Www.agilent.com/find/backtob asics 0 Network Analyzer Basics

Network Analyzer Basics www.agilent.com/find/backtobasics

1

Network Analyzer Basics


2

Network Analyzer Basics

Presented by:Jeff Murphy – Agilent TechnologiesRF/MW Application EngineerAtlanta, GA(678)566-6052 [email protected]

Agenda

•VNA Overview and Transmission Line Review•Network Analyzer Hardware and S-parameter Review•Error Modeling and Calibration •Cable/PCI Express Example Measurements•Balanced VNA Solutions•Connector handling•4-port ENA Vector Network Analyzer Demo (8.5 Ghz)


3

Example Network Analyzer Measurements - BPF CH1 S11 log MAG 5 dB/ REF 0 dB

CENTER 200.000 MHz SPAN 50.000 MHz

Return loss

log MAG 10 dB/ REF 0 dBCH1 S

21

START .300 000 MHz STOP 400.000 000 MHz

Cor

69.1 dB

Stopband

rejection

Insertion loss

SCH1 21 log MAG 1 dB/ REF 0 dB

Cor

Cor

START 2 000.000 MHz STOP 6 000.000 MHz

x2 1 2

m1: 4.000 000 GHz -0.16 dBm2-ref: 2.145 234 GHz 0.00 dB

1

ref 2


4

The Need for Both Magnitude and Phase

4. Time-domain characterization

Mag

Time

5. Vector-error correction

Error

MeasuredActual

2. Complex impedance needed to design matching circuits

3. Complex values

needed for device modeling

1. Complete characterization of linear networks

High-frequency transistor model

Collector

Base

Emitter

S21

S12

S11 S22


5

Transmission Line Terminated with Zo

For reflection, a transmission line terminated in Zo behaves like an infinitely long transmission line

Zs = Zo

Zo

Vrefl = 0! (all the incident power is absorbed in the load)

Vinc

Zo = characteristic impedance of transmission line


6

Transmission Line Terminated with Short, Open

Zs = Zo

Vrefl

Vinc

For reflection, a transmission line terminated in a short or open reflects all power back to source

In-phase (0o) for open, out-of-phase (180o) for short


7

High-Frequency Device Characterization

TransmittedIncident

TRANSMISSION

Gain / Loss

S-ParametersS21, S12

GroupDelay

TransmissionCoefficient

Insertion

Phase

ReflectedIncident

REFLECTION

SWR

S-ParametersS11, S22

ReflectionCoefficient

Impedance, Admittance R+jX

, G+jB

Return

Loss

Incident

Reflected

TransmittedRB

A

A

R=

B

R=


8

Reflection Parameters

dB

No reflection(ZL = Zo)

RL

VSWR

0 1

Full reflection(ZL = open,

short)

0 dB

1

=ZL ZO

ZL + OZ

Reflection Coefficient =

Vreflected

Vincident

= = Return loss = -20 log(),

Voltage Standing Wave Ratio

VSWR = Emax

Emin=

1 + 1 -

Emax

Emin


9

Network Analyzer BasicsAgenda



10

Switch

Source

R1

A

Port 1

R2

B

Port 2

Measurement

Receivers

Reference Receiver

Reference Receiver

General Network Analyzer Block Diagram


11

Smith Chart Review

Smith Chart maps

rectilinear impedanceplane onto polar plane

0+R

+jX

-jX

Rectilinear impedance plane

.

-90 o

0o180 o+-

.2

.4

.6

.8

1.0

90

o

Polar plane

Z = ZoL

= 0

Constant X

Constant R

Smith chart

LZ = 0

=±180 O1

(short) Z = L

= 0 O

1

(open)


12

Why Use S-Parameters?

relatively easy to obtain at high frequencies measure voltage traveling waves with a vector network

analyzer don't need shorts/opens which can cause active devices to

oscillate or self-destruct relate to familiar measurements (gain, loss, reflection

coefficient ...) can cascade S-parameters of multiple devices to predict

system performance can compute H, Y, or Z parameters from S-parameters if

desired can easily import and use S-parameter files in our electronic-simulation tools

Incident

TransmittedS21

S11Reflected S22Reflecte

dTransmitted

Incident

b1

a1b2

a2S12

DUT

b1= S11a1+S12a2

b2=S21a1 +S22a2

Port 1 Port 2


13

Measuring S-Parameters

S 11 = Reflected

Incident=

b1

a 1 a2 =0

S 21 =Transmitted

Incident=

b2

a 1 a2 =0

S 22 = Reflected

Incident=

b2

a 2 a1 =0

S 12 =Transmitted

Incident=

b1

a 2 a1 =0

Incident

TransmittedS

21

S11

Reflectedb1

a1

b2

Z0

Loada2 =0

DUTForward

Incident

Transmitted S

12

S22

Reflected

b2

a2b

a1=0

DUTZ0

Load Reverse

1


14

Agilent’s Series of RF Vector Analyzers

8753ET/ES series

3, 6 GHz – 50/75

rich feature set

PNA series (Highest Performance)

3, 6, 9 GHz - 2, 3 ports highest dynamic range internal Windows automation (open

Windows system) program via SCPI or COM/DCOM 50/75

8712ET/ES series

1.3, 3 GHz - 50/75

low cost narrowband

and broadband detection

IBASIC / LAN

ENA series (Mid Performance)

3, 8.5 GHz – 50 2, 3, 4 ports 7, 9 ports with test

set excellent RF

performance balanced

measurements internal VBA

automation

ENA-L series (Lowest Cost)

1.5, 3 GHz – 2 ports Low cost internal VBA

automation 50/75

Planned discontinuance June 2004


15

Agilent’s Series of Microwave Vector Analyzers

8510C series

110 GHz in coax

modular, flexible

pulse systems

Tx/Rx module testPNA/PNA-L series

20, 40, 50 GHz PNA & PNA-L 67 GHz PNA 110+ GHz w/ external test set

(PNA) highest dynamic range and

speed very low trace noise advanced LAN connectivity internal Windows automation program via SCPI or

COM/DCOM

8720ET/ES series 13.5, 20, 40 GHz economical fast, small,

integrated test mixers, high-

power ampsDiscontinued


16




17

Systematic errors due to imperfections in the analyzer and test

setup assumed to be time invariant (predictable)

Random errors vary with time in random fashion (unpredictable) main contributors: instrument noise, switch and

connector repeatabilityDrift errors

due to system performance changing after a calibration has been done

primarily caused by temperature variation

Measurement Error Modeling

Measured Data

Unknown Device

SYSTEMATIC

RANDOM

DRIFT

Errors:

CAL

RE-CAL


18

Systematic Measurement Errors

A B

SourceMismatch

LoadMismatch

Crosstalk

Directivity

DUT

Frequency response reflection tracking (A/R) transmission tracking

(B/R)

R

Six forward and six reverse error terms yields 12 error terms for two-port devices


19

What is Vector-Error Correction?

Process of characterizing systematic error terms

measure known standards remove effects from subsequent measurements

1-port calibration (reflection measurements) only 3 systematic error terms measured directivity, source match, and reflection

tracking Full 2-port calibration (reflection and

transmission measurements) 12 systematic error terms measured usually requires 12 measurements on four

known standards (SOLT) Standards defined in cal kit definition file

network analyzer contains standard cal kit definitions

CAL KIT DEFINITION MUST MATCH ACTUAL CAL KIT USED!

User-built standards must be characterized and entered into user cal-kit


20

Errors and Calibration Standards

Convenient Generally not

accurate No errors

removed Easy to perform Use when

highest accuracy is not required

Removes frequency response error

For reflection measurements

Need good termination for high accuracy with two-port devices

Removes these errors: Directivity Source match Reflection tracking

Highest accuracy Removes these

errors: Directivity Source, load match Reflection tracking Transmission tracking Crosstalk

UNCORRECTED RESPONSE 1-PORT FULL 2-PORT

DUT

DUT

DUT

DUT

thru

thru

ENHANCED-RESPONSE Combines response and 1-port Corrects source match for

transmission measurements

SHORT

OPEN

LOAD

SHORT

OPEN

LOAD

SHORT

OPEN

LOAD


21

Return Loss (Match) Before and After One-Port Calibration

Return Loss before 1-port calibration

data after 1-port calibration

0

20

40

60

6000 12000

2.0

Retu

rn L

oss (

dB

)

VS

WR

1.1

1.01

1.001

MHz


22

Response versus Two-Port Calibration

CH1 S21&M log MAG 1 dB/ REF 0 dB

Cor

CH2 MEM log MAG REF 0 dB1 dB/

Cor

Uncorrected

After two-port calibration

START 2 000.000 MHzSTOP 6 000.000 MHz

x2 1 2

After response calibration

Measuring filter insertion loss


23

• Variety of modules cover 300 kHz to 67 GHz

• 4-port versions available for < 9 GHz

• Choose from six connector types (50 and 75 )

• Mix and match connectors (3.5mm, Type-N, 7/16)

• Single-connection reduces calibration time makes calibrations easy to

perform minimizes wear on cables and

standards eliminates operator errors

• Highly repeatable temperature-compensated terminations provide excellent accuracy

ECal: Electronic Calibration (85060/90 series)

85093A Electronic Calibration Module30 kHz - 6 GHz

Microwave modules use a transmission line shunted by PIN-diode switches in

various combinations


24

Calibrating Non-Insertable Devices

When doing a through cal, normally test ports mate directly

cables can be connected directly without an adapter

result is a zero-length through What is an insertable device?

has same type of connector, but different sex on each port

has same type of sexless connector on each port (e.g. APC-7)

What is a non-insertable device? one that cannot be inserted in place of a

zero-length through has same connectors on each port (type

and sex) has different type of connector on each

port (e.g., waveguide on one port, coaxial on the other)

What calibration choices do I have for non-insertable devices?

use an uncharacterized through adapter use a characterized through adapter

(modify cal-kit definition) swap equal adapters adapter removal

DUT


25

Thru-Reflect-Line (TRL) Calibration

We know about Short Open Load Thru (SOLT) calibration...What is TRL?

A two port calibration technique Good for noncoaxial environments (waveguide,

fixtures, wafer probing) Uses the same 12 term error model as the

more common SOLT cal Uses practical calibration standards that

are easily fabricated and characterized

Two variations: TRL (requires 4 receivers) and TRL* (only three receivers needed)

Other variations: Line Reflect Match (LRM), Thru Reflect Match (TRM),

plus many others

TRL was developed for non-coaxial microwave

measurements


26

start with broadband frequency sweep (often requires microwave VNA)

use inverse-Fourier transform to compute time-domain resolution inversely proportionate to frequency span

CH1 S22 Re 50 mU/ REF 0 U

CH1 START 0 s STOP 1.5 ns

Cor

20 GHz

6 GHz

Time Domain Frequency Domain

t

f

1/s*F(s)

F(t)*dt0

t

Integrate

ft

f

TDRF -

1

TDR Basics Using a Network Analyzer

F -1


27

Time-Domain Gating TDR and gating can remove undesired reflections (a

form of error correction) Only useful for broadband devices (a load or thru for

example) Define gate to only include DUT Use two port calibration

CH1 MEM Re 20 mU/ REF 0 U

CH1 START 0 s STOP 1.5 ns

CorPRm

RISE TIME 29.994 ps 8.992 mm

1

2

3

1: 48.729 mU 638 ps

2: 24.961 mU 668 ps 3: -10.891

mU 721 ps

Thru in time domain

CH1 S11

&M log MAG 5 dB/ REF 0 dB

START .050 000 000 GHz STOP 20.050 000 000 GHz

Gate

Cor

PRm

1

2

2: -15.78 dB 6.000 GHz

1: -45.113 dB 0.947 GHz

Thru in frequency domain, with and without gating


28




29

What are Balanced Devices?Ideally, respond to differential and reject common-mode signals

Differential-mode signal

Common-mode signal

(EMI or ground noise)

Gain = 1

Differential-mode signal

Common-mode signal

(EMI or ground noise)

Gain = 1

Balanced to single-ended

Fully balanced


30

Balanced Components in Real World

• Mode conversions occur...

+

Differential to common-mode

conversion

Common-mode to differential conversion

Generates EMI

Susceptible to EMI


31

Complete Characterization Complete frequency domain views

Port 1

Single-endedBalanced port 1

Balanced

44434241

34333231

24232221

14131211

SSSS

SSSS

SSSS

SSSS

Stimulus

Resp

on

se

22CC21CC22CD21CD

12CC11CC12CD11CD

22DC21DC22DD21DD

12DC11DC12DD11DD

SSSS

SSSS

SSSS

SSSS

Common InDifferential Out

Differential In Differential Out

mode conversion terms

Differential InCommon Out

mode conversion

terms

Common In Common Out

Balanced port 2 Port 3

Port 2 Port 4


32

Attenuation, Return Loss, LCL- LAN cable

Sdd21, Ins Loss

Sdc11, LCL

Sdd11, Zin

Sdd11, Ret Loss

Test FixturePN 04380-60101

Pair to be tested


33

. . .

NEXT-1

NEXT- 4

DUT

Crosstalk Measurement

ex) Near-end Crosstalk (NEXT)

Power sum NEXT = NEXT-1 + NEXT-2 + NEXT-3 + NEXT-4

ACR NEXT = Attenuation – Power sum NEXT


34

50 ohms

50 ohms

45 ohms55 ohms

Unbalanced termination impedance causescrosstalk measurement errors

DUT

Terminations for Accurate Crosstalk Measurement


35

Power Sum NEXT Measurement- PCI Express Connector

VBA calculates Power Sum NEXT andplot it on the ENA’s screen.

Ret.Loss

Ins.Loss


36

Characteristic Impedance Zc Measurement- LAN CableCharacteristic Impedance Zc

(Calculated from Sdd11,Sdd21,Sdd12 and Sdd22 using built-in VBA.)


37

Current Issue

• How do you eliminate the influence of test fixtures from measurement results?

• Using the customized test fixture with calibration kit is one of solutions but these are very expensive and inflexible


38

Concept of In-Fixture Characterization

Exclude two-port network from measured S-parameter• De-embedding networks can be applied to individual ports• Undesired network is specified by Touchstone file (.s2p)

Remove unwanted test fixture effect

Network #1

Network #2

Network #3

www.agilent.com/find/backtobasics

39Network Analyzer Basics

Concept of In-Fixture Characterization• The ENA calculates S-parameters of each network

based on three measurement (OSL) results using the adapter characterization program

S11M

Edf: Forward Directivity ErrorEsf: Forward Source MatchErf: Forward Reflection Tracking

Erf

1

Edf Esf

StandardsOpen/Short/Load

Network #1


40

Agilent ENA Series RF NetworkAnalyzer, E5070A/71A• The ENA Series with Cascade’s probing System provides highly accurate in-fixture characterization method with easy operation

Cascade Microtech• Summit 9000 RF Probe Station• Air Coplanar Probe (ACP)• Impedance Standard Substrate (ISS)

Probing System Configuration


41

Measurement Example Each test port is characterized by using ENA with Cascade’s probe

• Adapter characterization program calculates S-parameter using the measured S11 data (O, S, L), and S11 definitions of standards (O, S, L)• ENA can export .s2p data for the fixture de-embedding Open

Std.Short Std.Load Std.


42




43

Agilent Solutions for Balanced Measurements• For RF wireless and general-purpose devices:

• ENA series is recommended choice (3, 8.5 GHz)• measure standard or mixed-mode S-parameters• fixture simulator to embed/de-embed

and transform test port impedances• 4-port ECal for fast and easy calibration

• For microwave or signal-integrity applications up to 50GHz (rise time 14.4ps)• N1948A,N1953/55/57B systems• consist of network analyzer,

test set, external software• time domain, eye diagrams,

RLCG extraction• ECal available up to 9 GHz


44

PLTS Complete Physical Layer Solution

4-PORT VNAs9,20,40,50GHz$90K - $200K

AGILENT 86100A/B2/4 CHANNEL TDR$60K - $75K

TEK CSA80002/4 CHANNEL TDR

Agilent N1900 Series


45

Complete Characterization Fast and accurate eye diagrams

Simulated Bit Pattern(Arbitrary Bitstream (ABS)

or User-defined)

Simulated Bit Pattern(Arbitrary Bitstream (ABS)

or User-defined)

EyeDiagram

EyeDiagram

Measured Data (TDR or

VNA)

Measured Data (TDR or

VNA)

Impulse Response

Impulse Response

ConvolutionConvolution


46

TDR-based or VNA-based PLTS System?There is no fundamental difference in the information content

between the time domain and the frequency domain (there is a difference in the capabilities of the two systems) – Eric Bogatin, GigaTest Labs Customer Concerns Ideal System

TDR-based

VNA-based Both

Greatest Ease of Use, Quick Set Up X Good First-Order Models X Calculates Excess Reactance X Best Dynamic Range (SNR) for very low loss components, low levels of mode conversion, crosstalk, etc.

X

Best Higher-Order Models X Characterize Small Coupling Effects X Highest Accuracy X Fixture De-Embedding Capability X S-Parameters X


47




48

Connector Considerations

A significant factor in repeatability and accuracy Selecting the best of several types for application

(grade) Compatibility Connectors are consumables

– limited lifetime– damaged connectors are costly– proper care maximizes lifetime


49

Slotted Female Centre Conductor


50

Connector Examples

Type F

BNC

SMC

Type N

APC 7

SMA

3.5 mm

2.92 mm or K

2.4 mm

MaleFemale FemaleMale


51

Cost of Connector Damage


52

To Learn More… To Learn More…

Signal Integrity Web Resource: www.agilent.com/find/si

PLTS Home Page: www.agilent.com/find/plts

Email Update Service: www.agilent.com/emailnotification

T&M Web Resource: www.agilent.com/find/products

Application Notes for VNAs www.agilent.com/find/na_appnotes

Support, Service, and Assistance from Agilent Contact Centers Worldwide:

United States: (800)829-4444

Channel Partners (partial list):

GigaTest Labs (Probing products, services, training ): www.gigatest.com

Cascade Microtech (High-speed probes ): www.cmicro.com

TDA Systems (IConnect, MeasureXtractor): www.tdasystems.com


53

To Learn More… To Learn More…

PNA Series Network Analyzers: www.agilent.com/find/pna

ENA Series Network Analyzers: www.agilent.com/find/ena

Electronic Calibration: www.agilent.com/find/ecal

Back To Basics Online Training: www.agilent.com/find/backtobasicsDifferential S-Parameter Measurements of PCI Express Connector Using the ENA Series Network

Analyzer (AN1463-3) 5988-9848EN

In-Fixture Characterization Using the ENA Series RF Network Analyzer with Cascade Microtech Probing System 5988-6522EN

An Introduction to Multiport and Balanced Device Measurements (AN 1373-1) 5988-5634EN

VNA-Based System Tests the Physical Layer - Application Note 1382-7 5988-5075EN

10 Hints for Making Better Network Analyzer Measurements - Application Note 1291-1B5965-8166E

Agilent 8510-13 Measuring Noninsertable Devices – Product Note 5956-4373E

Agilent AN 154 S-Parameter Design - 5952-1087

S-parameter Techniques – Application Note 95-1

Agilent AN 1287-3 Applying Error Correction to Network Analyzer Measurements5965-7709E

De-embedding and Embedding S-Parameter Networks Using a Vector Network Analyzer – AN 1364-15980-2784EN

Understanding the Fundamental Principles of Vector Network Analysis Application Note 1287-15965-7707E

Agilent AN 1287-9 In-Fixture Measurements Using Vector Network Analyzers 5968-5329E

Exploring the Architectures of Network Analyzers Application Note 1287-2 5965-7708E

Intro to the Fixture Simulator Function of the ENA Series RF NA: Network De-embedding/Embedding and Balanced Meas 5988-4923EN


54



Documents

Www.agilent.com/find/backtob asics 0 Network Analyzer Basics