NI Signal Generators

NI Signal Generators

ni.com | NI CONFIDENTIAL

Chinmay Anand Misra

Certified LabVIEW Developer

Staff Applications Engineer

Agenda

• Introduction to Signal Generators

• Specifications

• Types of Signal Generators

• Signal Generation Techniques

2ni.com | NI CONFIDENTIAL

• Signal Generation Techniques

• Signal Generation Modes

• Advanced Features (Streaming, Triggering, Synchronization)

• NI-FGEN Driver

Signal Genrators

• Electronic devices that generate repeating or non-

repeating electronic signals (in either the analog or digitaldomains).

• Generally used in designing, testing, troubleshooting, andrepairing electronic or electro-acoustic devices.


Comparison DAQ vs. Signal Generators

Analog Output DAQAnalog Output DAQAnalog Output DAQAnalog Output DAQ CardsCardsCardsCards SignalSignalSignalSignal GeneratorsGeneratorsGeneratorsGenerators

Low Cost ($1k to $2k) More Costly ($3k to $14k)

Limited Onboard Memory Deep Onboard Memory

Poor Spectral Purity Good Dynamic Specifications


Poor Spectral Purity Good Dynamic Specifications

Small Bandwidth Large Bandwidth

Low Sampling Rates High Sampling Rates

Limited Features Advanced Features

Analog Output DAQ Block Diagram

FIFO

DACFixed

Gain


20 MHz

VCXO

Div/N

Signal Generator Block DiagramWaveform

and Sequence

Memory

Variable

Attenuator/

Gain DAC

Digital pattern generation

Marker signal

Trigger Input

Digital

Filter


and Sequence

Gain

Low-pass

Analog Filter

100 MHz

VCXO

Div/NDDS

PLL

REF

CLK

Sample Rate


Bandwidth


Spurious Free Dynamic Range (SFDR)

Spurious Free Dynamic Range (SFDR)

A.K.A. Dynamic Range

Units: dB, dBc, dBm

Ex: 70 dBc

Level of

fundamental

Level of


Level of

highest

spur

Passband Flatness

Passband Flatness

How much does the amplitude of a


How much does the amplitude of a

tone change over frequency.

Units: dB

Ex: 0.25 dB

Total Harmonic Distortion (THD)

Total Harmonic Distortion (THD)

Sum of harmonic power levels

(Typically 2nd through 6th harmonics)

Units: dB, dBc, dBm

Ex: -80 dBc


Phase Noise

Phase Noise

Units: dBc/Hz

Ex: -135 dBc/Hz


Types of Signal Generators

• Periodic Signals: Sine, Square, Triangle, Ramp Up,

Ramp Down, DC, Noise, User Defined

• Any single cycle of a waveform can be represented by

214 points and stored into memory

Function Generator (FG)Function Generator (FG)Function Generator (FG)Function Generator (FG)


Arbitrary Waveform Generator (AWG)Arbitrary Waveform Generator (AWG)Arbitrary Waveform Generator (AWG)Arbitrary Waveform Generator (AWG)

• Large and complex waveforms

• Linking, looping, and scripting of waveforms

• Deep waveform and instruction memory

Signal Generation Modes

Signal Generation

Arbitrary Wfm GenerationFunction Generation


Arbitrary Wfm GenerationFunction Generation

Standard

Function

Frequency

List

Arbitrary

Signal

Arbitrary

SequenceScript

Function Generators Overview

5402540254025402 5404540454045404 5406540654065406

Type Function Clock Function

Bandwidth 20 MHz 105 MHz 40 MHz

Sample Rate 400 MS/s 300 MS/s 400 MS/s

Resolution (bits) 14 12 16

Memory Depth (MB) 16K Samples N/A 16K Samples


Output Voltage (V) ±5 ±1 ±5

Single Tone Better Good Better

Sine Sweep Best Better Best

Arbitrary Waveforms Good N/A Good

Price $2,499 $1,750 $4199

Arbitrary Waveform Generators Overview

5412541254125412 5421542154215421 5422542254225422 5441544154415441 5442544254425442 5450545054505450 5451545154515451

Type Arb Arb Arb Arb Arb Arb Arb

Bandwidth 20 MHz 43 MHz 80 MHz 43 MHz 43 MHz 145 MHz 145 MHz

Sample Rate 100 MS/s 100 MS/s 200 MS/s 100 MS/s 100 MS/s 400 MS/s 400 MS/s

Resolution

(bits)14 16 16 16 16 16 16

Memory Depth

(MB)8,32,256,512 8,32,256,512 8,32,256,512 8,32,256,512 32,256,512 128, 512 128, 512, 2GB


Output

Voltage (V)±6 ±6 ±6 ±6 ±1 ±1 ±2.5

Single Tone Better Best Best Best Best Best Best

Sine Sweep Good Good Good Good Good Good Good

Arbitrary

WaveformsBest Best Best Best Very Best Very Best Very Best

Price $3,999 $6,399 $7,299 $8,499 $9,999 $11,999 $13,499

Signal Generation Techniques

• Analog

• Digital Direct Synthesis

• Analog Mode downloads a waveform to memory and automatically


National Instruments

• Analog Mode downloads a waveform to memory and automatically selects the best clock mode, sample rate, and buffer size to produce the most accurate waveform possible.

What is DDS?

• Digital technique to create an analog frequency source from a single reference clock frequency

• The instrument downloads 16,384 samples (214 samples) that represent a single cycle of a standard waveform into the lookup memory.


Digital Direct Synthesis


Benefits of DDS over Analog Signal Generation

• DDS are more versatile and reliable

• High Frequency, Accuracy, and Resolution

• Phase Continuous and Fast Switching

• Wideband Tuning

• Temperature Stability


Signal Generation Modes

• Standard Function/Frequency List

• Frequency List mode not on all cards

• Arbitrary Waveform

• Generates waveforms from provided waveform arrays of data


• Arbitrary Sequence

• Generates waveforms on memory in the order you specify

• Script

• Generates a waveform according to a script

Memory

DAC

Arbitrary Waveform Mode


Create WaveformIn Software

DownloadWaveform

GenerateWaveform

Arbitrary Sequence Mode

•Linking and Looping1. Define segments

2. Loop segments to create stages


2. Loop segments to create stages

3. Link stages to create waveform - Create the

staging list

• Two sets of memory on the instruments• Waveform memory

• Instruction FIFO memory

1. Segments are loaded into the waveform memory

2. Linking and looping instructions are loaded into



2. Linking and looping instructions are loaded into the Instruction FIFO memory

3. The instrument puts together the waveform from the segments based on the instructions


• Build Complex Waveforms

• Optimize Memory Usage


Waveform A Waveform B Waveform C

Example Waveforms


timetime

Ch0Output


timetime

Instruction

FIFO

A: #6

B: #3

C: #9

Onboard Memory

What is Scripting?

• Generate complex waveform sequences • Generate waveform based on script triggersscript triggersscript triggersscript triggers• Commands include:

• Generate

• Repeat

• If / Else


• If / Else

• Wait

• Clear

PXI -5671PXI-5441 PXI -6562

3 Basic Steps of Scripting

Write Waveforms Write Script Initiate Generation


1 2 3

Configuring Script Triggers


PXI_Trig0scriptTrigger0 = FALSE scriptTrigger0 = TRUE scriptTrigger0 = FALSE

Repeat until Trigger

repeat until

scripttrigger0

script

repeatingwavefrm

generate

waveform0

generate


end script

generate

waveform2

generate

waveform1

Generated Signal

scripttrigger0 = TRUE

Wait until Trigger

Clear

scriptrigger0

wait until

scripttrigger0

script

TrigWait

generate

waveform1


scripttrigger0

end script

generate

waveform3

generate

waveform2

scripttrigger0 = FALSE

( wait period)


Generated Signal

Branching with If / Else

then

elseif scripttrigger0

script

ConditionalBranching

generate

generate

waveform1

generate

waveform3


end script

end if


Generated Signal

generate

waveform2

Note that Waveforms in Script Mode will finish

generating before moving to the next waveform

Streaming

• Used when waveform is bigger than your memory size

• Can be used in Waveform, Sequence, or Script Mode

• Write waveform data to “buffer” as you are generating


Streaming Steps

1. Setup a buffer in memory – streaming waveform


Streaming Steps

2. Fill Memory with Initial Waveform


Streaming Steps

3. Begin Generation


Streaming Steps

4. Write new blocks of data to your buffer


Triggering

• You can use triggering to start and step through all the

stages during a waveform generation

• Trigger sources (TTL)

• External (I/O connector)

• Over the RTSI Line or PXI backplane bus lines.


• Over the RTSI Line or PXI backplane bus lines.

• Software generated (internal)

• Triggering Modes

• Single, Continuous, Stepped, Burst

Triggering Mode – Single

• Single Trigger for 5412/5421/5422/5441/5450/5451

• Arbitrary Waveform Mode


• Arbitrary Sequence Mode

Triggering Mode - Continuous

• Continuous Trigger for 5412/5421/5422/5441/5450/5451




Triggering Mode – Stepped

• Stepped Trigger for 5412/5421/5422/5441/5450/5451




Triggering Mode – Burst

• Burst Trigger for 5412/5421/5422/5441/5450/5451




Synchronization of SMC cards

Signal Generator Block Diagram

D/A ConverterSMC

DACDigital FIR

2x, 4x, 8x

Onboard

MemoryAnalog

Filter

Waveform

GenerationDigital

Gain


DAC2x, 4x, 8x

InterpolationMemory

8 MB – 512 MBFilter

Trigger

and EventTiming and

Synchronization

Generation

Engine

Clocking

EngineDirect Digital

Synthesis

Gain

Multi Module Synchronization – Ref Clk

• Synchronization within chassis

Internal Reference Clock


External Reference Clock

Multi Module Synchronization –TClk

• Synchronization using three TClk VIs

• Single or Multi Chassis

• Single PC

• Triggers are used for any purpose (Start Trigger/Reference Trigger)

• Sample Clocks can be same or different


FGEN Configuration TClk Configuration

NI-FGEN

• Driver for NI 54xx cards

• Development Software:• LabVIEW & LabVIEW Real-Time

• LabWindows™ /CVI™

• LabWindows™ /CVI™ Real-Time Module

• Measurement Studio

• Microsoft Visual C++ (MSVC)


• Microsoft Visual C++ (MSVC)

• Microsoft Visual Basic 6.0

• Includes the FGEN Soft Front

Panel

• IviFgen Class Specificationcompliant

Programming Function Generators

• Programming• Register level

• Application programming interface (API)

• NI-FGEN• LabVIEW Express VIs for rapid Competitor


• LabVIEW Express VIs for rapid configuration

• Intuitive API layout

• Tight integration with other LabVIEW functions

• CVI, MStudio, Visual Studio support

Competitor

NI-FGEN

NI-FGEN General Programming Flow


niFGEN Initialize

Opens session to ARB

niFGENAbort Generation

Abort previous generation and Switch to Configuration Mode

niFGEN Configure Output Mode

Configure Mode to Arbitrary WaveformniFGEN Clear Arbitrary MemoryniFGEN Configure Clock Mode

niFGEN Create Waveform

Download a new Waveform to MemoryniFGEN Configure Arbitrary Waveform

Configures Arbitrary Waveform Gain and DC OffsetniFGEN Configure Sample Clock SourceniFGEN Set Sample RateniFGEN Configure Analog FilterniFGEN Configure Digital FilterniFGEN Output EnableniFGEN Initiate Generation

FGEN Soft Front Panel• SFP supports Arbitrary Waveform Mode

• Reads HWS, binary, and ASCII files

• Generate waveforms from files created with

Analog Waveform Editor


Thank you!

ni.com | NI CONFIDENTIALHigh-Speed Digitizers

Documents

NI Signal Generators