and vibration
coming from the environment. Below is an attenuation curve for the option.

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Dual-Time Base Frequency Verification (option)
GNSS-locked references find application in laboratories where the integrity of
the source must be beyond question. With a GNSS-locked source, there could
be a source malfunction that could cause the source to be in error. To be able
to detect a problem, the dual-time base literally adds a second GNSS receiver
and an embedded frequency counter to measure the accuracy of the primary
reference. In some applications, a second antenna is installed, or a splitter can
be used to drive both time-base references from a single antenna.
The average frequency of each gate can be monitored at this screen, allowing
the user to see the most recent sample from the 1, 10, and 100 second gate.
External PPS Locking
The unit may be configured to lock to an external PPS signal. The signal must
conform to 3.3 V CMOS into a 1000 Ohm load. Rise time must be less than
10ns and the pulse width must be greater than 10ms.

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GNSS Antenna (recommended)-HS1,HS2
The receiver’s antenna must have a clear view of the sky to acquire satellite
lock. Remember, it is the location of the antenna that will be given as the
position fix. The GNSS receiver provides power for the LNA in the antenna.
The unit was designed to provide 3.5 Vdc <25 mA of current.
Novus NA103A Novus NA106
Typical Antenna Specs:
Frequency Band 1574 –1607 MHz
Antenna Gain 2 dBic @ 90°
Amplifier Gain @ 3.0Vdc: 26dB (typ)
Polarization RHCP
Out-of-band Rejection >60dBc @ f0 ± 50MHz
Impedance 50Ω
VSWR 2.0 Max
DC Input 2.8V - 6V
Noise Figure <2.0dB
Power Consumption 25mA (typ)