IEEE1641 Signal

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IEEE1641Signal Test DefinitionA Quick
TutorialChris Gorringe
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Signals (and Waveforms)

• Within STD a signal definition is used to define
  the signal (set of waveforms) that have the
  particular characteristics required.
• The term signal is used to represent a definition
• e.g. bscTrapezoid
• A waveform is an instance, implementation or
  manifestation of a signal.
• A signal may be represented by many waveforms.
• E.g. Sinusoidal signal
• Sine Wave
• Cosine Wave

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Real Signals

• In order for a signal to be realisable (produced
  by a test system) the signal definition must
  contain
• Where the signal is required (Connection To UUT)
• When the signal is applied (Events)
• What are signal types attributes values

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Real Tests

• In order for a test to be realisable (produced by
  a test system) the test definition must have
  contain
• Where the test is made (Connection from UUT)
• When the measurement is made (Events)
• What limits/pass criteria is to be applied
• What are signal types attributes values

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Signals Types

• Signals characteristics are defined as the
  relationship between one property (dependent
  type, ordinates) and another property
  (independent type, abscissa)
• How voltage varies with time
• How temperature varies with distance
• How pressure should remain constant over time
• Can define characteristics as multiple signal
  types
• Need to make sure the properties are orthogonal.
• Voltage over time, Temperature over time
• Bad Example - Voltage 2V, Current 2mA
• Since these are related (VIR)
• Implies change the impedance to get desired
  effect.

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Examples
Pink Noise
Exponential Temperature decay
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Different Ways of thinking of a Sinusoidal Signal
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Signal COTS Support (Techi-Bit)

• Language Interfaces through IDL (Interface
  Definition Language)
• Resource Manager class
• IDispatch for scripts and test executives
• Support Co-classes for Visual Basic
• Support Dual Interfaces for C, Visual Studio,
  .NET
• XML Signal Schemas
• Define Signals and Tests in XML
• XML Signal definitions are used by the Resource
  Manager to create the signal
• XML Definition of Library Components (TSFs)

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Basic Signal Components

• Basic building blocks to create any signal
• Attributes configure individual BSCs
• Default values and units simplify use
• Signal passed through In connection

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Events

• Event sources
• Event conditioners
• Provide Sync and Gate

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Measurement

• Direct measurements can be made e.g. RMS
• Monitor signals for certain trigger conditions
  e.g. Greater Than
• Raise Events when trigger conditions are met
• Sequence measurements for analysis e.g. Find
  Next Peak
• IEEE 1641 achieves program sequencing though
  other languages

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BSC Listing
Signal Sources
Signal Conditioners
Event Sources Conditioners
Measurement
List is not 100 correct
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XML

• XML template is included in IEEE 1641 Annex I
• BSC names attributes and physical types are
  mapped onto XML tags
• Sinusoid XSD example -

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ILS example
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Test Signal Framework (TSF)

• Build your own re-useable signal definitions
• Framework enables mapping external attributes to
  internal attributes via formulae and event
  behaviour
• Popular ATLAS signal definitions carried into STD
  as TSFs

angle_rate
angle
trans_ratio
ampl
freq
channelWidth 3
phase angle - (2p /3) amplitude
trans_ratio frquency angle_rate
SML provides functional behavioural model
phase angle amplitude trans_ratio frquency
angle_rate
SYNCHRO
phase angle (2p /3) amplitude
trans_ratio frquency angle_rate
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Types of TSF Attributes

• Control Attributes
• An interface attribute is mapped onto a model
  property,
• Expressions or formulae
• An interface attribute is mapped onto a model
  property via an expression
• Period 1/freq
• delay range/c -- where c is constant speed of
  light
• Capability Attributes
• An interface attribute that is not mapped onto
  any signal model is regarded as a capability
  attribute. It holds information as to capability
  of the resource to supply the signal.
• e.g. current 2A - the resource must be capable of
  supplying a signal which may draw up to 2A
• Value Attributes
• A value attribute represents a value from the
  TSF, as such they tend to be read only
  attributes.
• When a interface attribute is mapped on to a
  model measurement attribute

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Generic Measure TSFs

• The concept of the generic measurement is that it
  provides an inverse function, or demodulating
  function, for any library component (TSF) or
  basic signal component (BSC) to measure any of
  their control attributes.
• Since users can define TSFs, the generic
  measurement is naturally extended and can be used
  to measure any control attribute of such a TSF
  signal.
• As an example of this principle reading back an
  RS232 message
• ltMeasure Asrs232 attributedata_word In
  /gt
• To read back a list of pulses from a
  PULSED_AC_TRAIN
• ltMeasure AsPULSED_AC_TRAIN attritutepulse_tra
  in In /gt
• Measure the rise time of a square(ish) wave
• ltMeasure AsTrapezoid attrituteriseTime In
  /gt
• The use of the generic measure is not restricted
  to measuring single attributes, an example of
  performing multiple measurements is
• ltMeasure AsSinusoid attributeac_ampl phase
  In /gt

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Waveform Aberration

• The generic measure selects the reference
  waveform described by the reference signal that
  contains the least error (best match) with
  respect to the input waveform. The attributes of
  the reference signal that produce the least error
  (best match) become the measured attributes.

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Measuring Waveform Aberration

• The generic measure can also be used to measure
  the actual waveform aberration by measuring the
  error (difference) between this reference
  waveform and the input waveform.
• Example measure the best match value or rms
  error between the input signal and reference
  signal
• ltMeasure AsTrapezoid nominaltrms In /gt

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Summary

• Given we thought we had a square wave (Green) but
  what we actually have to measure has some
  unexpected components (Blue)

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Definition Of Terms
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Period 1s ltMeasure AsSQUARE_WAVE attributeperiod /gt
Duty Cycle 75 ltMeasure AsSQUARE_WAVE attributeduty cycle /gt
Waveform Aberration trms 0.08467V ltMeasure AsSQUARE_WAVE nominaltrms /gt
Level 0 0.23V1 0.24931V2 ltInstantaneous GateState0 In /gt ltInstantaneous nameState0 ConditionLE nominal0 In/gt
Level 1 1.21V1 1.190972 ltInstantaneous GateState1 In /gt ltInstantaneous nameState1 ConditionGE nominal100 In/gt
nominal pk_pk ampl nominal pk_pk ampl pk_pk amplitude pk_pk 0.98V1 pk_pk 0.941772 pk_pk 0.95648V Level 1 level 0 ltMeasure AsSQUARE_WAVE attributeampl /gt
nominal amplitude nominal amplitude amplitude 0.49V1 0.47083V2 0.47824V (Level 1 level 0)/2 ltMeasure AsSQUARE_WAVE attributeampl /gt
DC Offset 0.72V1 0.72014V2 0.73098V (Level 1 Level 0)/2 ltMeasure AsSQUARE_WAVE attributedc_offset /gt
Max Instantaneous 1.46446V ltMaxInstantaneous In/gt
Min Instantaneous 0.16765V ltMainnstantaneous In/gt
Peak To Peak pk_pk 1.29681V ltPeakToPeak In /gt
Average av 0.97027V ltAverage In /gt
RMS trms 1.05444V ltRMS In/gt
Peak (Peak Pos) pk_pos 0.49319V ltPeak In /gt
Negative Peak pk_neg 0.80262V ltPeakNeg In /gt

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IEEE 1641 - STD

• Defines Signals and Tests
• Highlights the need to know measurement methods,
  in order to quote meaningful limits and therefore
  by implication portable tests
• Allows user defined signals and tests that are
  portable across systems, through TSFs
• Provides an integrated XML and IDL interface for
  using the standard, across different platforms
  and technologies.

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End
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IEEE 1641 - STDA Worked Example

• PQSK Signals and Error Vector Magnitude
  measurements
• The PQSK is a digital modulation technique the
  shifts the phase of a sinusoidal carrier
  depending on the value of the next set of
  digital bits
• 00 (0, 360) No phase shift
• 01 (90, -270) phase shift
• 10 (180, -180) phase shift
• 11 (270, -90) phase shift

00 01 10 11 11 01 10 01 01 11 01 11 11 01 01 01
01 01 00 11
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Phase Vs Time

• PQSK TSF with a data attribute
• Frequency capability attribute
• Formula to convert data onto the relevant phase
  value (mod 360) required
• Signal Model is ltWaveformStep typePlaneAngle
  points(data) /gt
• Relies on context, but is a simple model
• Use Generic Measure to demodulate the signal
• Convert the signal back into the message
• Measure the phase error associated with the
  message.

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Want Voltage vs Time Waveform

• PQSK TSF with a data attribute
• Frequency control attribute or carrier
• Formula to convert data onto the relevant digital
  data stream (L,H)
• Signal model is more complex
• Use generic measure to demodulate the signal
• Convert the signal back into the message
• Error vector magnitude is the rms value of the
  waveform aberration

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I Q Channels

• We can create a further TSF I_Q that separates
  out the I Q channels from the input signal by
  conditioning the input signal
• InSin(wt)
• InCos(wt)
• Then perform further processing or conditioning
  on these channels