1

Outline

• UWB Introduction

• UWB Applications and Industries

• Interference challenges in UWB systems and UWB Transmitter

• UWB Receivers

2

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

3

FCC Regulations

0.96

3.1 10.6

4

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

6

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)

7

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

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

Sensor Networks Applications

• Un-Detectable Control of Borders and Gas &Oil pipelines

• By using UWB Over Fiber (UOF), extending the range

10

4-UWB for Localization & Tracking

• Medium Bit rate Long Communication Links (>100m)

• Ranging/Localization in indoor/urban environments

• Robust against jamming/detection

11

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

Three Principles of Positioning

• TOA (Time of Arrival) & RTD (Round Trip Delay)

• TDOA (Time Difference of Arrival)

• AOA (Angle of arrival)

13

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.

14

UWB RFID Advantages • Communication and Tracking at same time

• Security

• Simple and Low Cost tag

15

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

Outline

• Interference challenges in UWB systems

• Conventional UWB pulses

• Hermite and proposed UWB pulse

• Proposed circuit for pulse implementation

• Simulation results

• Conclusion

17

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

18

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

20

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

22

Applicable UWB pulses

Without 5 GHz CosineAll Cosine Functions

Gaussian derived pulse :

23

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

2nd order Modified Hermite

Modified Hermite Pulse Up-Converted One 25

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

26

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

Quadratic Function

• For a fully quadratic function

two long channel MOS devices

used, each switches in its cycle

28

Overall Circuit

29

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

Simulation results

Time domain response Frequency domain response

FCC Indoor Mask

31

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

32

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

33

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

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

Future Works

• Major UWB Limitation– Short distance communications

– UWB over Fiber

– UWB pulse design with notches in Optics

36

New Design of UWB Receiver

37

• 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

40

Flashing Receiver topology41

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

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

44

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

• 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

Measurement ResultsImplementation of QAC receiver in 0.18µm

47

• 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

48

Communication andSub-cm Ranging

49

Thanks for your attention

50