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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. 5.1 I-UWB signal generators. 5.1.1 Avalanche( 雪崩 )Pulse Generators
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Chapter 5 Transmitter Design • 5.1 I-UWB signal generators • 5.2 Modulators • 5.3 I-UWB transmitters • 5.4MC-UWB transmitters • 5.5 Spectral encoded UWB communication system Harbin Institute of Technology (Weihai)
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. Harbin Institute of Technology (Weihai)
Question: • What can we do if a positive UWB signal is requested? Harbin Institute of Technology (Weihai)
Step Recovery Diode (阶跃恢复二极管) Pulse Generators Harbin Institute of Technology (Weihai)
5.1.3 Tunnel Diode Pulsers • 5.1.4 Pulse Circuits Suitable for Integrated Circuits Harbin Institute of Technology (Weihai)
Differential circuits, the H bridge Gaussian Doublet Harbin Institute of Technology (Weihai)
Programmable CMOS pulse generator Harbin Institute of Technology (Weihai)
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) Harbin Institute of Technology (Weihai)
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) Harbin Institute of Technology (Weihai)
Time-hopped pulse position modulation (TH-PPM) Harbin Institute of Technology (Weihai)
5.3.2 OOC-PPM Harbin Institute of Technology (Weihai)
5.3.3 DS-UWB Harbin Institute of Technology (Weihai)
5.3.4 Transmitter Reference (TR) UWB Harbin Institute of Technology (Weihai)
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. Harbin Institute of Technology (Weihai)
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 Harbin Institute of Technology (Weihai)
5.4.1 OFDM-UWB signals Harbin Institute of Technology (Weihai)
Multi-band OFDM UWB Solution for IEEE802.15.3a WPANsMarilynn P. Wylie-Green, Pekka A. Ranta and Juha SalokannelNokia Research Center, P.O. Box 407, FIN-00045 Nokia Group, Finland. Harbin Institute of Technology (Weihai)
IEEE P802.15-03/268r2 Harbin Institute of Technology (Weihai)
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 Harbin Institute of Technology (Weihai)