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Network Analyzer Basics
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Network Analyzer Basics
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) Presented by: Jeff Murphy – Agilent Technologies RF/MW Application Engineer Atlanta, GA (678) office Network Analyzer Basics
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Example Network Analyzer Measurements - BPF
log MAG 10 dB/ REF 0 dB CH1 S 21 START MHz STOP MHz Cor 69.1 dB Stopband rejection CH1 S 11 log MAG 5 dB/ REF 0 dB CENTER MHz SPAN MHz S CH1 21 log MAG 1 dB/ REF 0 dB Cor START MHz STOP MHz x2 1 2 m1: GHz dB m2-ref: GHz dB ref Return loss Insertion loss Network Analyzer Basics
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The Need for Both Magnitude and Phase
1. Complete characterization of linear networks 2. Complex impedance needed to design matching circuits 4. Time-domain characterization Mag Time 3. Complex values needed for device modeling High-frequency transistor model Collector Base Emitter 5. Vector-error correction Error Measured Actual Network Analyzer Basics
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Transmission Line Terminated with Zo
Zo = characteristic impedance of transmission line Zs = Zo Zo V inc Vrefl = 0! (all the incident power is absorbed in the load) For reflection, a transmission line terminated in Zo behaves like an infinitely long transmission line Network Analyzer Basics
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Transmission Line Terminated with Short, Open
Zs = Zo V inc Vrefl In-phase (0o) for open, out-of-phase (180o) for short For reflection, a transmission line terminated in a short or open reflects all power back to source Network Analyzer Basics
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High-Frequency Device Characterization
Incident Transmitted R B Reflected A REFLECTION TRANSMISSION Reflected Incident A R = Transmitted B = Incident R Group Return SWR Gain / Loss Loss Delay S-Parameters Impedance, Admittance Insertion S11, S22 Reflection S-Parameters Phase Coefficient S21, S12 Transmission R+jX, G+jB Coefficient G, r T,t Network Analyzer Basics
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G Reflection Parameters r F r G ¥ dB ¥ r V - Reflection Coefficient Z
= Z L - O + Reflection Coefficient V reflected incident r F G = r G Return loss = -20 log(r), Emax Emin Voltage Standing Wave Ratio VSWR = Emax Emin = 1 + r 1 - r No reflection (ZL = Zo) Full reflection (ZL = open, short) 1 r RL VSWR ¥ dB 0 dB 1 Network Analyzer Basics
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Network Analyzer Basics
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) Network Analyzer Basics
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General Network Analyzer Block Diagram
Source Switch Reference Receiver Reference Receiver R1 R2 A B Measurement Receivers Port 1 Port 2 Network Analyzer Basics
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Rectilinear impedance plane
Smith Chart Review . 90 o +R +jX -jX Rectilinear impedance plane Polar plane 1.0 .8 .6 ¥ ® .4 180 o + - .2 o -90 o Constant X Z = Zo Constant R L Smith Chart maps rectilinear impedance plane onto polar plane G = G L Z = 0 = ±180 O 1 (short) Z = L = O 1 G (open) Smith chart Network Analyzer Basics
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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 Transmitted S 21 11 Reflected 22 b 1 a 2 12 DUT = + Port 1 Port 2 Network Analyzer Basics
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Measuring S-Parameters
b S Incident 21 Transmitted 2 a 1 Z Load S Forward 11 Reflected DUT b a = 1 2 S 11 = Reflected Incident b 1 a 2 21 Transmitted S 22 = Reflected Incident b 2 a 1 12 Transmitted a = b 1 2 S 22 Reflected Z Load DUT Reverse a 2 b Transmitted S 12 Incident 1 Network Analyzer Basics
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Planned discontinuance June 2004
Agilent’s Series of RF Vector Analyzers 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 W 8753ET/ES series 3, 6 GHz – 50/75 W rich feature set ENA series (Mid Performance) 3, 8.5 GHz – 50 W 2, 3, 4 ports 7, 9 ports with test set excellent RF performance balanced measurements internal VBA automation Planned discontinuance June 2004 ENA-L series (Lowest Cost) 1.5, 3 GHz – 2 ports Low cost internal VBA automation 50/75 W 8712ET/ES series 1.3, 3 GHz - 50/75 W low cost narrowband and broadband detection IBASIC / LAN Network Analyzer Basics
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Agilent’s Series of Microwave Vector Analyzers
8720ET/ES series 13.5, 20, 40 GHz economical fast, small, integrated test mixers, high-power amps 8510C series 110 GHz in coax modular, flexible pulse systems Tx/Rx module test Discontinued PNA/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 Network Analyzer Basics
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Network Analyzer Basics
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) Network Analyzer Basics
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Measurement Error Modeling
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 repeatability Drift errors due to system performance changing after a calibration has been done primarily caused by temperature variation CAL RE-CAL Measured Data Unknown Device SYSTEMATIC RANDOM DRIFT Errors: Network Analyzer Basics
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Systematic Measurement Errors
B Crosstalk Directivity DUT Frequency response reflection tracking (A/R) transmission tracking (B/R) Source Load Mismatch Mismatch Six forward and six reverse error terms yields 12 error terms for two-port devices Network Analyzer Basics
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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 Network Analyzer Basics
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Errors and Calibration Standards
UNCORRECTED RESPONSE PORT FULL 2-PORT SHORT OPEN LOAD SHORT OPEN LOAD SHORT OPEN LOAD DUT thru Convenient Generally not accurate No errors removed DUT thru DUT 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 DUT Highest accuracy Removes these errors: Directivity Source, load match Reflection tracking Transmission tracking Crosstalk ENHANCED-RESPONSE Combines response and 1-port Corrects source match for transmission measurements Network Analyzer Basics
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Return Loss (Match) Before and After One-Port Calibration
Return Loss before 1-port calibration data after 1-port calibration 20 40 60 6000 12000 2.0 Return Loss (dB) VSWR 1.1 1.01 1.001 MHz Network Analyzer Basics
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Response versus Two-Port Calibration
Measuring filter insertion loss log MAG 1 dB/ REF 0 dB CH1 S 21 &M CH2 MEM log MAG 1 dB/ REF 0 dB Cor After two-port calibration After response calibration Uncorrected Cor 1 2 x2 START MHz STOP MHz Network Analyzer Basics
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ECal: Electronic Calibration (85060/90 series)
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 85093A Electronic Calibration Module 30 kHz - 6 GHz sa Microwave modules use a transmission line shunted by PIN-diode switches in various combinations Network Analyzer Basics
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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 Network Analyzer Basics
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TRL was developed for non-coaxial microwave measurements
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 Network Analyzer Basics
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TDR Basics Using a Network Analyzer
start with broadband frequency sweep (often requires microwave VNA) use inverse-Fourier transform to compute time-domain resolution inversely proportionate to frequency span Time Domain Frequency Domain t f CH1 S 22 Re 50 mU/ REF 0 U CH1 START 0 s STOP 1.5 ns Cor 20 GHz 6 GHz F -1 F(t)*dt ò t Integrate 1/s*F(s) t f f TDR F -1 Network Analyzer Basics
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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 S 11 &M log MAG 5 dB/ REF 0 dB START GHz STOP GHz Gate Cor PRm 1 2 2: dB GHz 1: dB GHz Thru in frequency domain, with and without gating CH1 MEM Re 20 mU/ REF 0 U CH1 START 0 s STOP 1.5 ns Cor PRm RISE TIME ps 8.992 mm 1 2 3 1: mU 638 ps 2: mU 668 ps 3: mU 721 ps Thru in time domain Network Analyzer Basics
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Network Analyzer Basics
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) Network Analyzer Basics
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What are Balanced Devices?
Ideally, respond to differential and reject common-mode signals Gain = 1 Differential-mode signal Balanced to single-ended Common-mode signal (EMI or ground noise) Gain = 1 Differential-mode signal Fully balanced Common-mode signal (EMI or ground noise) Network Analyzer Basics
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Balanced Components in Real World
Mode conversions occur... Differential to common-mode conversion + Generates EMI Susceptible to EMI Common-mode to differential conversion Network Analyzer Basics
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Complete Characterization Complete frequency domain views
Single-ended Balanced Port 1 Port 2 Balanced port 1 Balanced port 2 Port 3 Port 4 Common In Differential Out mode conversion terms Differential In Differential Out 44 43 42 41 34 33 32 31 24 23 22 21 14 13 12 11 S Stimulus Response S S S S DD 11 DD 12 DC 11 DC 12 S S S S DD 21 DD 22 DC 21 DC 22 S S S S CD 11 CD 12 CC 11 CC 12 S S S S CD 21 CD 22 CC 21 CC 22 Common In Common Out Differential In Common Out mode conversion terms Network Analyzer Basics
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Attenuation, Return Loss, LCL - LAN cable
Test Fixture PN Pair to be tested Sdc11, LCL Sdd21, Ins Loss Sdd11, Zin Sdd11, Ret Loss Network Analyzer Basics
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Crosstalk Measurement
NEXT-1 NEXT- 4 DUT ex) Near-end Crosstalk (NEXT) Power sum NEXT = NEXT-1 + NEXT-2 + NEXT-3 + NEXT-4 ACR NEXT = Attenuation – Power sum NEXT Network Analyzer Basics
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Terminations for Accurate Crosstalk Measurement
DUT 50 ohms 50 ohms 45 ohms 55 ohms Unbalanced termination impedance causes crosstalk measurement errors Network Analyzer Basics
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Power Sum NEXT Measurement - PCI Express Connector
Ret.Loss Ins.Loss VBA calculates Power Sum NEXT and plot it on the ENA’s screen. Network Analyzer Basics
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Characteristic Impedance Zc Measurement - LAN Cable
(Calculated from Sdd11,Sdd21,Sdd12 and Sdd22 using built-in VBA.) Network Analyzer Basics
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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 Network Analyzer Basics
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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 #2 Network #1 Network #3 Network Analyzer Basics
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Concept of In-Fixture Characterization
The ENA calculates S-parameters of each network based on three measurement (OSL) results using the adapter characterization program Erf 1 Edf Esf Standards Open/Short/Load Network #1 S11M Edf: Forward Directivity Error Esf: Forward Source Match Erf: Forward Reflection Tracking Network Analyzer Basics
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Probing System Configuration
Agilent ENA Series RF Network Analyzer, 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) Network Analyzer Basics
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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. Network Analyzer Basics
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Network Analyzer Basics
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) Network Analyzer Basics
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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 Network Analyzer Basics
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PLTS Complete Physical Layer Solution
Agilent N1900 Series PLTS Complete Physical Layer Solution 4-PORT VNAs 9,20,40,50GHz $90K - $200K AGILENT 86100A/B 2/4 CHANNEL TDR $60K - $75K TEK CSA8000 2/4 CHANNEL TDR Network Analyzer Basics
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Complete Characterization Fast and accurate eye diagrams
Simulated Bit Pattern (Arbitrary Bitstream (ABS) or User-defined) Measured Data (TDR or VNA) Impulse Response Convolution Eye Diagram Network Analyzer Basics
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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 Calculates Excess Reactance Best Dynamic Range (SNR) for very low loss components, low levels of mode conversion, crosstalk, etc. Best Higher-Order Models Characterize Small Coupling Effects Highest Accuracy Fixture De-Embedding Capability S-Parameters Network Analyzer Basics
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Network Analyzer Basics
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) Network Analyzer Basics
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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 Network Analyzer Basics
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Slotted Female Centre Conductor
Network Analyzer Basics
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Connector Examples Male Female Male Female Type F APC 7 BNC SMA SMC
3.5 mm 2.92 mm or K Type N 2.4 mm Network Analyzer Basics
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Cost of Connector Damage
Network Analyzer Basics
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To Learn More… Signal Integrity Web Resource: www.agilent.com/find/si
PLTS Home Page: Update Service: T&M Web Resource: Application Notes for VNAs Support, Service, and Assistance from Agilent Contact Centers Worldwide: United States: (800) Channel Partners (partial list): GigaTest Labs (Probing products, services, training ): Cascade Microtech (High-speed probes ): TDA Systems (IConnect, MeasureXtractor): Network Analyzer Basics
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To Learn More… PNA Series Network Analyzers: www.agilent.com/find/pna
ENA Series Network Analyzers: Electronic Calibration: Back To Basics Online Training: Differential S-Parameter Measurements of PCI Express Connector Using the ENA Series Network Analyzer (AN1463-3) EN In-Fixture Characterization Using the ENA Series RF Network Analyzer with Cascade Microtech Probing System EN An Introduction to Multiport and Balanced Device Measurements (AN ) EN VNA-Based System Tests the Physical Layer - Application Note EN 10 Hints for Making Better Network Analyzer Measurements - Application Note B E Agilent Measuring Noninsertable Devices – Product Note E Agilent AN 154 S-Parameter Design S-parameter Techniques – Application Note 95-1 Agilent AN Applying Error Correction to Network Analyzer Measurements E De-embedding and Embedding S-Parameter Networks Using a Vector Network Analyzer – AN EN Understanding the Fundamental Principles of Vector Network Analysis Application Note E Agilent AN In-Fixture Measurements Using Vector Network Analyzers E Exploring the Architectures of Network Analyzers Application Note E Intro to the Fixture Simulator Function of the ENA Series RF NA: Network De-embedding/Embedding and Balanced Meas EN Network Analyzer Basics
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Network Analyzer Basics
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) Network Analyzer Basics
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