Network Analyzer Basics

Transcription

1 Network nalysis is NOT. Router ridge Repeater Hub Your IEEE 80.3 X.5 ISDN switched-packet data stream is running at 47 MPS with -9 a ER of.53 X 0... What Types of Devices are Tested? Device Test Measurement Model Integration High Low Duplexers Diplexers Filters Couplers ridges Splitters, dividers Combiners Isolators Circulators ttenuators dapters Opens, shorts, loads Delay lines Cables Transmission lines Waveguide Resonators Dielectrics R, L, Cs Passive ntennas Switches Multiplexers Mixers Samplers Multipliers Diodes Device type RFICs MMICs T/R modules Transceivers Receivers Tuners Converters VCs mplifiers VCOs VTFs Oscillators Modulators VCtten s Transistors ctive Complex Response tool Simpl e Ded. Testers VS S VN TG/S SN NF Mtr. Imped. n. Param. n. Power Mtr. Det/Scope Harm. Dist. LO stability Image Rej. I-V LCR/Z Gain/Flat. Comprn Phase/GD M-PM Isolation Rtn Ls/VSWR Impedance S-parameters bsol. Power Gain/Flatness NF NF RFIC test Intermodulation Distortion Measurement plane ER EVM CP Regrowth Constell. Eye Full call sequence Pulsed S-parm. Pulse profiling DC CW Swept Swept Noise -tone Multi- Complex Pulsed- Protocol freq power tone modulation Simple RF Stimulus type Complex Lightwave nalogy to RF Energy Why Do We Need to Test Components? Transmitted Verify specifications of building blocks for more complex RF systems Ensure distortionless transmission of communications signals Lightwave linear: constant amplitude, linear phase / constant group delay nonlinear: harmonics, intermodulation, compression, Mto-PM conversion Ensure good match when absorbing power (e.g., an antenna RF KPWR FM 97

2 The Need for oth Magnitude and Phase genda. Complete characterization of linear networks. Complex impedance needed to design matching circuits 3. Complex values needed for device modeling ase S S S S High-frequency transistor model Emitter Collector 4. -domain characterization Mag 5. Vector-error correction Measured Error ctual What measurements do we make? Transmission-line basics Reflection and transmission parameters S-parameter definition Network analyzer hardware Signal separation devices Detection types Dynamic range T/R versus S-parameter test sets Error models and calibration Types of measurement error One- and two-port models Error-correction choices asic uncertainty calculations Example measurements ppendix Transmission Line asics Low frequencies wavelengths >> wire length current (I travels down wires easily for efficient power transmission measured voltage and current not dependent on position along wire High frequencies + - I wavelength or << length of transmission medium need transmission lines for efficient power transmission matching to characteristic impedance (Zo is very important for low reflection and maximum power transfer measured envelope voltage dependent on Transmission line Zo Zo determines relationship between voltage and current waves Zo is a function of physical dimensions and ε r Zo is usually a real impedance (e.g. 50 or 75 ohms Twisted-pair Coaxial a b w Coplanar w εr Waveguide h w Microstrip h normalized values ohm standard power handling capacity peaks at 30 ohms attenuation is lowest at 77 ohms characteristic impedance for coaxial airlines (ohms Power Transfer Efficiency Transmission Line Terminated with Zo Load Power (normalized RS RL / RS Maximum power is transferred when RL = RS RL For complex impedances, maximum power transfer occurs when ZL = ZS* (conjugate match Rs +jx -jx RL V inc Zs = Zo For reflection, a transmission line terminated in Zo behaves like an infinitely long transmission line Zo = characteristic impedance of transmission line Zo Vrefl = 0! (all the incident power is absorbed in the load

3 . Transmission Line Terminated with Short, Open Transmission Line Terminated with 5 Ω Zs = Zo Zs = Zo ZL = 5 Ω V inc V inc Vrefl In-phase (0 o for open, out-of-phase (80 o for short For reflection, a transmission line terminated in a short or open reflects all power back to source Standing wave pattern does not go to zero as with short or open Vrefl SWR High- Device Characterization S-Parameters S, S R REFLECTION = Reflection Coefficient Γ, ρ R Return Loss Impedance, dmittance R+jX, G+j Gain / Loss S-Parameters S, S TRNSMISSION Transmitted Transmitted = Transmission Coefficient Τ,τ R Insertion Phase Group Delay Reflection Parameters Reflection Coefficient No reflection (ZL = Zo 0 ρ d RL 0 d VSWR = V reflected Γ = ρ V incident Φ Return loss = -0 log(ρ, ρ = Γ = Z L Z O Z L + ZO Voltage Standing Wave Emax Ratio Emin Emax VSWR = Emin = + ρ - ρ Full reflection (ZL = open, short Smith Chart Review Transmission Parameters +jx 0 +R -jx Rectilinear impedance plane Smith Chart maps rectilinear impedance plane onto polar plane 0 Z L= Zo Γ = 0 Z L= 0 Γ Polar plane 90 o o. -90 o (short Z L = = ±80 O Smith chart Constant X Γ 0 o Constant R = 0 O (open V Transmission Coefficient = Τ = V Trans Insertion Loss (d = - 0 Log V Inc V Trans Gain (d = 0 Log V Inc V Transmitted V Transmitted V = 0 log τ = - 0 log τ = τ φ 3

4 Linear Versus Nonlinear ehavior f Sin 360 o * f * t Input f to f * Sin 360 o * f (t - t o phase shift = to * 360 o * f Output Linear behavior: input and output frequencies are the same (no additional frequencies created output frequency only undergoes magnitude and phase change Nonlinear behavior: output frequency may undergo frequency shift (e.g. with mixers additional frequencies created (harmonics, intermodulation Magnitude Criteria for Distortionless Transmission Linear Networks Constant amplitude over bandwidth of interest Phase Linear phase over bandwidth of interest Magnitude Variation with F(t = sin wt + /3 sin 3wt + /5 sin 5wt Phase Variation with F(t = sin wt + /3 sin 3wt + /5 sin 5wt Linear Network Magnitude Linear Network Magnitude Phase 45 /Div o Deviation from Linear Phase RF filter response Low resolution Use electrical delay to remove linear portion of phase response Linear electrical length added (Electrical delay function + yields Deviation from linear phase Phase /Div o High resolution Phaseφ φ ω φ Group Delay φ Group Delay (t g = d φ d ω = d φ 360 o * d f in radians in radians/sec in degrees f in Hertz (ω = π f ω ω t g t o Group delay ripple verage delay group-delay ripple indicates phase distortion average delay indicates electrical length of aperture of measurement is very important 4

5 Why Measure Group Delay? Characterizing Unknown Devices Phase d φ d ω f Phase d φ d ω f Using parameters (H, Y, Z, S to characterize devices: gives linear behavioral model of our device measure parameters (e.g. voltage and current versus frequency under various source and load conditions (e.g. short and open circuits compute device parameters from measured data predict H-parameters circuit performance Y-parameters under any source Z-parameters and load conditions V = hi + hv I = yv + yv V = zi + zi Group Delay Group Delay I = hi + hv I = yv + yv V = zi + zi f Same p-p phase ripple can result in different group delay f h = V I V=0 h = V V I=0 (requires short circuit (requires open circuit Why Use S-Parameters? relatively easy to obtain at high frequencies measure voltage traveling waves with a vector network analyzer dont 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 S Transmitted files in our electronicsimulation tools S a b S Port Port b a Transmitted S b = S a + S a b = S a + S a Forward S = S Measuring S-Parameters = Transmitted Z 0 Load S b Transmitted a Z S 0 Load b a = 0 a = 0 b = b a a = 0 = b a a = 0 Transmitted S S = S = Transmitted S = b a a = 0 = b a b a a = 0 Reverse Equating S-Parameters with Common Measurement Terms S = forward reflection coefficient (input match S = reverse reflection coefficient (output match S = forward transmission coefficient (gain or loss S = reverse transmission coefficient (isolation Criteria for Distortionless Transmission Nonlinear Networks Saturation, crossover, intermodulation, and other nonlinear effects can cause signal distortion Effect on system depends on amount and type of distortion and system architecture Remember, S-parameters are inherently complex, linear quantities -- however, we often express them in a log-magnitude format 5

6 8563 SPECTRUM NLYZER 9 khz -6.5 GHz INCIDENT (R REFLECTED ( TRNSMITTED ( SPECTRUM NLYZER 9 khz GHz. Measuring Nonlinear ehavior Most common measurements: using a network analyzer and power sweeps gain compression M to PM conversion using a spectrum analyzer + source(s harmonics, particularly second and third intermodulation products resulting from two or more RF carriers LPF LPF RL 0 dm TTEN 0 d 0 d / DIV CENTER MHz SPN 0.00 khz R 30 Hz V 30 Hz ST 0 sec mplitude Ratio What is the Difference etween Network and Spectrum nalyzers? Measures known signal Network analyzers: measure components, devices, circuits, sub-assemblies contain source and receiver display ratioed amplitude and phase (frequency or power sweeps offer advanced error correction mplitude Spectrum analyzers: Measures unknown signals measure signal amplitude characteristics carrier level, sidebands, harmonics... can demodulate (& measure complex signals are receivers only (single channel can be used for scalar component test (no phase with tracking gen. or ext. source(s genda What measurements do we make? Network analyzer hardware Error models and calibration Example measurements ppendix Generalized Network nalyzer lock Diagram SOURCE SIGNL SEPRTION Transmitted INCIDENT (R REFLECTED ( TRNSMITTED ( RECEIVER / DETECTOR PROCESSOR / DISPLY Signal Separation SOURCE Transmitted SIGNL SEPRTION Supplies stimulus for system Swept frequency or power Traditionally Ns used separate source Most gilent analyzers sold today have integrated, synthesized sources measure incident signal for reference separate incident and reflected signals splitter RECEIVER / DETECTOR PROCESSOR / DISPLY bridge directional coupler Detector Test Port 6

7 INCIDENT (R REFLECTED ( TRNSMITTED ( Directivity Directivity is a measure of how well a coupler can separate signals moving in opposite directions 0 Interaction of Directivity with the (Without Error rection RL = 40 d Data Max (undesired leakage signal (desired reflected signal Return Loss 30 Device Directivity dd in-phase 60 Directional Coupler Test port Directivity Device Data Min dd out-of-phase (cancellation Directivity Device Data = Vector Sum Detector Types Diode Scalar broadband (no phase information SOURCE Transmitted SIGNL SEPRTION RECEIVER / DETECTOR roadband Diode Detection DC RF C Tuned Receiver RF IF = F LO ± F RF DC / DSP IF Filter PROCESSOR / DISPLY Vector (magnitude and phase Easy to make broadband Inexpensive compared to tuned receiver Good for measuring frequency-translating devices Improve dynamic range by increasing power Medium sensitivity / dynamic range LO 0 MHz 6.5 GHz Narrowband Detection - Tuned Receiver Comparison of Receiver Techniques DC / DSP est sensitivity / dynamic range Provides harmonic / spurious signal rejection Improve dynamic range by increasing power, decreasing IF bandwidth, or averaging Trade off noise floor and measurement speed 0 d -50 d -00 d roadband (diode detection -60 dm Sensitivity higher noise floor false responses 0 d -50 d -00 d Narrowband (tuned-receiver detection < -00 dm Sensitivity high dynamic range harmonic immunity 0 MHz 6.5 GHz Dynamic range = maximum receiver power - receiver noise floor 7

8 INCIDENT (R REFLECTED ( TRNSMITTED ( H ld C or R m P H ld C or 50 MH-0GHz NETWORK NYZER C H S T R T MH z z MH T R T S H C D uplex er T est - Tx - nt and nt -Rx R m P H S log M G R E F 0 d 0 d/ C C H S log M G 0 d/ R E F 0 d PORT S TO P MH z z MH P TO S M H z P S S P S S M H z _ d d _ CTIVE CHNNEL RESPONSE STIMULUS INSTRUMENT STTE T HP-I STTUS PORT ENTRY R L R CHNNEL S Dynamic Range and ccuracy T/R Versus S-Parameter Test Sets 00 Error Due to Interfering Signal Transmission/Reflection Test Set S-Parameter Test Set 0 - Transfer switch Error (d, deg 0. + magn error phase error Dynamic range is very important for measurement accuracy! R R Port Port Port Port 0.0 Fwd Fwd Rev Interfering signal (d RF always comes out port port is always receiver response, one-port cal available RF comes out port or port forward and reverse measurements two-port calibration possible Processor / Display Internal Measurement utomation SOURCE markers limit lines SIGNL SEPRTION RECEIVER / DETECTOR PROCESSOR / DISPLY Transmitted pass/fail indicators linear/log formats grid/polar/smith charts CH STRT MHz STOP MHz CH MHz MHz STOP STRT Hld PSS PRm MHz PSS Hld Test - Tx-nt and nt-rx Duplexer PRm MHz S d _ CH d/ 0 d 0 REF MG log d _ d 0 REF d/ 0 MG log S CH Simple: recall states More powerful: Test sequencing available on 8753/ 870 families keystroke recording some advanced functions ISIC available on 87 family sophisticated programs custom user interfaces CDEFGHIJKLMNOPQRSTUVWXYZ / * = < > ( & "" ",. /? ; : [ ] TO 800 *WI" 3 OFF;*WI" 4 SSTOP" 5 CSPN" HZ;*WI" 7 OFF;:INIT;*WI" 8 ONCE" 9 ON" 0 WID" ON; *WI" XFR:POW:RT,0;DET NN; *WI" 3 OFF;:INIT;*WI" 4 ONCE" 5 ON;*WI" 6 END gilent s Series of HF Vector nalyzers Microwave 870ET/ES series 3.5, 0, 40 GHz economical fast, small, integrated test mixers, high-power amps 850C series 0 GHz in coax highest accuracy modular, flexible pulse systems Tx/Rx module test gilent s LF/RF Vector nalyzers Combination N / S 4395/ MHz (4395,.8 GHz (4396 impedance-measuring option fast, FFT-based spectrum analysis time-gated spectrum-analyzer option ISIC standard test fixtures RF 87ET/ES series.3, 3 GHz low cost narrowband and broadband detection ISIC / LN 8753ET/ES series 3, 6 GHz highest RF accuracy flexible hardware more features Offset and harmonic RF sweeps LF E500/ 80, 300 MHz economical fast, small target markets: crystals, resonators, filters equivalent-circuit models evaporation-monitor-function option 8

9 8563 SPECTRUM NLYZER 9 khz -6.5 GHz Spectrum nalyzer / Tracking Generator genda RF in TG out LO IF f = IF Spectrum analyzer Tracking generator Key differences from network analyzer: one channel -- no ratioed or phase measurements More expensive than scalar N (but better dynamic range Only error correction available is normalization (and possibly open-short averaging Poorer accuracy Small incremental cost if S is required for other measurements What measurements do we make? Network analyzer hardware Error models and calibration Example measurements ppendix Why do we even need error-correction and calibration? It is impossible to make perfect hardware It would be extremely expensive to make hardware good enough to eliminate the need for error correction Calibration Topics What measurements do we make? Network analyzer hardware Error models and calibration measurement errors what is vector error correction? calibration types accuracy examples calibration considerations Example measurements ppendix Measurement Error Modeling CL RE-CL 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 Measured Data Errors: SYSTEMTIC RNDOM Unknown Device DRIFT Systematic Measurement Errors Directivity response reflection tracking (/R transmission tracking (/R R Mismatch Crosstalk Six forward and six reverse error terms yields error terms for twoport devices Load Mismatch Types of Error rection response (normalization simple to perform only corrects for tracking errors stores reference trace in memory, thru then does data divided by memory vector requires more standards requires an analyzer that can measure phase accounts for all major sources of systematic error S a S m SHORT OPEN LOD thru 9

10 S m E D E RT S E RT E D E S E L E L E TT S m E X S m E X m E S E RT E S S E RT E S S E RT E S S a S TT E X S m E D E m S E TT m D RT S E L E L E m E X E S RT E RT E D E S E L E TT S m E X S m E X E m S E RT L E TT E m E X S m E X S E S E RT E S E L E L S m E X RT E S E L E E L S m E X What is Vector-Error rection? Reflection: One-Port Model Process of characterizing systematic error terms measure known standards remove effects from subsequent measurements -port calibration (reflection measurements only 3 systematic error terms measured directivity, source match, and reflection tracking Full -port calibration (reflection and transmission measurements systematic error terms measured usually requires measurements on four known standards (SOLT Standards defined in cal kit definition file network analyzer contains standard cal kit definitions CL KIT DEFINITION MUST MTCH CTUL CL KIT USED! User-built standards must be characterized and entered into user cal-kit RF in S M Ideal S RF in S M To solve for error terms, we measure 3 standards to generate 3 equations and 3 unknowns Error dapter E D E RT E S S SM = ED + E D E RT E S = Directivity = Reflection tracking = Match S M = Measured S = ctual ssumes good termination at port two if testing two-port devices If using port of N and reverse isolation is low (e.g., filter passband: assumption of good termination is not valid two-port error correction yields better results ERT S - ES S Return Loss (d efore and fter One-Port Calibration data before -port calibration data after -port calibration MHz VSWR ED ES a ERT ED ES ERT b Two-Port Error rection ED ES ERT = fwd directivity = fwd source match = fwd reflection tracking = rev directivity = rev source match = rev reflection tracking Each actual S-parameter is a function of all four measured S-parameters nalyzer must make forward and reverse sweep to update any one S- parameter Luckily, you dont need to know these equations to use network analyzers!!! Forward model Port EX Port S EL S ETT EX EL S ETT EX S E TT E L a b = fwd load match = fwd transmission tracking = fwd isolation = rev load match = rev transmission tracking = rev isolation a b a S a S = = = E TT ( + E L ( ( m E D + S a = S + ( ( ED m S ( Reverse model Port Port E RT m E D S m D + + ( ( E S m D + + ( ( E S ( + ( S + ( + S S EX m S ES ERT E D TT E ( ( E TT ( m D ( E S E TT E TT m D m X ( ( E S E E RT ( ( m X E S E L + E S E S RT S E L E E + ( ( ( E TT E TT E ( ( X m S D E m TT E ( ( E D E TT ( ( m S E TT b a E X Crosstalk: Signal Leakage etween Test Ports During Transmission Can be a problem with: high-isolation devices (e.g., switch in open position high-dynamic range devices (some filter stopbands Isolation calibration adds noise to error model (measuring near noise floor of system only perform if really needed (use averaging if necessary if crosstalk is independent of match, use two terminations if dependent on match, use with termination on output LOD LOD Convenient Generally not accurate No errors removed Errors and Calibration Standards UNCORRECTED RESPONSE -PORT FULL -PORT thru Easy to perform Use when highest accuracy is not required Removes frequency response error ENHNCED-RESPONSE Combines response and -port rects source match for transmission measurements SHORT OPEN LOD For reflection measurements Need good termination for high accuracy with twoport devices Removes these errors: Directivity match Reflection tracking SHORT OPEN LOD thru SHORT OPEN LOD Highest accuracy Removes these errors: Directivity, load match Reflection tracking Transmission tracking Crosstalk 0

11 Calibration Summary Reflection Example Using a One-Port Cal Reflection Reflection tracking Directivity match Load match * Test Set (cal type T/R (one-port error can be corrected error cannot be corrected enhanced response cal corrects for source match during transmission measurements S-parameter (two-port Transmission Transmission Tracking Crosstalk SHORT match Load match OPEN * ( LOD Test Set (cal type T/R S-parameter (response, isolation (two-port Directivity: 40 d ( (.89(.6(.89 =.00 Load match: 8 d (.6 6 d RL (.58 d loss (.89 Remember: convert all d values to linear for uncertainty calculations! ρ or loss (linear = 0 -d ( Measurement uncertainty: -0 * log ( =.4 d (-4.6d -0 * log ( = 6.4 d (+0.4 d 0 Using a One-Port Cal + ttenuator Directivity: 40 d ( (.89(.36(.6(.36(.89 =.00 (.89(.04(.89 =.09 Worst-case error = =.039 Load match: 8 d (.6 0 d attenuator (.36 SWR =.05 (.04 6 d RL (.58 d loss (.89 Measurement uncertainty: -0 * log ( = 4. d (-.9 d -0 * log ( = 8.5 d (+.5 d Low-loss bi-directional devices generally require two-port calibration for low measurement uncertainty Transmission Example Using Response Cal RL = 8 d (.6 RL = 4 d (.00 Thru calibration (normalization builds error into measurement due to source and load match interaction Calibration Uncertainty = ( ± ρ S ρ L = ( ± (.00(.6 = ± 0. d Filter Measurement with Response Cal Measuring mplifiers with a Response Cal match = 4 d (.00 d loss (.89 6 d RL (.58 Load match = 8 d (.6 match = 4 d (.00 6 d RL (.58 Load match = 8 d (.6 (.6(.58 =.00 (.6(.89(.00(.89 =.00 (.6(.58 =.00 Total measurement uncertainty: = d = d (.58(.00 =.03 Measurement uncertainty = ± ( = ±.07 = d d Total measurement uncertainty: = d = d (.58(.00 =.03 Measurement uncertainty = ± ( = ±.05 = d d

12 match = 35 d (.078 Filter Measurements using the Enhanced Response Calibration Effective source match = 35 d! d loss (.89 6 d RL (.58 Calibration Uncertainty = ( ± ρ S ρ L = ( ± (.078(.6 = ±.0 d Load match = 8 d (.6 Measurement uncertainty = ± ( (.6(.58 =.00 = ±.046 = + 0. d (.6(.89(.078(.89 = d (.58(.078 =.008 match = 35 d (.078 Using the Enhanced Response Calibration Plus an ttenuator Calibration Uncertainty = ( ± ρ S ρ L = ( ± (.078(.0366 = ±.0 d d loss (.89 6 d RL (.58 Effective load match = (.36(.36( =.0366 (8.7d 0 d attenuator (.36 SWR =.05 (.04 linear or 3.4 d nalyzer load match =8 d (.6 (.0366(.58 =.006 (.0366(.89(.078(.89 =.0005 (.58(.078 =.008 Measurement uncertainty = ± ( = ±.0093 = ± 0.08 d Total measurement uncertainty: = ± 0.4 d Total measurement uncertainty: = ± 0.09 d Calculating Measurement Uncertainty fter a Two-Port Calibration rected error terms: (8753ES.3-3 GHz Type-N Directivity = 47 d match = 36 d Load match = 47 d Refl. tracking =.09 d Trans. tracking =.06 d Isolation = 00 d Transmission uncertainty d loss (.89 6 d RL (.58 Reflection uncertainty S m = S a ± ( ED + S a ES + S as ael + S a( ERT = 058. ± ( * * *. 00 = 0.58 ±.0088 = 6 d d, d (worst-case S = S ± S ( E / S + S E + S S E E + S E + ( E m a a a a a I S a S L a L TT 6 = 089. ± 089. ( 0 / * *. 058* * = 0.89 ±.0056 = d ±0.05 d (worst-case Response versus Two-Port Calibration Measuring filter insertion loss CH S&M log MG d/ REF 0 d CH MEM log MG d/ REF 0 d fter two-port calibration fter response calibration Uncorrected x STRT MHz STOP MHz ECal: Electronic Calibration (85060/90 series Variety of modules cover 30 khz to 6.5 GHz Six connector types available (50 Ω and 75 Ω 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 Electronic Calibration Module 30 khz - 6 GHz Microwave modules use a transmission line shunted by PIN-diode switches in various combinations dapter Considerations reflection from adapter leakage signal Coupler directivity = 40 d Worst-case System Directivity 8 d 7 d desired signal ρ measured = Directivity + ρ adapter + ρ dapter dapting from PC-7 to SM (m PC-7 to SM (m SWR:.06 PC-7 to N (f + N (m to SM (m SWR:.05 SWR:.5 Termination has SM (f connectors PC-7 calibration done here 4 d PC-7 to N (m + N (f to SM (f + SM (m to (m SWR:.05 SWR:.5 SWR:.5

13 Calibrating Non-Insertable Devices Swap Equal dapters Method 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. PC-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 Port Port dapter Port Port Port dapter Port Port dapter Port ccuracy depends on how well the adapters are matched - loss, electrical length, match and impedance should all be equal. Transmission cal using adapter.. Reflection cal using adapter. 3. Measure using adapter. dapter Removal Calibration Calibration is very accurate and traceable In firmware of 8753, 870 and 850 series lso accomplished with ECal modules (85060/90 Uses adapter with same connectors as Must specify electrical length of adapter to within /4 wavelength of highest frequency (to avoid phase ambiguity Cal Port dapter Port dapter Cal Set Cal Port dapter Port dapter Cal Set [CL] [MORE] [MODIFY CL SET] [DPTER REMOVL] Port Port. Perform -port cal with adapter on port. Save in cal set.. Perform -port cal with adapter on port. Save in cal set. 3. Use DPTER REMOVL to generate new cal set. Thru-Reflect-Line (TRL Calibration We know about Short-Open-Load-Thru (SOLT calibration... What is TRL? two-port calibration technique Good for noncoaxial environments (waveguide, fixtures, wafer probing Uses the same -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 Port dapter Port 4. Measure without cal adapter. genda CH S Sweep - Filter Test log MG 0 d/ REF 0 d CH S log MG 5 d/ REF 0 d What measurements do we make? Network analyzer hardware Error models and calibration Example measurements ppendix 69. d Stopba nd rejectio n STRT MHz STOP MHz CENTER MHz CH S log MG d/ REF 0 d m: GHz d m-ref: GHz 0.00 d ref SPN MHz Return loss Insertion loss x STRT MHz STOP MHz 3

14 0 Optimize Filter Measurements with Swept-List Mode Power Sweeps - Compression Segment 3: 9 ms (08 points, -0 dm, 6000 Hz CH S log MG d/ REF 0 d PRm Linear sweep: 676 ms (0 pts, 300 Hz, -0 dm Segment : 87 ms (5 points, +0 dm, 300 Hz Swept-list sweep: 349 ms (0 pts, variable Ws & power PSS Segment 5: 9 ms (38 points, +0 dm, 300 Hz Output Power (dm Compression region Linear region (slope = small-signal gain Saturated output power STRT MHz STOP MHz Segments,4: 5 ms (5 points, +0 dm, 300 Hz Input Power (dm Power Sweep - Gain Compression CH S og MG d/ REF 3 d d.3 dm STRT -0 dm CW 90.7 MHz STOP 5 dm d compression: input power resulting in d drop in gain M (d PM (deg mplitude M to PM Conversion Measure of phase deviation caused by amplitude variations Power sweep Test Stimulus M - PM Conversion = Mag(Pm out Mag(m (deg/d in M (d PM (deg Mag(m i n mplitude Output Response Mag(M o ut Mag(Pm o ut M can be undesired: supply ripple, fading, thermal M can be desired: modulation (e.g. QM Q M to PM conversion can cause bit errors I Measuring M to PM Conversion :Transmission Log Mag.0 d/ Ref -5.7 deg :Transmission /M Phase 5.0 deg/ Ref.50 d Ch:Mkr dm 0.48 d Ch:Mkr.00 d 0.86 deg Start dm Start dm CW MHz CW MHz Stop 0.00 dm Stop 0.00 dm Use transmission setup with a power sweep Display phase of S M - PM = 0.86 deg/d genda What measurements do we make? Network analyzer hardware Error models and calibration Example measurements ppendix dvanced Topics time domain frequency-translating devices high-power amplifiers extended dynamic range multiport devices in-fixture measurements crystal resonators balanced/differential Inside the network analyzer Challenge quiz! 4

15 impedance -Domain Reflectometry (TDR Zo What is TDR? time-domain reflectometry analyze impedance versus time distinguish between inductive and capacitive transitions With gating: analyze transitions inductive analyzer standards transition capacitive transition non-zo transmission line time TDR asics Using a Network nalyzer Domain t 0F(t*dt start with broadband frequency sweep (often requires microwave VN use inverse-fourier transform to compute time-domain resolution inversely proportionate to frequency span TDR t t F - Integrate F - Domain /s*f(s f f CH S Re 50 mu/ REF 0 U CH STRT 0 s 0 GHz 6 GHz STOP.5 ns -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 CH S&M log MG 5 d/ REF 0 d Use two-port calibration CH MEM Re 0 mu/ REF 0 U PRm RISE TIME ps 8.99 mm CH STRT 0 s 3 : mu 638 ps : 4.96 mu 668 ps 3: mu 7 ps Thru in time domain STOP.5 ns PRm Gate : d GHz : d GHz Thru in frequency domain, with and without gating STRT GHz STOP GHz Ten Steps for Performing TDR. Set up desired frequency range (need wide span for good spatial resolution. Under SYSTEM, transform menu, press "set freq low pass" 3. Perform one- or two-port calibration 4. Select S measurement * 5. Turn on transform (low pass step * 6. Set format to real * 7. djust transform window to trade off rise time with ringing and overshoot * 8. djust start and stop times if desired 9. For gating: set start and stop frequencies for gate turn gating on * adjust gate shape to trade off resolution with ripple * 0. To display gated response in frequency domain turn transform off (leave gating on * change format to log-magnitude * * If using two channels (even if coupled, these parameters must be set independently for second channel -Domain Transmission RF Input -Domain Filter Tuning Triple Travel RF Output Main Wave Leakage CH S log MG 0 d/ REF 0 d Gate off CH S log MG RF Leakage 5 d/ REF 0 d Surface Wave Triple Travel Deterministic method used for tuning cavity-resonator filters Traditional frequency-domain tuning is very difficult: lots of training needed may take 0 to 90 minutes to tune a single filter Need VN with fast sweep speeds and fast time-domain processing Gate on STRT - us STOP 6 us 5

16 PRm Hld PRm Hld log M G 0 d/ REF 0 d _ d CH S log M G 0 d/ REF 0 d _ d CH ST RT MHz CH ST RT MHz MHz MHz PSS PSS STOP MHz STOP MHz Filter Reflection in Domain Tuning Resonator #3 Set analyzer s center frequency = center frequency of the filter Measure S or S in the time domain Nulls in the time-domain response correspond to individual resonators in filter Easier to identify mistuned resonator in time-domain: null #3 is missing Hard to tell which resonator is mistuned from frequency-domain response djust resonators by minimizing null djust coupling apertures using the peaks in-between the dips -Translating Devices Medium-dynamic range measurements (35 d 8753ES Ref In FREQ OFFS ON off LO MENU 8753ES High-dynamic range measurements (00 d High-Power mplifiers Ref In 8753ES Preamp ttenuator Filter ttenuator DOWN CONVERTER UP CONVERTER RF > LO Ref out Ref in Reference mixer Preamp UT R Start: 900 MHz Start: 00 MHz Stop: 650 MHz Stop: 350 MHz Fixed LO: GHz RF < LO VIEW MESURE Filter ttenuator LO power: 3 dm RETURN CH CONV MES log MG 0 d/ REF 0 d ttenuat or ttenuator UT +43 dm max input (0 watts! 870ES Option 085 STRT MHz STOP MHz ESG-D4000 Powe r splitt er 858 High-Power mplifier Test System High-Dynamic Range Measurements Multiport Device Test CH MEM LOG 5 d/ REF 3 d CH MEM LOG 5 d/ REF 3 d PRm vg 0 PRm vg 0 Standard 8753ES 8753ES Special Option H6 CH S 8753 H39 Duplexer Test - Tx-nt and nt-rx Multiport analyzers and test sets: improve throughput by reducing the number of connections to s with more than two ports allow simultaneous viewing of two paths (good for tuning duplexers include mechanical or solid-state switches, 50 or 75 ohms degrade raw performance so calibration is a must (use two-port cals whenever possible gilent offers a variety of standard and custom multiport analyzers and test sets CH CH STRT MHz STRT MHz STOP MHz STOP MHz 6

17 Ch Z: R phase 40 / REF 0 : 5.6 U STRT MHz INCIDENT (R MHz Min STOP MHz REFLECTED ( TRNSMITTED ( 87050E/87075C Standard Multiport Test Sets Test Set Cal Eliminates Redundant Connections of Calibration Standards Once a month: perform a Test Set Cal with external standards to remove systematic errors in the analyzer, test set, cables, and fixture Test Set Cal SelfCal -port Reflection Connections -port Through Connections Fixture 8-port 8-port For use with 87E family 50 Ω: 3 MHz to. GHz, 4, 8, or ports 75 Ω: 3 MHz to.3 GHz, 6 or ports Once an hour: automatically perform a SelfCal using internal standards to remove systematic errors in the analyzer and test set Test Set Cal and SelfCal dramatically improve calibration times Systems offer fully-specified performance at test ports 4-port 4-port Test Set Cal Traditional VN Calibration In-Fixture Measurements Measurement problem: coaxial calibration plane is not the same as the in-fixture measurement plane Characterizing Crystal Resonators/Filters E500/ Network nalyzer Calibration plane Measurement plane Fixture E D E S SEG STRT STOP POINTS POWER IFW MHz MHz 00 0 dm 00Hz E T Error correction with coaxial calibration Loss Phase shift Mismatch > END 3.05 MHz MHz 00 Example of crystal resonator measurement 0 dm 00Hz alanced-device Measurements TN-4000 series (4-port test set + software measure tough singled-ended devices like couplers measure fully-balanced or single-ended-to-balanced s characterize mode conversions (e.g. common-to-differential incorporates 4-port error correction for exceptional accuracy works with 8753ES and 870ES analyzers more info at Traditional Scalar nalyzer Example: 8757D/E processor/display source SOURCE requires external detectors, couplers, bridges, splitters good for low-cost microwave scalar applications SIGNL SEPRTION RECEIVER / DETECTOR PROCESSOR / DISPLY Transmitted RF R RF R Channel Partner Reflection Detector ridge Termination Detector Detector Transmission 7

18 INCIDENT (R REFLECTED ( TRNSMITTED ( Directional Coupler Directivity One Method of Measuring Coupler Directivity 50 d Directivity = Coupling Factor (fwd x Loss (through arm Isolation (rev Directivity (d = Isolation (d - Coupling Factor (d - Loss (d 0 d Test port Examples: Directivity = 50 d - 0 d = 30 d Coupler Directivity 35 d (.08.0 (0 d (reference short 50 d 30 d 0 d Test port Directivity = 50 d - 30 d - 0 d = 0 d.08 (35 d (normalized Directivity = 35 d - 0 d = 35 d 60 d 0 d 0 d Test port Directivity = 60 d - 0 d - 0 d = 30 d load ssume perfect load (no reflection 50 Ω 50 Ω Directional ridge Detector 50 Ω Test Port 50-ohm load at test port balances the bridge -- detector reads zero Non-50-ohm load imbalances bridge Measuring magnitude and phase of imbalance gives complex impedance "Directivity" is difference between maximum and minimum balance N Hardware: Front Ends, Mixers Versus Samplers DC / DSP Mixer-based front end It is cheaper and easier to make broadband front ends using samplers instead of mixers SOURCE Sampler-based front end S Harmonic generator DC / DSP SIGNL SEPRTION RECEIVER / DETECTOR PROCESSOR / DISPLY f frequency "comb" Transmitted Three Versus Four-Receiver nalyzers Why re Four Receivers etter Than Three? TRL TRL* Transfer switch Transfer switch 870ES Option 400 adds fourth sampler, allowing full TRL calibration R Port Port 3 receivers more economical TRL*, LRM* cals only includes: 8753ES 870ES (standard Port R R Port 4 receivers more expensive true TRL, LRM cals includes: 870ES (option C TRL* assumes the source and load match of a test port are equal (port symmetry between forward and reverse measurements this is only a fair assumption for three-receiver network analyzers TRL four receivers are necessary to make the required measurements TRL and TRL* use identical calibration standards In noncoaxial applications, TRL achieves better source and load match correction than TRL* What about coaxial applications? SOLT is usually the preferred calibration method coaxial TRL can be more accurate than SOLT, but not commonly used 8

19 Challenge Quiz. Can filters cause distortion in communications systems?. Yes, due to impairment of phase and magnitude response. Yes, due to nonlinear components such as ferrite inductors C. No, only active devices can cause distortion D. No, filters only cause linear phase shifts E. oth and above. Which statement about transmission lines is false?. Useful for efficient transmission of RF power. Requires termination in characteristic impedance for low VSWR C. Envelope voltage of RF signal is independent of position along line D. Used when wavelength of signal is small compared to length of line E. Can be realized in a variety of forms such as coaxial, waveguide, microstrip 3. Which statement about narrowband detection is false?. Is generally the cheapest way to detect microwave signals. Provides much greater dynamic range than diode detection C. Uses variable-bandwidth IF filters to set analyzer noise floor D. Provides rejection of harmonic and spurious signals E. Uses mixers or samplers as downconverters Challenge Quiz (continued 4. Maximum dynamic range with narrowband detection is defined as:. Maximum receiver input power minus the stopband of the device under test. Maximum receiver input power minus the receivers noise floor C. Detector -d-compression point minus the harmonic level of the source D. Receiver damage level plus the maximum source output power E. Maximum source output power minus the receivers noise floor 5. With a T/R analyzer, the following error terms can be corrected:. match, load match, transmission tracking. Load match, reflection tracking, transmission tracking C. match, reflection tracking, transmission tracking D. Directivity, source match, load match E. Directivity, reflection tracking, load match 6. Calibration(s can remove which of the following types of measurement error?. Systematic and drift. Systematic and random C. Random and drift D. Repeatability and systematic E. Repeatability and drift Challenge Quiz (continued 7. Which statement about TRL calibration is false?. Is a type of two-port error correction. Uses easily fabricated and characterized standards C. Most commonly used in noncoaxial environments D. Is not available on the 870ES family of microwave network analyzers E. Has a special version for three-sampler network analyzers 8. For which component is it hardest to get accurate transmission and reflection measurements when using a T/R network analyzer?. mplifiers because output power causes receiver compression. Cables because load match cannot be corrected C. Filter stopbands because of lack of dynamic range D. Mixers because of lack of broadband detectors E. ttenuators because source match cannot be corrected 9. Power sweeps are good for which measurements?. Gain compression. M to PM conversion C. Saturated output power D. Power linearity E. ll of the above nswers to Challenge Quiz. E. C C D E 9