gregory mazzaro agilent e4438c siames research...

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NC STATE UNIVERSITY

Gregory Mazzaro

SIAMES Research GroupNorth Carolina State University

Time-Frequency Effects in Wireless Communication Systems

Ph.D. Dissertation Defense

Tektronix TDS684Bdigitizing oscilloscope

Agilent E8267Cvector signal generator


Tektronix AWG2021waveform generator

September 28, 20094:00pm, MRC 463

NC STATE UNIVERSITY

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Time-Frequency Effects: Presentation Overview

• Motivations — The “Big Picture”

• Original Contributions vs. Previous Research

• Completion of Tasks & Conclusions

linear transient distortion in narrowband systems

nonlinear transient distortion in narrowband systems linear metrology of bandpass RF components

nonlinear metrology of bandpass RF systems appendices — the “How-To” section

• New Chapter: Linear Amplification by Time-Multiplexed Spectrum

• Summary & What’s Next?

26 slides

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Time-Frequency Effects: Motivations (Chapter 1)

• The limitations of the steady-state frequency domain

• Co-site interference

• multiple radios in close proximity operate with same frequencies• circuit-field coupling, nonlinear mixing, long-tail transients

• Testing of integrated assemblies

• higher levels of integration fewer access points for testing• need non-destructive methods for testing integrated structures

• Improvement of transmitter linearity

• new comm. systems implement spectrally-efficient modulation schemes• need ways to meet stringent specs. for linearity & signal quality

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Why look at the time domain? i.e. When is steady-state analysis inadequate? for narrowband systems

e.g. for filters of higher order

simulated

simulated

measured

• What is the nature of these effects?

• How can they be mitigated?

• How can they be usedto the advantageof a system designer?

Time-Frequency Effects: Motivations (Chapter 1)

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Time-Frequency Effects: Nature of Transients (Chapter 2)

• time-frequency effects caused by bandpass filters

coupled resonatorsWhy focus on filters?(a) they are ubiquitous in wireless communications devices

(b) they are most likely to produce unintended transient behaviorwith continued application of traditional steady-state design

narrowband, greatest reactive energy storage capability

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Time-Frequency Effects: Prior Work vs. My Work (Chapter 2)

Studies of bandpass transients were done for 2nd-order filters…

I’ve extended the study to 7th-order, narrowband filters

…to show that transients last a lot longer than the expected s

Little quantitative evaluation of such effects on comm. systems was performed…

I’ve measured ISI and IMD for frequency-hopping scenarios

…to demonstrate that filter transients can produce co-site interference

Resonant-circuit measurement is typically linear, steady-state, 2-port…

I’ve created new 1-port time-domain methods to measure Q, B, S21

…which add to our current collection of non-destructive tests

Most linearization techniques require a priori knowledge of nonlinearities…

I’ve developed a time-multiplexing method for reducing AM distortion

…which does not require predistortion, feedback, or calibration

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Time-Frequency Effects: Publications

G. J. Mazzaro, M. B. Steer, K. G. Gard, and A. L. Walker,“Response of RF networks to transient waveforms:Interference in frequency-hopped communications,”

IEEE Trans. Microw. Theory Tech., Vol. 56, No. 12, pp. 2808-2814, Dec. 2008.

G. J. Mazzaro, M. B. Steer, and K. G. Gard,“Filter characterisation using one-port pulsed RF measurements,”IET Micro. Ant. Prop., Vol. 3, No. 2, pp. 303-309, Mar. 2009.

G. J. Mazzaro, K. G. Gard, and M. B. Steer,“Low distortion amplification of multisine signalsusing a time-frequency technique,”

2009 IEEE MTT-S Int. Microw. Symp., Boston, MA, June 2009, pp. 901-904.

(2 others as primary author, 3 others as secondary author)

G. J. Mazzaro, M. B. Steer, and K. G. Gard,“Intermodulation distortion in narrowband amplifier circuits,”accepted to IET Micro. Ant. Prop., Sept. 2009.

G. J. Mazzaro, K. G. Gard, and M. B. Steer,“Linear amplification by time-multiplexed spectrum,”submitted to IET Circuits Devices Syst., Sept. 2009.

publishedjournals

publishedconference

papers

unpublishedjournals

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Time-Frequency Effects: Table of Contents, Preliminary Exam

1 Overview

Motivations, ObjectivesOriginal contributionsPublished & unpublished works

2 Review of Time-Frequency Concepts

Important time-frequency quantitiesReview of analysis techniquesTransients in narrowband systemsExtraction of resonant circuit parameters

3 Linear Transient Distortion in Wireless…

Single-tone pulsed filter responseSwitched-tone filter responseTransient response from lowpass prototypingCase study: frequency hopping systems

4 Linear Metrology of Bandpass RF Components

Equivalence of quality factor-- time & frequencyExtraction of resonator Q from RF pulse decayResonator separation methodDetermination of bandwidth from RF pulse decay

5 Nonlinear Metrology of Bandpass RF Systems

Generating multi-tone signal from switched sourceIMD in frequency-hopping systems

6 Remote Characterization of RF Devices

Linear & nonlinear wireless reflectionsCanonical radios & FRS/GMRS radiosSwitched-tone, one-port filter passband extraction

7 Conclusions & Future Work

same as current versionrearranged

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Time-Frequency Effects: Table of Contents, Current Version

1 Overview

Motivations, ObjectivesOriginal contributionsPublished & unpublished works

2 Review of Time-Frequency Concepts

Important time-frequency quantitiesReview of analysis techniquesTransients in narrowband systemsExtraction of resonant circuit parameters

3 Linear Transient Distortion in Wireless…

Single-tone pulsed filter responseResonator separation methodSwitched-tone filter responseLinear wireless switched-tone reflectionsTransient response from lowpass prototypingCase study: frequency hopping systems

same as previous versionrearrangednew material

4 Linear Metrology of Bandpass RF Components

Equivalence of quality factor-- time & frequencyExtraction of resonator Q from RF pulse decayDetermination of bandwidth from RF pulse decayDetermination of S-parameters from short pulses

5 Nonlinear Metrology of Bandpass RF Systems

Generating multi-tone signal from switched sourceNon-linear wireless switched-tone reflectionsSwitched-tone, one-port filter passband extractionIMD in frequency-hopping systems

6 Linear Amplification by Time-Multiplexed Spectrum

Distortion reduction theory: 2 and 4 tonesExperimental validation: narrow- and wide-bandLinear signal recovery: theory & measurement

7 Conclusions & Future Work

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Time-Frequency Effects: Linear Transient Distortion (Chapter 3)

7th-order 900-MHz 4% Chebyshev bandpass filter

higher-order filters respondmore slowly than expected

filters store/release reactive energyin a frequency-dependent cascade

0

900 MHz 34 MHz4.7 ns

2 2 900 MHzQ

f

f1

• How do transients behave inhigher-order bandpass systems?

Vin :

single-tone pulse applied to bandpass filter

MTT, 12/08

Nearest prior work:Tucker/Eaglesfield (1946) -- traces & solutions for 3rd-order filters

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f2f1

“switched-tone” signal:

1 s 1 s

stimulus frequency switched at t = 0 ns

it is possible to produce amomentary interference patternwith a switched-tone source

+ a bandpass filter

Nearest prior work:Hatton (1951) & McCoy (1954) --

amplitude & frequency transients for pulses & chirps in RLC circuits

• How do transients behave in higher-order bandpass systems?

MTT, 12/08

(slow) (fast) overlap


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2 102

s S j

2 1

2lp

out1

i

n j tS t

ii

V t Ae Be

bandpass transient responsesmay be computed as time-scaledlowpass transient responses

2 10 0

0 0

bp 2out

1 2

2

in S t j t j ti

i

j t j t j t

AV t e e e

B e e e

bp lp 2 1out 0 outcos

2V t t V t stimulus tone switched on at t = 0 ns, off at t = 250 ns

Nearest prior work: Blinchikoff (2001) -- response (only) at center frequency

MTT, 12/08

• How can we model these transient effects (mathematically)?


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• What are the effects of these transients on wireless communications?

Filtered frequency-hopping pulses, 900-MHz 4% filterUser 1 at 10 dBm, User 2 at -20 dBm900 MHz, 100 ns guard interval

measured

sharp filtering can degrade received signal-to-noise ratio

Nearest prior work:Chohan/Fidler (1973) -- impact on FSK

& PSK, no metric

measured

MTT, 12/08


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Time-Frequency Effects: Nonlinear Distortion (Chapter 5)

IET, 09/09

Measured IM3 for single switching eventUser 1 at -11 dBm, User 2 at -11 dBm, no guard interval

filter passband = 885 to 915 MHz, Phillips BGA2748 amplifier

• What other effects impactcommunication systems?

sharp filteringwith amplification

generates intermodulation

Nearest prior work:

Vendik/Samoilova (1997) – IMD by filtering alone,charge carrier density & conductor defects

pulses in a neighboring bandcan generate IMD in your band

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Time-Frequency Effects: Linear Metrology (Chapter 4)

900-MHz stimulus tone turned off at t = 0 ns

the Q factor of the outer resonatorsin a chain may be determinedwith time-domain analysis

simulated

2 20ln ln R

tV V t

1 1 21

N N N1 N1 N N1

(0) (0) (0) 2 (0)dV V I Vdt R C C R C

• How do we measure parametersof coupled resonator circuits?

IET, 03/09

Nearest prior work:Pereda (1992) -- Prony analysis,

dielectric resonators, not a ‘coupled’ structure

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the bandwidthof a narrowband circuit

may be estimatedfrom its RF pulse decay,

without its S-parameters

• How else can we use transients to measure resonant circuits?

Pulse decay response and RF envelope7th-order 3% Chebyshev filter0-dBm 900-MHz tone removed at t = 1 us

measured

Nearest prior work:Dunsmore (1999) – tuning filtersby equalizing distances between nulls

2 1

1Bt t

bp lp 2 1env2

d g t h tdt

2t1t

2t1t

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2-port S-parameters can be extractedfrom short-pulse time-domain responses

• How else can we exploit transients for metrology?

Nearest prior work:Courtney (1999) –

permittivity measurements, nanosecond impulses

Time- & frequency-domain views, short pulses465-MHz 1% Chebyshev filters

simulated

simulated

measured

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Time-Frequency Effects: Nonlinear Metrology (Chapter 5)

a device’s passbandcan be extracted from 1 port

• Can we exploit filter properties for nonlinear measurements?

IP3 of an amplifier can be measuredusing a filter & switched-tone source

Nearest prior work: Walker (2005) –steady-state two-tone testing

Simulated fast-switching filter response7th-order 465-MHz Chebyshev design(a) input, 1 tone, (b) output, 1 tone, (c) output, 2 tones

Passband extraction for bandpass filter7th-order 900-MHz Chebyshev design

IET, 09/09

measured

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Time-Frequency Effects: Wireless Testing (Chapters 3 & 5)

Wireless linear switched-tone reflection capture(a) block diagram, (b) oscilloscope trace

Wireless non-linear switched-tone retransmission capture(a) block diagram, (b) average IM3 power plot

• Can filter transientsbe captured remotely?

Yes, switched-tone phenomenacan be captured wirelessly.

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• How can we improve linearity by applying time-frequency techniques?

the IMD associated with amplitude modulationcan be reduced by trading signal bandwidthfor smaller Peak-to-Amplitude Ratio

Wideband & narrowband spectra for N = 10generated by Agilent N6030A + QM3337A modulator

measured

measured

IET, 09/09

Distortion reduction for N = 20non-multiplexed (red) vs. multiplexed (blue)Ophir 5162 amplifier

Linear Amplification by Time-Multiplexed Spectrum (Chapter 6)

LITMUScircuit architecture

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• How can we improvelinearity with time-frequency techniques?

by rapidly time-multiplexing / amplifying / filtering a signal,distortion is reduced for equivalent desired AM signal power

Nearest prior work: Hung et. al. (2002) – optical CATV network

Time-Frequency Effects: LITMUS (Chapter 6)

IMS, 06/09

Distortion reduction for N = 4 with filteringnon-multiplexed (red) vs. multiplexed (blue)Ophir 5162 amplifier

Demonstration of linear signal recovery with low-loss filterwideband unfiltered (top) vs. narrowband filtered (bottom)

time domain (left) vs. frequency domain (right)

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Time-Frequency Effects: Summary (Chapter 7)

Narrowband transients last longer than expected.

(a) identified resonant cascade as a source of long tails(b) developed a differential-equation simplification(c) showed frequency-dependence of the tails causes pulse overlap(d) evaluated ISI and IMD for frequency-hopping scenarios

Used filter transients to develop new measurement techniques:

(a) Q-factor of a single resonator(b) bandwidth, without S-parameters(c) broadband S-parameters from a single time-domain trace(d) device passband from a single input port

Time-multiplexing & filtering — LITMUS:reduces IMD associated with amplitude modulation

co-site interference

non-destructive testing

transmitterlinearity

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Time-Frequency Effects: Future Research (Chapter 7)

(1) How can we design systemsto avoid narrowband transients?

(2) Can more information be extractedfrom pulsed & switched-tone responses?

(3) How can LITMUS be grafted onto existing modulation formats?

Garfield Minus Garfield

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Time-Frequency Effects: Appendices

A — Instrument Control & Calibration

how to set up & program the equipmentin our lab to reproduce my results

B — fREEDA Elements

documentation for simulations

C — Matlab Helper Functions (data processing)

D — Cauer 1 vs. Cauer 2 Filter Designs

how transient responses differ forType 1 vs. Type 2 (same S21, different S11)

E — Filters Used in This Study

S-parameters, group delay, manufacturers & pricing

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What’s Next?

Army Research Laboratory

2800 Powder Mill RoadAdelphi, MD

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Thank you…

…to my committee members,

Dr. Michael Steer, Dr. Kevin Gard,

Dr. Mohammed Zikry, Dr. Keith Townsend,

Dr. Devereux Palmer

…to everyone who shared MRC 438 with me for three years,

…to Vadum,

…and to everyone else here today.

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Tektronix TDS684Bdigitizing oscilloscope



Tektronix AWG2021waveform generator

…and they lived happily ever after.

The End.

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Time-Frequency Effects: Resonator Separation (Chapter 3)

• What is the natureof filter transients?

Long-tail behavior is attributedto the resonant cascade.

Resonator-separation simulation methodcircuit in ADS (above) and voltage at filter output (left)

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Time-Frequency Effects: Tucker/Eaglesfield (1946)

differential operators (precursor to Laplace Transforms) can be used to solve for analytical forms for pulse responses

oscilloscopes can capture filtered pulse envelopes

• commonly-used6-elementbandpassfilter

Filtered Pulse Responses

while analyzing non-ideal (transmission-characteristic) filters…

“Transient response of filters,” Wireless Engineer, Vol. 23, pp. 36-42 & 84-90, Feb-Mar. 1946

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Time-Frequency Effects: Hatton (1951) & McCoy (1954)

“Simplified FM transient response,” MIT, Cambridge, MA, Tech. Rep. 196, Apr. 1951“FM transient response of band-pass circuits,” Proc. IRE, vol. 42, no. 3, pp. 574-579, Mar. 1954

overshoots in amplitude & frequency are possiblefor input frequency transitions within a filter’s passband

• amplitude transients & frequency transientsfor a single resonator

Normalized Amplitude Transients Normalized Frequency Transients

while comparing frequency-modulation to amplitude-modulation…

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Time-Frequency Effects: Blinchikoff (2001)

Filtering in the Time and Frequency Domains, Raleigh, NC: SciTech Publishing, Inc., 2001.

• lowpass vs. bandpass transient responses

transient response at midbandis a time-scaled version of thelowpass turn-on response

0cosb l Nu t u t t

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Time-Frequency Effects: Chohan/Fidler (1973)

Normalized Frequency Transients

frequency step as a percentage of B,2nd-order filter

phase step,2nd-order filter

• frequency transients,steps of phase/frequencyat filter input

generalized earliernarrowband Laplace methodsfor any order & any Q value

while investigating filtering effectson FSK- and PSK-type signals…

“Generalised transient response of bandpass transfer functions to FSK and PSK-type signals,”

Electronics Letters, vol. 9, no. 14,pp. 320-321, July 1973.

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Time-Frequency Effects: Vendik/Samoilova (1997)

• resonators: transmission line& microstrip

attributed nonlinearities to(a) crystalline structure(b) charge carrier density(c) Abrikosov vortices

resistance is a function of current

“Nonlinearity of superconducting transmission line and microstrip resonator”

IEEE Trans. Microw. Theory Tech., vol. 45,no. 2, pp. 173-178, Feb. 1997.

2

1 1 20

( , )( , ) 1 I x tR x t RI

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Time-Frequency Effects: Pereda (1992)

“Computation of resonant frequencies and quality factors of open dielectric resonatorsby a combination of finite-difference time-domain and prony’s methods,”

IEEE Microwave and Guided Wave Letters,vol. 11, no. 2, pp. 431-433, Nov. 1992.

• estimation of quality factor from resonant decay

reduced time to compute resonant frequencies and quality factor using FDTD and Prony analysis

Prony analysis

while investigating resonancein dielectric resonators…

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Time-Frequency Effects: Dunsmore (1999)

“Tuning band pass filters in the time domain,”IEEE MTT-S Int. Microw. Symp., Anaheim, CA, June 1999, pp. 1351-1354.

showed how to tune individual resonators using time-domain return loss

while working at Hewlett-Packard Microwave Instruments Division…

• time-domain coupled-resonator filter tuning

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Time-Frequency Effects: Courtney (1999)

• frequency measurements from time-domain traces

while trying to determine broadband permittivity and permeabilityof a sample material…

found a way to measure and by time-domain-reflectometrywith nanosecond impulses

“One-port time-domain measurement of the approximate permittivity and permeability of materials”IEEE Trans. Microw. Theory Tech., vol. 47, no. 5, pp. 551-555, May 1999.

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Time-Frequency Effects: Walker (2005)

“Behavioral modeling and characterization of nonlinear operation in RF and microwave systems,”

Ph.D. dissertation, North Carolina State University, Raleigh, NC, May 2005.

• remote characterizationof wireless devices

probed devices with two-tone continuous waves, received steady-state third-order intermodulation

identified RF communication bands using nonlinear front-end properties

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Time-Frequency Effects: Hung et. al. (2002)

• nonlinear distortion reduction by time-multiplexing

“Optical sampled subcarrier multiplexing scheme for nonlinear distortion reduction in lightwave CATV networks,” Electronics Letters, vol. 38, no. 25, pp. 1702-1704, Dec. 2002.

found a way to reduce IMDby transmittingsubcarrier frequenciesin different time slots

working with optical cable television transmission…

gregory mazzaro agilent e4438c siames research...

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