Novus NR2310D-O/G User manual

USERS GUIDE
NR2310D-O/G
REVISION
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DATE
071720
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www.novuspower.com
NR2310D-O/G
10 Channel GNSS Locked Frequency Reference with RS232,
Display and optional Ethernet-SNMP
All information provided herein is the proprietary property 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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Summary ....................................................................................................................4
Summary of Configuration Options..........................................................................4
The Time Base............................................................................................................5
Temperature Compensated Crystal Oscillator (TCXO)............................................5
Oven-Controlled Crystal Oscillator ..........................................................................6
Atomic Oscillator.........................................................................................................7
GNSS/GPS Disciplined Oscillator (GPSDO)...............................................................8
Dual-Time Base Frequency Verification (option).......................................................10
GNSS Receiver.........................................................................................................11
Sensitivity..............................................................................................................11
TTFF (Time to First Fix) ........................................................................................11
PPS ..........................................................................................................................14
PPS Availability.....................................................................................................14
Cable Delays.........................................................................................................15
Pulse Width...........................................................................................................15
Factory Default Settings........................................................................................15
Output Drive..............................................................................................................16
PPS Accuracy.......................................................................................................16
PPS Holdover .......................................................................................................16
NMEA - RS232 .........................................................................................................18
Base Unit Block Diagram..........................................................................................21
Phase Noise Performance........................................................................................23
Controls and indicators .............................................................................................23
Channel Status- Front panel LED’s .......................................................................23
Oven- LED front Panel..........................................................................................24
Digital Display (Optional).......................................................................................24
Time/Date/Lock Status..........................................................................................24
GNSS/GPS Status................................................................................................25
UTC Mode.............................................................................................................25
GMT offset............................................................................................................26
Channel Status .....................................................................................................26
Next and Select Buttons........................................................................................26
RS232 NMEA / Alert –DB9 Male (Optional).........................................................27
Rear Panel - Outputs ................................................................................................28
Channel 1 through 10 output connectors –BNC or SMA.......................................28
PPS –SMA (with GPS locking option) ..................................................................28
Alert –BNC-SMA..................................................................................................29
Power In................................................................................................................29
Antenna Connection (with GNSS option only).......................................................29
Functional Description (Base NR2310D-OG)............................................................31
Outputs.................................................................................................................31

USERS GUIDE
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Built-in Test...............................................................................................................31
Power Supplies.....................................................................................................31
Specifications............................................................................................................33
Technical Specifications........................................................................................33
Environmental and Mechanical .............................................................................34
LIMITED HARDWARE WARRANTY.........................................................................35

USERS GUIDE
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Summary
Summary of Configuration Options
A multi-channel based reference for very demanding telecommunications,
precision scientific research and calibration. The multi-use platform can be
configured with several performance options:
1. a range of stability options
2. high reliability (full redundancy is offered with the new NR2300 line)
3. display and user interface
4. local and remote monitoring via RS232
5. Ethernet port to allow remote monitoring and control

USERS GUIDE
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The Time Base
Novus crystal-based frequency reference products are based upon either
TCXO or OCXO technology. Temperature compensated crystal oscillators will
normally use an AT cut crystal and electronically compensate the device with
temperature. An OCXO device uses a SC (stress compensated) crystal and
the part is held at a fixed temperature to minimize temperature drift.
Temperature Compensated Crystal Oscillator (TCXO)
The TCXO implementation results in a temperature stable reference in the
single digit parts per million.
Comparison of AT vs SC Cut Crystal
Over a broad temperature range, an AT cut crystal performs very well and
much easier to compensate electronically. It is also a simpler crystal to

USERS GUIDE
NR2310D-O/G
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manufacture than a SC cut device. For applications where a stability of a few
ppm is acceptable, a TCXO can be a cost-effective alternative.
The SC cut results in a much higher Q device and achieves much lower phase
noise than the AT cut. The device is also more sensitive to pressure and
temperature variation and is therefore mounted in a temperature-controlled
hermetic chamber.
Oven-Controlled Crystal Oscillator
An OCXO device affords a reference that is almost two orders of magnitude
more stable than the TCXO. OCXO oven temperature is in the range of 90°C.
The devices heat-up and become stable within ~ 5 minutes.
OCXO Frequency Error from Cold Start
Typical OCXO
-2.00E+02
-1.50E+02
-1.00E+02
-5.00E+01
0.00E+00
5.00E+01
1
13 25 37 49 61 73 85 97
109 121 133 145 157 169 181 193 205 217 229 241
Error in Hz
Time in seconds
Frequency Error 1 to 250 seconds

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Atomic Oscillator
Another type of time base is an atomic reference. These devices use a change
in atomic state of an isotope of Cesium or Rubidium for stability. Instead of a
stability of ±50 ppb/year for a typical OCXO - stability of ±1 ppb/year is very
common.
Atomic sources are very complex and while a very stable source, phase noise
performance may not be acceptable for many applications.
RUBIDIUM SOURCE TYPICAL PHASE NOISE PERFORMANCE
For applications requiring the stability of an atomic source but also requiring
low phase noise, a low phase noise OCXO is disciplined to an atomic source.
The phase noise for the NR2110-R/O has phase noise improved by well over
20 dB by this technique.

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RUBIDIUM SOURCE WITH OCXO –TYPICAL PHASE NOISE PERFORMANCE
GNSS/GPS Disciplined Oscillator (GPSDO)
When the stability of an atomic or crystal source is not sufficient a GNSS
disciplined source is an option. A GNSS receiver is installed and timing
information from the GNSS is used to discipline the timing device. Timing
accuracy to a ~E-12 is readily achievable.
The GNSS is used to provide timing for a control loop that modulates the
OCXO to bring it in alignment with the PPS timing information. A GNSS timing
source has considerable short-term instability due to the numerous radio
effects - multi-path, signal weakness, etc. In order to develop a stable
reference, the GNSS timing waveform is used to discipline a low noise source
with a Kalman Filter. A good example of the improved jitter performance of a
Kalman Filter is shown below:

USERS GUIDE
NR2310D-O/G
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KALMAN FILTER PERFORMANCE
The control loop that modulates the OCXO frequency can become very
complex. In its simplest form, the GNSS clock is used to create a DDS that is
then used in what is basically a PLL to develop an error signal to correct the
OCXO frequency. However, the GNSS synthesized clock is modulated by the
radio transmission artifacts which have very low frequency content. Designing
a loop to deal with sub-1 Hz noise is a challenge.
More advanced loops take on the task of controlling the OCXO frequency with
the PPS with sophisticated signal processing techniques. The improvement in
performance for low-frequency content can be dramatic for close-in phase
noise. The following phase noise curve is an example of a conventional PLL
structure versus a signal processing loop. Close-in phase noise is reduced by
more 20 dB.

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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.