Safran Mro-50 Ruggedized User Manual (+ PDF)

Introduction
mRO system description
1. Principle of operation and basic configuration
2. Physics Package (patented)
3. Electronics Package
  1. Atomic resonance signal capture
  2. Temperature controllers
  3. C-field
  4. Telemetries
  5. Frequency adjustment
The mRO-50 Ruggedized SPECIFICATIONS
mRO-50 Ruggedized installation and operation
1. Introduction
2. Safety!
3. Environmental Responsibility
4. Shipping and receiving information
5. Mounting
6. Pin Layout:
7. Normal operation
8. Serial interface operation
  1. Introduction
  2. Serial interface connection
  3. mRO-50 Ruggedized parameters monitoring
  4. Center frequency adjustment
  5. ID
9. Lock monitor

1. Introduction

The MRO-50 Ruggedized is a frequency reference device that is ideal
for military communications, electronic warfare, and avionics
applications. It is designed to offer low power consumption, high
accuracy and retrace, high frequency stability, and operation in
harsh environments with low frequency drift.

2. mRO system description

The MRO-50 Ruggedized system comprises a vapor cell filled with
metallic rubidium that contains both isotopes 85Rb (72%) and 87Rb
(28%). The cell is placed inside a cylinder with a gap to which the
microwave power derived from the Voltage Controlled Oscillator
(VCO) is coupled. The rubidium atoms in the cell occur with equal
probability in the two hyperfine energy levels of the ground state
5S (F=2 and F=3).

2.1 Principle of operation and basic configuration

To detect the clock transition between the two levels, the atoms
need to be manipulated in such a way that most of them occur in
only one level. This is done by optical pumping via a higher lying
state (5P). The C-field (static magnetic field) splits the Zeeman
levels of the 85Rb hyperfine ground-state 5S. The clock transition
between the mF = 0 levels is only second-order sensitive to the
applied magnetic field.

2.2 Physics Package (patented)

The physics package of the MRO-50 Ruggedized system is patented. It
comprises a vapor cell filled with metallic rubidium that contains
both isotopes 85Rb (72%) and 87Rb (28%). In addition, the cell is
filled with a buffer gas which collides with rubidium atoms so as
to keep them away from the cell walls and restrict their movement.
As a result, the rubidium atoms are practically frozen in place for
the interaction time with the microwave field. In this way, the
Doppler-effect is essentially removed and a narrow line width
results.

2.3 Electronics Package

The electronics package of the MRO-50 Ruggedized system comprises
the following components:

Atomic resonance signal capture
Temperature controllers
C-field
Telemetries
Frequency adjustment

2.3.1 Atomic resonance signal capture

The level of the transmitted pump light is detected by a photodiode
after the cell. When a microwave field resonant with the clock
transition F=2*F=3 is coupled to the interaction region, the level
F=3 is repopulated and light absorption is enhanced. A sweep of the
microwave field over the resonance is detected as a small dip in
the transmitted light level after the cell.

2.3.2 Temperature controllers

The MRO-50 Ruggedized system has temperature controllers that
ensure the vapor cell is maintained at an elevated temperature.

2.3.3 C-field

The C-field (static magnetic field) splits the Zeeman levels of the
85Rb hyperfine ground-state 5S. The clock transition between the mF
= 0 levels is only second-order sensitive to the applied magnetic
field.

2.3.4 Telemetries

Telemetries are used to monitor the performance of the MRO-50
Ruggedized system.

2.3.5 Frequency adjustment

The frequency adjustment component corrects the frequency of the
crystal oscillator so that the (fixed) phase-locked loop keeps the
microwave VCO exactly on the atomic resonance maximum.

3. The mRO-50 Ruggedized SPECIFICATIONS

The specifications of the MRO-50 Ruggedized system are listed in
the user manual.

4. mRO-50 Ruggedized installation and operation

4.1 Introduction

The user manual provides instructions for the installation and
operation of the MRO-50 Ruggedized system.

4.2 Safety!

Safety instructions must be followed during the installation and
operation of the MRO-50 Ruggedized system.

4.3 Environmental Responsibility

Environmental responsibility must be considered during the
installation and operation of the MRO-50 Ruggedized system.

4.4 Shipping and receiving information

Shipping and receiving information is provided in the user manual.

4.5 Mounting

The MRO-50 Ruggedized system must be mounted following the
instructions provided in the user manual.

4.6 Pin Layout:

The pin layout of the MRO-50 Ruggedized system is provided in the
user manual.

4.7 Normal operation

Instructions for normal operation of the MRO-50 Ruggedized system
are provided in the user manual.

4.8 Serial interface operation

4.8.1 Introduction

The MRO-50 Ruggedized system can be operated via a serial
interface.

4.8.2 Serial interface connection

Instructions for connecting to the serial interface are provided in
the user manual.

4.8.3 mRO-50 Ruggedized parameters monitoring

The parameters of the MRO-50 Ruggedized system can be monitored via
the serial interface.

4.8.4 Center frequency adjustment

The center frequency of the MRO-50 Ruggedized system can be
adjusted via the serial interface.

4.8.5 ID

The ID of the MRO-50 Ruggedized system can be accessed via the
serial interface.

4.9 Lock monitor

A lock monitor is included in the MRO-50 Ruggedized system to
monitor its performance.

View Fullscreen

MRO-50 RUGGEDIZED
User Manual

Contents

1. Introduction

2. mRO system description

2.1 Principle of operation and basic configuration

2.2 Physics Package (patented)

2.3 Electronics Package

2.3.1 Atomic resonance signal capture

2.3.2 Temperature controllers

2.3.3 C-field

2.3.4 Telemetries

2.3.5 Frequency adjustment

3. The mRO-50 Ruggedized SPECIFICATIONS

4. mRO-50 Ruggedized installation and operation

4.1 Introduction

4.2 Safety!

4.3 Environmental Responsibility

4.4 Shipping and receiving information

4.5 Mounting

4.6 Pin Layout:

4.7 Normal operation

4.8 Serial interface operation

4.8.1 Introduction

4.8.2 Serial interface connection

4.8.3 mRO-50 Ruggedized parameters monitoring

4.8.4 Center frequency adjustment

4.8.5 ID

4.9 Lock monitor

1. Introduction
Safran Timing Technology SA used its over 25 years of experience in manufacturing ultra-stable Rubidium oscillator for ground and space applications to produce a miniaturized Rubidium Oscillator (mRO) with dimensions, packaging and pinout of crystal oscillators (OCXO), measuring 50.8 mm x 50.8 mm x 20 mm. The clock is ruggedized to operate in harsh environment (large temperature range, stringent mechanical stress). It delivers a square reference signal at 10 MHz (0 to 3V) with outstanding performances for a steady power consumption below 0.57 W at room temperature.
Such frequency references are well suited for applications demanding low power consumption, accuracy and retrace, high frequency stability, operation in harsh environment and low frequency drift such as military comms, electronic warfare or airborn & avionics.
The mRO is described in this document divided into 4 chapters:
· A brief introduction
· A simple description of the principle of the clock
· The specifications of the system
· The operation manual
2. mRO system description
2.1 Principle of operation and basic configuration
The mRO-RUG is a miniature rubidium clock and essentially 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. While the frequency of the VCXO is at the convenient standard frequency of 10 MHz, the rubidium clock frequency is at 3.036 GHz in the microwave range. The microwave signal is directly generated with a second voltagecontrolled oscillator (VCO). The phase-stable link between the two oscillators is established with a fractional-N PLL (phase-locked loop).
The rubidium atoms are confined in a vapor cell at an elevated temperature. The cell is placed inside a cylinder with a gap to which the microwave power derived from the VCO is coupled. The 85Rb atoms in the cell occur with equal probability in the two hyperfine energy levels of the ground state 5S (F=2 and F=3).
In order to detect the clock transition between these two levels, the atoms need to be manipulated in such a way that most of them occur in only one level. This is done by optical pumping via a higher lying state (5P). Figure 1 shows the atomic energy levels and transitions involved in the optical pumping process on the D1-line at 795 nm.

Figure 1: 85Rb optical pumping (D1 line)

Figure 2: The C-field (static magnetic field) splits the Zeeman levels of the 85Rb hyperfine ground-state 5S. The clock transition between the mF = 0 levels is only second-order sensitive to the applied magnetic field.

The pump light comes from a VCSEL (Vertical Cavity Surface Emitting Laser) which is tuned to resonance with the transition between the ground-state F=3 level and the (un-resolved) excited states F’=2,3. The pump light excites 85Rb atoms which are in the upper hyperfine level (F=3) to the short-lived excited state 5P from which they decay to the two ground state levels (F=2,3) with equal probability. Since pumping occurs continuously out of the F=3 level, a steady-state is reached where most atoms are found in the F=2 level.
The level of the transmitted pump light is detected by a photodiode after the cell. When a microwave field resonant with the clock transition F=2*F=3 is coupled to the interaction region, the level F=3 is repopulated and light absorption is enhanced. A sweep of the microwave field over the resonance is detected as a small dip in the transmitted light level after the cell.
This signal from the photodiode is fed into a synchronous detector whose output generates an error signal which corrects the frequency of the crystal oscillator so that the (fixed) phase-locked loop keeps the microwave VCO exactly on the atomic resonance maximum.
The vapour cell is filled with metallic rubidium that contains both isotopes 85Rb (72%) and 87Rb (28%). In addition the cell is filled with a buffer gas which collides with rubidium atoms so as to keep them away from the cell walls and restrict their movement. As a result the rubidium atoms are practically “frozen in place” for the interaction time with the microwave field. In this way the Doppler-effect is essentially removed and a narrow line width results.
The cell region is also surrounded by a pair of C-field coils which generate a small axial static magnetic field to resolve the Zeeman sub-transitions of the hyperfine line and select the clock transition, i.e. the one with the least magnetic sensitivity, see Figure 2. To further reduce the magnetic sensitivity, the complete physics package is placed inside a magnetic shield.
Figure 3 gives a basic overview of the different functional blocks of the rubidium atomic clock. The rubidium clock consists of two different packages. First, the Physics Package noted PP, which includes the VCSEL, the rubidium vapor cell, the cylinder coupling the microwave to the rubidium atoms, two C-field coils and an optical filter. Second, the Electronics Package noted EP, which includes the microwave generation, the detection circuitry, temperature controllers, monitoring and signal processing.

Figure 3: miniaturized

Rubidium

atomic

clock principal block

diagram

2.2 Physics Package (patented)
The main design characteristics of the PP are its low power consumption, small size and mass, along with minimal environmental sensitivities and mechanical ruggedness.
All parts of the PP are incorporated into a DIL-14 package hermetically sealed off under Xenon atmosphere to reduce temperature exchange by convection and minimize electrical power consumption.
The light source selected for its compactness and low power consumption is a Vertical Cavity Surface Emitting Laser (VCSEL) at 795 nm. It is coupled to a glass blown cell filled with Rubidium and buffer gas surrounded by a cavity coupled to the microwave signal.
The cavity has two purposes: 1) couple the Rubidium atoms to the microwave field as mentioned previously but also 2) transfer the heat to the cell and make a thermally stable environment around the glass cell as an oven. Both components, VCSEL and Cell, are temperature stabilized.
The design is completed with Helmholtz coils, an optical filter and the photodetector.
2.3 Electronics Package
2.3.1 Atomic resonance signal capture
The mRO-RUG transition is a microwave transition at 3.036 GHz.
The microwave resonance which occurs as a dip in the optical signal after transiting the cell, is detected by a photodiode.
The basic purpose of the EP is to synchronize the entering microwave frequency, derived from a temperature compensated crystal oscillator (TCXO), to this absorption dip. It is achieved by tuning the microwave frequency to maximum optical absorption.
Frequency variations of the microwave signal are transformed into DC current changes at the photodetector. The dip, visualized in the photocurrent versus microwave frequency curve of Figure 4 is very small: on the order of 1% of the total photocurrent.
Since DC detection of the dip is not feasible, an AC detection method is used for the following reasons:
· The dip amplitude is very small compared to the total photocurrent.
· The slope of the derivative of the dip photocurrent versus microwave frequency corresponds to roughly 100 pA/Hz. AC detection is the only solution to have a good signal/noise ratio since the photo-detector with associated amplifier are affected by flicker noise.
The AC method involves square wave frequency modulation of the microwave signal at a rate of approximately 105 Hz. As shown in Figure 4, the modulated microwave frequency flips between 2 discrete frequency values f1 and f2. The resulting photo-current i(t) appears also (after the transient) at 2 discrete values i1 and i2. The difference between i1 and i2 produces the error signal used to adjust the crystal oscillator center frequency until the mean value of f1 and f2 is exactly equal to the rubidium hyperfine frequency.

Figure 4: Atomic resonance: error signal detection
2.3.2 Temperature controllers
Since the temperature of the VCSEL and the Cell must be adjusted independently, two separated heaters are necessary to control the temperature of the PP main parts. The temperatures are controlled by compensating thermal losses using heating elements (no cooling). Temperature regulation servo-loops are based on a temperature sensor (NTC within a Wheatstone bridge), Proportional-Integral (PI) regulator and a heating element.
2.3.3 C-field
A pair of C-field coils inside the PP generate a magnetic field which separates the rubidium spectral lines. This magnetic field allows fine-tuning of the output frequency by shifting the rubidium resonance frequency by the second-order Zeeman effect. A stabilized current drives the coils. The current is adjustable for fine-tuning of the output frequency and can be set by a software interface or by an analog voltage applied to the mRO pin #1.
2.3.4 Telemetries
The user can access these data from a software GUI shown in Figure 5. Telemetry parameters shown include: · Error signal of the atomic lock loop · DC signal on photodiode · VCSEL temperature · Control signal of the VCSEL temperature controller · Cell temperature · Control signal of the Cell temperature controller · EP temperature · VCSEL driving current · Voltage across the VCSEL · Control voltage of the 10 MHz crystal

Figure 5: Control and monitoring software for the mRO-50
More details are given in 4.8.3. More specific information on the mRO-50 Ruggedized – Evaluation Kit document
2.3.5 Frequency adjustment
The C-field coil within the PP provides fine frequency adjustment capabilities. The value of the output frequency is settable by applying an analog voltage to pin #1 (see 4.8.4) or by software by step of 3 ppt (part per billion, i.e. 10-12). The microwave frequency at 3.036 GHz can be set in steps of approximately 3.8 Hz by software (see 4.8.4). The corresponding fractional resolution is 1,24 ppb (10-9).
3. The mRO-50 Ruggedized SPECIFICATIONS
The specifications of this product are available on our website.
4. mRO-50 installation and operation
4.1 Introduction
This chapter of the manual contains information regarding the installation and operation of the mRO-RUG. It is recommended to read this chapter carefully prior to operate the unit.

4.2 Safety!

– Use proper ESD precautions

– Ensure that all cables are properly connected

· The equipment contains small quantities of rubidium metal hermetically sealed inside the glass lamp and cell assemblies, hence, any dangers arising from ionizing radiation are caused for human health (exemption set in article 3 to Council directive 96/29/Euratom).
· For further information, ask for the «rubidium product data sheet». · Handling the product in a reasonably foreseeable conditions do not cause any risk for human health,
exposure to the SVHC (substances of very high concern) would require grinding the component up.
4.3 Environmental Responsibility
· The equipment contains materials, which can be either re-used or recycled. · Do not deposit the equipment as unsorted municipal waste. Leave it at an authorized local WEEE
collection point or return to Safran to ensure proper disposal.
· To return the appliance: · Submit a support ticket at [email protected] and request an RMA. · We will contact you for more information and/or with shipment process details.
4.4 Shipping and receiving information
The mRO-50 RUG is packaged and shipped in a foam-lined box. The unit is inspected mechanically and electrically prior to shipment. Upon receipt of the unit, a thorough inspection should be made to ensure that no damage has occurred during shipping. If any damage is discovered, please contact
SAFRAN TIMING TECHNOLOGIES SA PHONE: +41 32 732 16 66
CH-2000 NEUCHATEL / SWITZERLAND
Should it be necessary to ship the unit back, the original case and packing should be used. If the original case is not available, a suitable container with foam-packing is recommended.

CAUTION
Care must be taken for the transportation of the mRO-RUG to ensure that the maximum acceleration due to a shocks 50g/11ms is not exceeded.
mRO-RUG contains glass bulbs, crystal resonators.
When mRO-RUG integrated into an instrument, such instrument shall be packed in a suitable container, similar to containers generally use for the transportation of instruments like scope, video display or computer.

4.5 Mounting
CAUTION
Care must be taken to ensure that the maximum operating temperature is not exceeded, (+80°C) as measured at the unit’s base plate) This maximum temperature can be reached when operating the unit into forced air flow at +80°C.
The mRO-50 RUG is a well shielded unit, using several magnetic shield. Nevertheless, some consideration must be given to the operating location of the unit, regardless of its application. To minimize frequency offsets and/or non-harmonic distortion, the unit should not be installed near equipment generating strong magnetic fields such as generators, transformers, etc… The general information for the mechanical interface of the mRO-RUG unit is provided in Figure 6 (all dimensions in mm [inch]).

50.8* *

4.6 Pin Layout:
PIN FUNCTION

8×0.8 PINS

Frequency Adjust (Analog 0-3V)

GND

8 76 4

6.11

10MHz square output (0-3V)

2.7

GND

0.51

Power 5V or 3.3V depending on model

2.06

/LOCK (Bit)

TxD

20.3

3.4

21.84

RxD

38.58

40.6

41.66

5 5 x 2-56 UNC 2.3

(manufacturer ACCU ref.: SSC-2-56-5/32-A2)

50.8 *

40.6

38.6

36.2

35.6

32.6

5.08 18.8

5.09 0
4.45

5.3

20 * 0.87

*± 0.4 mm
All other quotes are ± 0.2 mm

Figure 6: Mechanical interface and dimensions of the mRO-50 RUG

4.7 Normal operation
When 5 or 3.3 Vdc, depending on the option, is applied to pin #5 (+), the unit will immediately generate a 10 MHz signal from the crystal oscillator. Within approximately 120 seconds after application of input power, the unit will “lock”, i.e. the crystal is now synchronised by the atomic resonant frequency. The unit is able to provide a single signal called `/lock ‘ (pin #6) which toggles from high to low level when the internal crystal oscillator is locked to the Rb atomic resonance (see 4.9). The center frequency is tunable by applying an ultra-stable analog voltage to pin #1. It is also possible to adjust the frequency by software (see 4.8.4).
4.8 Serial interface operation 4.8.1 Introduction
The mRO-50 RUG integrates a micro-controller with A/D and D/A embedded converters. The micro-controller is used to set the parameters of the clock but also to lock the TCXO on the Rb absorption `dip’. The built-in serial interface allows an automatic parameter adjustment during the manufacturing process as well as a fine and coarse adjustment of the center frequency. All the working parameters are stored in a builtin EEPROM memory and are accessible through the serial interface for monitoring. The user must send commands with the following pattern (TxD):
command | carriage return to validate command Example: monitor1<CR> or PIL_cfield 0960<CR>
Remark: the system removes the line feeds and spaces and is case insensitive. The returned response is decomposed as following (RxD):
response (if there is) + carriage return + line feed Example: 0123<CRLF> or error response (if there is) + ” ?” + 8 bits number corresponding to the error type + carriage return + line feed Example: 0123 ?08<CRLF>
4.8.2 Serial interface connection
The data transfer from the mRO-50 RUG is made by direct connection to a PC or standard terminal. The data transfer parameters are the following:
· bit rate: 9600 bits/s
· parity: none
· start bit: 1 · data bits: 8
· stop bit: 1

IMPORTANT NOTE
In most cases, the serial PC interface accepts the 0 to 3.3V level and a direct connection can be made.

Figure 7: Communication polarity of the mRO-50 RUG

4.8.3 mRO-50 Ruggedized parameters monitoring

The parameters monitoring is readable through the serial interface and with the use of the single command `MONITOR1` followed by a carriage return character. The mRO-50 RUG will respond to this command with an ASCII/HEX coded string as shown below.

AAAABBBBCCCCDDDDEEEEFFFFGGGGHHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOO<CRLF>

(example: 08F90BCE10CC0F8C09600BFC07E207E507C00B5F0D970D1B09D709554D05<CRLF>)

This string is composed of the 15 parameters. The DEC(X) function is the conversion of the hexadecimal to decimal value. Each returned byte is an ASCII coded hexadecimal value. The value are coded full range (4800: 0x0000 to 0x12C0 and 4095: 0x0000 to 0x0FFF) but are truncated into the software of the mRO.

· (AAAA) Rubidium cell temperature setpoint: during the optimization of the clock, the temperature of

the glass cell is adjusted to maximize the ratio absorption and power consumption. The temperature at

this maximum is define as setpoint.

10 000 × X

RNTC( Ohm ) =

1-X

with

–

DEC(AAAA) 4800

T (°C)

298.15

4100 × 298.15 × ln(10-5×RNTC )

4100

–

273.14

–

The highest hexadecimal value is 0x0BB8 which corresponds to 101°C. · (BBBB) LASER temperature setpoint: the temperature of the–VCSEL is set to match the laser

wavelength to the Rubidium resonance for a fixed driving current. The temperature determined during

this process is fixed as setpoint.

–

20 000 × X

RNTC( Ohm ) =

1-X

with X = 1 — DEC(BBBB) 4800

T(°C)

298.15

4100 × 298.15 × ln(10-5×RNTC) +

— 273.15 4100
–

· T(ChCeChCig)hLeAstShEeRxcaudrerceinmtaslevtaploueinitsd0uxr0inEg49stwarhti-cuhpc:-oafrtreerspswonitdcsh-t–oon1,0t0h°eCm. RO-50 runs the process of

locking the light source to the Rubidium resonance which lasts-70 seconds. During this process, the

current driving the VCSEL is converge to the value which

efinxeadbletos

a high value.-The the lock.

light

control –

loop

closed

and

the

current

will

3 × DEC(CCCC) 1000

I(mAmp) =

480065595 × 3 × -510

The maximum driving current is 1.8 (DDDD) C-field current setpoint: a

mAmp (0x1130-). small current crosses

the

pair

C-field

coils

which

generate

small

axial static magnetic field to resolve the Zeeman su6b5-5t9r5ansitions of the hyperfine line and select the clock transition.

I(Amp) =

3 × (4800 – DEC(DDDD)) 106 ×

4800

510

The

maximum

current

the

C-field

5882

µ-Amp

(0x0000). 65595

–

65595

—-

(EEEE) locking

tDhieffleigrehnttsioaluirncteetgorathtoerRDuYbNidAiuMmICmsaextitminugm:-aaftbesrosrwptiitocnh—-wonhi,cthhelamstRs O70-5s0ecruonnsdtsh. eDuprrioncgetshsisof

period, a voltage bias is added converge to the absorption.

the

iVn(pVuotlt)of=t3he×-lDig4E8hC0t(0EloEEcEk)co–r–rector

ensure

that

the

controller

will

The voltage range is from 0 to 3 V (0x0000 to 0x-1265C509)5.

—

· (FFFF) TCXO control voltage: the control voltage of the local -oscillator (TCXO) is corrected in real time

to lock its frequency to the Rubidium atomic tran-sition at 3.03-6GHz.

3 × DEC(FFFF)

The

TCXO

control

voltage

swing

V(Volt) = from -1.5 V to

65595 – 1.5 V (0x0800

– to

0x07FF).

· (GGGG) Atomic signal monitoring (15th sample)-: c6o55rr9e5sponds to the amplitude of the left interrogation signal (see 2.3.1).

V(Volt) =- 3 × D6E5C5(9G5GGG) 4095

–

The voltage range is from 0 to 3 V (0x0000 to 0x06F5F59F5).

· (HHHH) Atomic signal monitoring (31st sam-ple): corresponds to the amplitude of the right

interrogation signal (see 2.3.1).

3 × D6E5C5(9H5HHH)

V(Volt) =

–

4095

The voltage range is from 0 to 3 V (0x0000 t-o 0x06F5F59F5). · (IIII) Photodetector current: corresponds to the amplitude of the current at the output of the detector.
I(nA) = 1.5 – 3 × DEC(IIII) × 100000 4095

The current range is from -15 Amp to 15 A–mp (0x0FFF to 0x0000).

(JJJJ) LASER temperature temperature controller.

controller

voltage: is the voltage 3 × DEC(JJJJ)

driving –

the

heater

the

VCSEL

V(Volt)-=- 4095

The voltage range is from 0 to 3 V (0x0000-to 0x0FFF).

–

· (KKKK) Rubidium cell temperature controller voltage: is the voltage driving the heater of the glass cell

temperature controller.

V(Volt)-=

DEC(KKKK) 4095

–

The voltage range is from 0 to 3 V (0x0000hex to 0x0FFF).
· (LLLL) LASER driver voltage: is the voltage -driving the current source of the VCSEL. 3 × DEC(LLLL)
V(Volt) = 4095

The voltage range is from 0 to 3 V (0x0000 to 0x0FFF).

· (MMMM) LASER voltage: is the voltage across the VCSEL to monitor the good health of the

component.

3 × DEC(MMMM)

V(Volt)-=

4095

– The voltage range is from 0 to 3 V (0x0000-to 0x0FFF).
· (NNNN) EP temperature: is the temperature of the main electro-nic board.

47 000 × X

DEC(NNNN)

RNTC(Ohm) = 1 – X

with X = 4095

T(°C)

298.15

4100 × 298.15 × ln(10-5×RNTC)

4100

–

273.14

· (OOOO) mRO-50 status:
bit 00: CPULowPower mode 0 = DISABLE | 1 = ENABLE bit 01: state lock LASER current / temperature LASER 0 = CLOSE | 1 = OPEN bit 02: internal logic bit 03: state of the thermal compensation 0 = ON | 1 = OFF bit 04: state of the crystal oscillator control loop 0 = CLOSE | 1 = OPEN bit 05: not used bit 06: Forget MON_satom PIL_vc loop_0 0 = NO | 1 = YES bit 07: Forget MON_satom PIL_vc loop_1 0 = NO | 1 = YES bit 08: modulation status 0 = OFF | 1 = ON bit 09: Need sync 0 = NO | 1 = YES bit 10: temperature of the glass cell ready ? 0 = NO | 1 = YES bit 11: temperature of the LASER ready ? 0 = NO | 1 = YES bit 12: Need update R1 and R5 0 = NO | 1 = YES bit 13: internal logic bit 14: clock locked ? 0 = NO | 1 = YES bit 15: auto-start 0 = DISABLE | 1= ENABLE

IMPORTANT NOTE
Commands may not be taken into account or the mRO-50 RUG may return incorrect information during about 200 ms every 3 days due to an internal update of parameters.

4.8.4 Center frequency adjustment
The output frequency is adjustable digitally and by applying an analog voltage to pin #1. Analog voltage: must be low noise and stable to avoid any degradation of the mRO-50 RUG performance. This voltage is added to the voltage driving the current source of the coils. Spectratime recommends a buffer as close as possible to pin #1.
IMPORTANT NOTE
Pin #1 (IN analog frequency adjustment) must not be connected to any voltage potential if not used (not
Care must be taken to the stability of the voltage applied to pin #1 to not degrade the long term frequency stability of the clock. The frequency sensitivity to the voltage is about 8E-14/V. Digital frequency adjustment: is divided into fine and coarse. The fine tuning acts on the polarization of the C field and the coarse on the frequency of the digital PLL. The fine adjustment is about 30 Hz/step@10 MHz and the coarse about 12.4 mHz/step@10 MHz. The value is coded on 16 bits but are truncated in the software.
· Fine frequency adjustment: is achieved with the command `PIL_cfield’. · PIL_cfield <CR>: return the current value in 16 bits not signed hexadecimal in the range of 0x0640 à 0x0C80 (example: 0x0960<CRLF>). · PIL_cfield XX<CR>: add an offset to the current value of cfield. The parameter is used as long as the clock is running, a reboot will load the initial value of PIL_cfield. XX is a 8 bits signed hexadecimal word settable from 0x80 à 0x7F. · PIL_cfield XXXX<CR>: change the value of cfield. The parameter is used as long as the clock is running, a reboot will load the initial value of PIL_cfield. XXXX is a 16 bits not signed hexadecimal word settable from 0x0640 à 0x 0C20. · PIL_cfield LOAD<CR>: return the initial value of PIL_cfield on 16 bits not signed hexadecimal. · PIL_cfield SAVE<CR>: save the current value of PIL_cfield as initial value. · PIL_cfield SAVE XXXX<CR>: save the 16 bits not signed hexadecimal word XXXX as initial value of PIL_cfield.
· Coarse frequency adjustment: is achieved with the command `FD’ followed by a carriage return character. The customer must change the frequency step by step waiting at least 6 seconds between each step. · FD<CR>: return the current value in 32 bits not signed hexadecimal in the range of 0x000000000 à 0x003FFFFF of the denominator of the fractional digital PLL. · FD XX<CR>: add an offset to the current value of FD. The parameter is used as long as the clock is running, a reboot will load the initial value of FD. XX is a 8 bits signed hexadecimal word settable from 0x80 à 0x7F. · FD XXXXXXXXX<CR>: change the value of FD. The parameter is used as long as the clock is running, a reboot will load the initial value of FD. XXXXXXXX is a 32 bits not signed hexadecimal word settable from 0x000000000 à 0x003FFFFF (FD is set to adjust the output coarsely). · PLL SAVE<CR>: save the current value of FD as initial FD.
IMPORTANT NOTE
Safran advice to use the fine frequency tuning function. A wrong use of the coarse tuning may unlock the clock.

4.8.5 ID
The `ID’ command returns information about the clock in ASCII as below. VVVVVVVVVVVVVVVVVVVVVVVVVV WWWWWWWW XXXXXXXXXXXXXX YYYYYYYY ZZZZZZZZ ZZZZZZZZ ZZZZZZZZ<cr><lf>

(VVVVVVVVVVVVVVVVVVVVVVVVVV) Part number

(WWWWWWWW) Serial number

(XXXXXXXXXXXXXX) firmware version

(YYYYYYYY) developer information

(ZZZZZZZZ ZZZZZZZZ ZZZZZZZZ) checksum

4.9 Lock monitor
LED device may be directly connected to the `lock monitor output’ according to Figure 8.

Figure 8: electronic scheme for LED lock monitoring

safran-navigation-timing.com

March 31, 2023