Multipactor Manual 160

7/31/2019 Multipactor Manual 160

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ESA / ESTEC Multipactor calculator

manual / help file. (issue 1.6)

(April 2007)

S.J.G. Strijk

ESA / ESTEC

Noordwijk

http://multipactor.esa.int The Netherlands


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Table of contents

1. Introduction

Disclaimer

2. Programme features

3. Detailed description of the programmeThe menu bar functionsFile, (Load, Save, Exit)

RF-tools, (WG matching transformer, Mismatch calculator, Skindepth calculator,Venting calculator, EMC Shielding effectiveness on venting holes / slots,

EMC Radiated emission & susceptibility analysis, Units converter,Pressure Units converter)

Diagnostic Tools, (Show measured Points, Electron Cloud Growth)

Print analysis,

Print screen,

Configure, (Enter Company / project name, Out-of-limit Warnings, Show Startup,Thin / Thick lines)

Marker menu, (Display marker menu, Select Voltage or Power, Clear markers)

ECSS standard,

Manual / helpInfo (About, Check for Updates)

4. Inputs required by the programmeSingle Carrier; Carrier Frequency, Carrier power

Multi Carrier; No of Carriers, Carrier Frequencies and their power levels

Medium selection

Surface type

ECSS defined Component type

5. Select Graph FunctionStandard analysis (Hatch & Williams)

Frequency domainTime domain

Power Distribution vs Time

Complementary Cumulative Distribution Function (CCDF)(providing In-phase, Tri-angular, Parabolic, BPSK, QPSK, Random (square) and Random(Gaussian) carrier phase distributions in Time domain and CCDF.)

6. Outputs provided by the programme7. How to predict multipactor breakdown using the Multipactor calculator8. RF-tools

WG lambda impedance transformer calculator

Mismatch calculator

Skin depth graph

Venting and Outgassing calculator

Waveguide insertion loss calculator (Rect. & Circular WG)

EMC Shielding effectiveness of venting holes / slots

EMC Radiated emission & susceptibility analysis

Units converter

Pressure units converter

9. Diagnostic ToolsShow measured Points

Electron Cloud Growth

10. References11. Annex


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1. IntroductionReasons for development;

To provide a standard analysis and reporting tool to the European space industry (compatible with

the European Cooperation for Space Standardization (ECSS) standard: ECSS-E-20-01A, Multipactordesign and test) thereby providing a low threshold for RF engineers to perform reliable and

consistent multipactor analysis at component, equipment, subsystem and system level.

General remarks

The programme will allow , (comma) or the . (period) as decimal separator for data entries

depending on your PCs default configuration. (printouts and screen display will follow this setting)

Most of the continental European countries will have the comma, while the UK, USA and others will

have the period as standard decimal separator configured.

A number ofkeyboard short cuts had been defined allowing certain functions to be executed

quickly: Pressing Q orq will close any popup window (calculators etc.) from the main calculator

window. Pressing S ors will popup the print screen window, while pressing P orp will popup the

print analysis window.

The user data entry fields are having a white background, while calculated data is shown on a yellow

background or red when out-of-limit. Clicking an orange coloured label will provide a different

function, scale property or opens up a new (calculator) window.

Changing any of the input parameters will bring you back to the standard analysis mode.

Disclaimer

This programme is provided free of charge to the European space industry to standardise the

analysis and reporting of multipactor sensitive space equipment.

The results obtained with this programme have been verified against a number of publicised

sample cases where good agreement had been found.

For the multi-carrier case the programme provides additional analysis to allow the use of the

20gap-crossing rule to be assessed and to alleviate the testing requirements.

However, many more well documented test cases are needed to verify this rule before it

becomes an ECSS-E-20-01 requirement rather the recommendation as it is to date.It therefore remains the responsibility of the user to demonstrate to their customer the validity

of the cases analysed using this programme.


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1. Programme Features;Performs single- and multi-carrier multipactor analysis on; parallel gap, Microstrip,

Stripline, standard 50ohm connector types, user defined co-ax, square co-ax, rectangular WG gaps

and full size circular WG. Random carrier frequencies and power levels are now supported.

The relative di-electric constant is fixed to 1 (air / vacuum) for Microstrip, Stripline, Connectors and

co-axial structures. This allows transitions/gaps in-between MIC-circuits and co-axial structures to

be assessed.

Gap-height, Strip-width, Strip thickness, Co-axial (circular & square) inner and outer dimensions and

the inside WG gap height are user definable (except in circular WG).

The programme uses the calculated or user defined impedance of the medium selected together with

the power levels and no of carriers entered to calculate its breakdown peak-voltage and hence its

available ECSS defined margins.

A Voltage Multiplication Factor (VMF) and field strength is calculated for the mediums user co-ax

and WG based on the impedance ratios between the input and gap impedance, considering zeropower loss. Alternatively the user could enter an externally derived VMF (i.e. based on a Q factor) or

field strength, which is used to calculate the margins and recommendations.

Contains database of physical data of all typical RF / wave connectors rectangular waveguidesbetween 320MHz (R3/WR2300) and 140GHz (R1200/WR8) and circular waveguides between

2.42GHz (C25/WC329) and 116GHz (C890/WC9)

Calculates the multipactor mode boundary limits for all generally used surface materials, based on

the previous work from Woode/Petit and AEA Technology UK, under ESTEC contract.

Allows selection of the component types as defined in the ECSS-E-20-01 standard for single and

multi carrier use for the calculation of the different margins required by this standard.

Allows Company and project name to be inserted and saved.

(This will show up on all printed reports)

Provides print out of material data used by the programme.

Provides print out of multipactor mode data.

Allows a project analysed to be saved and recalled.

Makes use of an intuitive interactive graphical user interface (GUI) designed for the MS Windows

environment. (W98, NT4, 2000, XP (prof), possibly Vista )

Provides additional tools to ease design and testing efforts.

Mismatch calculator

Skin depth graph

Waveguide impedance transformer calculator

Waveguide insertion loss calculator (rectangular & circular WG)

Venting and outgassing calculator



Units converter

Pressure units converter

Allows measured data points to be entered and displayed for reporting purposes.

Electron cloud growth vs time calculator (incl. T20)


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2. Detailed description of the programme

Start-up Screen

(Mouse clicking on any of the 2 logos or press Esc will start the programme proper)

The menu bar functions

The menu bar has File, RF-tools, Diagnostic tools, Print analysis, Print screen, Configure,

Markers, ECSSstandard, Manual / help and Info options available.

****************

Within the File menu one can load or save a data file by giving it a user defined name.

Using the exit option from this menu will automatically save the last configuration analysed as

Set-up file, which is loaded again when starting the programme.

****************

Within the RF-tools menu, a Mismatch calculator, a Skin depth graph, a Waveguide impedance

transformer calculator, a Waveguide insertion loss calculator (Rect. & Circ. WG), a Venting and

Out gassing calculator, an EMC Shielding effectiveness of venting holes / slots, an EMC

Radiated emission & susceptibility analysis, a Units converter and a Pressure units converter

are available to ease the design and testing of RF units, transmission lines and WG multipactor test

samples.

Detailed description of each one is given further down.

****************


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Within the Diagnostic tools menu, one can enter measured data points onto the Hatch & Williams

graphs for the various materials and an Electron cloud growth vs time calculator, including T20 for

the various materials is given. Details are given in section 9.

****************

Selecting the Print analysis option from the menu orpressing P orp from the keyboard will popup a print

window allowing any on-line printer to be selected (incl.

PDF writer when installed), to select the print orientation,

and the number of copies to be selected. From this window

the Multipactor analysis report, the material data or the mode

data can be selected for printing.

****************

Selecting the Print screen option from the menu or pressing S ors from the keyboard will popup the

print screen window allowing the screen to be captured (the small window disappears for 1 second)

after which the captured screen can be printed using any to be selected on-line printer and / or saved.

(File format is bmp) (Only part of the captured screen is shown for verification)

****************

Selecting the Markers option from the menu bar will allow the marker menu to be displayed in the

graph. (The marker menu can also be called up by right hand clicking the mouse.)

The individual markers are to be activated by clicking on the marker line within the menu. (only

one marker could be active at anyone time) The marker selected and activated will show the > in

front, after which the mouse pointer can be used to position the marker (click) within the graph.

Clicking with the mouse on the selected marker in the menu again will memorise the marker value

read. (The > will disappear.) This could be repeated for up to 4 different markers after which theDelta marker could be used to show the delta between any of the marker combinations available.

(Keep on clicking this marker to select the correct delta marker i.e. 1-2, 1-3, 2-3, etc. Delta marker is

given in dB)


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From the Markers menu or the right hand mouse click an option is available to select marker

readings to be displayed in Voltage or Watt.

The Clear markers option will let the marker menu disappear.

****************

The Enter Company & project name

function in the Configure menu, allows

your company name and project name to

be entered, which is saved when closing

this window. The company and project

name are printed in the header of the

multipactor analysis report.

***************

The Out-of-limit warnings when entering incorrect data could be enabled or disabled. (show or

dont show) When disabled, the programme will limit the data input field to proper engineering

values without further warning to the user.

Show Logos will display the ESA and ECSS logos like when starting the programme.

The line thickness of the lines in all graphs can be selected between Thick (default, useful for real

time presentations) and Thin (allowing more accurate marker readings to be made)

****************

The ECSS standard function is activating your Acrobat reader and will show the full ECSS-E-20-

01A standard for on-line consultation.

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The Manual / help function has brought you to this help file, again after having launched your

Acrobat reader.

****************


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Within the Info function, an About function gives you general information (issue) about the

programme and when clicking the ESA orECSS pictures, will start your web browser to direct

you to these sites.

A Check for update function is

available, which when activated

will check on the server for an

update. When available you could

open up your browser to download

it yourself.

(No active updating implemented)

***************


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4. Inputs required by the program;

Using the graphical user interface, all required inputs are to be entered at the left-hand side of the

window and it is recommended that the carrier data be entered first as it will allow the programme toselect various settings automatically. (i.e. WG type selection )

From the carrier entry subframe you can select

single- or multi carrier operation.

Single carrier case

Enter the carrier frequency within the range 0.01GHz to 140GHz, in GHz using the period . or

comma , as decimal separator depending on your local PC settings.

The RF carrier power (dBm or Watt) shall be entered. (80dBm = 100KW max.)

(The conversion from dBm to Watts or back is displayed immediately in the adjacent input field)


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Multi carrier case

Click the green Carrier Data Entry Form button to show this form.

Up to 50 carrier frequencies and their power level can be entered in random sequence or added later.

(Frequency sorting will be done when closing the form or when clicking the Sort Data button.)

A clear all button is available to reset all fields to zero and the previous dataset button to call up the

old data available when opening up this form.

A fast way to fill out the form for the equal frequency separation and power level case is availablefrom the Fast carrier entry sub frame.

Within this subframe, a Delta Freq Ratio input is available allowing the delta frequency to expanded

or compressed between 0.5 and 1.5 times for experimental purposes. (set to 1.0 with equal freq

spacing)

The maximum frequency one can enter is 140GHz, but be forewarned to enter frequencies falling

inside a single waveguide bandwidth, as you will not notified about it when trying to select a

waveguide type later.

The RF power per carrier (dBm or Watt) shall be entered. (80dBm/carrier = 100KW/carrier max.)

The conversion from dBm to Watts or back is displayed immediately in the adjacent input field.

Once the fast carrier data is entered, use the Auto fill button to enter it onto the form.


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Medium selection

Presently 8 different mediums are supported, (parallel plate gap, Microstrip, Stripline, Co-axial

connector, User co-axial, Square co-axial, rectangular and circular waveguide) from which a

selection shall be made using the drop down box. The corresponding sub frame will show up, with

the appropriate data entry fields, allowing physical data to be entered.

Gap (Parallel plate)

The standard gap or parallel plate option is available to allow an arbitrary transmission media to be

analysed where the user is to define the impedance, which can be entered within the range 0.1 and

10000ohm with the default impedance set to 50ohm.

Gap height is to be entered in mm.

Microstrip

The microstrip gap option allows the microstrip impedance to be calculated from the user entered

physical data. Gap distance (300mm max.), strip-width (50mm max.) and strip thickness (5mm

max.) are to be specified.

The relative di-electric constant r, is fixed to 1 that of course being the correct vacuum gapcondition for a Multipactor breakdown. The microstrip definition requires only one ground plane.

(see annex 1)

Stripline

Similar to the microstrip gap option above, a stripline option is available to allow the stripline

impedance to be calculated from the given physical data. Gap distance (halve total height, 300mm

max.), strip-width (100mm max.) and strip thickness (5mm max.) are to be entered. Also here had

the relative di-electric constant, been fixed to 1. The stripline definition requires the stripline to be

physically centred in between two ground planes. (see annex 1.)

Co-axial connector type

From the drop-down box select the connector type, (type N, TNC, sma, APC 7, 3.5, 2.9, 2.4, 1.85, 1.0)

which will display the corresponding physical separation (in mm) between the inner and outer walls of

the connector. (Data taken from manufacturers drawing sheets)

Important remark

For type N, TNC and sma cable connectors, the connector-to-cable rather then the connector-to-

connector interface is the typical multipactor limiting part in a cable assembly due to the air gaps

present.

These air gap dimensions could vary per cable type, connector type and manufacturer.

The user should select medium User co-ax when they are different from the standard connector

database dimensions. (the connector backnut typically has the same inside dimensions as the

connector-to-connector interface but could vary with the cable diameter, i.e. 0.19 or 0.29)

The foam or solid di-electric will prevent the multipactor inside the cable or connector itself.

The air di-electric type connectors like the APC series would allow breakdown at the

connector-to-connector interface as well. This is could also be the case for the sma connector where

retracting Teflon di-electric (at low temperatures) could create dangerous air gaps when not properly

conditioned before assembly.


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User defined co-ax. (Circular)

The user-defined (circular) co-ax will allow any non-standard size or impedance to be calculated

given the users entered physical dimensions for the outer inside diameter (100mm max.) and the

centre-conductor outside diameter. Di-electric constant is fixed at 1 for air/vacuum.

Square co-ax. (Bar line)

The square co-ax allow the impedance to be calculated given the users entered physical dimensions

for the outer inside dimension and the centre conductor outside dimension. Di-electric constant is

fixed at 1 for air/vacuum.

Rectangular WG type

From the drop-down box select the waveguide type, (R3/WR2300 till R1200/WR8, IEC compatible)

in the range 0.32GHz to 140GHz. When the frequency had been given before and medium rect. WG

had been selected, the programme automatically selects the right WG type for you.

One can still select the first higher or lower WG size if it will support the frequency.

(note: nominal useful bandwidth equals 1.25 till 1.9 times cut off frequency)

Circular WG type

From the drop-down box select the waveguide type, (C25/WC329 till C890/WC9, IEC compatible)

in the range 2.42GHz to 116GHz. When the frequency had been given before and medium circular

WG had been selected, the programme automatically selects the right WG type for you.

One can still select the first higher or lower WG size if it will support the frequency.


Gap

If gap (parallel plate) had been selected, this input field allows a gap up to 300mm to be entered.

If co-axial connector, user co-ax or square co-ax had been selected this field changes colour toyellow, will show the physical separation between inner and outer connector and is not changeable.

(Obtained from the connector manufacturers data sheets for standard connectors)

When WG had been selected it will show as a maximum, the height of the WG or less if a smaller

value had been given before, a reduced WG height (gap height) can be entered here. (Not greater

then WG height)

Impedance

When gap had been selected, the impedance can be entered here up to 10000ohm (default is 50ohm).

In all other cases the calculated impedance at the frequency, is displayed in this field and is not user

changeable. (the data input field turns yellow)

Width & thickness (T)

When Stripline or Microstrip had been selected, the width & thickness data fields will appear and

allow the strip-width and strip-thickness (T) to be entered. The distance between strip and ground

plane shall be entered in the gap data field. (see annex 1 for the exact definition).

(The di-electric constant is fixed at 1 for air/vacuum.)

O.diam & I.diam

When user co-ax had been selected, these fields will allow the outer (shield) inside diameter(O.diam) and the centre conductor diameter (I.diam) to be entered.



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Outside & Inside

When square co-ax had been selected these fields will allow the outside (larger) and the inner

dimensions of a square co-axial line to be entered.


Voltage Multiplication Factor (VMF) and field strength

In single carrier operation, with mediums User Co-ax or rect. WG selected, a Voltage

Multiplication Factor (VMF) or field strength could be entered.

However, the programme calculates the VMF and the normalised (Vp/cm 1Watt) field strength,

based on the calculated gap impedance relative to the input impedance. (details are given in annex )

All power, voltage and the appropriate ECSS margins are calculated using the entered VMF.

A VMF reset button had been added to go back to the programme calculated VMF.

This feature is useful when evaluating the effect of enhanced electrical fields inside filters due to

their Q-factor. The VMF or field strength figures shall be obtained from external circuit (filter)

design programmes.

Surface type

From the drop-down box the surface material, i.e. Gold, Silver, Aluminium, Alodine or Copper can

be selected. Different voltage breakdown thresholds are applicable for the different materials as

defined in the ECSS-E-20-01A standard (table A-6), which are required to calculate the appropriate

margins.

ECSS defined Component type

For the single-carrier case, three different component types had been defined:

i.e. 1, 2 or 3, for which different ECSS-E-20-01A standard required margins are applicable.

Component type 1, The RF paths are entirely metallic (with known secondary electron emission

properties) or are metallic with a non-organic surface treatment that increases the multipactionthreshold.

Component type 2, The RF paths contain or can contain dielectrics or other materials for which the

multipaction performance is well defined.

Component type 3, allcomponents not classified as Type 1 or Type 2.

In the multi-carrier case only component type 1, had been defined by the standard with margins for

type 2 and 3 under investigation. However, for type 1 two different margins had been defined;

Type 1a, when the single carrier threshold margin is above the equivalent CW peak power.

Type 1b, when the single carrier threshold is below the equivalent CW peak power.

ECSS-E-20-01 Quote; In this case, the margins are defined with respect to a power level, P20,

corresponding to the peak power of the multi-carrier waveform whose width at the single carrierthreshold is equal to the time taken for the electrons to cross the multipacting region 20 times.

The programme will automatically apply the correct margin in this case.


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5. Select Graph function

For the multi carrier case a Select Graph Function dropdown box provides the options, Standard

analysis (Hatch & Williams graphs), Frequency domain, Time domain, Power distribution vs time,

and the Complementary Cumulative Distribution Function (CCDF).

When Time domain had been selected, a Phase distribution dropdown box will allow a choice to be

made between; In-phase, Tri-angular, Parabolic, BPSK, QPSK, Random (square) and Random

(Gaussian) carrier phase distributions.

The phase distribution can be altered in the Time domain only, after which the recalculated data can

be shown with the other functions. (i.e. Power distribution vs time, and the CCDF functions)

For the BPSK, QPSK and Random distributions a Repeat button is available allowing re-running

the analysis (random carrier phase assignment) and to monitor the effect in time domain, Power

distribution vs time and CCDF modes.

6. Outputs provided by the programmeGeneral

The outputs are provided both in graphical, (centre window) and in numerical formats with results in

the various data fields at the top and right-hand side of the calculator window.

As of version 1.5 the programme had been optimised for use on 1024x768 screen resolution or better

and no longer support the old 800x600 resolution. (However, the program screen size remains

1024x768 pixels for any higher screen resolution selected)

Continuous cursor reading is available when the mouse cursor is moved over the graphical part of

the window. When the Cursor readings label is orange, a different cursor reading function is

available. i.e. to toggle between Voltage vs. GHzmm and Power vs. GHzmm

The cursor function varies with the graphical function displayed.

A new feature is the actual Fieldstrength information at both the input

and in the gap.This is only available in single carrier mode and mediums waveguide or

user co-ax.

The ECSS threshold levels, V_thres(V) and P_thres(W) at Fmin, are

now directly given in the ECSS analysis sub frame.


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Single carrier analysis

The actual calculated margin with respect to the ECSS boundary line (black) is given in dB with

respect to the RMS power level.

For mediums User Co-ax and rect. WG a fieldstrength output subframe is available showing the

input power scaled actual fieldstrengths (Vp/cm) at the input and in the gap.

A coloured box within the ECSS subframe at the bottom right-hand side of the window will show

whether this margin is sufficient (green box) and to refrain from testing, marginal (orange box) with

batch, unit or qualification testing as required, or insufficient margin (red box) with analysis failed.

The margins are defined in the ECSS-E-20-01A standard (tables 2, 3 and 4) with strict requirements

for the type of testing required i.e., no testing required, batch, unit or qualification testing, or analysis

failed.

Single carrier example showing modes (Fd product line crosses mode 9)

The result obtained can be printed in tabular format for use in a report and / or a copy of the screen

can be made which can be saved or plotted directly from within the programme.

(See the menu bar functions section before)

The Fd product (GHzmm), the mode order and the calculated T-20 time (ns) are given in the output

fields above the centre window.


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Multi-carrier analysis

When in multi carrier mode a Select Graph Function dropdown box provides the options, Standard

analysis (Hatch & Williams graphs), Frequency domain, Time domain, Power distribution vs time

and the Complementary Cumulative Distribution Function (CCDF).

When the Time domain function had been selected, a Phase distribution dropdown box will allow a

choice to be made between; In-phase, Tri-angular, Parabolic, BPSK, QPSK, Random (square) and

Random (Gaussian) carrier phase distributions.

Changing any of the input parameters will bring you back to the standard analysis mode.

As of this version (1.60) the P-20 power levels and margins are calculated using the power

distribution function over a time interval set by the carrier frequency separation and no longer using

the previously used worst-case boundary condition lines (green) as proposed by [5].

As the method in [5] was only suitable for equal carrier frequency separation a new and fast method

had been developed for use with unequal carrier frequency separation.

As can be seen from the next 3 graphs, a substantial improvement in P20 level and margin is

obtained using this power distribution function showing that the all carrier in-phase condition is not

necessarily the worst operating condition for multipactor free operation considering that the voltageshave to exceed the threshold for a period of at least T20 before multipactor could start. (also see the

electron cloud growth function available in the diagnostic tools menu)

The carrier in-phase condition would of course still generate the highest peak voltages.

The horizontal black line represent the ECSS defined boundary as calculated for the minimum

freq*gapwidth product and surface material selected.

Example of all carriers in-phase showing the T20 / P20 box and the old worst case boundary

conditions (green lines) as per ref. [5]


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Example of the same case using triangular phase distribution.

Example of the same case using parabolic phase distribution.


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The Power distribution vs time function.

As of this version (1.60) a new function had been added allowing a fast determination of the P20

levels without the need for time consuming phase optimisation routines to find an (arbitrary) carrier

phase function such as to minimise the power level over the T20 window.

The P-20 power levels and margins are calculated using the power distribution function over a time

interval set by the carrier frequency separation. For equal frequency separation this is the inverse of

the carrier separation, for unequal frequency separation this is the inverse of the minimum carrier

separation among the carriers, providing a unique repetitive time interval.

When all signal amplitudes within this time interval are sorted in amplitude and converted back to

power, a power distribution vs time is created where the P20 level is simply obtained from the

intersection with the calculated T20.

This is available for the different phase distributions, showing that the P20 and peak power levels are

changing considerably thereby providing substantially higher margins.

Remark

The hereby proposed power distribution vs time approach is considered especially useful

for the evaluation of random carrier frequencies and power levels.

It will still have to be verified by further testing and possibly modelling before being

accepted for the update of the ECSS standard.

However, for the time being this function serves to help the understanding of signal

amplitude distribution and their relation to the T20 and P20 calculation.


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The Complementary Cumulative Distribution Function (CCDF)

A different way of presenting the signal envelope of a multi carrier signal is the Complementary

Cumulative Distribution Function (CCDF) as had been described in Agilent application note

5968-6875E. (a copy is available from the Multipactor Calculator website.)

CCDF plot of a 10-carrier signal using carrier in-phase distribution. (showing a 10dB peak-to-

mean ratio)

The Cumulative Distribution Function (CDF) is obtained by computing the integral of the

Probability Density Function (PDF) of a set of (measured) data.

The Complementary Cumulative Distribution Function (CCDF) is the complement of the CDF

(CCDF = 1- CDF) which curve is obtained by converting the y-axis to logarithmic form and starting

the x-axis at 0dB.

The logarithmic y-axis provides better resolution for low-probability events.

Remarks

The purpose of the CCDF graphs is to derive at more realistic margins for multi-carrier

operation in the future.

Knowing the worst case boundary conditions, represented by the green boundary lines in the

time domain graphs for the equal frequency spacing case, it is believed that only a proper

knowledge of the signal statistics together with the verification of the 20-gap crossing rule

(conditions) will provide a way forward to improved multi-carrier margins to be implemented

in a next update of the ECSS-E-20-01A Multipactor standard.

This CCDF graph function is for the time being an optional tool to start the process of treating

the multi-carrier signal in a statistical way, which is possibly supported by measurement

instruments providing the same functionality.


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CCDF plot of a 10-carrier signal using parabolic phase distribution.

CCDF plot of a 10-carrier signal using a random phase distribution.


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CCDF plot of a 10-carrier signal using QPSK phase distribution.

A different gap dimension (0.5mm) shows the ratio T20 / period to have changed to 16.67% in the

above example with the vertical black line intersecting with the signal giving a 1.42dB aboveaverage.


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6. How to predict single carrier multipactor breakdown using the Multipactor calculator.After the basic inputs have been entered, i.e.; freq, medium, gap dimension, and surface material,

activate the Marker menu and select Marker reading; power.

Select a marker and position it at the intersection of the vertical Fd product line with the lower limit

of the mode order first crossed by the Fd line. The marker reading is giving the expected breakdown

level in Watts. (see graph below)

This could be quite different from the ECSS defined mode envelope line, in particular between

modes 1 and 3 where differences up to 6dB are possible.

The result could now be saved, printed, (table or screen copy) for reporting purposes.

The warnings and margins are to be ignored in this case, as we are just to find the expected

multipactor onset level for comparison with measured results for instance.


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7. RF toolsWG lambda impedance transformer calculator

The first RF-tool available is the single step Lambda wave-guide transformer, which is a useful

tool for the design of multipactor test samples.

The transformer screen as shown above will start with the frequency and gap height values copied

from the main Multipactor calculator form.

However, any frequency between 0.32GHz and 140GHz can be entered, with the nominal WG-type

being calculated by the programme. One higher or lower WG size can be selected, provided the

frequency is within 1.05 to 1.95 times its cut off frequency.


The gap height (mm) can be entered with the nominal WG height being the maximum value.

All the relevant transformer section dimensions and impedances are calculated and displayed.

Note

The plotting routine for the magnitudes of S11 and S21 is not available yet.


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Mismatch calculator

The mismatch calculator will allow return loss (dB), VSWR or reflection co-efficient to be entered for a

source and a load and will show the corresponding parameters converted instantly.

Individual port match loss and actual mismatch loss between source and load is calculated.

The phase of either source and/or load could be optimised (conjugate matching) to minimise the actual

mismatch loss.

In addition the maximum VSWR, mismatch and phase errors are calculated and displayed.

Hovering with the cursor over the various input and output fields will reveal the actual formulae or the

data input ranges used by the calculator.


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Skin depth graph

This calculator will calculate the skin depth in microns for various materials (Silver, Copper, Gold,

Brass 70/30, Aluminium, Platinum, Chromium, Tantalum) over the frequency range 0.1 till 100GHz.

Entering a frequency and selecting a material will give the skin depth instantly in the skin depth box.

Material surface resistivity and conductivity are given in their boxes.

The black line represents the transfer function, which is dependant on material conductivity.

The green line starts at the entered frequency and shows the skin depth at the graph left hand scale.

The cursor will allow more accurate numerical readout from the graph.

Clicking the orange question mark box will show a brief operating instruction as shown in picture

above. Clicking on this operating instruction will let it disappear.


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Venting calculator

From the select graph function Unit pressure vs. time (min) the venting calculator will calculate

and plot the pressure-versus-time, given the user inputs: Area, venting hole diameter (mm),

venting hole length (mm), no of holes, the type ofsurface material and its surface treatment

(where available).

The Area (and Volume) can easily be calculated for the rectangular box case by clicking on either

the Volume orArea orange labels. These will call-up a small Volume & Area calculator, as shownbelow. The calculated output data is directly transferred to the main venting calculator window and

the result is directly displayed.

(When no longer used, the calculator can be closed or will disappear after 1 min with the entered

data stored on disk)

The volume data is not utilised by the venting calculator, as this will typically only have a small

effect during the first 5-10 min. of pump down. The material out gassing properties will determine

the long-term pressure inside a unit.

Physical data on the (circular) venting holes can be entered as usual.

The standard venting calculator unit for out gassing rates is the Pa m/s while unit pressure versus

time is available in Pa ormbar. Clicking on the orange pressure graph label will toggle between Pa

and mbar.


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The venting calculator has a substantial set of material outgassing data for 15 types of metals and

16 other materials including: glues, plastics, rubber, Teflon, Mylar, etc.

For many of the materials a number of different surface treatments can be selected from as these

have a great influence on the outgassing rates.

For the actual material chosen, the 1hr, 4hr, 10hr and 100hr outgassing rates are shown at the bottom

right-hand side of the calculator.

Clicking on the orange unit label allows you to toggle between: Pa m/s, mbar-l/s-cm2

and

Torr-l/s-cm2with the results calculated and displayed. (As shown above)

The outgassing data shown on a yellow background are actual acquired/measured * * outgassing

values, while the ones with a grey background are calculated (inter- or extrapolated) by the

programme. (Data is typically valid at room temperature only)

The blue (sloped) line will instantly show the pressure-versus-time for the physical dimensions andmaterial data entered.

A cursor will now follow the blue line. Its location can be fixed by (left) mouse clicking, thereby

alternating between cursor track and cursor freeze modes.

A horizontal red line at 1E-3 Pa (1E-5 mbar) is given which is considered the correct and save

pressure to aim for with your venting design to ensure the proper pressure range for multipactor

rather then corona breakdown.

The vertical black line at the inter section of the blue and red line is the actual time it takes to vent to

this 1E-3 Pa pressure with the numerical result given at the centre right-hand side Venting time data

output field.

In case the calculated venting time is longer then 10000 min (about 1 week) this output field will

turn red, while venting times longer then 100000 min (about 69days) is no longer displayed.

For practical reasons like reduced testing time and immediate operational availability, it is

recommended to design the venting capability to be such as to reach the required save pressure

within 24 hrs. For critical applications like large cavity filters, one should aim at less then one hour,

such as to avoid cavity wall deformation due to fast vacuum chamber pump down.

It should be noted that the outgassing data used by the calculator were measured/available at room

temperature mainly. It is reported in literature* that the outgassing rate is very strongly dependant on

temperature and that for instance a quick temperature increase from 28C to 60C had increased the

actual pressure ten times.


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The outgassing data for virtually all unbaked metallic surfaces is dominated by desorption of

adsorbed gasses of which the main constituent is H2O amounting to between 85% and 90% with the

remainder being H2, CH4, CO and CO2, as had been observed over the first 1000 min of pump down

time. The hygroscopic nature of these surfaces makes the actual outgassing rate very dependant on

the treatment and storage conditions.

Where no extensive measured outgassing data was available, the venting calculator is using a slope

of 1.2 in the log-log curve in the plot of total out gassing rate versus time, which is commensurate

with a system/unit being vented to normal clean room pressure and humidity.

This slope could be 1.3 for a very high humidity storage condition or as low as 0.6 when vented to 1

bar of high purity N2.

Venting vacuum systems to dry N2 would be good engineering practice to keep vacuum systems and

(RF) equipment dry thereby reducing pump down and venting time considerably.

(The starting pressure data entry window is disabled and just shows the default ambient pressure in

Pa or mbar.)

From the select graph function Material out gassing rates versus Time (hr), the outgassing rates

vs. time for the material selected will be shown. (Pa m/s versus time)

* Model for water out gassing from metal surfaces I, II & III by Minxa Li and H.F. Dylla

JOURNAL OF VACUUM SCIENCE AND TECHNOLOGY July/Aug 1993, July/Aug 1994, July/Aug

1995

** See annexed updated material data from ESA, ESTEC/QMC


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Ariane 5 Fairing inside Pressure vs. Time

To aid the design of equipment to be flown on the Ariane 5 launcher, a typical Fairing inside

pressure versus time is provided. (Use the select graph function)

* source; Ariane 5 User manual, (ArianeSpace)


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Waveguide insertion loss calculator

A new feature added with version 1.60 is the waveguide insertion loss calculator allowing the loss to

be calculated over the frequency range 0.32GHz and 1100GHz for rectangular waveguide

(R3/WR2300 till R9200/WR1, IEC compatible) in mode TE10 and over 2.42GHz to 116GHz for

circular waveguide (C25/WC329 till C890/WC9, IEC compatible) for modes TE01, TE11 and

TM01.

A fast selection of the right waveguide size (frequency band) is done by just entering the frequency

of interest. Then select rectangular or circular WG type, and the mode for circular WG.

Surface material selection is available, Silver, Copper, Gold, Aluminium, L111 Alu.Alloy, Brass

70/30, Platinum, Chromium or Tantalum, for which the resistivity and conductivity are given.

The skindepth is calculated at the cursor frequency.

A tracking cursor eases the fixing of the cursor readout (only horizontal movement required) and will

now be correctly printed.

The cursor location can be fixed by (left) mouse clicking, thereby alternating between cursor track

and cursor freeze modes.


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The shielding effectiveness (SE) of circular holes and/or slots is calculated instantly by entering the

number and physical data of the holes and slots.

(Entering 0 for the No of holes or slots will ignore this calculation.)

Results are given graphically in dB vs. frequency over the range 0.1 till 100 GHz.

A specific total SE (holes and slots) at a user-entered frequency is given at the right hand side of the

calculator.

Pressing the ? button will provide the information and formulae used in this calculator.

To complete the EMC analysis in terms of allowed radiated emission & susceptibility levels, a

separate calculator is available under the right hand side button.

(Also available directly from the RF-tools menu)

Note

SE is typically a worst-case figure depending on inside box dimensions and how the E-fields are

coupled from the circuitry to the venting holes or slots and the physical location of these holes or

slots.


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Although this being a generic EMC or RF link calculator, the radiated emission (RE) and/or radiatedsusceptibility (RS) for equipment could be calculated as well.

The RE calculation is valid for the far field only which is indicated by the far field box. Simply

entering the data will provide the E-field in V/m and dBV/m.

The output from shielding effectiveness (SE) calculation could be used to modify the EIRP or to

subtract from E-field (dBV/m) to work out the expected radiated E-field.

In a similar way could the equipment RS be evaluated. The Rx power is calculated for a given

antenna gain at frequency and E-field. The received levels inside equipment could be estimated by

setting the antenna gain to 0dB and subtracting the calculated SE values.

Units converter

Just a small calculator providing conversion for

Length, Area, Volume, Mass, Temperature and

Magnetic Fieldstrength to help the non-metric

engineers to convert to the metric standard used

throughout this programme.


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Pressure & Outgassing rate units converter

The different units for pressure and out gassing rates used throughout the years had made life not

easy in comparing results quickly.

To ease the conversion of pressure units this calculator provides the conversion from Atmosphere,

bar, mbar orPascal, back to any of these.

The lower halve of the calculator provides out gassing rate unit conversion from Pa m/s,

mbar-l/s-cm2

orTorr-l/s-cm2

, back to any of these.

This calculator will also accept scientific data notation entry.

(This calculator is also directly available from the Multipactor calculator RF tools menu or could be

called up from the venting calculator using the orange Unit conv. button at the lower left-hand

corner.)

8. REFERENCES1. A.J. Hatch, H.B. Williams,Journal of Applied Physics 25, 417 (1954)2. A. Woode, J.Petit, Diagnostic investigations into the Multipactor Effect etc.,ESTEC working paper 1556,

Nov 19893. A.J. Marrison, R. May, J.D. Sanders, A.D. Dyne, A.D. Rawlins, J. Petit, A Study of Multipaction in Multicarrier

RF components,Report No AEA/TYKB/31761/01/RP/05 Issue 1, Jan. 19974. Multipaction Design and Test,ECSS standard ECSS-E-20_01A, April 20035. D. Wolk, D. Schmidt, T. Schlipf, A novel approach for calculating the multipaction threshold level in

multicarrier operation, Proceedings of ESTEC workshop Mulcopim 20036. Ariane 5 User manual, Arianespace7. Characterizing Digitally Modulated Signals with CCDF curves,Agilent Application Note 5968-6875E


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9. Annex 1Wave Guide

The waveguide impedance calculation is based on the power-voltage definition;

b = gap height

a = waveguide broad-side dimension

= free space wavelength

= cutoff wave length of the waveguide

Z0 =Impedance of waveguide using the Power-Voltage definition

Microstrip

The practical microstrip circuit uses a continuous substrate material as a support.

However, to analyse transitional regions in between substrates or substrate to connector interfaces,

the air gaps may pose dangerous regions for multipactor to develop/exist.

The microstrip model [1] used in the programme has the effective di-electric constant fixed at 1

(air/vacuum) but allows the normal physical parameters to be entered, i.e. gap (depicted by h in the

sketch above), strip width (W) and strip thickness (t).

Stripline

Similar conditions and applications as described for the microstrip case are applicable for the

Stripline option.

The stripline model assumes the strip to be centred in height with the gap definition to be halve the

overall inside stripline height. Finite strip thickness is taken care of by the programme.

2

c

0

0

1

1

a

b240Z

=


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(User) Co-ax.

The impedance of co-axial lines is given as: Zo= 138*Log10 (D/d)

Whereby D equals the inner diameter of the outer conductor and d the diameter of the inner

conductor.

Square co-ax (barline)

The impedance of a square co-axial line (square-ax) is given as:

When B/A > 1.08 : Zo = 136.7 * Log10(0.9259 * B/A)

When 1.001 > B/A < 2.5: Zo = 188.31 / (1.12 + 4 * A / (B - A))

Whereby A equals the inside dimension of the outer conductor and B the outside dimension of the

inner conductor.

Voltage Multiplication Factor (VMF)

The definition of VMF used in the programme is: V2/V1 whereby V1 equals the voltage across the

WG or Co-ax input impedance and V2 equals the voltage across the gap.

When zero power loss is assumed from the input through the gap then:

P1=P2 V1/Z1 = V2/Z2 whereby Z1 =impedance at the input

Z2= impedance in the gap

Hence: VMF= sqr(Z2/Z1)

Fig. below: an example of the VMF (blue line) dependence over the frequency bandwidth of aband pass filter as calculated by an external filter design program.

Multipactor Manual 160

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