Ultra-Wideband Technology
Post on 09-Jan-2016
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Outline
• UWB Introduction
• UWB Applications and Industries
• Interference challenges in UWB systems and UWB Transmitter
• UWB Receivers
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Introduction(Definition)
• UWB transmitter signal BW:
• Or, BW ≥ 500 MHz regardless of fractional BW
fu-fl
) fu+fl(
2
≥ 0.20
Where: fu= upper 10 dB down point fl = lower 10 dB down point
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UWB Signals• Impulse Radio (IR) or narrow time-duration pulses• multi-band orthogonal frequency-division multiplexing (MB-OFDM)
5
The key attributes of UWB technology
• High data rates communication and high-precision ranging applications
• High multipath and jamming immunity
• Extremely difficult to detect by unintended users
• Co-existence capability
• Low cost, low power and single chip architecture
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Pulsed UWB applications
Communications
Short/medium Range Communications Links
Radar
Ground penetrating radarsThrough wall radars Imaging and ranging
Intelligent Sensors
TelemetryMotion Detectors Intelligent Transport SystemsNext generation RFIDs
Other
Medical Applications Indoor localization (GPS
assisted)
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FCC UWB Device Classifications
• Report and Order authorizes 5 classes of devices with different limits for each:– Imaging Systems
• Ground penetrating radars, wall imaging, medical imaging• Thru-wall Imaging & Surveillance Systems
– Communication and Measurement Systems• Indoor Systems • Hand-held Systems
– Vehicular Radar Systems• collision avoidance, improved airbag activation, suspension
systems, etc – RTLS
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Security and Air force Applications
• Preventing the air units from
striking each other
• Micro Air Vehicles (MAV),
Each side 15 cm,
for security operations
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Sensor Networks Applications
• Un-Detectable Control of Borders and Gas &Oil pipelines
• By using UWB Over Fiber (UOF), extending the range
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4-UWB for Localization & Tracking
• Medium Bit rate Long Communication Links (>100m)
• Ranging/Localization in indoor/urban environments
• Robust against jamming/detection
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Localization
• Localisation / ticketing / logistics systems for control / safety / navigation in public environments and transportations
– Communications must be very robust and reliable as the positioning and the data transfer can be related to payment operations
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Three Principles of Positioning
• TOA (Time of Arrival) & RTD (Round Trip Delay)
• TDOA (Time Difference of Arrival)
• AOA (Angle of arrival)
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UWB RFID/ RLTS Technical Attributes
• Small Tag Size Down to 1” x 1” x1” or smaller
• Long Tag Life Up to 7+ years @ 1Hz Blink Rate
• High Resolution/ Accuracy Real-time location accuracies of <1 ft with line of sight
• High Tag Throughput Up to 5000+ tags/ second presence and 2500+ tags/ second locate (in a typical four receiver set-up)
• High Tag Transmission Rate Up to 200 times/ second possible
• Excellent Performance in Pulse response operates well in high multipath environmentsMetallic Environments
• Long Range Up to 600+ ft line-of-sight with high-gain antenna presence and up to 300 ft between receivers locate
There are seven key technical attributes that UWB RTLS offers the customer the ability to control their most critical business processes and high-value assets.
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UWB RELATED INDUSTRIES
• XtremeSpectrum• Time Domain• General Atomics• AetherWire & Location• Multispectral Solutions (MSSI)• Pulse-Link• Appairent Technologies• Pulsicom• Staccato communications • Intel• TI• Motorola
• Perimeter players
– Sony
– Fujitsu
– Philips
– Mitsubishi
– Broadcom
– Sharps
– Samsung
– Panasonic
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Outline
• Interference challenges in UWB systems
• Conventional UWB pulses
• Hermite and proposed UWB pulse
• Proposed circuit for pulse implementation
• Simulation results
• Conclusion
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Possible interferers in UWB systems
• Most significant interferer 802.11a (5GHz WLAN)
• Avoiding 802.11a
– MB-OFDM
• Eliminating Band #2
– IR-UWB & DS-UWB
• Using UWB lower Band
• Using UWB upper Band
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Effects of Narrowband interferers on UWB system
SNR (dB) of UWB in the presence of 802.11a interferer
dUWB- (m) in LOS
d802.11a 1 3 6 10
1 15 7 2 -1
5 28 19 14 10
10 32 24 20 16
None 51 42 37 33
dUWB- (m) in NLOS
d802.11a 1 3 6 10
1 10 -6 -17 -25
5 22 5 -5 -13
10 37 10 0 -8
None 46 29 19 1119
Effects of Narrowband interferers on UWB circuit
• IR-UWB covering the whole band → the interferer
is in-band → no pre-filtering → corrupted signal!!
• Easier in MB-OFDM →the interferer is out of band
→ pre-filter
– 2nd and 3rd order modulation of interferer
• UWB receiver desensitization due to large interferer
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Effects of UWB on Narrowband system
SNR in the presence of UWB interferer
d802.11a- (m) in NLOS
dUWB 1 3 6 10
1 31 14 4 -3
5 42 25 15 7
10 47 30 20 12
None 52 36 26 18
Data rate in the presence of UWB interferer
d802.11a- (Mbps) in NLOS
dUWB 1 3 6 10
1 54 9 0 0
5 54 36 9 0
10 54 48 18 0
None 54 54 36 1221
Solution for In-Band interferers of IR-UWB
• IR-UWB, low power, low complexity compare with MB-OFDM
– Of great interest
• Covering the whole spectrum can be done by designing such a pulse featuring frequency nulls
Intended UWB pulse
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Modified Hermite Pulses• Hermite polynomials are the finite sum of terms like
• To be orthogonal Modified Hermite pulse
• Inherent nulls in the power spectrum of this pulse the main
motivation behind this work
– Complete Coexistence of UWB and the NB system located in the null
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Designed PulseDesigned UWB Pulse
• The major problem is 5 GHz
WLAN, 2nd order Hermit is
OK!
• 2nd order Hermit pulse modified
to be implementable in analog
circuits
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Circuit Analysis• 6 blocks needed:
1. Square function
• MOS device square law
• Trans-linear circuits
2. Exponential function
• Bipolar device
• MOS device in sub-threshold region
3. Multiplier for mathematical multiplication
4. Mixer for up converting
5. VCO for cosine function
6. An input ramp stage
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Quadratic Function
• For a fully quadratic function
two long channel MOS devices
used, each switches in its cycle
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Important parameters
• The input DC biasing determines the current
• R value chosen to keep MOS in saturation
• The Cosine function determines the null frequency
• The tuning circuit is placed for fine tuning due to
process variation
• The input ramp determines the BW of the pulse
and the number of the nulls in the spectrum30
Fine tuning of the nulls by the gain of the tuning circuit
20 dB gain increase of tuning circuit
Tuning circuit normal gainInput ramp for both
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Pulse Characteristics
Pulse PropertiesPulse Bandwidth Up to 12 GHz
Number of the nulls 2 to 6 nulls in the UWB spectrum
Null depth Up to 50 dB
Coarse tuning Cosine for up-converting
Fine tuning Input ramp voltage, Tuning circuit gain
Power consumptionQuadratic and exponential functions- 4
mA
Multiplier and Mixer- 15 mA
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Conclusion
• The proposed UWB pulse features frequency nulls in the UWB spectrum
• The pulse can be coarse or fine tuned by the input ramp voltage, frequency of the cosine function and gain of the tuning circuit
• As a result no SNR degradation would occur for the NB system located in the null, and the NB system wouldn’t be disturbed
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Conclusion• No SNR degradation in UWB system will occur
because of no overlapping with NB system• NB system in the null would be considered out
of band and pre-filtering can be done without any loss of data
• On chip filtering of the NB system can be done since the Q of the filter is relaxed due to the null existence
• An IR-UWB transceiver covering the whole spectrum can be accomplished
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Future Works
• Major UWB Limitation– Short distance communications
– UWB over Fiber
– UWB pulse design with notches in Optics
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• Main challenge in UWB is in Rx:• large bandwidth,
• high required timing precision
• difficult signal synchronization
TX and RX Block Diagram
Main difference of all RX topologies Location of ADC ( in A , B or C in RX
Block Diagram) Matched filter correlation (coherent or
incoherent) Pulse template 38
Receiver topologies
1. Fully digital (FD)• 4 bit : high power• 1 bit : low power but bad performance when interference
2. Transmitted reference (TR)3. Energy detector(ED)
• Data pulse as its own reference• Self-mixing of the noisy input signal• Impossible BPSK (PPM)
4. Flashing• high SNR• low interference environments
5. Quadrature Analog correlation (QAC)39
Windowed sine wave as a template in matched filter to avoid complexity (Loss 1dB) (Input)(LO)+(windowed integration) = Correlation with windowed sine wave( template)
Quadrature Analog correlation receiver (QAC)
Quadrature Analog correlation (QAC)
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Simulation Results
Bad performance of 1 bit FD in the strong interferer increasing loss of the QAC in more dense multipath channels, due to
its simplified channel compensation the excellent performance of the QAC receiver in interference
dominated environments43
QAC receiver has excellent EPUB.
Comparison between Different TopologiesFigure of Merit:
“Energy/Useful Bit” or EPUB (the best parameter to tare-off between power and performance)
Four channel models1 path: LOSG: Gaussian Noisei: Interference
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Implementation challenges
1. Template misalignment and clock offset• Low Sensitivity and jitter up to 300ps• Compensation of Clock offset by tracking the rotation
of (I,Q) constellation vector in digital
2. IQ imbalance• up to 10 degree can be tolerated
3. Phase noise• out-of-band interferers to be mixed inside band• Dither around the ideal point in the constellation (noise
for tracking loop)
4. ADC resolution
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• Flexibility in operation • Operation with a 0-960MHz and 3-5GHz front-end• Pulses with a bandwidth from 500MHz to 2GHz• Pulse period from 20nsec to 200nsec• PN code 1 to 63 pulses per bit(PG:0dB to 18dB)• Data-rates from 80kbps to 50Mbps
• Operation phases• Acquisition Phase: Channel estimation, Synchronization ,
RX-TX Clock-offset estimation.• Detection Phase: detect the data, clock-offset and
tracking
Design Considerations
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• Acquisition Phase1. Search for the best window position2. Search for the correct code phase for this window only
• QAC in multipath• Performance loss in multipath channels• Loss Compensation by multi-window integration
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