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Network Analyzer Basics Network Analyzer Basics Copyright 2000 Network Analysis is NOT. … Router Bridge Repeater Hub Your IEEE 802.3 X.25 ISDN switched-packet data stream is running at 147 MBPS with -9 a BER of 1.523 X 10 . . . Network Analyzer Basics Copyright 2000 Lo w Integration High W hat Types of Devices are Tested? Duplexers Diplexers Filters Couplers Bridges Splitters, dividers Co mbiners Isolators Circulators Attenuators Adapters Opens, shorts, loads Delay lines Cables Trans mission lines W aveguide Resonators Dielectrics R, L, C's Passive Network Analyzer Basics RFICs M MICs T/R modules Transceivers Receivers Tuners Converters VC As A m plifiers Antennas S witches M ultiplexers Mixers Sa mplers M ultipliers Diodes Device type VC Os VTFs Oscillators M odulators VC Atten’s Transistors Active Copyright 2000 Co mplex Device Test Measurement Model 84000 RFIC test Ded. Testers VSA Response tool SA Harm. Dist. L O stability Image Rej. VNA SNA NF Mtr. NF Imped. An. Simpl e Full call sequence Pulsed S-parm. Pulse profiling Gain/Flat. Co mpr'n Phase/GD A M-P M Isolation Rtn Ls/VS W R Impedance S-parameters TG/SA Param. An. Intermodulation Distortion NF BER EV M A CP Regrowth Constell. Eye LCR/Z I-V Measure ment plane Absol. Po wer Gain/Flatness Power Mtr. Det/Scope DC CW Swept freq modulation Simple Network Analyzer Basics Swept power RF Noise 2-tone Multi- Stimulus type Complex tone Pulsed- Protocol Co mplex Copyright 2000 Lightwave Analogy to RF Energy Incident Transmitted Reflected Lightwave D UT RF Network Analyzer Basics Copyright 2000 W hy Do W e Need to Test Components? • Verify specifications of “building blocks” for more complex RF systems • Ensure distortionless transmission of com munications signals – linear: constant amplitude,linear phase / constant group delay – nonlinear: harmonics,intermodulation, compression, AMto-PM conversion • Ensure good match when absorbing power (e.g., an antenna) KPWR Network Analyzer Basics FM 97 Copyright 2000 The Need for Both Magnitude and Phase S21 1. Complete characterization of linear networks S11 S22 S12 2. Complex impedance needed to design matching circuits 4. Time-domain characterization Mag 3. Complex values needed for device modeling High-frequency transistor model Time 5. Vector-error correction Error Base Collector Measured E mitter Network Analyzer Basics Actual Copyright 2000 Agenda ● ● ● ● ● Network Analyzer Basics W hat measurem ents do we make? ➨ Transmiss ion-line basics ➨ Ref lection and transmission parameters ➨ S-parameter def inition Network analyzer hardware ➨ Signal separat ion devices ➨ Detect ion types ➨ Dynamic range ➨ T/R versus S-parameter tes t sets Error models and calibration ➨ Types of measurement er ror ➨ One- and two-por t models ➨ Error -correction choices ➨ Basic uncer tainty calculations Exa mple measurements Appendix Copyright 2000 Transmission Line Basics + I - Low frequencies re length ● wavelengths >> wi I)travels down wires easily for efficient ● current ( power transmission ltage and current not dependent on ● measured vo position along wire High frequencies r << length oftransmission ● wavelength ≈ o medium ransmission lines for efficient power ● need t transmission isticimpedance (Zo) is ● matching to character very importantforlow reflection and maximu m Network Analyzer Basics power transfer measured envelope voltage dependenton Copyright 2000 Transmission line Zo • • Zo determines relationship between voltage and current waves Zo is a function of physical dimensions and εr Zo is usually a realimpedance (e.g. 50 or 75 ohms) 1.5 Twiste d-pair attenuation is lowest at 77 ohms 1.4 Wave guide 1.3 a 1.2 b εr Coaxial h normalized values • 1.1 1.0 0.9 0.8 h 0.7 w1 Network Analyzer Basics power handling capacity peaks at 30 ohms 0.6 w w2 Coplanar 50 ohm standard 0.5 10 Microstrip 20 30 40 50 60 70 80 90100 characteristicimpedance for coaxial airlines (ohms) Copyright 2000 Power Transfer Efficiency RS For co mplex im pedances, maximu m power transfer occurs when ZL = ZS* (conjugate match) RL Rs Load Power (normalized) 1.2 +jX 1 -jX 0.8 0.6 RL 0.4 0.2 0 0 1 2 3 4 5 6 7 8 9 10 RL / RS Maximu m power is transferred when RL = RS Network Analyzer Basics Copyright 2000 Transmission Line Terminated with Zo Zs = Zo Zo = characteristic impedance of transmission line Zo V inc Vrefl = 0! (allthe 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 Copyright 2000 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 trans mission line terminated in a short or open reflects all power back to source Network Analyzer Basics Copyright 2000 Transmission Line Terminated with 25 Ω Zs = Zo ZL = 25 Ω V inc Vrefl Standing wave pattern does not go to zero as with short or open Network Analyzer Basics Copyright 2000 High-Frequency Device Characterization Incident Transmitted R B Reflected A TRA NS MISSIO N REFLECTION Reflected Incident = SWR S-Parameters S11, S22 Reflection Coefficient Γ, ρ Network Analyzer Basics A Transmitted R Incident Return Loss Impedance, Ad mittance R+jX, G+jB B = R Group Delay Gain / Loss S-Parameters Transmission S21, S12 Coefficient Τ,τ Insertion Phase Copyright 2000 Reflection Parameters Reflection Coefficient Γ Vreflected = =ρ Vincident Return loss = -20 log(ρ), ρ Φ = ZL − ZO ZL + ZO Γ = E max E min Voltage Standing Wave Ratio E max VS W R = E min = 1+ρ 1-ρ Full reflection (ZL = open, short) No reflection (ZL = Zo) 0 ρ 1 ∞ dB RL 0 dB 1 VS W R ∞ Network Analyzer Basics Copyright 2000 S mith Chart Review . o +jX 90 Polar plane 1.0 .8 .6 0 +R .4 ∞→ + 180o - o .2 0 ∞ 0 -jX -90o Rectilinear impedance plane Constant X Constant R Z L = Zo S mith Chart maps rectilinear impedance plane onto polar plane Network Analyzer Basics Γ= 0 ZL = Z L = 0 (short) Γ= 1 Γ =1 O ±180 (open) 0 S mith chart Copyright 2000 O Transmission Parameters V Incident V Transmitted D UT Transmission Coefficient = VTransmitted Τ V = V Incident Trans Insertion Loss (dB) = - 20 Log V V Gain (dB) = 20 Log V Network Analyzer Basics Trans = - 20 log = τ∠φ τ Inc = 20 log τ Inc Copyright 2000 Linear Versus Nonlinear Behavior A * Sin 360o * f (t - to) A Linear behavior: ● Time to Sin 360o * f * t A Time f 1 D UT Input ● phase shift = to * 360o * f input and output frequencies are the same (no additional frequencies created) output frequency only undergoes magnitude and phase change Frequency Output Nonlinear behavior: f 1 ● Frequency Time ● f Network Analyzer Basics 1 Frequency output frequency may undergo frequency shift (e.g. with mixers) additionalfrequencies created (harmonics, intermodulation) Copyright 2000 Criteria for Distortionless Transmission Linear Networks Linear phase over bandwidth of interest Magnitude Constant amplitude over bandwidth ofinterest Phase Frequency Frequency Network Analyzer Basics Copyright 2000 Magnitude Variation with Frequency F(t) = sin wt + 1/3 sin 3wt + 1/5 sin 5wt Time Time Magnitude Linear Network Frequency Network Analyzer Basics Frequency Frequency Copyright 2000 Phase Variation with Frequency F(t) = sin wt + 1 /3 sin 3wt + 1 /5 sin 5wt Linear Network Time Magnitude Time Frequency 0° Frequency -180 ° Frequency -360 ° Network Analyzer Basics Copyright 2000 Deviation from Linear Phase Use electrical delay to remove linear portion of phase response Phase 45 /Div RF filter response Deviation from linear phase o o (Electrical delay function) + Frequency Low resolution Network Analyzer Basics yields Frequency Phase 1 /Div Linear electricallength added Frequency High resolution Copyright 2000 Group Delay Frequency ω tg Group delay ripple ∆ω to φ Phase Average delay ∆φ Frequency Group Delay (tg)= −d φ dω φ ω φ = −1 360 o dφ *df in radians in radians/sec ● ● ● group-delay ripple indicates phase distortion average delay indicates electricallength of DUT aperture of measurement is very important in degrees f in Hertz (ω = 2 π f) Network Analyzer Basics Copyright 2000 Phase Phase W hy Measure Group Delay? f f φ ω −d φ dω Group Delay Group Delay −d d f f Sa me p-p phase ripple can resultin different group delay Network Analyzer Basics Copyright 2000 Characterizing Unknown Devices Using param eters (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 pred ict circu itperformance under any source andmeters load Y-parameters Z-para H-para meters cond V1 i =tions h11I1 + h12V2 I1 = y11V1 + y12V2 V1 = z11I1 + z12I2 I2 = h21I1 + h22V2 Network Analyzer Basics I2 = y21V1 + y22V2 V2 = z21I1 + z22I2 h11 = V1 I1 V2=0 (requires short circuit) h12 = V1 V2 I1=0 (requires open circuit) Copyright 2000 W hy Use S-Parameters? relatively easy to obtain at high frequencies ltage traveling waves with a vector network analyzer ■ measure vo 't need shorts/opens which can cause active devices to oscillate ■ don or self-destruct late to familiar measurements (gain,loss, reflection coefficient...) ● re f multiple devices to predict system ● can cascade S-parameters o performance rom S-parameters if desired ● can co mpute H, Y, or Z parameters f S 21 Incident Transmi tedin our electronicilyimpor t and use S-parameter filtes ● can eas a1 b2 simulation tools S11 ● D UT Reflected b1 Port 1 Transmitted Port 2 S 12 S 22 Reflected a2 Incident b1 = S 11a1 + S 12 a 2 b2 = S21 a1 + S 22 a 2 Network Analyzer Basics Copyright 2000 Measuring S-Parameters a1 b1 S 11 21 = = Transmitted Incident a2 = 0 b1 = a 1 b = a Load D UT Reflected Reflected Incident b2 Transmitted 21 Z0 S 11 Forward S S Incident a2 = 0 S 22 Reflected Incident = 2 1 a2 = 0 S 12 = Transmitted Incident a1 = 0 Z0 b2 = a 2 b = a a1 = 0 1 2 a1 = 0 b2 D UT Load S 22 Reverse Reflected a2 b 1 Transmitted Network Analyzer Basics S 12 Incident Copyright 2000 Equating S-Parameters with Com mon Measurement Terms S11 S22 S21 S12 = forward reflection coefficient (input match) = reverse reflection coefficient (output m atch) = forward transmission coefficient (gain or loss) = reverse transmission coefficient (isolation) Re me mber, S-para m eters are inherently co mplex, linear quantities -- however, we often express the m in a log-magnitude format Network Analyzer Basics Copyright 2000 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 arch itecture Time Frequency Network Analyzer Basics Time Frequency Copyright 2000 Measuring Nonlinear Behavior Most com m on measurements: ● using a network analyzer and power sweeps ➨ gain compress ion ➨ A M to PM convers ion rum analyzer + ● using a spect source(s) ➨ harmonics, par ticularly second and third ➨ in termodulation products resulting from two or more RF carriers 8563A LPF LPF Network Analyzer Basics SPE CT R U M AN A LYZ E R RL 0 dBm ATTEN 10 dB 10 dB / DIV 9 kHz - 26.5 GHz DUT CENTER 20.00000 MHz RB 30 Hz VB 30 Hz SPAN 10.00 kHz ST 20 sec Copyright 2000 W hat is the Difference Between Network and Spectrum Analyzers? . Measures known signal A mplitude A mplitude Ratio 8563A measure components, devices, circuits, sub-assemblies ● conta in source and receiver ● disp lay ratioed amplitude and phase (frequency or power sweeps) ● of fe rlyzer advanced error Network Ana Basics correction ● 9 kHz - 26.5 Measures unknown signals Frequency Network analyzers: SPE CT R U M AN A LYZ E R G Hz Frequency Spectru m analyzers: ● ● ● ● measure signal amplitude characteristics carrierlevel, sidebands, harmonics...) can demodulate (& measure) complex signals are receivers only (single channel) Copyright can be used for scalar component 2000 test (no h ) itht ki t Agenda ● ● ● ● ● Network Analyzer Basics W hat measurements do we make? Network analyzer hardware Error models and calibration Example measurements Appendix Copyright 2000 Generalized Network Analyzer Block Diagram Incident Transmitted D UT Reflected S O U R CE SIGN AL SEPA R ATION INCIDENT (R) REFLECTED (A) TRA NS MITTED (B) RE CEIVER / DETECTO R PR O CESS O R / DISPLAY Network Analyzer Basics Copyright 2000 Source ● ● ● ● Supplies stimulus for system Swept frequency or power Traditionally NAs used separate source Most Agilent analyzers sold today have integrated, synthesized sources Network Analyzer Basics Copyright 2000 Incident Transmitted D UT Signal Separation Reflected SOURCE SIGN AL SEP A R ATION INCIDENT (R) REFLECTED (A) TRA NS MITTED (B) R E C EIVER / DETECT O R P R O C ESS O R / DISPLAY measure incident signal for reference • separate incident and ref lected signals • splitter bridge directional coupler Network Analyzer Basics Detector Test Port Copyright 2000 Directivity Directivityis a measure of how well a coupler can separate signals moving in opposite directions (undesired leakage signal) (desired reflected signal) Test port Directional Coupler Network Analyzer Basics Copyright 2000 Interaction of Directivity with the D UT (Without Error Correction) 0 Data Max Directivity Device Return Loss D UT RL = 40 dB 30 Add in-phase 60 Network Analyzer Basics Device Device Directivity Frequency Data Min Add out-of-phase (cancellation) Data = Vector Sum Directivity Copyright 2000 Incident Transmitted Detector Types D UT Reflected SOURCE Diode Scalar broadband (no phase information) SIGN AL SEP A R ATION INCIDENT (R) REFLECTED (A) TRA NS MITTED (B) R E C EIVER / DETECT O R P R O C ESS O R / DISPLAY DC RF AC Tuned Receiver IF = F LO ± F RF RF AD C / DSP Vector (magnitude and phase) IF Filter LO Network Analyzer Basics Copyright 2000 Broadband Diode Detection Easy to make broadband ● Inexpensive compared to tuned receiver ing frequency-translating devices ● Good for measur ing power ● Improve dynamic range by increas tivity / dynamic range ● Mediu m sensi ● 10 MHz 26.5 GHz Network Analyzer Basics Copyright 2000 Narrowband Detection -Tuned Receiver AD C / DSP Best sensitivity / dynamic range ides harmonic / spurious signal ● Prov rejection ing ● Improve dynamic range by increas power, decreasing IF bandwidth, or averaging f noise floor and ● Trade of measurement speed ● 10 MHz Network Analyzer Basics 26.5 GHz Copyright 2000 Co mparison of Receiver Techniques Broadband (diode) detection 0 dB 0 dB -50 dB -50 dB -100 dB -100 dB -60 dBm Sensitivity higher noise floor ● fa lse responses ● Narrowband (tuned-receiver) detection < -100 dBm Sensitivity high dynamic range ● harmonic immuni ty ● Dyna mic range = maximum receiver power receiver noise floor Network Analyzer Basics Copyright 2000 Dynamic Range and Accuracy Error Due to Interfering Signal 100 - Error (dB, deg) 10 + phase error Dyna mic range is very important for measurem ent accuracy! 1 magn error 0.1 0.01 0.001 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 -50 -55 -60 -65 -70 Interfering signal (dB) Network Analyzer Basics Copyright 2000 T/R Versus S-Parameter Test Sets S-Para meter Test Set Trans mission/Reflection Test Set Source Source Transfer switch R R B A Port 1 Port 2 Fwd Port 2 Port 1 Fwd D UT RF always comes out port 1 ● por t 2 is always receiver ● response, one-port ca l Network Analyzer Basics available ● B A ● ● ● D UT Rev RF comes out port 1 or port 2 forward and reverse measurements Copyright two-port calibration 2000 possible Processor / Display Incident Transmitted D UT 50 MH-20GHz NETWORK ANYZER A CTIVE C H A N N EL Reflected CH 1 CH 2 S 21 S 12 log MA G log MA G 10 dB / 10 dB / S O U R CE E NT RY 1_ -1.9248 dB 1_ -1.2468 dB RE F 0 dB RE F 0 dB R ES P O N S E 839.470 000 MH z P Rm Duplexer T est - Tx-Ant and A nt-Rx Cor 1 1 Hld SIGNAL SEP A R ATION P AS S 1 880.435 000 MH z STIMUL US R CHA N N EL INSTR U M E NT STATE P Rm Cor 2 INCIDENT (R) REFLECTED (A) T TRA NS MITTED (B) P AS S Hld HP-IB STAT US CH 1 S T AR T 775.000 000 MH z CH 2 S T AR T 775.000 000 MH z S TO P 925.000 000 MH z S TO P 925.000 000 MH z P O RT 1 P O RT 2 RECEIVER / DETECTO R PR O CESS O R / DISPLAY CH1 CH2 S21 S12 log MAG log MAG 10 dB/ 10 dB/ 1_ -1.9248 dB 1_ -1.2468 dB REF 0 dB REF 0 dB 839.470 000 MHz PRm Duplexer Test - Tx-Ant and Ant-Rx Cor 1 markers ● l imitlines ● pass/ failindicators ● l inear/log formats ● gr id/polar/Smith charts ● Network Analyzer Basics 1 Hld PASS 1 880.435 000 MHz PRm Cor 2 PASS Hld CH1 START 775.000 000 MHz CH2 START 775.000 000 MHz STOP 925.000 000 MHz STOP 925.000 000 MHz Copyright 2000 R L S Internal Measurement Automation Simple: recallstates More powerful: ● Test sequencing ■ ■ ■ ● available on 8753/ 8720 families keystroke recording some advanced functions IBASIC ■ ■ ■ available on 8712 family sophisticated programs custom user interfaces ABC DEF G HIJKLM N O P Q RSTUV W X YZ0123456789 + -/* = < > ( ) & "" ",./ ? ;:'[] 1 ASSIGN @ Hp8714 TO 800 2 OUTPUT @ Hp8714;"SYST:PRES; *WAI" 3 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT OFF;*WAI" 4 OUTPUT @ Hp8714;"DISP:ANN:FRE Q1:M O DE SSTOP" 5 OUTPUT @ Hp8714;"DISP:ANN:FRE Q1:M O DE CSPAN" 6 OUTPUT @ Hp8714;"SENS1:FRE Q:CENT 175000000 HZ;*WAI" 7 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT OFF;:INIT1;*W AI" 8 OUTPUT @ Hp8714;"DISP:WIND1:TRAC:Y:AUTO ONC E" 9 OUTPUT @ Hp8714;"CALC1:MARK1 ON" 10 OUTPUT @ Hp8714;"CALC1:MARK:FUNC B WID" 11 OUTPUT @ Hp8714;"SENS2:STAT ON; *WAI" 12 OUTPUT @ Hp8714;"SENS2:FUNC 'XFR:PO W:RAT 1,0';DET NBAN; *WAI" 13 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT OFF;:INIT1;*W AI" 14 OUTPUT @ Hp8714;"DISP:WIND2:TRAC:Y:AUTO ONC E" 15 OUTPUT @ Hp8714;"ABOR;:INIT1:CONT ON;*WAI" 16 END Network Analyzer Basics Copyright 2000 Agilent’s Series of HF Vector Analyzers Microwave 8510C series 8720ET/ES series ● ● ● ● ● 13.5, 20, 40 GHz economical fast, small,integrated test mixers, high-power amps ● ● ● ● RF 8712ET/ES series ● ● ● ● 1.3, 3 GHz low cost narrowband and broadband detection IBASIC / LAN 8753ET/ES series ● ● ● ● ● Network Analyzer Basics 110 GHz in coax highest accuracy modular, flexible pulse systems Tx/Rx module test 3, 6 GHz highest RF accuracy flexible hardware more features OffseCopyr t and ight 2000 harmonic RF sweeps Agilent’s LF/RF Vector Analyzers Co mbination NA / SA 4395A/4396B ● ● ● ● ● ● 500 MHz (4395A), 1.8 GHz (4396B) impedance-measuring option fast, FFT-based spectrum analysis time-gated spectrum-analyzer option IBASIC standard test fixtures E5100A/B ● ● LF ● ● ● ● Network Analyzer Basics 180, 300 MHz economical fast, small target markets: crystals, resonators, filters equivalent-circuit models evaporation-monitor-function option Copyright 2000 Spectrum Analyzer / Tracking Generator RF in IF 8563A SPE CT R U M AN A LYZ E R 9 kHz - 26.5 GHz LO DUT Spectrum analyzer TG out f = IF D UT Tracking generator Key differences from network analyzer: ● ● ● ● ● one channel -- no ratioed or phase measurements More expensive than scalar NA (but better dynamic range) Only error correction available is normalization (and possibly open-short averaging) Poorer accuracy S mallincremental costif SA is required for other measurements Network Analyzer Basics Copyright 2000 Agenda W hat measurements do we make? ● Network analyzer hardware ● Error models and calibration ● Example measurements ● Appendix W hy do we even need error-correction and calibration? ● I tisimpossible to make perfect hardware ● I t would be extremely expensive to make hardware good enough to eliminate the need for error correction ● Network Analyzer Basics Copyright 2000 Calibration Topics W hat measurements do we make? ● Network analyzer hardware ● Error models and ca libration ● measurement er rors ● what is vector er ror correction? ● cal ibration types ● accuracy examples ● cal ibration considerations ● Example measurements ● Appendix ● Network Analyzer Basics Copyright 2000 Measurement Error Modeling CA L -C RE AL Systematic errors ● due to imperfect ions in the analyzer and test setup ● assumed to be t ime invariant (predictable) Rando m errors ● vary wi th time in random fashion (unpredictable) ● main cont ributors: instrument noise, switch and connector repeatability Drift errors ● due to system per formance changing aftera calibration has been done ● pr imarily caused by temperature variation Errors: Measured Data Network Analyzer Basics SYSTE M ATIC RAN D O M DRIF T Unknown Device Copyright 2000 Systematic Measurement Errors R A Directivity B Crosstalk D UT Frequency response ● re flection tracking (A/R) ● t ransmission tracking (B/R) Source Mismatch Load Mismatch Six forward and six reverse error terms yields 12 error terms for twoport devices Network Analyzer Basics Copyright 2000 Types of Error Correction ● response (normalization) simple to perform only corrects fortracking errors thru stores reference trace in me mory, then does data divided by me mory vector requires more standards requires an analyzer that can measure phase accounts for all major sources of systematic error ■ ■ ■ ● ■ ■ ■ SHORT S11a OPEN S11m Network Analyzer Basics thru LOAD Copyright 2000 W hat is Vector-Error Correction? ● Process of characterizing systematic error terms measure known standards remove effects from subsequent measurements ● 1-port cal ibration (reflection measurements) only 3 systematic error terms measured directivity, source match, and reflection tracking ● Ful l 2-port calibration (reflection and transmission measurements) 12 systematic error terms measured usually requires 12 measurements on four known standards (SOLT) ● Standards def ined in cal kit definition file network analyzer contains standard cal kit definitions C AL KIT DEFINITION MUST MATC H A CTU AL CAL KIT USED! Network Analyzer Basics User-built standards must be characterized and entered into user al kit ■ ■ ■ ■ ■ ■ ■ ■ ■ Copyright 2000 Reflection: One-Port Model Error Adapter RF in Ideal RF in 1 E D = Directivity S11A ES ED E RT = Reflection tracking E S = Source Match S11 M S11 M S11A E RT S11 M = Measured S11A = Actual ● ● To solve for error terms, S11A we measure 3 standards S11 M = ED + to generate 3 equations 1 - ES S11A E RT and 3 unknowns Assumes good termination at porttwo iftesting two-port devices If using port 2 of NA and DUT reverse isolation islow (e.g.,filter passband): assumption of good termination is not valid two-port error correction yields better results ■ ■ Network Analyzer Basics Copyright 2000 Before and After One-Port Calibration 0 2.0 data before 1-port calibration 1.1 VS W R Return Loss (dB) 20 40 1.01 data after 1-port calibration 60 1.001 6000 Network Analyzer Basics M Hz 12000 Copyright 2000 Two-Port Error Correction Reverse model Forward model Port 1 Port 2 E RT' Port 1 EX Port 2 S 21 a1 a1 ED ES S 21A S 11 A b1 E RT S 22 S 12 ETT A EL E L' b2 S 11 b1 A b2 A S 22 A E S' E D' a2 a2 S 12 A E TT' E X' A ED = fwd directivity E S = fwd source match E RT = fwd reflection tracking E L = fwd load match E TT = fwd transmission tracking E X = fwd isolation E D' = rev directivity E S' = rev source match E RT' = rev reflection tracking E L' = rev load match E TT' = rev transmission tracking E X' = rev isolation Each actual S-parameter is a function of allfour measured S-parameters ● Analyzer must make forward and reverse sweep to update any one S-parameter ● Lucki ly, you don't need to know these equations to use network Network Analyzer Basics analyzers!!! S11a = S S S − ED − ED ' − E X S12 m − E X ' ( 11m )(1 + 22 m )( ) E S ' ) − E L ( 21m E TT ' E TT E RT ' E RT S S S − E D' − ED ' − E X S12 m − E X ' (1 + 11m )( ) E S ' ) − E L ' E L ( 21m E S )(1 + 22 m E TT ' E TT E RT ' E RT S21a = S22 m − E D ' S21m − E X )(1 + ( E S ' − E L )) E RT ' E TT S S S − E X S12 m − E X ' − ED − ED' (1 + 11m )( ) E S ' ) − E L ' E L ( 21m E S )(1 + 22m E RT ' E RT E TT E TT ' S12 a = S − EX ' S − ED ( 12m )(1 + 11m ( E S − E L ' )) E TT ' E RT S S S − ED − ED' − E X S12m − E X ' (1 + 11m )( ) E S ' ) − E L ' E L ( 21m E S )(1 + 22 m E TT ' E TT E RT ' E RT ( ● ( S22 a = (1 + S 22m − E D ' E RT ' )( 1 + S 21m − E X S12 m − E X ' S11m − E D )( ) ES ) − E L ' ( E TT ' E TT E RT S 21m − E X S12 m − E X ' S 22 m − E D ' S11m − E D )( ) ES ' ) − E L ' E L ( E S )(1 + E TT ' E TT E RT ' E RT Copyright 2000 ● Crosstalk: Signal Leakage Between Test Ports During ion CanTransmiss be a problem wi th: D UT high-isolation devices (e.g., switch in open position) high-dynamic range devices (some filter stopbands) ● Iso lation calibration adds noise to error model(measuring near noise floor of system) only perform ifreally needed (use averaging if necessary) if crosstalk is independent of DUT match, use two terminations if dependent on DUT match, use DUT with termination on output ■ ■ ■ ■ ■ ■ LOAD Network Analyzer Basics D UT D UT LOAD Copyright 2000 Errors and Calibration Standards U N C O R RE CTED FULL 2-PORT RESP O NSE 1-PORT SHORT D UT OPEN thru ● ● ● LOAD Convenient Generally not accurate No errors removed ● Easy to perform Use when highest accuracy is not required Re moves frequency response error ● ● ● EN H A N CE D-RESP O NSE Co mbines response and 1-port Corrects source match for transmission measurements Network Analyzer Basics OPEN OPEN LOAD LOAD D UT ● ● SHORT D UT ● ● SHORT For reflection measurements Need good termination for high accuracy with twoport devices Re moves these errors: Directivity Source match Reflection tracking thru D UT ● ● Highest accuracy Re moves these errors: Directivity Source,load match Reflection tracking Transmission tracking Copyrigh t lk Cross ta 2000 Calibration Summary Reflection Test Set (cal type) T/R SHORT S-parameter (one-port) (two-port) OPEN ● Reflection tracking ● Directivity ● Source match ● Load match LOAD Test Set (cal type) Trans mission T/R S-parameter (two-port) (response, isolation) error can be corrected ● Trans mission Tracking ● Crosstalk ● Source match ( ● Load match error cannot be corrected * enhanced response cal corrects for source match during transmission measurements Network Analyzer Basics * ) Copyright 2000 Reflection Example Using a One-Port Cal Load match: 18 dB (.126) Directivity: 40 dB (.010) .158 (.891)(.126)(.891) = .100 Re me mber: convert all dB values to linear for dB lat uncertainty ca (-lcu ) ions! D UT ρ orloss(linear) = 10 20 16 dB RL (.158) 1 dB loss (.891) Measure ment uncertainty: -20 * log (.158 + .100 + .010) = 11.4 dB (-4.6dB) -20 * log (.158 -.100 -.010) = 26.4 dB (+10.4 dB) Network Analyzer Basics Copyright 2000 Using a One-Port Cal + Attenuator Directivity: 40 dB (.010) .158 Load match: 18 dB (.126) 10 dB attenuator (.316) S W R = 1.05 (.024) Measure ment uncertainty: -20 * log (.158 + .039) = 14.1 dB (-1.9 dB) -20 * log (.158 -.039) = 18.5 dB (+2.5 dB) D UT 16 dB RL (.158) 1 dB loss (.891) Low-loss bi-directional devices generally require two-port (.891)(.024)(.891) = .019 calibration Worst-case error = .010 + .010 + .019 = .039 for low measure ment uncertainty (.891)(.316)(.126)(.316)(.891) = .010 Network Analyzer Basics Copyright 2000 Transmission Example Using Response Cal RL = 18 dB (.126) RL = 14 dB (.200) Thru calibration (normalization) builds error into measurement due to source and load match interaction Calibration Uncertainty =(1 ± ρS ρL) = (1 ± (.200)(.126) = ± 0.22 dB Network Analyzer Basics Copyright 2000 Filter Measurement with Response Cal Source match = 14 dB (.200) DUT 1 dB loss (.891) 16 dB RL (.158) Load match = 18 dB (.126) 1 (.126)(.158) = .020 (.126)(.891)(.200)(.891) = .020 (.158)(.200) = .032 Total measure ment uncertainty: +0.60 + 0.22 = + 0.82 dB -0.65 - 0.22 = - 0.87 Network Analyzer Basics dB Measurement uncertainty = 1 ± (.020+.020+.032) = 1 ± .072 = + 0.60 dB - 0.65 dB Copyright 2000 Measuring Amplifiers with a Response Cal Source match = 14 dB (.200) DUT 16 dB RL (.158) Load match = 18 dB (.126) 1 (.126)(.158) = .020 (.158)(.200) = .032 Total measure ment uncertainty: +0.44 + 0.22 = + 0.66 dB -0.46 - 0.22 = - 0.68 Network Analyzer Basics dB Measurement uncertainty = 1 ± (.020+.032) = 1 ± .052 = + 0.44 dB - 0.46 dB Copyright 2000 Filter Measurements using the Enhanced Response Calibration Effective source match = 35 dB! Source match = 35 dB (.0178) DUT 1 dB loss (.891) 16 dB RL (.158) Load match = 18 dB (.126) Calibration Uncertainty =(1 ± ρS ρL) = (1 ± (.0178)(.126) = ± .02 dB 1 Measurement uncertainty = 1 ± (.020+.0018+.0028) (.126)(.158) = .020 = 1 ± .0246 = + 0.211 dB (.126)(.891)(.0178)(.891) = .0018 - 0.216 dB (.158)(.0178) = .0028 Total measurem ent uncertainty: 0.22 + .02 = ± 0.24 dB Network Analyzer Basics Copyright 2000 Using the Enhanced Response Calibration Plus an Attenuator 10 dB attenuator (.316) S W R = 1.05 (.024 linear or 32.4 dB) Analyzer load match =18 dB (.126) Source match = 35 dB (.0178) DUT 1 dB loss (.891) 16 dB RL (.158) Calibration Uncertainty =(1 ± ρS ρL) = (1 ± (.0178)(.0366) = ± .01 dB Effective load match = (.316)(.316)(.126) + .024 = .0366 (28.7dB) 1 Measurement uncertainty = 1 ± (.006+.0005+.0028) (.0366)(.158) = .006 = 1 ± .0093 (.0366)(.891)(.0178)(.891) = .0005 = ± 0.08 dB (.158)(.0178) = .0028 Total measurem ent uncertainty: 0.01 + .08 = ± 0.09 dB Network Analyzer Basics Copyright 2000 Calculating Measurement Uncertainty After a Two-Port DUT 1 dB loss (.891) Calibration 16 dB RL (.158) Corrected error terms: (8753ES 1.3-3 GHz Type-N) Directivity dB Source match = Load match dB Refl.tracking = dB Trans. tracking .026 dB Isolation = = 47 Reflection uncertainty 36 dB 2 = 47 S 11m = S11a ± ( E D + S11a E S + S 21a S12 a E L + S11a (1 − E RT )) .019 = 0.158 ± (.0045 + 0.158 2 *.0158 + 0.8912 *.0045 + 0.158*.0022 ) = 0.158 ± .0088 = 16 dB +0.53 dB, -0.44 dB (worst-case) = 100 dB Trans mission uncertainty S 21m = S 21a ± S 21a ( E I / S 21a + S11a E S + S 21a S12 a E S E L + S 22 a E L + (1 − E TT )) = 0.891 ± 0.891(10 −6 / 0.891 + 0.158*.0158 + 0.8912 *.0158*.0045 + 0.158*.0045+.003) = 0.891 ± .0056 = 1 dB ±0.05 dB (worst-case) Network Analyzer Basics Copyright 2000 Response versus Two-Port Calibration Measuring filter insertion loss C H1 S21& M C H2 M E M log MA G log MA G Cor 1 dB/ 1 dB/ REF 0 dB REF 0 dB After two-port calibration After response calibration Cor x2 1 START 2 000.000 MHz Network Analyzer Basics Uncorrected 2 ST OP 6 000.000 MHz Copyright 2000 ECal: Electronic Calibration (85060/90 series) • • • Variety of modules cover 30 kHz to 26.5 G Hz Six connector types available (50 Ω and σα 75 Ω) Single-connection reduces calibration time makes calibrations easy to perform minimizes wear on cables and standards eliminates operator errors Highly repeatable temperatureMicrowave modules use a compensated terminations provide transmission line shunted by excellent accuracy PIN-diode switches in various 85093A Electronic Calibration Module 30 kHz - 6 GHz ■ ■ ■ ■ • combinations Network Analyzer Basics Copyright 2000 Adapter reflection from Considera t ions desired signal adapter leakage signal ρ m easured = Directivity + ρ adapter + ρ D UT Coupler directivity = 40 dB Adapter W orst-case System Directivity 28 dB 17 dB 14 dB Network Analyzer Basics D UT Termination D UT has SMA (f) connectors AP C-7 calibration done here Adapting from APC-7 to SMA (m) APC-7 to SMA (m) S W R:1.06 APC-7 to N (f) + N (m) to SMA (m) S W R:1.05 S W R:1.25 APC-7 to N (m) + N (f)to SMA (f) + SMA (m) to (m) S W R:1.05 S W R:1.25 S W R:1.15 Copyright 2000 Calibrating Non-Insertable Devices W hen doing a through cal, normally test ports m ate directly ● cables can be connected d irectly without an adapter ● resul tis a zero-length through W hat is an insertable device? ● has same type of connector, but d ifferent sex on each port ● has same type of sex less connector on each port (e.g. APC-7) W hat is a non-insertable device? ● one that cannot be inser ted in place of a zerolength through ● has same connectors on each por t (type and sex) ● has d ifferent type of connector on each port (e.g., waveguide on one port, coaxial on Network Analyzer Basics the other) W hat alibration hoi es do I have for non- D UT Copyright 2000 Swap Equal Adapters Method Port 1 Port 1 Adapter A Port 1 Port 1 Port 2 D UT D UT Network Analyzer Basics Accuracy depends on how well the adapters are matched -loss, electrical length, match and impedance should all be equal 1. Transmission cal using adapter A. Port 2 Adapter B Port 2 2. Reflection cal using adapter B. Adapter B Port 2 3. Measure D UT using adapter B. Copyright 2000 Adapter Re moval Calibration ● ● ● ● ● Calibration is very accurate and traceable In firmware of 8753, 8720 and 8510 series Port 1 Also accomplished with ECal modules (85060/90) Uses adapter with same connectors as DUT Must specify electricallength of adapter to within 1/4 wavelength of highest frequency (to avoid phase ambiguity) Cal Adapter Port 1 D UT Port 2 Adapter Port 2 B 1. Perform 2-port cal with adapter on port2. Save in cal set 1. Adapter B 2. Perform 2-port cal with adapter on port1. Save in cal set 2. Cal Set 1 Port 1 Cal Adapter Port 2 Cal Set 2 [CAL] [MORE] [MODIFY CAL SET] [ADAPTER RE M O VAL] Port 1 Network Analyzer Basics D UT Adapter B Port 2 3. Use ADAPTER RE M O VAL to generate new cal set. 4. Measure DUT without cal adapter. Copyright 2000 Thru-Reflect-Line (TRL) Calibration W e know about Short-Open-Load-Thru (SOLT) calibration... W hat is TRL? ● A two-por t calibration technique ● Good for noncoaxia l environments (waveguide, fixtures, wafer probing) ● Uses the same 12term error model as the more com mon SOLT cal ● Uses pract ical calibration standards tha t was developed for nonTRL are easily fabricated and characterized coaxial microwave ● Two var iations: TRL (requires 4 receivers) measurements and TRL* (only three receivers needed) ● Other var iations: Line-Reflect-Match (LRM), Thru-Reflect-Match (TR M), plus many others Network Analyzer Basics Copyright 2000 Agenda ● ● ● ● ● Network Analyzer Basics W hat measurements do we make? Network analyzer hardware Error models and calibration Example measurements Appendix Copyright 2000 Frequency Sweep - Filter Test CH1 S 21 log MAG 10 dB/ REF 0 dB CH1 S 11 log MAG 5 dB/ REF 0 dB Cor Stopba nd rejectio n 69.1 dB START .300 000 MHz STOP 400.000 000 MHz CH1 S 21 SPAN 50.000 MHz CENTER 200.000 MHz log MAG 1 dB/ REF 0 dB Return loss Cor 4.000 1000 GHz - m1: 0.16 dB m2-ref: 2.145 234 GHz 0.00 dB ref 2 Cor Insertion loss x2 1 2 START 2 000.000 MHz Network Analyzer Basics STOP 6 000.000 MHz Copyright 2000 Optimize Filter Measurements with Swept-List Mode Segment 3: 29 ms (108 points, -10 dBm, 6000 Hz) CH1 S 21 log MAG 12 dB/ REF 0 dB PRm S wept-list sweep: 349 ms (201 pts, variable B W's & power) PASS Linear sweep: 676 ms (201 pts, 300 Hz, -10 dB m) Segment 5: 129 ms (38 points, +10 dBm, 300 Hz) Segment 1: 87 ms (25 points, +10 dBm, 300 Hz) START 525.000 000 MHz STOP 1 275.000 000 MHz Segments 2,4: 52 ms (15 points, +10 dBm, 300 Hz) Network Analyzer Basics Copyright 2000 Output Power (dBm) Power Sweeps -Co mpression Saturated output power Co mpression region Linear region (slope = small-signal gain) Input Power (dB m) Network Analyzer Basics Copyright 2000 Power Sweep -Gain Compression C H1 S21 1og MA G 1 dB/ REF 32 dB 30.991 dB 12.3 dBm 1 dB co mpression: 1 0 START -10 dB m Network Analyzer Basics C W 902.7 MHz input power resulting in 1 dB drop in gain ST OP 15 dB m Copyright 2000 A M to PM Conversion A mplitude Measure of phase deviation caused by a Power mplisweep tude variations ● AM (dB) Mag(Ami n) ● D UT A M can be undesired: supply ripple,fading, thermal A M can be desired: modulation (e.g. QA M) PM (deg) Test Stimulus Q Time A mplitude AM (dB) A M - PM Conversion = Mag(P m (deg/d ) Mag(A m B) out in) Mag(AM o ut) PM (deg) Mag(Pm o ut) Output Response Network Analyzer Basics Time I A M to PM conversion can cause bit errors Copyright 2000 Measuring AM to PM Conversion 1:Transmission Log Mag 1.0 dB/ 2:Transmission /M Phase 5.0 deg/ Ch1:Mkr1 20.48 dB Ch2:Mkr2 0.86 deg Ref 21.50 dB Ref -115.7 deg -4.50 dB m 1.00 dB Use transmission setup with a power sweep ● Disp lay phase of S21 ● A M - PM = 0. 86 deg/dB ● 2 1 2 1 Start -10.00 dB m Start -10.00 dB m Network Analyzer Basics C W 900.000 MHz C W 900.000 MHz 1 Stop 0.00 dBm Stop 0.00 dBm Copyright 2000 Agenda ● W hat measurements do we make? Network analyzer hardware Error models and calibration Example measurements ● Appendix ● ● ● ● ● ● Network Analyzer Basics Advanced 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! Copyright 2000 Time-Domain Reflectometry (TDR) ● W hat is TDR? time-domain reflectometry analyze impedance versus time distinguish between inductive and capacitive transitions With gating: analyze transitions inductive analyzer standards transition ■ ■ ■ ● ■ impedance ■ Zo time capacitive transition Network Analyzer Basics non-Zo transmission line Copyright 2000 TDR Basics Using a Network Analyzer start with broadband frequency sweep (often requires microwave VN ● use inverse-Four ier transform to compute time-domain ● resolut ion inversely proportionate to frequency span ● Time Do main Frequency Do main F C H1 S 22 -1 Cor 50 mU/ REF 0 U 20 GHz f t ∫ F(t)*dt Re 6 GHz t Integrate 1/s*F(s) 0 TDR F t Network Analyzer Basics -1 f C H1 START 0 s ST OP 1.5 ns Copyright 2000 Time-Domain Gating TDR and gating can remove undesired reflections (a form of error correction) ● Only usefu lfor broadband devices (a load or thru for example) ● Def ine gate to only include D UT C H1 S11& M log MA G 5 dB/ REF 0 dB ● Use two-por t calibration ● PR m Cor C H1 M E M Re PR m Cor 2 20 mU/ REF 0 U 1: -45.113 dB 0.947 G Hz 2: -15.78 dB 6.000 G Hz Gate 1: 48.729 mU 638 ps RISE TIME 29.994 ps 8.992 m m 2: 24.961 mU 668 ps 1 3: -10.891 mU 721 ps 2 3 Thru in time domain C H1 START 0 s Network Analyzer Basics ST OP 1.5 ns 1 Thru in frequency domain, with and without gating START .050 000 000 GHz ST OP 20.050 000 000 GHz Copyright 2000 Ten Steps for Performing TDR 1. Set up desired frequency range (need wide span for good spatial resolution) 2. Under SYSTEM, transform menu, press "set freq low pass" 3. Perform one- or two-port calibration 4. Select S11 measurement * 5. Turn on transform (low pass step) * 6. Set format to real * 7. Adjust transform window to trade off rise time with ringing and overshoot * 8. Adjust start and stop times if desired 9. For gating: ● set s tart and stop frequencies for gate ● tu rn gating on * ● adjust gate shape to t rade offresolution with ripple * 10. To display gated response in frequency domain * If● us ing channe lso (even if coupga led) ,these must be set tu rntwo trans form ff (leave ting on)parameters * independent r second channel itude * ● changely fofo rmat to log-magn Network Analyzer Basics Copyright 2000 Time-Domain Transmission RF Input RF Output C H1 Main Wave Leakage S21 log MA G Surface W ave Triple Travel C H1 S21 log MAG 10 dB/ REF 0 dB 15 dB/ REF 0 dB Cor Cor RF Leakage Triple Travel Gate off Gate on Network Analyzer Basics ST OP 6 us START -1 us Copyright 2000 Time-Domain Filter Tuning • • Deterministic method used fortuning cavity-resonator filters Traditionalfrequencydomain tuning is very difficult: lots oftraining needed may take 20 to 90 minutes to tune a single filter Need VNA with fast sweep speeds and fast timedomain processing ■ ■ • Network Analyzer Basics Copyright 2000 Filter Reflection in Time Do main • • • Network Analyzer Basics Set analyzer’s center frequency = center frequency ofthe filter Measure S11 or S22 in the time domain Nullsin the time-domain response correspond to individual resonators in filter Copyright 2000 Tuning Resonator #3 • • • • Network Analyzer Basics Easier to identify mistuned resonator in time-domain: null #3 is missing Hard to tell which resonatoris mistuned from frequencydomain response Adjust resonators by minimizing null Adjust coupling apertures using the peaks in-between the dips Copyright 2000 Frequency-Translating Devices Medium-dynamic range measurements (35 dB) High-dynamic range measurements (100 dB) FRE Q OFFS O N off 8753ES 8753ES LO MENU Ref In 1 2 Filter DO WN C O NVE RTER Ref out UP C O NVE RTER Attenuator Attenuator Ref in RF > LO Reference mixer RF < LO Start: 900 MHz Stop: 650 MHz Start: 100 MHz Stop: 350 MHz Fixed LO: 1 GHz LO power: 13 dBm VIE W M EASU RE Filter Attenuator RETU R N CH1 CONV MEAS log MAG 10 dB/ REF 10 dB D UT Attenuator Attenuat or Powe r splitt er ES G-D4000A START 640.000 000 MHz Network Analyzer Basics STOP 660.000 000 MHz Copyright 2000 High-Power Amplifiers Prea mp 8753ES Source Ref In Prea mp UT ADUT R B A A UT +43 dBm max input (20 watts!) 8720ES Option 085 85118A High-Power Amplifier Test System Network Analyzer Basics Copyright 2000 High-Dynamic Range Measurements C H1 M E M C H2 M E M LO G LO G 15 dB/ REF 3 dB 15 dB/ REF 3 dB • • PR m Cor Avg 10 PR m Standard 8753ES Cor Avg 10 • 8753ES Special Option H16 C H1 C H2 Network Analyzer Basics START 775.000 000 M Hz START 775.000 000 M Hz ST OP 1000.000 000 M Hz ST OP 1000.000 000 M Hz Copyright 2000 Multiport Device Test 8753 H39 CH1 CH2 S 21 S 12 log MAG log MAG 10 dB/ 10 dB/ REF 0 dB REF 0 dB 1_ -1.9248 dB 1_ -1.2468 dB 839.470 000 MHz PRm Duplexer Test - Tx-Ant and Ant-Rx Cor 1 1 Hld PASS 1 880.435 000 MHz PRm Cor 2 PASS Hld CH1 START 775.000 000 MHz CH2 START 775.000 000 MHz Network Analyzer Basics STOP 925.000 000 MHz STOP 925.000 000 MHz Multiport analyzers and test sets: ● improve throughput by reducing the number of connections to D UTs with more than two ports ● al low simultaneous viewing oftwo paths (good for tuning duplexers) ● inc lude mechanical or solid-state switches, 50 or 75 ohms ● degrade raw per formance so calibration is a must (use two-port cals whenever possible) ● Agi lent offers a variety of standard and custom multiport analyzers and test sets Copyright 2000 SelfCal 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 87050E/87075C Standard Multiport Test Sets Fixture D UT Once an hour: automatically perform a • • • • • For use with 8712E family SelfCal using internal standards to remove systematic errors in the 50 Ω: 3 MHz to 2.2 GHz, 4, 8, or 12 ports analyzer and test set 75 Ω: 3 MHz to 1.3 GHz, 6 or 12 ports Test Set Cal and SelfCal dramatically improve calibration times Systems offer fully-specified performance at test ports Network Analyzer Basics Copyright 2000 Test Set Cal Eliminates Redundant Connections of Calibration Standards Through Connections Reflection Connections 12-port 12-port 8-port 8-port 4-port 4-port 0 100 Network Analyzer Basics 200 300 400 0 25 ■ Test Set Cal ■ Traditional VN A Calibration 50 75 Copyright 2000 In-Fixture Measurements Measure ment problem: coaxial calibration plane is not the same as the in-fixture measurement plane Measurement plane Calibration plane Fixture ED ES ET Error correction with coaxial calibration D UT ● ● ● Network Analyzer Basics Loss Phase shift Mismatch Copyright 2000 Characterizing CrystalResonators/Filters Ch1 Z: R phase 40 / REF 0 1: 15.621 U E5100A/B Network Analyzer 31.998 984 925 MHz Min Cor 1 START 31.995 MHz SE G START STOP POINTS ST OP 32.058 MHz PO W E R IFB W 1 31.995 MHz 32.008 MHz 200 0 dB m 200Hz > 2 32.052 MHz 32.058 MHz 200 0 dB m 200Hz EN D Exa mple of crystal resonator measurement Network Analyzer Basics Copyright 2000 Balanced-Device Measurements • ATN-4000 series (4-port test set + software) measure tough singled-ended devices like couplers • measure ful ly-balanced or single-ended-to-balanced DUTs ize mode conversions (e.g. com mon-to-differential) • character ional accuracy • incorporates 4-port error correction for except • works with 8753ES and 8720ES analyzers • more info at ww w.atnm icrowave.co m • σα Channel Partner Network Analyzer Basics Copyright 2000 Traditional Scalar Analyzer Incident Transmitted D UT Reflected SOURCE SIGN AL SEP A R ATION processor/display INCIDENT (R) REFLECTED (A) TRA NS MITTED (B) R E C EIVER / DETECT O R source P R O C ESS O R / DISPLAY Example: 8757D/E ● requi res external detectors, couplers, bridges, splitters ● good forlow-cost microwave scalar appl ications RF R A B RF Detector R Detector Detector Bridge Reflection D UT D UT Termination Trans mission Network Analyzer Basics Copyright 2000 A B Directional Coupler Directivity Coupling Factor (fwd) x Loss Directivity = (through arm) Isolation (rev) Directivity (dB) = Isolation (dB) - Coupling Factor (dB) - Loss (dB) 50 dB Exa mples: 20 dB Test port 50 dB Directivity = 50 dB - 20 dB = 30 dB 30 dB Test port Directivity = 50 dB - 30 dB - 10 dB = 10 dB 10 dB 60 dB 20 dB Test port Directivity = 60 dB - 20 dB - 10 dB = 30 dB 10 dB Network Analyzer Basics Copyright 2000 One Method of Measuring Coupler Directivity 1.0 (0 dB) (reference) Coupler 35 tdB Direc ivit( y.018) Source short .018 (35 dB) (normalized) Directivity = 35 dB - 0 dB = 35 dB Source Network Analyzer Basics load Assume perfect load (no reflection) Copyright 2000 Directional Bridge 50 Ω 50 Ω Detector ● ● ● 50 Ω Test Port ● Network Analyzer Basics 50-ohm load at test port balances the bridge -- detector reads zero Non-50-ohm load imbalances bridge Measuring magnitude and phase ofimbalance gives complex impedance "Directivity"is difference between maximu m and minimu m balance Copyright 2000 Incident NA Hardware: Front Ends, Mixers Versus Sa mplers Transmitted D UT Reflected SOURCE SIGN AL SEP A R ATION INCIDENT (R) REFLECTED (A) TRA NS MITTED (B) R E C EIVER / DETECT O R P R O C ESS O R / DISPLAY Sa mpler-based front end AD C / DSP S AD C / DSP Mixer-based front end Harmonic generator f frequency "comb" Itis cheaper and easier to make broadband front ends using sa mplers instead of mixers Network Analyzer Basics Copyright 2000 Three Versus Four-Receiver Analyzers Source Source Transfer switch Transfer switch R1 R A A B B R2 Port 1 Port 2 3 receivers ● ● ● more economical TRL*, LR M* cals only includes: 8753ES 8720ES (standard) ■ ■ Network Analyzer Basics Port 2 Port 1 4 receivers ● ● ● more expensive true TRL, LRM cals includes: 8720ES (option 400) 8510C ■ ■ Copyright 2000 W hy Are Four Receivers Better Than Three? TRL TRL* 8720ES Option 400 adds fourth sa mpler, allowing full TRL calibration ● TRL* assumes the source and load match of a test port are equal (port sym metry between forward and reverse measurements) thisis 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* W hat about coaxial applications? S OLT is usually the preferred calibration method coaxial TRL can be more accurate than SOLT, but not commonly used ■ ■ ● ■ ■ ● ● ■ ■ Network Analyzer Basics Copyright 2000 Challenge Quiz 1. Can filters cause distortion in co m m unications systems? A. Yes, due to impairment of phase and magnitude response B. 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. Both A and B above 2. Which statem ent about trans mission lines is false? A. Usefulfor efficient transmission of RF power B. Requires termination in characteristicimpedance forlow VSW R C. Envelope voltage of RF signalisindependent of position along line D. Used when wavelength of signalis small compared to length ofline E. Can be realized in a variety offorms such as coaxial, waveguide, microstri 3. Which statem ent about narrowband detection is false? A. Is generally the cheapest way to detect microwave signals B. 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 Network Analyzer Basics Copyright 2000 Challenge Quiz (continued) 4. Maximu m dyna mic range with narrowband detection is defined as: A. Maximum receiverinput power minus the stopband of the device under te B. Maximum receiverinput power minus the receiver's noise floor C. Detector 1-dB-compression point minus the harmonic level of the source D. Receiver damage level plus the maximu m source output power E. Maximum source output power minus the receiver's noise floor 5. With a T/R analyzer, the following error terms can be corrected: A. Source match, load match, transmission tracking B. Load match, reflection tracking, transmission tracking C. Source 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 measure ment A. Systematic and drift B. Systematic and random C. Random and drift D. Repeatability and systematic E. Repeatability and drift Network Analyzer Basics Copyright 2000 Challenge Quiz (continued) 7. Which statem ent about TRL calibration is false? A. Is a type oftwo-port error correction B. Uses easily fabricated and characterized standards C. Most com monly used in noncoaxial environments D. Is not available on the 8720ES family of microwave network analyzers E. Has a specialversion for three-sampler network analyzers 8. For which co mponent is ithardest to get accurate trans mission and reflection measure ments when using a T/R network analyzer? A. Amplifiers because output power causes receiver compression B. Cables because load match cannot be corrected C. Filter stopbands because of lack of dynamic range D. Mixers because oflack of broadband detectors E. Attenuators because source match cannot be corrected 9. Power sweeps are good for which measurements? A. Gain compression Network Analyzer Basics B. AM to PM conversion C. Saturated output power Copyright 2000 Answers to Challenge Quiz 1. E 2. C 3. A 4. B 5. C 6. A 7. D 8. B 9. E Network Analyzer Basics Copyright 2000