4 Bandpass Signaling Principles and Circuits.ppt

Chapter 4
Bandpass Signaling Principles and Circuits
1
Introduction(chapter objectives)
Complex envelopes and modulated signals
Spectra of bandpass signals
Nonlinear munication circuits(mixers, phase-locked loops, frequency synthesizers, and detectors)
Transmitters and receivers
Software radios
2
Introduction(main goals)
Mastering how to plex envelope of bandpass waveform.
The principle of bandpass filtering and linear distortion
Bandpass sampling theorem
Nolinear distortion
Detector circuits
Knowing PLL, DDC, general principle of Transceiver, concept of software radios
3
Introduction
The munication signal is obtained by modulating a baseband analog or digital signal onto a carrier.
Complex envelope can represent any type of bandpass signal.
4
Envelope Representation of Bandpass Waveforms
general representation for bandpass digital and analog signals
Representation for modulated signal
Representation for bandpass noise
5
Envelope Representation of Bandpass Waveforms
Definition1: baseband waveform
having a spectral magnitude that is nonzero for frequencies in the vicinity of the origin (i,e,..f=0) and negligible elsewhere.
For example: the information source signal; audio signal munication system.
6
Envelope Representation of Bandpass Waveforms
Definition2: bandpass waveform
having a spectral magnitude that is nonzero for frequencies in some band concentrated about at frequency ƒ= ± ƒc ,where ƒc >>0. The spectral magnitude is negligible eleswhere . ƒc is called the carrier frequency.
7
Envelope Representation of Bandpass Waveforms
Definition3: Modulation
the process of imparting the source information onto a bandpass signal with a carrier frequency by the introduction of amplitude or phase perturbations or both.
This bandpass signal is called the modulated signal s(t), and the baseband source signal is called the modulating signal m(t) .
8
Envelope Representation of Bandpass Waveforms
The definiti