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UWB Radars: Possibilities and

Problems

Dr. Amit Kumar Mishra

Department of ECEIIT Guwahati

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Signposts!

Plan of presentation:

UWB radars: an introduction

UWB radars: types

UWB radars: usages

Problems and challenges

Talk timing = 20min (talk) + 10min (QA)

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UWB: A brief introduction

Ultra wide band

BW > 20% of central frequency, OR

BW > 500 MHz

Three types:

Impulse UWB radar

LFM UWB radar

Noise UWB radar

Recent FCC regulation

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UWB Spectrum FCC ruling permits UWB spectrum overlay

1.6 1.9 2.4

Bluetooth,

802.11b

Cordless Phones

Microwave OvensGPS

PCS

5

802.11a

-41 dBm/Mhz Part 15 Limit

UWB

Spectrum

Frequency (Ghz)

Emitted

Signal

Power

10.63.1

FCC ruling issued 2/14/2002 after ~4 years of study & public

debate

FCC believes current ruling is conservative

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Summary of the FCC Rules

Significant protection for sensitive systems GPS, Federal aviation systems, etc.

Lowest Limits Ever by FCC

Incorporates NTIA recommendations

Allows UWB technology to coexist with existingradio services without causing interference

The R&O rules are designed to ensure that existing andplanned radio services, particularly safety services, are

protected.

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Some typical advantages of UWB

Multipath immunity

Ease of signal generation and processing architectures (!) Radar

Inherent high precision sub-centimeter ranging

Wideband excitation for detection of complex, low RCS targets

Geolocation/Positioning Sub-centimeter resolution using pulse leading edge detection

passes through building blocks, walls, etc. (LOS not required) Low Cost

Nearly all-digital architecture

ideal for microminiaturization into a chipset Frequency diversity with minimal hardware modifications

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UWB Radar types

LFM UWB radars: Not much different from

any other radar system

Noise Radar: UWB feature from the BW of

noise

Impulse Radar: Time frequency

uncertainty!

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LFM UWB Radar

Tx signal is a simplechirp with UWBproperties

e.g. VHF radar image 20-90 MHz (but BW >

25% of fc)

In use since long

Problems: target modeling!

too much information!Courtesy SDMS

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Noise UWB Radar

The question is how you model noise!

Advantages:

Frequency diversity

Immunity to detection, jamming etc.

Spectral efficiency (little cross-interference

between 2 noise radars)

Many proofs of concept available

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Impulse UWB radar

Non-sinusoidal waveforms

Fav. Shape: Gaussian waveforms Autocorrelation is Gaussian shape!

FT is also Gaussian shape!

Major advantages obtained from timedomain analysis

Impulse waveform: ~1ns Depth of pulse: ~ 30cm

Finer resolution

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Possibilities of impulse radar

Resolution

Target identification

Low elevation performance (time of arrival is different!)

Antenna pattern depend on signal characteristics

Both range and X-range resolution improved by higherBW

Immunity to interference and noise

Decreased dead-zone

MTI without using Doppler

Theoretically no side-lobes!

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Ranging and Imaging Capabilities

Many early applications of modern

UWB technology were in radar systems

Sub-nanosecond time resolution leadsto precision ranging and imaging

capabilities

Capabilities result from the largerelative and coherent bandwidth

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Bio-medical sensing using UWB

radar imaging

the required power for a UWB to image human

body is much lower than the permitted

maximum level of electro-magnetic (EM) energy

One of the major uses of UWB radar imaging forbiomedical purpose has been to get information

about the heart beat of a person. Termed as

heart rate variability (HRV), this diagnosed

information has been shown to be of immense

utility

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Imaging through obstacles

Foliage penetration (FOPEN) has been an

active research area for the military radar

community

With UWB techniques, systems can have

both good resolution as well as FOEN

capabilities

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Problems and challenges

Impulse radar:

Shape change during propagation

Time domain analysis: yet to achieve all the promises

Noise radar: Yet to fully prove its capacities

Energy control is difficult

LFM radar: Not suitable for FCC based utilities

Difficult and costly to generate UWB using LFM

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Related Standards

IEEE 802.15 : Wireless Personal Area Network (WPAN)

IEEE 802.15.1 : Bluetooth, 1Mbps

IEEE 802.15.3 : WPAN/high rate, 50Mbps

IEEE 802.15.3a: WPAN/Higher rate, 200Mbps, UWB IEEE 802.15.4 : WPAN/low-rate, low-power, mW level, 200kbps

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FCC UWB Device

Classifications

R&O authorizes 5 classes of devices Different limits for each:

Imaging Systems

1. Ground penetrating radars, wall imaging, medical imaging2. Thru-wall Imaging & Surveillance Systems

Communication and Measurement Systems3. Indoor Systems

4. Outdoor Hand-held Systems

Vehicular Radar Systems5. collision avoidance, improved airbag activation,

suspension systems, etc.

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Summary of Preliminary R&O

Limits

Application Frequency Band for Operation at Part 15 Limits

UserRestrictions

Imaging 3.1 to 10.6 GHz

(GPR

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0.96 1.61

1.99

3.1 10.6

GPS

Band

UWB Emission Limit for Indoor Systems

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0.96 1.61

1.99

3.110.6

GPS

Band

UWB Emission Limit for Outdoor Hand-held

Systems

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0.96 1.61

1.99

3.1 10.6

Operation is limited to law enforcement, fire and rescue organizations, scientific research

institutions, commercial mining companies, and construction companies.

GPS

Band

UWB Emission Limits for GPRs, Wall Imaging, &

Medical Imaging Systems

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0.96 1.61

1.99 10.6

Operation is limited to law enforcement, fire and rescue organizations.

Surveillance systems may also be operated by public utilities and industrial entities.

GPS

Band

UWB Emission Limits for Thru-wall Imaging &

Surveillance Systems