In the name of God
Tehran University
School of Electrical and Computer Engineering
Class presentation for the course: “Custom Implementation of DSP Systems”
SYNTHETIC INSTRUMENT
By:
Mohsen Javadi
Instructor:
Dr. S. M. Fakhraie
All the materials are copy rights of their respective authors
as listed in references
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OUTLINE
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History of Automated Measurement
Synthetic Instruments
Advantages of Synthetic Instruments
Vector Signal Analyzer Implemented as a
Synthetic Instrument
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HISTORY OF AUTOMATED MEASUREMENT

people started using these inexpensive
computers to control measurement devices
measurements to be made faster
 The knowledge for operating the instruments is
encapsulated in software that anybody can run
 With computer-controlled measurement devices,
you still needed a separate measurement device for
each separate measurement
 It seemed fortunate that you didn't necessarily
need a different computer for each measurement.

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HISTORY OF AUTOMATED MEASUREMENT

rack-em-stack-em
putting all these computer-controlled instruments
into one big en-closure
 They could have a whole slew of measurements
made with the touch of a button
 The computer would run all the instruments and
record the results
 some systems got so big that you needed to carry

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HISTORY OF AUTOMATED MEASUREMENT

Modular Instruments
measurement instruments were put into smaller, plug-in
packages that connected to a common bus
 Modular packaging can eliminate redundancy
 Modular design saves money in theory. In practice,
however, cost savings are often not realized with modular
packaging
 when you want to add another
instrument, you add another
measurement specific
hardware module
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Modular Instruments [6]
SYNTHETIC INSTRUMENTS
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With a synthetic instrument, ideally you add nothing
but software to add another instrument
Digital hardwired logic versus CPU[3]
A LabVIEW based RF Synthetic Instrument[6]
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SYNTHETIC INSTRUMENTS
Many of these benefits are a direct result of the
modularity aspect of the SI, which consists of
 The sampled data delivered by the ADC in a
DSP-based instrument can be used to analyze
different attributes of the input signal

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Synthetic Instrument Context[4]
SYNTHETIC INSTRUMENTS
The sampled data time series can be analyzed to
extract time-domain attributes of the signal
 The most common signal processing task is the
transformation of the time series to its spectral
representation
 Frequency-domain attributes and parameters
extractable from the transformed signal include
frequency, bandwidth, transfer functions, and gain
and phase distortions

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SYNTHETIC INSTRUMENTS
Direct analysis of the sampled time series offers a
high-detail time-localized sample-by-sample
 analysis of its spectral representation offers a
low-detail, long-time averaged examination
 Modern DSP technology offers a third level of
time signal analysis to disclose and quantify
underlying short-term time-domain signal
structures


example of a middle-detail time
analysis of a sampled data signal is
its time-varying amplitude and phase
profile not observable in the time
series or its spectral representation
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SI front- and back-end options[1]
ADVANTAGES OF SYNTHETIC INSTRUMENTS

Eliminating Redundancy
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Power Supply
Front Panel Controls
Computer Interfaces
Computer Controllers
Mechanical Enclosures
Signal Processing
Measurement Integration
The data set is seen as an integrated whole that is
analyzed, categorized, and visualized
 This is in contrast with the more prevalent way of
approaching test where a separate measurement is done
in a sequential process with each test

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ADVANTAGES OF SYNTHETIC INSTRUMENTS

Measurement Speed

synthetic instrument does a measurement that is
exactly tuned to the needs of the test being performed.
Nothing more, nothing less

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For example, there is a speed-accuracy trade-off
the most efficient measurement techniques and
algorithms can be used
Longer Service Life

Synthetic measurement systems
can be reprogrammed
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Reduce costs by reusing hardware for many applications[6]
VECTOR SIGNAL ANALYZER
IMPLEMENTED AS
A SYNTHETIC INSTRUMENT
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QUADRATURE MODULATION
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s(t)= A(t)cos(ω0t + θ(t))
s(t, nTSym)= An cos(ω0t + θn)
s(t, nTSym)=An cos(θn)cos(ω0t)−An sin(θn)sin(ω0t)
In=An cos(θn) Qn=An sin(θn)
s(t, nTSym)=In cos(ω0t) − Qn sin(ω0t)
QAM modulator for the input vector I(n)+ jQ(n)[1]
16-point constellation with a binary Gray code[1]
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QUADRATURE DEMODULATOR
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
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it must estimate and remove unknown frequency and
phase offsets of the quadrature oscillator and time
sampling process
VSA does not require all of this support
there are channel and implementation effects; thus,
there will be a difference betweenthe modulator input
and the demodulator output
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Constellation space showing a demodulated I–Q point, possible
modulated I–Q points, decision boundaries, and an error vector[1]
QAM demodulator[1]
VSA
Synthetic Instrument Context[4]
Baseband sampled 16-QAM demodulator [1]
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16-QAM modulator [1]
VSA. High-quality DSP-based receiver [1]
VSA IMPLEMENTATION
A normal receiver will include an equalizer
 The VSA-based receiver does not use its equalizer in
the same fashion
 The radio receiver section of the VSA instrument must
acquire carrier frequency and phase from the
modulated signal to perform its demodulation task
 This is performed with a high-quality DSP-based PLL
 To minimize phase jitter in the demodlation process,
the PLL bandwidth must be small
 to acquire it in reasonable time and with a reasonable
offset frequency, the PLL bandwidth must be large
 the loop bandwidth is variable
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
VSA IMPLEMENTATION

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the radio receiver part of the VSA instrument must
accommodate input signals with arbitrary bandwidths and
arbitrary symbol rates
To control the complexity of the signal collection process
the VSA front end will likely have a fixed antialiasing filter
 a high-performance ADC operating at a fixed input sample
rate
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The processing performed by the VSA must include the
option of arbitrary resampling from the fixed input sample
rate
The timing jitter introduced by the resampling operation
must be significantly smaller than the timing jitter
expected to be measured
This means the arbitrary resample must be of extremely
high quality
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EVM
Demodulated constellation and EVM plots of a healthy modulator [1]
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Demodulated constellation and EVM plots for a modulator with phase jitter [1]
EVM
[1]
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[1]
REFERENCES
1)
Robert Wade Lowdermilk, Member, IEEE, and fredric j. harris, Life
Fellow, IEEE ,“Vector Signal Analyzer Implemented as a Synthetic
Instrument”, 2009 IEEE
2)
Gaetano Pasini’, Pier Andrea Traverse', Domenico Mirri’, Gaetano
Iuculano3, Fabio Filicori ,“Hardware Implementation of a Broad-Band
Vector Spectrum Analyzer Based on Randomized Sampling”,IMTC
2004.
3)
“ Synthetic Instruments Concepts and Applications” ,Copyright ©
2005 Elsevier Inc
4)
Peter Pragastis, Michael N. Granieri ,“The Up Converter – A Critical
Synthetic Instrument Technology”,2008 phase matrix
5)
Joe Fleagle ,“TRADEOFFS IN SYNTHETIC INSTRUMENT DESIGN
AND APPLICATION”,2005 IEEE.
6)
http://zone.ni.com/devzone/
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Thanks For
Your
Attendance
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