Formation of sub-nanosecond UWB impulse using sharp edge ...

Formation of sub-nanosecond UWB impulse using sharp edge generator and planar antenna

M. Greitans, E. Hermanis, G.SupolsInstitute of Electronics and Computer Science,

Dzerbenes 14, Riga, LV1006, Latvia,e-mail: [email protected]

Electronics 2010, May 18-20, KTU, VGTU Lithuania

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Outline• Introduction• Motivation and goals• UWB pulse generation• UWB antennas• Experimental setup and results• Conclusions

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What is UWB?

Fractional bandwidth (measured at the -10dB (fh -fl )/fc , > 20% or total BW > 500 MHz.

FCC/ITU-R Definition UWB

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UWB types:• Direct sequence (DS) UWB:

using the whole available spectrum▫ transmitting very short

pulses (impulse radio)• Multiband: dividing the

available spectrum into several bands, each having a minimum of 500 MHz of bandwidth.

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Pulse based UWB. Why?• Advantages

▫ Mixed localisaton and data transfer possibility▫ Simple transmitter side design▫ Noise-like spectrum

• Applications▫ Wireless comunication systems▫ Road information systems (Car <-> Road signs)▫ Non-contact medical examination▫ Localisation, positioning

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Motivation and goals• To gain experience/knowledge in design of

wideband/microwave systems• UWB impulse generation, antenna,

localization and data transfer experiments• Practical goals:

Universal UWB antenna test systemGround penetrating radar (GPR)Through wall imaging device (TWI)

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Different aproaches

A)

B)

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Different aproaches

A)

B)

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UWB pulse generation

Antenna is a part of UWB pulse generator!

Principle Test system

UWB impulse is formed as an antenna step response

ObjectImpact Response

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A fast rise time differential pulse generator in combination with a Bow-Tie type antenna on a lossy dielectric

UWB pulse generation

A Step Recovery Diode (SRD) is used as a differential pulse sharpener

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Typically used antennas

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UWB antenna requirements• Small size (for embeded

devices)• Effective energy transfer• Linear phase delay• Wide frequency range

impedance matching• Short step response (radar

applications)• Non-resonant (multi resonant)• 0 < Q factor < 1

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Antenna couple used for experiments

• A Bow-Tie type antena is used

• Antenna is made on a lossy dielectric material

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Experimental setup

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Real-world look

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Receivers side

Stroboscopic converter

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Transmitters side

Differential microstrip line with SRD at the end

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Measurements

0 2 4 6 8 10 12 14 16-1

-0,8

-0,6

-0,4

-0,2

0

0,2

0,4

0,6

0,8

1

Time [ns]

0 2 4 6 8 10 12 14 16-0,6

-0,4

-0,2

0

0,2

0,4

0,6

Two types of antenna

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Pulse spectrum

0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0 3 5 0 0 4 0 0 0 4 5 0 01 0 - 2

1 0 - 1

1 0 0

frequency (MHZ)

rela

tive

ampl

itude

Impulse spectrum

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Conclusions• Experimental setup is developed for further

research• Obtained first results confirms the correctness of

the approach• Some experience in high frequency design is

gained

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Questions?

Research is supported by ESF grant:

2009/0219/1DP/1.1.1.2.0/APIA/VIAA/020R&D Center for Smart Sensors and Networked Embedded Systems