electromagnetic compatibility at satellite level

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ELECTROMAGNETIC COMPATIBILITYAT SATELLITE LEVEL

Emiliano Scione

[email protected]

2015, Thales Alenia Space

2

This training course is divided in the following modules, each one dealing with a specific technical topic:

• Introduction & Definition

• EMC standards and normative

• EMC design rules

• Modelling for CE analyses in FD

AGENDA


3

Introduction & Definition


Electromagnetic Compatibility:The satellite system shall be able to operate properly andachieve the performance for which it was designed workingwithin the electromagnetic environment provided by themission:• All the unit composing system shall mantain their nominal

performances

• RF transponder shall work with no interferences

• Satellite materials shall not accumulate charge to notcause electrostatic discharge

INTRODUCTION & DEFINITIONS 4


Electromagnetic environment: different electromagnetic environment are experienced by satellite and compatibility at different level shall be ensured by EMC engineer

• Electro Magnetic Compatibility (EMC)

• Radio Frequency Compatibility (RFC)

• Electro Static Discharge Compatibility (ESD)

5INTRODUCTION & DEFINITIONS


Electro Magnetic Compatibility (EMC)

• Conducted Interferences

• Radiated E- field Interferences

• Radiated H-field Interferences

INTRODUCTION & DEFINITIONSEMC

6


Radio Frequency Compatibility (RFC)

• The antenna and all on board receivers/transmitters shallbe compatible with internal/external radio frequencydisturbance

INTRODUCTION & DEFINITIONSRFC

7


8

Electrostatic discharge Compatibility (ESD)

•Charged particles which invest satellite with its surfaces can accumulate on:

• High-resistive dielectrics• Floating metals

•Particles that does not flow to satellite ground increase local voltage potential that overcome material local breakdown voltage ad generate ESD

INTRODUCTION & DEFINITIONSESD


9INTRODUCTION & DEFINITIONS


10

EMC standards and normative


EMC standards and normativeStandard

11

EMISSION:

Equipment under test called SOURCE (electronic unit, subsystem, satellite system etc..) shall not introduce noise/interference towards surroundingunits called VICTIMS.

CE (Conducted Emission)

I e V (30 Hz-50 MHz)

RE (Radiated Emission)

Electric field V/m (14 kHz – 18 o 40GHz) Magnetic fieldAC [Tesla] (30 Hz - 50kHz)DC [Tesla]



12

SUSCEPTIBILITY (or IMMUNITY):

Nominal behavior of equipment under test called VICTIM (electronic unit, subsystem, satellite system etc..) shall not be disturbed by from nominalbehavior of surrounding units (called SOURCES) .

CS (Conducted Susceptibility)


RS (Radiated Susceptibility)



• EMC can be subject to two different interpretations:

• Commercial equipment: the manufacturers shallnot interfere with the electromagnetic environment(ecological interpretation)

• System (aerospace, automotive, military): the manufacturer shall design an equipment whichshall be compatible with the system where it isinstalled (functional interpretation)


13


CIVIL STANDARDS: Not professional, used for commercial and consumer electronics. Calls for CE marking standards: CEI-EN 55022/55024 - CISPR

MILITARY STANDARDS: indicate setup and requirements (masks) Test for Aerospace, Automotive, Space

EMC Requirements for unit and systems: MIL-STD-461 e 462 MIL-STD-464, Electromagnetic Environmental Effects Requirements For Systems Last Release: MIL-STD-461-F (10/12/2007) ECSS-E-ST-20-07C, ECSS-E-ST-20C, ECSS-E-HB-20-07 (21 January 2010)

ESD Requirements & Guidelines: ECSS-E-ST-20-06C, Spacecraft Charging NASA-TP2361, Design Guidelines for Assessing and Controlling Spacecraft Charging

Effects MIL-STD-1809, Space Environment for USAF Space Vehicles NASA-HDBK-4002, Avoiding Problems Caused By Spacecraft On-orbit Internal Charging

Effects

The main difference between the 2 standard consists in the fact that the military standard requirements are more stringent (eg. RS tests performed in the range 18 or 40 GHz with amplitudes up to 200 V / m)


• Conducted and radiated emission tests aim atlimiting unwanted emission from the equipmentunder test (EUT): voltages and currents on signaland power lines, radiated electric and magnetic fiedsfrom cables and EUT boxes

• Emission is always generated by the time variationsof voltages and currents

dtdvCi

dtdiLv


15

EMC standards and normativeEmission

CONDUCTED EMISSION

The test is performed by measuring a current level, which shall be translated into the specification level by a suitable corrective factor (insertion loss of the current probe)

16


• If P2 e P1 are referred to the same resistance the following relationships are equivalent

1

210

1

210

VVlog20dB

PPlog01dB

30WdBMdB120YdBXdB

Wm

VuV

17


CE Time Domain Ripple

CE Frequency domain

CE Time domain In rush

EMC standards and normativeEMISSION

18


DUT

LISN

Battery

To the Receiver


19


DUT LISNTo the EMI receiver


20


For the tests that use the military standard it is used the standard setup shown in the MIL-STD-461-F or G (DRAFT)

EMC standards and normativeLISN

21


CE Test on power line frequency domain (30 Hz-50 MHz)

CE Test on power line, time domain

Conducted Emission standard setup


22


LISN (Line Impedence Stabilization Network) is using during unitconducted test provide the unit with a standard and stable inputimpedance, similar to the one seen by EUT at S/C level

PCDUBatteriaHARNESS ZZZLISN


23


Typical LISN behaviour


24


Radiated Emission E-field Radiated Emission H-field

Radiated Emission


25


DUT

Battery

LISN

LPB Antenna

Cable


26



27


Rod

Bi-conica L.P.B.


28



29



RE plot– Pol V RE Plot– Pol H

Example Measurement of Emitted by an electronic device (Military standard)

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31

SUSCEPTIBILITY (or IMMUNITY):

Nominal behavior of equipment under test called VICTIM (electronic unit, subsystem, satellite system etc..) shall not be disturbed by from nominalbehavior of surrounding units (called SOURCES) .

CS (Conducted Susceptibility)


RS (Radiated Susceptibility)



EMC standards and normativeSUSCEPTIBILITY

DUT

Susceptibility signal

Transmit antenna

Current probe

Power and signal cables

32



CS Test sulle linee di alimentazione nel dominio della frequenza

CS Test sulle linee di alimentazione nel dominio del tempo

33



DUT

LISN

34



RS Test Electric Field Frequency Domain RS Test Magnetic Field Frequency Domain

35


EMC standards and normativeESD

ESD condotta

ESD radiata

ESD condotta

ESD Radiata

The ESD tests are performed both in a conducted and radiated

Specific waveform generators specially designed for this type of test are used

36


EMC standards and normative

CONDUCTED ESD RADIATED ESD

37


EMC standards and normative Thales Alenia Space – L’Aquila EMC Test Facility38


39

EMC design rules


EMC design rulesEMC Control Plan

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EMC design rulesBonding

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The bonding is used to minimize the impedance between themechanical interfaces used for common mass of satellite

Ideally the common ground should be at zero volts

In fact, the presence of non-ideal junction (screws, glues, notperfectly conductive materials) causes the presence of common-mode voltages that lead to disturbances on the common mass hasinductive or capacitive behavior

It is measured the resistance in DC and AC impedance between theunit chassis and the satellite panel on which it is mounted. Typicallythe maximum value in DC that you must have beween EACHconductive point of the unit chassis and EACH conductive point ofthe satellite structure is about 20mOhm.

To meet the requirement in DC the unit must be fixed to thestructure by means of high conductivity mechanical interfaces(Bonding Strap). Typically each strip of units should have strengthequal to each max 2.5mOhm. Since, however, take into account thatthe impedance varies with the size of the bonding strap and with thefrequency.

Aluminium strap 1,8 cm width 0 - 10 MHz

0.0001

0.0010

0.0100

0.1000

1.0000

10.0000

100.0000

1000.0000

0 10 100 1000 10000 100000 1000000 10000000

Frequency (Hz)

Impe

danc

e (O

hm)

Length [cm] = 10Length [cm] = 50Length [cm] = 100Length [cm] = 1502.5 mOhm

ttz0.22350.5

tzl2log2.303l10*2L 5


EMC design rulesBonding

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EMC design rulesGrounding

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BONDING: it relates to the mechanical interfaces that make up the satellite structure

GROUNDING: the reference of the supply lines to the nearest mass

The problem of the electric mass, to give substantially an equipotential reference surface to returns, is in two main cases: the return of the power supplies and the return of signals

Grounding: 1 Power return 2 Signal Reference Ground 3 Chassis Ground



44

Common Mode Noise: in the connections between units (especially those with return on the mass of the satellite structure) the signal is disturbed by spurious Voltages induced by impedance series inherent in satellite mass not ideal

Satellite GND

Z*I

Z*I voltage drop due to current returnZ depends on the resistance of the ground plane, its skin effect impedance and the impedance induced by the distance of the go wire from the ground plane

A B

A B Signal HOT line



45

Grounding philosophy:

1. Floating Ground2. Single Point Ground (SPG)3. Multiple Point Ground (MPG)4. Distributed Single Point Ground (DSPG)



46

FLOATING GROUNDAdvantages:• Absence of common mode interference

Disadvantages:• the presence of interference caused by Stray Capacitance• Susceptibility to Electrostatic discharge

Satellite GROUND structure



47

SINGLE POINT GROUND (SPG)Advantages:• Absence of common mode interference• Susceptibility to Electrostatic discharge

Disadvantages:• the presence of interference caused by Stray Capacitance• Reduction in the efficiency of unit shielding

Used for Power Lines




48

MULTIPLE POINT GROUND (MPG)Advantages:• Immunity Electrostatic discharge• Absence of interference caused by Stray Capacitance

Disadvantages:• Interference presence of Common Mode




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DISTRIBUTED SINGLE POINT POINT GROUND (DSPG)Advantages:• Immunity Electrostatic discharge• Absence of interference caused by Stray Capacitance• The absence of interference of Common ModeDisadvantages:• high cost: it includes Tx and Rx balanced

Used for Signal I/F




50

To effectively reduce the common mode noise the DSPG scheme it may only be used in the presence of receivers and transmitters balanced

The transmission line must be balanced and preferably shielded (with twisted wires)

Not RFUser

Load

Pwr Bus Main

Load

Load

RFUser

Load

Pwr Bus Ret

MainPower

DistributionUnit

Pwr Bus Main

Pwr Bus Main

Pwr Bus Main

Pwr Bus Main

Pwr Bus Ret

Pwr Bus Ret

Pwr Bus Ret

Pwr Bus Ret

UNIT 1

UNIT n

.

.

.

.

.

.

.


D3: EMC design rulesShielding

51

To minimize emissions and susceptibility on electronic units integrated on thesatellite it is used shielded or double-shielded cables

The chassis of the electronic units are used not only for mechanical reasonsalso as shielding effect to protect the internal circuitry from the surroundingradiation noise

Equipment with a shielded cable

Equipment with an unshieded cable

Dirty box

Filters


D3: EMC design rulesShielding

52


EMC design rulesShielding

53



54

Source Infinite distanceSusceptible circuit

EZ Ex

SourceSusceptible circuit

SourceSusceptible

circuit

Orthogonalization

Impenetrable barrier



55

Shielding Effectiveness (SE): it indicates a measure of the attenuation in [dB] offer a generic shielded structure



56

Shielding Effectiveness SdB

Pi power density in the test point before the shield insertionPt power density in the test point after the shield insertion

Ei e Hi Electric and magnetic incident fieldEt e Ht Electric and magnetic transmitted field

t

idB P

Plog10S

t

i

t

idB H

Hlog20EElog20S


EMC design rulesGasketing

57

FINGER STRIP

CONNECTORGASKETS

FOAM GASKETS

KNITTED WIRE MESH


EMC design rulesGasketing

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Conducted EMC (CE) filtering and typical requirements on power linesConducted Requirements

59

Filtering activity allows EMC design engineer to:

to control unit conducted emission respecting Customer required CE maskover the required frequency range (30 Hz-50 or 100 MHz)

to make the unit immune to external conducted noise, on the basis of the required susceptibility level specified in the applicable documentation



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61



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63

• Power line filters differ from conventional filters for thefollowing reasons:

• they do not work in load matching conditions becausepower lines do not have well defined load conditions attheir ends

• interference suppression shall be implemented over alarge frequency range(30 Hz- 100 MHz) where filterelements may change their characteristics due topossibile resonance effects

• AC or DC power line currents and voltages may biasfilters components affecting their performances

• filter size is an impotant parameter because power linefilters shall usually be installed in small spaces

EMC design rulesFiltering


64

UUT

Ip Icm/2

Icm/2In

Idm

Idm

Power source

Icm

dmcm

n

dmcm

p

III

III

2

2

2np

dm

npcm

III

III

Ip is the current of thepositive line of the unitunder test.

In the current of thenegative line of the unitunder test.

They can be decomposedin a sum of a commonmode term Icm/2 and adifferential mode termIdm.

The main generatorsof Icm and Idm areDC/DC switchingconverters, coupledradiated interferencesand conductedinterferences due tothe power source,which cause afrequency dependantcurrent emission(emitted current infrequency domain) .While the DCabsorption is due tothe unit nominal work.



65

ZA ZE

IEMI (CM)

IA+IEMI(DM)E

ZA ZE

I’EMI (CM)

I’EMI(DM)E



66

Filters shall be designed to suppress common mode and differentialmode interference

Common mode inductor is a fundamental component of filters

The permeability of magnetic materials is function of the appliedmagnetic field, which is proportional to the current

Common mode inductors are made of two windings on a toroidalhigh permeability ferrite core. The windings are wound in opposition with perfect simmetry in such a way that the core is notsaturated by the differential mode power current absorbed by the load.



67

In the ideal case where L = M the CM coil has no effect on the differential mode currents (Fig. B), but presents an inductance 2L in series to the two conductors for the common mode current (Fig. C)

So the common mode currents see a high impedance, while the differential mode currents pass unaltered. In case you want to reduce the differential mode currents, then simply change the direction of a winding for high differential mode impedance

A very much used device for blocking common mode currents is the Common-mode Choke It is made by wrapping the two wires of the circuit to be protected on a ferromagnetic torus as in

the figure (the same number of windings)



68

Ferrite coils reduce common mode currents

Differential currents generate magnetic fluxes in opposite directions

Common mode currents generate magnetic fluxes in the same directions



69

SAR power supply

Digital unit

Typical EMI filters of Space equipment



70

MODULE D6Modelization for CE analyses in FD


Modelling for CE analyses in FD71

P/T_PWR Bus Regulated/Unregulated

Sol

ar A

rray

Avionic

Units

Other S/SUnits

SADM

SADM

Battery

PowerDistribution Unit

2(OPTIONAL)

BATT_PWR Bus

Sar Electronics

Regulated/Unregulated Power Bus

Panel nPanel 2

Panel 1

Unit 1

Unit 2

SAR Antenna

Unit 3

Payload (P/L)Platform (P/T)

Power Distribution

Unit 1

Unit 1

Unit 2



Typical SAR Mission Power: 5 kW up to 10kW peak



The approach foreseen to verify conducted compatibility foresees 2 step

STEP 1: EMC conducted test are performed on satellite equipment by supplier (Leonardo, Ruag,Airbus etc…)

STEP 2: The unit measurement data are imported in a complete satellite model (developed inKeysight ADS environment) to verify total voltage ripple

Scope of EMC conducted analysis is to predict the total conducted interference generated bySatellite units on the specified regulation point (PCDU side)

Compliance to susceptibility requirements (used for unit qualification) can be evaluated atsystem level.

The impact of an out of specification, in terms of conducted emission, at unit level can beevaluated at system level.



Each unit shall respect EMC conducted emission requirements which are described by current masks coming from TAS-I experience, ECSS and MIL standard.

Typical requirement for CE-FD common mode

Typical requirement for CE-FD differential mode



The unit model takes into account a resistor which represents the unit DC powerconsumption, the EMI filter, and some noise generators in order to produce the sameemitted current (both common and differential mode) in the selected frequency range (e.g.30Hz-50MHz), when the unit is connected to the standard setup, defined by therequirement or measured during a test campaign.

CE-FD limit mask

EMC Test result



I_ACSRC7

Freq=freqIac=

I_ACSRC6

Freq=freqIac=

Battery_COSMOBattery3

1

2

AWG22_300cmAWG22_300cm3

3

4

1

2

CC33C=1.0 uF

CC34C=1.0 uF

CC35C=10 mF

RR28R=25 Ohm

RR27R=25 Ohm

RR30R=10 mOhm

LL9

R=L=1 uH

RR29R=10 mOhm

LL10

R=L=1 uH


3

4

1

2

I_ProbeI1n_mis

I_ProbeI1p_mis


3

4

1

2

LL20

R=L=2 mH

LL21

R=L=2 mH

XFERPXFer3

K=1Lp=100 HN=1

LL19

R=L=86.4 uH

RR51R=1.87 Ohm

CC52C=24 uF

LL18

R=L=29.6 uH

CC50C=22 uF

CC51C=22 uF

RR50R=100 Ohm

RR48R=47.5 kOhm

RR49R=47.5 kOhm

CC49C=4.7 uF

RR52R=23.26 Ohm

RR42R=2.21 kOhm

RR43R=2.21 kOhm

CC45C=44 uF

CC46C=44 uF

RR44R=5.62 MOhm

RR45R=5.62 MOhm

RR46R=5.62 MOhm

RR47R=5.62 MOhm

CC47C=44 uF

CC48C=44 uF

EMI filter

Cables

Currentprobes

LISN

Cable

Power source

Common mode current noise

generator

Differential mode current

noise generator

Load resistance



ADS Agilent as a circuit simulator has been selected since it offers simple tools for dataimport/export, it allows to perform simulation both in time and frequency domain, and itoffers a simple method to manage large circuits by the means of libraries and a levelstructure.

SweepPlanSwpPlan1

Reverse=noSweepPlan=UseSweepPlan=Start=11000000 Stop=50000000 Step=1000000 Lin=Start=1100000 Stop=10000000 Step=100000 Lin=Start=110000 Stop=1000000 Step=10000 Lin=Start=11000 Stop=100000 Step=1000 Lin=Start=1100 Stop=10000 Step=100 Lin=Start=110 Stop=1000 Step=10 Lin=Start=30 Stop=100 Step=1 Lin=

SWEEP PLAN

ACAC1

Step=Stop=50 MHzStart=30 Hz

AC

VARVnoise_CM_STT_P

Imask_CE_CM_PCDU_users=file{DAC2, "Imask_CE_CM_PCDU_users"}Imask_CE_DM_PCDU_users=file{DAC1, "Imask_CE_DM_PCDU_users"}Inoise_DM_SBT_P=file{DAC3, "Inoise_DM_SBT_P"}Vnoise_CM_SBT_P=file{DAC4, "Vnoise_CM_SBT_P"}Vnoise_CM_SBT_M=file{DAC4, "Vnoise_CM_SBT_M"}Inoise_DM_SBT_M=file{DAC3, "Inoise_DM_SBT_M"}

EqnVar

DataAccessComponentDAC4

iVal1=freqiVar1="freq1"ExtrapMode=Interpolation ModeInterpDom=RectangularInterpMode=LinearType=Generalized Multi-dimensional DataFile="Vnoise_CM_SBT.mdf"

DAC


iVal1=freqiVar1="freq1"ExtrapMode=Interpolation ModeInterpDom=RectangularInterpMode=LinearType=Generalized Multi-dimensional DataFile="Inoise_DM_SBT.mdf"

DAC


iVal1=freqiVar1="freq1"ExtrapMode=Interpolation ModeInterpDom=RectangularInterpMode=LinearType=Generalized Multi-dimensional DataFile="Imask_CE_DM_PCDU_users.mdf"

DAC


iVal1=freqiVar1="freq1"ExtrapMode=Interpolation ModeInterpDom=RectangularInterpMode=LinearType=Generalized Multi-dimensional DataFile="Imask_CE_CM_PCDU_users.mdf"

DAC

Libraries and sublevels

Data management

The noise generators determination can be performed using ADS Agilent and a dedicatedprocedure composed by three main steps.



Evaluation of CE generated by SAR Antenna unit on Power Distribution unit

P/T_PWR Bus Regulated/Unregulated

Sol

ar A

rray

AvionicUnits

Other S/SUnits

SADM

SADM

Battery

PowerDistribution Unit

2(OPTIONAL)

BATT_PWR Bus

Sar Electronics


Panel nPanel 2

Panel 1

Unit 1

Unit 2

SAR Antenna

Unit 3

Payload (P/L)Platform (P/F)

Power Distribution

Unit 1

Unit 1

Unit 2


Regulated/Unregulated Power BusCE INPUT



ADS MODEL(40 TPSU)



When all the units are connected together,the voltage level at the regulation point canbe evaluated and compared with the unitsusceptibility requirement, in order toquantify EMC MARGIN

Margin= 20*Log(Vcs/Vce_total)



The effects of an out of spec at unit level can be evaluated at satellite level introducing these out of spec in the unit model noise generator.

Furthermore a worst case analysis can be performed using CM and DM noise generators taking into account peak levels from worst case emission of unit heritage


References81

Bruno Audone, “Compatibilità Elettromagnetica – Interferenza e Immunità di apparati e sistemi” Mc Graw-Hill

Clayton R. Paul “Introduction to Electromagnetic Compatibility” Wiley

Donald R. White “EMC Encyclopedia Handbook”

B. Keiser “Principles of Electromagnetic Compatibility” Artec House

Michel Mardiguian “Controlling Radiated Emissions by Design”

electromagnetic compatibility at satellite level

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