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1 Outline UWB Introduction UWB Applications and Industries Interference challenges in UWB systems and UWB Transmitter UWB Receivers 2.

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Presentation on theme: "1 Outline UWB Introduction UWB Applications and Industries Interference challenges in UWB systems and UWB Transmitter UWB Receivers 2."— Presentation transcript:

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3 Outline UWB Introduction UWB Applications and Industries Interference challenges in UWB systems and UWB Transmitter UWB Receivers 2

4 Introduction(Definition) UWB transmitter signal BW: Or, BW ≥ 500 MHz regardless of fractional BW fu-flfu-fl ) f u +f l ( 2 ≥ 0.20 Where: f u = upper 10 dB down point f l = lower 10 dB down point 3

5 FCC Regulations

6 UWB Signals Impulse Radio (IR) or narrow time-duration pulses multi-band orthogonal frequency-division multiplexing (MB-OFDM) 5

7 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 6

8 Pulsed UWB applications Communications Short/medium Range Communications Links Radar Ground penetrating radars Through wall radars Imaging and ranging Intelligent Sensors Telemetry Motion Detectors Intelligent Transport Systems Next generation RFIDs Other Medical Applications Indoor localization (GPS assisted) 7

9 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 8

10 Security and Air force Applications Preventing the air units from striking each other Micro Air Vehicles (MAV), Each side 15 cm, for security operations 9

11 Sensor Networks Applications Un-Detectable Control of Borders and Gas &Oil pipelines By using UWB Over Fiber (UOF), extending the range 10

12 4-UWB for Localization & Tracking Medium Bit rate Long Communication Links (>100m) Ranging/Localization in indoor/urban environments Robust against jamming/detection 11

13 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 12

14 Three Principles of Positioning TOA (Time of Arrival) & RTD (Round Trip Delay) TDOA (Time Difference of Arrival) AOA (Angle of arrival) 13

15 UWB RFID/ RLTS Technical Attributes Small Tag SizeDown to 1” x 1” x1” or smaller Long Tag LifeUp to 7+ 1Hz Blink Rate High Resolution/ Accuracy Real-time location accuracies of <1 ft with line of sight High Tag ThroughputUp to tags/ second presence and 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 environments Metallic 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. 14

16 UWB RFID Advantages Communication and Tracking at same time Security Simple and Low Cost tag 15

17 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 16

18 Outline Interference challenges in UWB systems Conventional UWB pulses Hermite and proposed UWB pulse Proposed circuit for pulse implementation Simulation results Conclusion 17

19 Possible interferers in UWB systems Most significant interferer a (5GHz WLAN) Avoiding a – MB-OFDM Eliminating Band #2 – IR-UWB & DS-UWB Using UWB lower Band Using UWB upper Band 18

20 Effects of Narrowband interferers on UWB system SNR (dB) of UWB in the presence of a interferer d UWB - (m) in LOS d a None d UWB - (m) in NLOS d a None

21 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 – 2 nd and 3 rd order modulation of interferer UWB receiver desensitization due to large interferer 20

22 Effects of UWB on Narrowband system SNR in the presence of UWB interferer d a - (m) in NLOS d UWB None Data rate in the presence of UWB interferer d a - (Mbps) in NLOS d UWB None

23 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 22

24 Applicable UWB pulses Without 5 GHz CosineAll Cosine Functions Frequency Domain(GHz) Time Domain Gaussian derived pulse : 23

25 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 24

26 2 nd order Modified Hermite Modified Hermite Pulse Up-Converted One Frequency Domain(GHz) Time Domain 25

27 Designed Pulse Designed UWB Pulse The major problem is 5 GHz WLAN, 2 nd order Hermit is OK! 2 nd order Hermit pulse modified to be implementable in analog circuits 26

28 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 27

29 Quadratic Function For a fully quadratic function two long channel MOS devices used, each switches in its cycle 28

30 Overall Circuit 29

31 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 spectrum 30

32 Simulation results Time domain responseFrequency domain response FCC Indoor Mask 31

33 Fine tuning of the nulls by the gain of the tuning circuit 20 dB gain increase of tuning circuit Tuning circuit normal gain Input ramp for both 32

34 Pulse Characteristics Pulse Properties Pulse BandwidthUp to 12 GHz Number of the nulls2 to 6 nulls in the UWB spectrum Null depthUp to 50 dB Coarse tuningCosine for up-converting Fine tuningInput ramp voltage, Tuning circuit gain Power consumption Quadratic and exponential functions- 4 mA Multiplier and Mixer- 15 mA 33

35 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 34

36 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 35

37 Future Works Major UWB Limitation – Short distance communications – UWB over Fiber – UWB pulse design with notches in Optics 36

38 New Design of UWB Receiver 37

39 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

40 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

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42 Flashing Receiver topology 41

43  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) 42

44 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 environments 43

45 QAC receiver has excellent EPUB. Comparison between Different Topologies Figure of Merit: “Energy/Useful Bit” or EPUB (the best parameter to tare-off between power and performance) Four channel models 1 path: LOS G: Gaussian Noise i: Interference 44

46 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 45

47 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 46

48 Measurement Results  Implementation of QAC receiver in 0.18µm 47

49 Acquisition Phase 1.Search for the best window position 2.Search for the correct code phase for this window only QAC in multipath Performance loss in multipath channels Loss Compensation by multi-window integration 48

50 Communication and Sub-cm Ranging 49

51 Thanks for your attention 50


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