Six-Port Reflectometer: an Alternative Network Analyzer for THz Region Guoguang Wu
Outline General Background of Network Analyzer Principles of Six-Port Reflectometer WR-15 Six-port Reflectometer Design, Measurement Setup Results as Network Analyzer Results as an Embedded Sensor into other Systems Other Potential Applications (beyond network analyzer) 3/19/2009 2
What is Network Analyzer? not about computer networks referred to electrical networks used to analyze the properties of them especially to measure reflection and transmission operating frequencies range from 9 khz to 500 GHz 3/19/2009 3
Why Test Components? Verify specifications of building blocks for more complex radio-frequency (RF) system Ensure distortionless transmission of communications signals Linear behavior: input and output frequency are the same output frequency only undergoes magnitude and phase change Nonlinear behavior: output frequency may undergo frequency shift (e.g. with mixers) additional frequencies created (harmonics) Ensure good match when absorbing power (e.g. an anteanna) 3/19/2009 4
How Commercial Network Analyzer Works? (Signal Separation) 3/19/2009 5
Outline General Background of Network Analyzer Principles of Six-Port Reflectometer WR-15 Six-port Reflectometer Design, Measurement Setup, and Initial Data Results as Network Analyzer Results as an Embedded Sensor into other Systems: measuring mismatch between two adjacent stages in a frequency multiplier chain. Other Potential Applications (beyond Network Analyzer) 3/19/2009 6
Overview of Six-port Technique Engen invented six-port technique in 1977 *. Six-port technique is a method of network analysis. Six-port reflectometer (SPR): measure only reflection coefficient. Six-port network analyzer (SPNA): measure both reflection and transmission. * IEEE MTT-25(12), pp1075, 1977 3/19/2009 7
Network Analysis Methodology Comparison Conventional (commercial, four-port) NA: signal separation method Six-port VNA (reflectometer): signal interference method 3/19/2009 8
Calibration Procedure Comparison b Commercial VNA a 2 3, b4 ( Γ) b2 Six-port reflectometer 2 b3 a2 Pi ( bi ) ( w) Γ( ) b b 4 2 = Γ Γ 1 1 K ζ 1 M ρ b 5 b 4 b 2 6 b 4 2 b w 3 wl 2 b 4 K 1 b 3 w b 4 N M w 2 2 3/19/2009 9 w = b 3 b 4
Six-Port Theory: Determination of w and Γ Intersection of Circles determines ratio b 3 /b 4 true Γ related by bilinear transform: requires four-port calibration First step of six-port calibration is to get the value of five network constants: 1. w 1 (real) 2. w 2 (complex) 3. ρ (scalar) 4. ζ (scalar) 3/19/2009 10
Determining the Network Constants Sliding Termination Method Γ = c (constant) Γ = f ( x), where x is the sliding position Six-port detection port Reference plane 3/19/2009 11
First Step of Six-Port Calibration Sliding Termination Method Quadratic Surface in P-space maps out an ellipse: P P A 3 3 P 5 P + 2 B + C + 2 D + 2 E 5 + F = 0 ( ) 2 ( ) ( P 5 ) 2 ( P 3 ) 2 P 4 P 4 P 4 P 4 ( ) P 4 Where, A = a B = ζ (c a b)/2 C = ζ 2 b D = [R 2 (b a c) + a(a b c)]/2 E = ζ [R 2 (a b c) + b(b a c)]/2 F = [R 4 + R 2 (c a b) + ab] a = w 1 R 2 c b = R 2 c c = w 2 1 P5/P4 ζ = 1/ K 2 0 4 3 2 1 0 1 2 3 4 P3/P4 3/19/2009 12
General Six-Port Calibration Strategy Measure Response of Power Detectors to Sliding Load Plot Power Ratios Against One-Another Ellipse in P-plane Determine Five Coefficients via Least-Squares Fit, A, B, C, D, E F F F F F Algebraically Determine Six-Port Network Constants Calibrated Effective Four-Port Using One of Several Standard Methods 3/19/2009 13
Comparing Six-port Reflectometer to Conventional Network Analyzer Advantage Simpler structure; fewer components Less expensive Easily embedded to other systems No need for phase-locked signal sources Drawbacks (mainly due to broadband nature of signal detection) Limited dynamic range, typically limited to 50 60 db Sensitive to spurious signals (e.g. harmonics) 3/19/2009 14
Outline General Background of Network Analyzer Principles of Six-Port Reflectometer WR-15 (V-Band, 50-75 GHz) Six-port Reflectometer Design, Measurement Setup and Initial Data Results as Network Analyzer Results as an Embedded Sensor into other Systems: measuring mismatch between two adjacent stages in a frequency multiplier chain. Other Potential Applications (beyond Network Analyzer) 3/19/2009 15
Block Design Low Pass Filter Probe 3/19/2009 16 Diode
Basic Measurement Setup Configuration Six-port source Isolator DUT DUT s include fixed load, short, sliding shorts, sliding loads: for calibration; various WR15 components: as network analyzer; frequency multiplier (doubler) D124 B63: as embedded sensor. 3/19/2009 17
Measurement Setup 3/19/2009 18
Initial Data (Standing Wave by Sliding Short) 67 GHz as an Example Voltage Response (mv) 10 8 6 4 2 0 1 6 11 16 21 Position (a.u.) V1 V2 V3 3/19/2009 19
Outline General Background of Network Analyzer Principles of Six-Port Reflectometer WR-15 Six-port Reflectometer Design, Measurement Setup, and Initial Data Results as Network Analyzer (measured 7 different components) Results as an Embedded Sensor into other Systems: measuring mismatch between two adjacent stages in a frequency multiplier chain. Other Potential Applications (beyond Network Analyzer) 3/19/2009 20
Six-Port Calibration Results Compared to Commercial Network Analyzer for Four Couplers 0-5 Coupler #1 0 Coupler #2-10 -5 Gamma(dB) -15-20 -25 Gamma(dB) -10-15 -30 Gamma(dB) from HP8510-35 Gamma from six-port reflectometer -40 50 52 54 56 58 60 62 64 66 68 70-20 Gamma(dB) from HP8510 Gamma from six-port -25 50 52 54 56 58 60 62 64 66 68 70 Frequency(GHz) Frequency(GHz) 0 Coupler #3 0-5 Coupler #4-5 -10 Gamma(dB) -10-15 -20 Gamma(dB) from HP8510 Gamma from six-port reflectometer -25 50 52 54 56 58 60 62 64 66 68 70 Frequency(GHz) Gamma(dB) -15-20 -25-30 -35 Gamma(dB) from HP8510-40 Gamma from Six-port reflectometer -45 50 52 54 56 58 60 62 64 66 68 70 Frequency(GHz) 3/19/2009 21
Six-Port Calibration Results Compared to Commercial Network Analyzer for Horn Antenna and Two Low Pass Filters 0 Low Pass Filter #1 Gamma(dB) 0-10 -20-30 -40-50 Horn Antenna Gamma(dB) from HP8510 Gamma from six-port reflectometer Gamma(dB) -5-10 -15-20 Gamma(dB) from HP8510 Gamma from six-port reflectometer -25 50 52 54 56 58 60 62 64 66 68 70 0-5 Frequency(GHz) Low Pass Filter #2-60 50 55 60 65 70 Frequency(GHz) Gamma(dB) -10-15 -20 Gamma(dB) from HP8510-25 Gamma from six-port reflectometer -30 50 52 54 56 58 60 62 64 66 68 70 Frequency(GHz) 3/19/2009 22
Outline General Background of Network Analyzer Principles of Six-Port Reflectometer WR-15 Six-port Reflectometer Design, Measurement Setup, and Initial Data Results as Network Analyzer Results as an Embedded Sensor into other Systems: measuring mismatch between two adjacent stages in a frequency multiplier chain. Other Potential Applications (beyond Network Analyzer) 3/19/2009 23
Why Study a Frequency Multiplier Chain? (THz Gap) Source: Virginia Diodes, Inc. Source: Virginia Diodes, Inc Power Available (dbm) 40 30 20 10 0-10 -20 dbm 30 20 10 0-10 -20 mw 1000 100 10 1.1.01 Source: Virginia Diodes, Inc. -30 3/19/20090 500 1000 1500 24 Frequency(GHz)
How Output Power Changed by Introducing Six-Port Reflectometer V1 V1 V2 Output Power(mW) 250 200 150 100 50 S D60 D124 0 116 117 118 119 120 121 122 123 124 125 126 Frequency (GHz) v1=10v; v2=24v; without six-port v1=17v;v2=24v;without six-port v1=10v;v2=24v;with six-port v1=17v;v2=24v;with six-port 3/19/2009 25
Γ Magnitude Results at V1=24V 10 S11 Magnitude, db 0-10 -20-30 -40 58 59 60 61 62 63 Frequency, GHz V2=8v V2=10v V2=12v V2=14v V2=17v 3/19/2009 26
Γ Phase Results at V1=24V Phase(Degree) 180 120 60 0-60 -120 8v24 10v24 12v24 14v24 17v24-180 58 59 60 61 62 63 Frequency(GHz) 3/19/2009 27
Comparison of Γ and Output Power at Input Bias of V 1 =24 V S11 Magnitude, db 10 0-10 -20 V2=8v V2=10v -30 V2=12v V2=14v V2=17v -40 58 59 60 61 62 63 Frequency, GHz Power(mV) 250 200 150 100 50 0-50 V2=8v V2=10v V2=12v V2=14v V2=17v 58 59 60 61 62 63 Frequency (GHz) 3/19/2009 28
Outline General Background of Network Analyzer Principles of Six-Port Reflectometer WR-15 Six-port Reflectometer Design, Measurement Setup, and Initial Data Results as Network Analyzer Results as an Embedded Sensor into other Systems: measuring mismatch between two adjacent stages in a frequency multiplier chain. Other Potential Applications (beyond Network Analyzer) 3/19/2009 29
Potential Application I: Near-Field Imaging 3/19/2009 30
Potential Application II: Dielectric Measurements on Fluids fluids 3/19/2009 31
Summary Introduced a general background of network analyzer Explained principles of Six-Port Reflectometer Demonstrated a WR-15 Six-port Reflectometer the results are in great agreement with commercial network analyzer when measuring variant components. used as an embedded sensor into a frequency multiplier chain and measured the mismatch between two adjacent stages Proposed other potential applications THz near-field imaging dielectric measurements on polar liquids 3/19/2009 32
Thank You!
Research Motivation In-situ monitoring of the performance and operation of adjacent stages in a frequency multiplier chain. Directly measure the impedance mismatch between adjacent stages using an embedded sensing circuit (sixport reflectometer). Use it for studying the behavior of multipliers and as a guide for adjusting external operating parameters that impact performance of the entire chain. 3/19/2009 34
Appendix I: How to Get Ellipse Eqs. 3/19/2009 35
Appendix I: How to Get Ellipse Eqs. (continued) 3/19/2009 36
Appendix I: How to Get Ellipse Eqs. (continued 2) 3/19/2009 37
First Step of Six-Port Calibration (Engen s Sliding Termination Method) Constraining Relation between b 3, b 4, b 5, and b 6 : ( P 3 ) 2 ( P 5 ) 2 a + b ζ + c ρ + (c a b) ζ + (b a c) ρ P 4 2 2 P 6 P 4 P 4 ( ) 2 ( P 3 P 5 ) 2 P 4 P 3 P 6 ( ) 2 P 4 + (a b c) ζ ρ ( P 5 P 6 ) P + a(a b c) + b(b a c) ζ 5 2 P 4 P 6 P 4 + c(c a b) ρ + abc = 0 P 4 P 3 P 4 Where, a = w 1 w 2 2 b = w 2 2 c = w 1 2 3/19/2009 38
First Step of Six-Port Calibration continued Constrain Γ to lie on a circle (i.e., sliding termination) maps into circle in w-plane w R R 2 2 c = and recall Quadratic Surface in P-space maps out an ellipse: P w w2 = ρ P 2 6 P P A 3 3 P 5 P + 2 B + C + 2 D + 2 E 5 + F = 0 ( ) 2 ( ) ( P 5 ) 2 ( P 3 ) 2 P 4 P 4 Where, A = a B = ζ (c a b)/2 C = ζ 2 b D = [R 2 (b a c) + a(a b c)]/2 E = ζ [R 2 (a b c) + b(b a c)]/2 F = [R 4 + R 2 (c a b) + ab] P 4 3/19/2009 39 P 4 a = w 1 R c 2 b = R c 2 c = w 1 2 ζ = 1/ K 2 P5/P4 4 3 2 1 ( ) P 4 4 0 0 1 2 3 4 P3/P4
Reflection Coefficient(dB) Appendix II: More Examples of 20 20 log( Γ kl ) 20 log( ΓΓ kkl ) 20 log( Γ ks ) 20 log( ΓΓ kks ) 20 0 20 40 Calibration Standard Results 52 GHz Sliding Loads from SDDOew Sliding Loads from SDDL Sliding Shorts from SDDOew Sliding Shorts from SDDL Reflection Coefficient(dB) 30 20 log( Γ kl ) 20 log( ΓΓ kkl ) 20 log( Γ ks ) 20 log( ΓΓ kks ) 20 0 20 40 54 GHz Sliding Loads from SDDOew Sliding Loads from SDDL Sliding Shorts from SDDOew Sliding Shorts from SDDL 56.653 60 0 5 10 15 20 25 50.76 60 0 kl 27, kkl 27, ks, kks 23 0 5 10 15 20 25 Sling positions 0 kl 27, kkl 27, ks, kks Sling positions 23 55 GHz 60 GHz 30 20 Sliding Loads from SDDOew Sliding Loads from SDDL Sliding Shorts from SDDOew Sliding Shorts from SDDL 30 20 Sliding Loads from SDDOew Sliding Loads from SDDL Sliding Shorts from SDDOew Sliding Shorts from SDDL Reflection Coefficient(dB) 20 log( Γ kl ) 20 log( ΓΓ kkl ) 20 log( Γ ks ) 20 log( ΓΓ kks ) 0 20 40 Reflection Coefficient(dB) 20 log( Γ kl ) 20 log( ΓΓ kkl ) 20 log( Γ ks ) 20 log( ΓΓ kks ) 0 20 40 60 60 66.83 80 0 5 10 15 20 25 0 kl 27, kkl 27, ks, kks Sling positions 23 70.729 80 0 5 10 15 20 25 0 kl 27, kkl 27, ks, kks Sling positions 23 3/19/2009 40
Basic Probe Simulation Model 1 3 4 5 2 Waveguide size: 148*74 (WR15, 50~75GHz) Channel size: 20*13 Channel distance: 40 Microstrip width: 6 MLine characteristic impedance Z 0 : 50.48 Ohm Substrate width:19 Substrate thickness:3 Unit: mils S Parameters (db) 0-10 -20-30 -40-50 -60 S11 S21 S31 S41 S51-70 50 55 60 65 70 75 3/19/2009 41 Frequency (GHz)