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Chapter 5 Transmitter Design

5.1 I-UWB signal generators 5.2 Modulators 5.3 I-UWB transmitters 5.4 MC-UWB transmitters 5.5 Spectral encoded UWB communication

system

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5.1 I-UWB signal generators

5.1.1 Avalanche(雪崩 )Pulse Generators A transistor driven into avalanche breakdown

can produce a very fast-rise time pulse. The device is biased somewhere between BVCEO

and BVCEX with the base biased at zero volts or a small negative voltage.

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Question:

What can we do if a positive UWB signal is requested?

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Step Recovery Diode (阶跃恢复二极管 ) Pulse Generators

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5.1.3 Tunnel Diode Pulsers 5.1.4 Pulse Circuits Suitable for Integrated

Circuits

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Differential circuits, the H bridge

Gaussian Doublet

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Programmable CMOS pulse generator

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5.2 Modulators

Carrier-based system Amplitude modulation or on/off keying(OOK) Pulse position modulation (PPM) Biphase pulse polarity modulation (antipodal

PAM) Pulse width modulation (PWM)

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5.3 I-UWB transmitters

Time-hopped pulse position modulation

(TH-PPM) Optical orthogonal coded PPM (OOC-PPM) Direct sequence spread spectrum

modulation (DS) Transmitted reference (TR) Pilot waveform assisted modulation (PWAM)

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Time-hopped pulse position modulation (TH-PPM)

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5.3.2 OOC-PPM

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5.3.3 DS-UWB

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5.3.4 Transmitter Reference (TR) UWB

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5.4 MC-UWB transmitters

A single data stream is split into multiple parallel data streams of reduced rate, with each stream transmitted on a separate frequency (subcarrier).

Each carrier is modulated at a low enough rate to minimize inter-symbol interference (ISI).

Subcarriers must be properly spaced so that they do not interfer.

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For a N subcarrier system, each subchannel is tolerant of N times as much dispersion as the original single carrier system.

MC-UWB use orthogonal UWB pulse trains and multiple subchannels to achieve reliable high bit rate transmission and spectral efficiency.

Advantages: better time resolution->better performance in multipath fading channels; better spectrum utilization->higher bit rate communications; simple decoupled system design->simple transmitter implementation

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5.4.1 OFDM-UWB signals

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Multi-band OFDM UWB Solution for IEEE802.15.3a WPANs

Marilynn P. Wylie-Green, Pekka A. Ranta and Juha SalokannelNokia Research Center, P.O. Box 407, FIN-00045 Nokia Group,

Finland.

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IEEE P802.15-03/268r2

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5.5 Spectral encoded UWB system

A multiple access scheme with interference suppression capability

Transmitted signal spectrum can be conveniently shaped to suppress NBI.

Signal will be spread in time

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