Patent ID: 6950481
Filing Date: 2005-09-27
Classification: H03D,H04L

Abstract:
1. An apparatus for practicing a method for extracting information from a vestigial sideband amplitude-modulation signal generated in accordance with a modulating signal, said method for extracting information from said vestigial sideband amplitude-modulation signal comprising the steps of: mixing said vestigial sideband amplitude-modulation signal with a first beat frequency different from a earner frequency of said vestigial sideband amplitude-modulation signal, said first beat frequency being of such value as to generate a first mixing result that is translated in frequency to have a carrier at an offset frequency; mixing said vestigial sideband amplitude-modulation signal with a second beat frequency different from the carrier frequency of said vestigial sideband amplitude-modulation signal and from said first beat frequency, said second beat frequency being of such value as to generate a second mixing result that is translated in frequency to have a carrier at said offset frequency; and combining said first and second mixing results, which have respective frequency spectra that are images of each other, to form said double-sideband amplitude-modulation signal with its carrier frequency at said offset frequency; for converting said vestigial sideband amplitude-modulation signal to said double-sideband amplitude-modulation signal containing similar information, and said method for extracting information from said vestigial sideband amplitude-modulation signal further comprising the step of detecting the information contained in said double-sideband amplitude-modulation signal, said apparatus comprising: a local oscillator for generating local oscillations of a frequency and phase controlled by an automatic-frequency-and-phase-control signal; a balanced modulator connected for amplitude-modulating said local oscillations in accordance with said offset frequency, to generate a balanced modulator output signal essentially consisting of a first beat frequency component and a second beat frequency component; a mixer connected for mixing said balanced modulator output signal with said vestigial sideband amplitude-modulation signal, to generate a mixer output signal including said double-sideband amplitude-modulation signal; an image-rejection filter connected for supplying said double-sideband amplitude-modulation signal as a selective response to said mixer output signal; a phase-splitter connected for generating a complex response to said double-sideband amplitude-modulation signal said image-rejection filter supplies as a selective response to said mixer output signal; a complex multiplier connected for multiplying said complex response to said double-sideband amplitude-modulation signal by a complex carrier the frequency of which equals said offset frequency, to generate an in-phase synchronous detection response and a quadrature-phase synchronous detection response; and circuitry for generating said automatic-frequency-and-phase-control signal from said quadrature-phase synchronous detection response supplied thereto, which automatic-frequency-and-phase-control signal is applied to said local oscillator to complete an automatic-frequency-and-phase-control loop for adjusting the frequency and phase of the local oscillations generated by said local oscillator so that said in-phase synchronous detection response reproduces the modulating signal in accordance with which said vestigial sideband amplitude-modulation signal was generated.