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UWB Antennas &

Measurements

Gabriela Quintero

MICS UWB Network Meeting

11/12/2007

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Outline

UWB Antenna Analysis Frequency Domain

Time Domain

Measurement Techniques Peak and Average Power Measurements

Spectrum Analyzer Settings

Fourier Series

Fourier Transform

UWB Measurements

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Outline

UWB Antenna Analysis Frequency Domain

Time Domain

Measurement Techniques Peak and Average Power Measurements

Spectrum Analyzer Settings

Fourier Series

Fourier Transform

UWB Measurements

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UWB Antennas

Impulse radio UWB pulse (3.1 10.6 GHz)

MICS pulse (4 4.5 GHz)

Time and frequency domain Analysis Still with basic antenna architectures

Monopole

Vivaldi

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Time and Frequency Domain

Two different softwares used to characterizethe antennas

Ansoft HFSS FD

Frequency Sweep at all frequencies Parameters in FD (S11, Gain, E-field, etc.)

CST Microwave Studio TD

Select the pulse BW

Parameters in FD (S11, Gain, etc.)

E-field in TD

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Frequency Domain Transfer Function - S21

Relates the output voltage with the inputvoltage

Can be derived from the Friis TransmissionEquation

And obtain

( ) ( ) ( )j r

cr tV H V e

=

( )( )2

2 2P 1 1 ( , ) ( , )

4

rcdt cdr t r t t t r r r t

t

e e D D

P R

2r

=

( )

2

11

( )1 ( , , )

( ) 4

rcdt t t t

t

Ve S E

V R

=

Tx Rx

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Frequency Domain

HFSS

SimulationS11

E-field

Transfer

FunctionMatlab

Pulse PSD

Rx Pulse

PSDIFFT

Rx Pulse

TD

Tx Rx

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Monopole System

0 2 4 6 8 10 12 14 16 18 20-35

-30

-25

-20

-15

-10

-5

0

Return Loss

Frequency [GHz]

Magnitude[dB]

Simulated

Measured

0 5 10 15 200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Normalized Magnitude

Frequency [GHz]

Simulated

Measured

0 5 10 15 20-500

-450

-400

-350

-300

-250

-200

-150

-100

-50

0

Frequency [GHz]

Phase [radians]

S11

HFSS

NWA

TF S21

Rx + Tx Pulse

PSDRx + Tx Pulse

0 2 4 6 8 10 12-120

-100

-80

-60

-40

-20

0

20

Frequency [GHz]

Gauss

ianPulse[dB]

Power Spectral Density

0 2 4 6 8 10 12-120

-100

-80

-60

-40

-20

0

20

MIC

SPulse,

[dB]

Frequency [GHz]

Input

Simulated

Measured

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

-1

-0.5

0

0.5

1

Time [ns]

GaussianPulse

Input Vs. Output pulse (normalized)

-1 0 1 2 3 4-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

M

ICSPulse

Time [ns]

Input

Simulated

Measured

Tx Rx

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0 5 10 15 200

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Normalized Magnitude

Frequency [GHz]

Simulated

Measured

0 5 10 15 20-500

-450

-400

-350

-300

-250

-200

-150

-100

-50

0

Frequency [GHz]

Phase [radians]

0 2 4 6 8 10 12 14 16 18 20-35

-30

-25

-20

-15

-10

-5

0Return Loss

Frequency [GHz]

Magnitude[dB]

Simulated

Measured

Vivaldi SystemS11

HFSS

NWA

TF S21

Rx + Tx Pulse0 2 4 6 8 10 12-120-100

-80

-60

-40

-20

0

20

Frequency [GHz]

Gaussian

Pulse,

[dB]

Power Spectral Density

Input

Simulated

Measured

0 2 4 6 8 10 12-120

-100

-80

-60

-40

-20

0

20

MICSP

ulse,

[dB]

Frequency [GHz]

Rx + Tx Pulse

PSD0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

-1

-0.5

0

0.5

1

Time [ns]

Gaussia

nPulse

Input Vs. Output pulse (normalized)

Input

Simulated

Measured

-1 0 1 2 3 4-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

MICS

Pulse

Time [ns]

Tx Rx

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CST: Monopole Antenna

4.25 GHz 6.85 GHz

H-plane

E-plane

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CST: Vivaldi Antenna

4.25 GHz 6.85 GHz

H-plane

E-plane

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0 0.5 1 1.5 2 2.5 3 3.5 4-1

-0.5

0

0.5

1

UWB Pulse

0 2 4 6 8 10 12 14 16-1

-0.5

0

0.5

1

MICS Pulse

Input Pulse

E-field at 80

Time Domain

0 0.5 1 1.5 2 2.5 3 3.5-1

-0.5

0

0.5

1

UWB Pulse

0 2 4 6 8 10 12 14 16-1

-0.5

0

0.5

1

MICS Pulse

Input Pulse

E-field at 80

Monopole Vivaldi

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Time Domain

Fidelity Factor Measures the faithfulness with which a device

reproduces the time shape of the input signal.

f(t) = Input signal at antenna terminals r(t) = Radiated E-field in time domain

The signals are normalized to have unit

energy

and2/1

2

)(

)()(

=

dttr

trtr

1/ 22

( ) ( )

( )

f tf t

f t dt

=

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Time Domain

The fidelity parameter,F, is determined by

the peak of the cross-correlation function of

the signals

max ( ) ( )F f t r t dt

= +

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Time Domain

CST

Simulation

E-field (t,, )

Input signal

Fidelity

Factor

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Time Domain

0

30

60

90

120

150

180

-150

-120

-90

-60

-30

0.70.8

0.91

Vivaldi Fideli ty Factor

UWB PulseMICS Pulse

0

30

60

90

120

150

180

-150

-120

-90

-60

-30

0.70.8

0.91

Monopole Fideli ty Factor

UWB PulseMICS Pulse

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Outline

UWB Antenna Analysis

Frequency Domain

Time Domain

Measurement Techniques Peak and Average Power Measurements

Spectrum Analyzer Settings

Fourier Series

Fourier Transform

UWB Measurements

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MEASUREMENTS

Average Power Peak Power

TP

PTPPE

effavg

avgeff

=

==

0

0

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MEASUREMENTS

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Spectrum Analyzer

RBW VBW

Scan Time

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Spectrum Analyzer

Line Spectrum Pulse Spectrum

A pulse repetition rate equal to the resolution bandwidth is the demarcation line

between a true Fourier-series spectrum, where each line is a response

representing the energy contained in that harmonic, and a pulse or Fourier-

transform response.Agilent Spectrum Analyzers Series.Application note 150-2

pp. 32

1B> or B>PRF

T

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Line Spectrum

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Line Spectrum

All individual frequency components are resolved.

Line spacing is 1kHZ = PRF

Spacing of sidelobe minima is 10kHz =

The amplitude of each line will not change whenRBW is changed, as long as RBW

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Line Spectrum

Pulse DesensitizationOnly valid for Fourier line spectrum.

( )10 10

10

[ ] 20log 20log

[ ] 10log ( )

= =

=

eff

L eff

avg

effpeak

dB PRF T

PdB PRF

P

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Pulse Spectrum

Its a combination of time and frequency

display.

The lines that form the envelope are pulse lines

in time domain.

Each line is displayed when a pulse occurs.

Frequency domain display of the spectrum

envelope.

The amplitude of the envelope increase linearly as

RBW increases. (As long as RBW < 0.2/ eff).

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Pulse Spectrum

-30dBm CW carrier modulated by a pulsetrain with a PRF of 100Hz, eff= 100s and

RBW = 1kHz = 0.1/ eff

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Pulse Spectrum

In Figure 23, we lost the linear relationship between bandwidthand display amplitude RBW > 0.2/ eff . The resolution of thesidelobes is lost to a great extent.

In Figure 24 RBW = 1/ eff, we get a display with an amplitudepractically equal to the peak amplitude of the pulsed signal.

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Pulse Spectrum

Pulse desensitization correction factor

RBW

BK

RBWKdB

imp

effp

=

= )(log20][ 10

K= 1.617 for Agilnet ESA Series856x or 859x

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Average Power

FCC Definition The average limit is

500 uV/m, as

measured at 3meters with a 1 MHz

resolution bandwidth

(RBW). Equivalentto an EIRP of -41.25

dBm/MHz

0 2 4 6 8 10 12-80

-75

-70

-65

-60

-55

-50

-45

-40

FCC Indoor Spectral Mask

EIRP[dBm/MH

z]

Frequency [GHz]

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Average Measurements

If 10 kHz > VBW >10 Hz Video averaging should be used in

conjunction with peak hold.

If NO dithering or PPM

Line spectrum setting (VBW RBW)

RBW < 0.3 PRF Average level = highest line in the

emission line spectrum

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Average Measurements

If dithering or PPM True pulse spectrum settings

A pulse desensitization correction factor

would be added to the measurement toobtain a peak level.

The average is calculated using the dutycycle factor in dB

( )10[ ] 10logavg

eff

peak

PdB PRF

P

=

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Peak Measurements

pp. 174

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Peak Measurements

Peak level when measured over a

bandwidth of 50 MHz

50MHz widest victim receiver that is likely tobe encountered.

Peak measurements based on a 50 MHz

(resolution) bandwidth may not be feasible.

The widest available RBW that can beemployed for peak measurements is 3 MHz.

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Peak Measurements

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Peak Measurements

Peak emission level of 0 dBm/50 MHz

= 58mV/m at 3 meters is adopted.

Equivalent to:

A peak EIRP of -24.44 dBm/3 MHz

Peak field strength of 3.46 mV/m at 3

meters with a 3 MHz RBW.

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Rules of Thumb

Line Spectrum Pulse Spectrum

RBW

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QUESTIONS?