waveguide-based measurements at terahertz frequencies
TRANSCRIPT
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Robert M. Weikle, IIGuoguang Wu
Huilin Li
Charles L. Brown Department of Electrical and Computer EngineeringUniversity of Virginia
Jeffrey L. Hesler
Virginia Diodes, Inc.Charlottesville, VA
Anthony R. Kerr
Central Development LaboratoryNational Radio Astronomy Observatory
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
OVERVIEW
Scattering-Parameter Measurements at Submillimeter Wavelengths
Flange Alignment and Repeatability
Flange Alignment and Calibration
• Four-Port and Six-Port Approaches• Six-Port Reflectometer Operation• WR-2.8 Six-Port Reflectometer• In-Situ Measurement with Embedded Six-Ports
• Waveguide Flange Types• Ring-Centered Flange Repeatability
• Calibration Standards Resistant to Misalignment• Calibration by Null Double Injection
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Scattering Parameter Measurements atSubmillimeter Wavelengths
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide-Based Scattering Parameter Measurements
VDI WR-1.5 Frequency Extension Module(500—750 GHz)
VDI Frequency Extenders with a Rhodeand Schwarz ZVA 40 Network Analyzer
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Basic S-Parameter Measurement Architectures
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Intersection of Circles determinesratio b3/b4
“true” Γ related by bilinear transform:requires four-port calibration
Six-port to four-port reduction requiresknowledge of five “network constants:”
1. w1 (real)2. w2 (complex)3. ρ (scalar)4. ζ (scalar)
Determination of complex ratio w = b3/b4
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Constraining Relation between b3 , b4 , b5 , and b6 :
a + b ζ + c ρ + (c – a – b) ζ + (b – a – c) ρ
+ (a – b – c) ζ ρ + a(a – b – c) + b(b – a – c) ζ
+ c(c – a – b) ρ + abc = 0
P3P4
( )2 P5P4
( )22 2 P6P4
( )2 P3P5P4
( )2P3P6
P4( )2
P5P6P4
( )2P3P4
P5P4
P6P4
Where,
a = w1 – w22 b = w2
2 c = w12
Sliding Load Method (G. Engen)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Constrain Γ to lie on a circle (i.e., sliding termination) maps into circle in w-plane
Quadratic Surface in P-space maps out an ellipse:
A + 2 B + C + 2 D + 2 E + F = 0P3P4
( )2 P5P4
( )2 P3P4
( ) P5P4
( )P3P5P4
( )2
Where,
w – Rc2 = R2
A = a B = ζ (c – a – b)/2C = ζ 2bD = [R2(b – a – c) + a(a – b – c)]/2E = ζ [R2(a – b – c) + b(b – a – c)]/2F = [R4 + R2(c – a – b) + ab]
a = w1 – Rc2
b = Rc2
c = w12
ζ = 1/| K |2
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
General Calibration Strategy :
1. Measure Response of Power Detectors to Sliding Load2. Plot Power Ratios Against One-Another Ellipse in P-plane3. Determine Five Coefficients via Least-Squares Fit,
4. Algebraically Determine Six-Port Reduction Coefficients5. Calibrated Effective Four-Port Using One of Several Standard Methods
AF
BF
CF
DF
EF, , , ,
Note:
1. Only five detectors used thus far 5 port reflectometer2. Several sign ambiguities are encountered in intermediate steps determining
a, b, c, ζ, and R2
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Comparison of Four-Port and Six-Port Approaches
Four-Port Architecture Six-Port Architecture
Measurement of Magnitude/PhaseLarger Dynamic RangeEasier Calibration Procedure
Increased Complexity and Cost
(Heterodyne Approach) (Power Detection Approach)
Measurement of Magnitudes OnlyDynamic Range limited by detectorsComplex Calibration Procedure
Simple Hardware ImplementationRelatively Inexpensive and Low-Profile
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Example: WR-2.8 Six-Port Reflectometer
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Example: WR-2.8 Six-Port Reflectometer(response to offset shorts)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Example: WR-2.8 Six-Port Reflectometer(calibrated measurements of delayed shorts and
waveguide match)
285 GHz 335 GHz
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Example: WR-15 In-Situ Six-Port Reflectometer
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Example: WR-15 In-Situ Six-Port Reflectometer(detector response)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Example: WR-15 In-Situ Six-Port Reflectometer(comparison with HP 8510C)
Waveguide Coupler
Horn Antenna
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Example: WR-15 In-Situ Six-Port Reflectometer(VDI Frequency Doubler Chain)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Alignment and Repeatability
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Misalignment and Repeatabilitystandard MIL spec 0.75” round (UG-387)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Misalignment and RepeatabilityAnti-Cocking flange
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Misalignment and RepeatabilityBoss-and-socket flange (Lau and Denning)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Misalignment and RepeatabilityRing-Centered flange (A.R. Kerr)
Prototype WR-5 (140—220 GHz) ring-centered flange sections with anti-cocking rim and extended boss to permit mating with alignment ring (seen on the right boss)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Misalignment and Repeatability
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Misalignment and Repeatability
140 GHz 180 GHz 220 GHz
Anti-cockingflange
Ring-centeredflange
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Waveguide Flange Alignment and Calibration
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Four Calibration Standards:
1. Flush Short Circuit2. Two offsets with unknown (but
different) phases3. Open Waveguide Flange
NOTE: None of these standards require precise alignment of waveguides
Waveguide Calibration: Flange Misalignment
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Effects of Waveguide Misalignment on Calibration Standards
Simulated return loss of misaligned matchedload (7% offset in E-plane)
Simulated phase error of misaligned matcheddelayed short (7% offset in E-plane)
Measured return loss of purposely misaligned matched load (~7% offset in E-plane)
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Measured load is offset short verification standard
Comparison of Various Calibration Schemes
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Comparison of Various Calibration Schemes
Measured component is waveguide E-H tuner
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Six-Port Calibration by Null Double InjectionConcept: Simultaneously Drive Source and Measurement Ports with Pair of
Phase-Locked Sources
b5 = Kb3 + Lb4
b6 = Mb3 + Nb4
Adjust Sources to Null b4 :
Adjust Sources to Null b3 :
b5 = Kb3
b6 = Mb3
P5P3
= |K|2 =
P6P3
= |M|2 =
1ζ
1ρ
b5 = Lb4
b6 = Nb4
P5P4
= |L|2 =
P6P4
= |N|2 =
w1
ζ
2
w2
ρ
2
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
Six-Port Calibration by Null Double Injection (cont’d):Adjust Sources to Null b5 :
Kb3 + Lb4 = 0P4 KP3 = = L 2
w12
P6P4
= |M|2 LK
NM
2– +
21 w1 – w2ρ=P6P4
b6 = M b3 + N b4
WMI: Making Reliable Measurements at Millimeter and Submillimeter Wavelengths
Waveguide-Based Measurements at Terahertz Frequencies
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Waveguide-Based Measurements at Terahertz Frequencies
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