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UWB Radars: Possibilities and Problems

Signposts!. Plan of presentation:UWB radars: an introductionUWB radars: typesUWB radars: usages Problems and challengesTalk timing = 20min (talk) 10min (QA). UWB: A brief introduction. Ultra wide bandBW > 20% of central frequency, ORBW > 500 MHzThree types:Impulse UWB radarLFM UWB radarNoise UWB radarRecent FCC regulation.

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UWB Radars: Possibilities and Problems

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    1. UWB Radars: Possibilities and Problems Dr. Amit Kumar Mishra Department of ECE IIT Guwahati

    3. 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

    4. UWB Spectrum FCC ruling permits UWB spectrum overlay

    5. 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 existing radio services without causing interference The R&O rules are “designed to ensure that existing and planned radio services, particularly safety services, are protected.”

    6. 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

    7. 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!

    8. LFM UWB Radar Tx signal is a simple chirp with UWB properties e.g. VHF radar image 20-90 MHz (but BW > 25% of fc) In use since long Problems: target modeling! too much information!

    9. 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

    10. Impulse UWB radar Non-sinusoidal waveforms Fav. Shape: Gaussian waveforms Autocorrelation is Gaussian shape! FT is also Gaussian shape! Major advantages obtained from time domain analysis Impulse waveform: ~1ns Depth of pulse: ~ 30cm Finer resolution

    11. 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 higher BW Immunity to interference and noise Decreased “dead-zone” MTI without using Doppler Theoretically no side-lobes!

    12. Ranging and Imaging Capabilities Many early applications of modern UWB technology were in radar systems Sub-nanosecond time resolution leads to precision ranging and imaging capabilities Capabilities result from the large relative and coherent bandwidth

    13. 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 for biomedical 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

    14. 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

    15. 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

    16. 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

    17. FCC UWB Device Classifications R&O authorizes 5 classes of devices – Different limits for each: Imaging Systems Ground penetrating radars, wall imaging, medical imaging Thru-wall Imaging & Surveillance Systems Communication and Measurement Systems Indoor Systems Outdoor Hand-held Systems Vehicular Radar Systems collision avoidance, improved airbag activation, suspension systems, etc.

    18. Summary of Preliminary R&O Limits *Indoor and outdoor communications devices have different out-of-band emission limits

    19. UWB Emission Limit for Indoor Systems

    20. UWB Emission Limit for Outdoor Hand-held Systems

    21. UWB Emission Limits for GPRs, Wall Imaging, & Medical Imaging Systems

    22. UWB Emission Limits for Thru-wall Imaging & Surveillance Systems

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