From GHz to THz: The Essentials of Very High Frequency ... · PDF file• Generation of THz...

© Virginia Diodes Inc. &

Agilent Technologies 2012

From GHz to THz: The Essentials of Very

High Frequency Signal Measurements

Virginia Diodes, Inc.

Agilent Technologies, Inc.

Dr. Jeffrey L. Hesler, CTO, Virginia Diodes, Inc.





This Presentation

• Explain the technologies that enable mmwave work

• Provide examples of applications for mmwave technologies

• Show the test equipment solutions available

• Review options for calibration and probing

• Show the levels of test performance available today





Applications Above 100GHz Compact Range Radar Radio Astronomy

Applications: Basic Science – the primary driver Concealed Weapons Detection Collision Avoidance Radar Detection of Chem./Bio. Hazards Wideband & Secure Communications Medical Diagnostics Test & Measurement

UML / ERADS

ALMA / NRAO





The transition from electronics to optics

No transistors, semiconductor lasers, isolators, switches, tunable attenuators

No broadly accepted standards – power, flanges, connectors

High transmission line losses

Microstrip ~ 1 dB/mm @ 600 GHz

Waveguide ~0.08 dB/mm @ 600 GHz

Atmospheric losses 0.0002 dB/mm (typ.) at 600 GHz

0.02 dB/mm at 557 GHz Water line

Machining challenges

3 THz operation requires channel width < 25 um!

Challenges Above 100GHz



Virginia Diodes • Company founded to respond to the needs of the

scientific community for THz sources, receivers

and instruments.

• Founded in 1996, focused on diodes

• Reorganized in 2001, added components

and systems

• Originally focused mainly on astronomy,

spectroscopy and plasma diagnostics

• Field now expanding

• Imaging, radar, EPR/NMR,

communications and general THz test

and measurement

• Developed a full range of broadband electrically

tunable solid state sources

and detectors

• Components from 50 GHz to 3 THz

• Ambient, no mechanical tuning

• Applying this state-of-the-art technology to THz

VNA Extenders

• Also Source and Spectrum Analyzer

Extenders

ALMA (NRAO)

THz Network Analysis



THz Diode IC

THz circuits are very small, but surprisingly robust!

Thickness ~5 um (for size scale,

red blood cells 5-10 um!)





VDI is a small, high technology company focused on the emerging field of

Terahertz Technology

Advanced scientific base & emerging new applications

Together Virginia Diodes, Inc. (VDI) and Agilent Technologies have

demonstrated:

Full waveguide band sources

Signal analysis, and

Fully calibrated VNA measurements

Throughout the frequency range from 50GHz through 1.1THz, and

beyond!

Continued growth in THz applications

requires the availability of quality test and

measurement equipment…



Core Technology: Use nonlinear devices to extend the

frequency range of traditional microwave electronics

X3

Microwave Technology VDI Technology

X8

Schottky Diodes

Planar Advanced

fabrication

technology

CAD Design

• First-time design

• Broadband &

Tunerless

• High Efficiency

40 GHz 16.7 GHz

320 GHz 40 GHz

1.5W 20mW





Component Example: Balanced Varactor Doubler

Waveguide input & output

Careful choice of circuit

configuration

Balanced design allows

for broad bandwidth and

high efficiency

CAD Design to allow

tunerless operation



Frequency Multipliers

Output 265-400 GHz

Input 88-133 GHz

Tunerless

Ambient operation

Rugged and repeatable

Core component for

VNA Extenders

WR-2.8X3 (265-400 GHz)

0

1

2

3

4

265 315 365

Eff

icie

ncy (

%)

Frequency (GHz)



Signal Source Extenders

Motivation:

• Generation of THz power to enable basic

measurements of either active or passive components

Example:

• Sources for use as the local oscillator for Astronomy

receivers

• Lowest noise highest sensitivity



Broadband High Power Varactors

• High power can be used to drive THz multiplier chains

0

50

100

150

200

250

300

350

400

450

100 110 120 130 140 150

Ou

tpu

t P

ow

er

(mW

)

Output Frequency (GHz)

D123R1 (B1-02) D123R1 (B1-03)



Example: Proposed 1.2-1.6 THz Source

• Cover 1.2-1.6 THz with 5-10

uW output power

• Two varactor chains to cover

130-180 GHz

• Combined using

Waveguide Diplexer

• Cascaded broadband

frequency triplers after the

diplexer

• Diplexer gap between the

bands can be centered at the

1.4 THz water line



Astronomy LO: Solid-state source at

3.1THz – in the lab…

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

3030 3050 3070 3090 3110 3130 3150 3170 3190

Po

wer

(uW

)

Frequency (GHz)

WR0.34X9 Output Power

A THz Diode IC



Signal Source Extenders

Motivation:

• Generation of THz power to enable basic

measurements of either active or passive

components

Examples:

• Broadband signal sources to allow full waveguide

band measurements with high signal-to-noise



Broadband sources – Example WR2.2 325-500GHz

-30

-25

-20

-15

-10

-5

0

5

10

300 320 340 360 380 400 420 440 460 480 500 520

Ou

tpu

t (d

Bm

)

Frequency (GHz)

WR2.2 AMC Output Power

• Synthesizer (e.g. PSG) Extender to THz

• Turn-key Source

• State-of-the-art Output Power



VDI WR9.0 THz Starter Kit: 82-1100 GHz

•WR-9 – 82-125 GHz •Pout ~ 25 mW

•WR-4.3 – 170-250 GHz •Pout ~ 3 mW

•WR-2.8 – 265-375 GHz •Pout ~ 0.7 mW

•WR-2.2 – 340-500 GHz •Pout ~ 0.18 mW

•WR-1.5 – 510-750 GHz •Pout ~ 30 uW

•WR-1.0 – 795-1100 GHz

•Pout ~ 4 uW 0.0001

0.001

0.01

0.1

1

10

100

0 500 1,000

Po

we

r (m

W)

Frequency (GHz)

WR9.0x3 WR4.3x2 WR2.8x3

WR2.2x2 WR1.5x3 WR1.0x3

• Series of cascaded multipliers and detectors

• Tunerless, instantaneous sweeping over >

40% bandwidth

• Rapidly interchangeable components

• Turn-key operation

• Built-in AM modulation and Power Control

capability

• For use with detectors

• Detectors are available for all bands

• Responsivity 2500 V/W at WR-10, 500

V/W at WR-1.0



VDI System Development

• VDI has developed a wide range of THz systems

• ESR/EPR/NMR Measurement systems

• Passive Radiometers

• Spectrum Analyzer Extenders for Signal Analysis

• Vector Network Analyzer Frequency Extenders



Signal Analysis

Motivation:

• As researchers develop new sources of THz

power, a primary challenge is accurate

measurement of the spectral quality of the signal.

Example:

• In the case of frequency multiplier systems, such

as the VDI modules, one primary concern is the

presence and magnitude of unwanted harmonics.

So, let’s look at these harmonics using a PXA and

frequency extender module.



Demonstration of Signal Analysis

VDI WR1.5 TxRx Module

(500-750GHz)

Agilent

PXA

Agilent

PSG



Spectral purity of a 625 GHz Signal



Phase Noise Measurement at 700 GHz



Displayed Average Noise Level (DANL) Meas.

In WR1.0 waveguide band – 750-1,100GHz



The enabling technology for these

measurements is the high quality

heterodyne receivers that were

previously developed for science…

0

2

4

6

8

10

12

14

380 400 420 440 460 480 500 520 540 560 580 600 620

Convers

ion L

oss (

dB

, D

SB

)

Frequency (GHz)

WR1.9SHM Conversion Loss

Wang et al (NASA-GSFC)



VDI System Development

• VDI has developed a wide range of THz systems

• ESR/EPR/NMR Measurement systems

• Passive Radiometers

• Spectrum Analyzer Extenders for Signal

Analysis

• Vector Network Analyzer Frequency Extenders



• VNA are used to measure the

complex scattering parameters

of a DUT

• Why is complex important?

• Needed to fully

characterize a device

• Needed to transform to

time domain

• Enables advanced

calibration routines

• VNA Configuration

• Incident wave sampled by

reference mixer (R)

• Scattered waves sampled by

measurement mixers (A & B)

• Measured vector ratios A/R

and B/R of calibration

standards and DUT are used

to determine the DUT

response

Vector Network Analyzers



-20

-15

-10

-5

0

330 430

Mag

. (d

B)

Frequency (GHz)

-20

-15

-10

-5

0

330 430

Mag

. (d

B)

Frequency (GHz)

2-Port TRL Calibration

Measurement using Normalization • Calibration used to

remove effect of

systematic measurement

errors

• Requires complex

measurements

• Example: Measurement of

WR-2.2 Coupler

• Response Calibration

(i.e. simple

normalization)

• Full 2-Port TRL

Calibration

• Dramatic improvement in

quality of measurement

• Useful even for

magnitude only

measurements (e.g.

SWR)



Virginia Diodes VNA Extenders WR-1.5 VNA Extender

• VDI Extenders available from WR-10 (75-110

GHz) thru WR-1.0 (750-1050GHz)

• State-of-the-art Dynamic range & Test Port

Power

• 120 dB (typ.) at WR-10 (70-110 GHz)

• 110 dB (typ.) at WR-3.4 (220-325 GHz)

• 100 dB (typ.) at WR-1.5 (500-750 GHz)

• 60 dB (typ.) at WR-1.0 (750-1050 GHz)

• Excellent amplitude and phase stability



Extension of VNA to THz

Agilent PNAX

RF

LO

Ref.

Meas.

VDI WR-2.2 (325-500 GHz)

VNA Extender

Operation to ~50GHz

Operation to THz



Full TxRx Extender Layout



Frequency Extension of a VNA



THz Waveguide Calibration

¼-Wave

Calibration Shim

• Typical VDI Waveguide Calibration Kit at

WR-3.4 and lower

• 2 Waveguide Loads

• 2 Waveguide Shorts

• 3 eighth-wave shims

• 2 quarter-wave shims

• To allow TRL calibration

• 1 Precision Waveguide Straight Section

• Calibrations: TRL, SOLT, Offset Short,

Offset Load, …

• VDI Calibration Kit at WR-2.2 and above

• Quarter-wave shim is thin and fragile

Move to SOLT using precision load

• 2 Waveguide Loads

• Precision Loads, 50 dB RL typical

• 2 Waveguide Shorts

• 2 Waveguide Quarter-wave Delayed Shorts

• 1 Precision Waveguide Straight Section

• Calibration: SOLT



Vector Network Analysis

• Motivation:

• Perform calibrated measurements of components

and devices at THz

• Measurements ranging from waveguide,

quasi-optical, and on-wafer

• Example:

• Measurements of Waveguide Loss and Interface

Reflection



WR-1.5: Amplitude & Phase Stability

10/25/2012 35

-1

-0.5

0

0.5

1

500 600 700

Ma

g(S

21

) (d

B)

Frequency (GHz)

S12(DB) S21(DB)

-20 -15 -10

-5 0 5

10 15 20

500 600 700

Ph

as

e(S

21

) (d

eg

)

Frequency (GHz)

S12(DEG) S21(DEG)

• Look at amplitude & phase

stability of system over one hour

• Stability is important to

maintain the calibration

during the measurements

• Measured for full 2-port

WR-1.5 extender

• 1-port stability typically

5-10 times better

• Stability was measured in

general laboratory space

• Poorly controlled

thermal environment

• Significantly improved

performance can be

achieved in a controlled

thermal environment



WR-1.5 (500-750 GHz) TRL Measurements

10/25/2012 36

-50

-40

-30

-20

-10

0

490 540 590 640 690

Ma

gn

itu

de (

dB

)

Frequency (GHz)

Diagonal Feedhorns

Horn B2-01 Horn B2-14

-100

-80

-60

-40

-20

0

-0.05 0.00 0.05 0.10 0.15 0.20

Ma

gn

itu

de (

dB

)

Time (ns)

Time Domain Reflection

Horn B2-01 Horn B2-14

Reflection

from

Aperture

Reflection

from

Interface

• First, look at the measurement of RL of a

diagonal feedhorn

• 25 dB gain, smooth-walled diagonal

horn

• Return Loss 20-30 dB

• One horn has waveguide alignment

issue

• Very challenging to measure

this without VNA

• Now working with machinists

to tighten tolerances




10/25/2012 37

-80

-70

-60

-50

-40

-30

-20

-10

0

490 540 590 640 690

Lo

ss (

dB

)

Frequency (GHz)

1-15 Up 1-15 Down

1” Precision

Waveguide

-100

-80

-60

-40

-20

0

-0.1 0.0 0.1 0.2 0.3 0.4 0.5

Ma

gn

itu

de

(d

B)

Time (ns)

S11(DB) S22(DB)

Reflections from Interfaces

• Next, look at measurements of a

1” precision straight waveguide

section

• Return loss better than 25 dB over

most of band

• Reflections are from the

waveguide interfaces

• Next, look at insertion loss…




0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

490 540 590 640 690

Lo

ss (

dB

/mm

)

Frequency (GHz)

WR-1.5 Waveguide Loss (E-plane Split)

Theoretical

Loss

557 GHz

Water Line

• The waveguide loss

matches the theoretical well

• Measured loss for VDI

waveguide typically 1-1.5

times the theoretical loss

• Excess believed to be

caused by a

combination of surface

roughness and gold

conductivity

(impurities)

• The peak at 557 GHz is

caused by a water vapor

line




10/25/2012 39

0

0.05

0.1

0.15

0.2

490 540 590 640 690

Lo

ss (

dB

/mm

)

Frequency (GHz)

WR-1.5 Waveguide Loss (E-plane Split)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

490 540 590 640 690

Lo

ss (

dB

/mm

)

Frequency (GHz)

WR-1.5 Waveguide Loss (H-Plane Split)

Bend Loss Bend Loss 5 * Theory

E-plane

Split

H-plane Split

• VDI blocks typically made in two-

pieces, using a split-block technique

• For most components an E-plane split

is used

• No currents crossing split loss

similar to solid waveguide

• For an H-plane waveguide bend an H-

plane split must be used instead

• Currents are crossing the split

• Try to minimize the effect of split

by careful machining, soft gold,

and clamping

• However, loss of H-plane split

components is much higher at THz

• ~5 time theoretical loss for solid

guide for this component

• Shows importance of mechanical

issues at THz



WR-1.0 VDI VNA Extender

-10

-8

-6

-4

-2

0

750 950

Ma

g (

dB

)

Frequency (GHz)

S21 for 1” Waveguide Piece

S21 S12 1.4*Theoretical Loss

• Dynamic range 60 dB typical

• With 10 Hz IF Bandwidth

• Excellent amplitude and phase stability

• +/-10 degrees and +/-0.8dB, under normal

operating conditions

• THz Measurements using SOLT calibration




Motivation:

• Perform calibrated measurements of

components and devices at THz

• Measurements ranging from waveguide,

quasi-optical, and on-wafer

Example:

• Quasi-optical Measurement of Dielectric

Constant



Quasi-Optical VNA Measurements

RF, LO & IF

Signal

Cables

50 GHz

VNA VDI WR-2.2

Extenders

Quasi-optical

Dielectric

Measurement

Setup

325-500

GHz

• Quasi-optical dielectric measurements performed at Agilent





Thz Quasi-Optical Calibration

Material assumptions:

• Flat parallel faced samples

• Sample in non-reactive region

• Beam spot is contained in sample

• Known thickness > 20/360 λ

l

Reflection

(S11 )

Transmission

(S21 )

r and r

Transmission Free-Space



Mm-Submm Wave System



Thru

Reflect

Match

TRM Calibration



TRL Calibration

Thru

Reflect

Line

Move the antenna away to compensate for the thickness of the short. Move it back for the next step.

Move the antenna away on a quarter-wavelength and then back in the original position.

Precise positioning fixtures are expensive





Gated Reflect Line (GRL) Calibration Two Tiered Process

Two port calibration at waveguide or coax input into antennas removes errors associated with network analyzer and cables.

ECal, SOLT or TRL Cal done here





Gated Reflect Line (GRL) Calibration Two Tiered Process

Two additional free space calibration standards remove errors from antennas and fixture.

Reflect

(metal plate of

known thickness)

Line

(empty fixture)



Free Space 75-110GHz Quasi-Optical System



Measurement Results




Motivation:

• Perform calibrated measurements of components

and devices at THz

• Measurements ranging from waveguide, quasi-

optical, and on-wafer

Example:

• On wafer measurements of THz transistors



On Wafer Probing for

Submillimeter-Wave Devices • Transistors and MMIC’s are approaching operation at 1 THz

• Current Characterization based on Fixturing Components

• Need for Direct On-Wafer Measurement

• No De-embedding of Fixture

• Rapid Measurement/Assessment

• Development of Device Models

480 GHz LNA mounted in a waveguide fixture

(courtesy of Northrup Grumman Aerospace

Systems, IEEE MICROWAVE AND WIRELESS

COMPONENTS LETTERS, VOL. 20, NO. 5,

MAY 2010, pp. 289-291)



-180

-120

-60

0

60

120

180

-30

-25

-20

-15

-10

-5

0

500 550 600 650 700 750

Ph

ase [d

egre

es]

S-Pa

ram

ete

rs [

dB

]

Frequency [GHz]

S21

S11

S21

WR-1.5 Micromachined Probes –

RF Performance TRL Measurements from Northrup Grumman

Images courtesy of W.R. Deal

• World’s first TRL calibration above 500 GHz!

• DMPI (dmprobes.com) wafer probes with VDI THz Extenders

• Reck et al., IEEE-TST 2011, pp. 349-363

• The probe design is being extended to 1.1 THz for use with VDI 1.1 THz extenders



Summary

• Terahertz technology is an emerging field with many

established applications in basic science, as well as a host

of commercial applications that are now under development.

• A primary need is fast, convenient and accurate Test &

Measurement tools.

• Full waveguide band frequency extenders are now available

for signal generators and signal analyzers up to 1.1 THz

• Scientific Applications are driving development to 3.1 THz

and beyond!





Questions?

From GHz to THz: The Essentials of Very High Frequency ... · PDF file• Generation of THz...

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Transcript of From GHz to THz: The Essentials of Very High Frequency ... · PDF file• Generation of THz...