US 6,608,869 B1 · Dual-carrier heterodyne for separating orthogonal components of complex amplitude-modulation signals

Abstract

A method for receiving a modulated carrier wave with asymmetrical upper and lower sidebands, which carrier wave may be suppressed, is described. A first down-converter in the receiver heterodynes the asymmetrical upper and lower sidebands of the modulated carrier wave being received with a first heterodyning signal, to generate a first down-conversion result superposed on the image thereof in a first final-intermediate-frequency signal offset from zero frequency. To do this, the first heterodyning signal essentially consists of two component frequencies, one below the lower sideband and the other above the upper sideband of the modulated carrier wave. A second down-converter in the receiver heterodynes the asymmetrical upper and lower sidebands of the modulated carrier wave being received with a second heterodyning signal that is the Hilbert transform of the first heterodyning signal. This is done to generate a second down-conversion result superposed on the image thereof in a second final-intermediate-frequency signal offset from zero frequency. The receiver further comprises a first demodulator for demodulating the first down-conversion result to recover an in-phase baseband signal and a second demodulator for demodulating the second down-conversion result to recover a quadrature-phase baseband signal.

Claims32

Dependent claims

A method for separately recovering in a radio receiver first and second components of the modulating signal used to generate a complex-amplitude-modulation signal transmitted to and received by said radio receiver, said first and second components of said modulating signal being mutually orthogonal to each other, said method comprising the steps of:

converting the complex-amplitude-modulation signal received by said radio receiver to a penultimate intermediate-frequency signal and amplifying the power in said penultimate intermediate-frequency signal compared to the complex-amplitude-modulation signal received by said radio receiver;
generating a first pair of equal-amplitude heterodyning signals separated in frequency by twice the carrier frequency of a first final intermediate-frequency signal;
heterodyning said penultimate intermediate-frequency signal with said first pair of equal-amplitude heterodyning signals to generate said first final intermediate-frequency signal;
synchrodyning said first final intermediate-frequency signal to recover, as a real first baseband signal, said first of the orthogonal components of said modulating signal;
generating a second pair of equal-amplitude heterodyning signals separated in frequency by twice the carrier frequency of a final intermediate-frequency signal, which said second pair of equal-amplitude heterodyning signals are in quadrature phasing with said first pair of equal-amplitude heterodyning signals of like frequencies;
heterodyning said penultimate intermediate-frequency signal with said second pair of equal-amplitude heterodyning signals to generate a second final intermediate-frequency signal;
and
synchrodyning said second final intermediate-frequency signal to recover, as a real second baseband signal, said second of the orthogonal components of said modulating signal.

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converting the complex-amplitude-modulation signal received by said radio receiver to a penultimate intermediate-frequency signal and amplifying the power in said penultimate intermediate-frequency signal compared to the complex-amplitude-modulation signal received by said radio receiver;
generating complex oscillations including an in-phase oscillation component and a quadrature-phase oscillation component;
heterodyning said penultimate intermediate-frequency signal both with said in-phase oscillation component and with said quadrature-phase oscillation component to generate orthogonal components of a first final intermediate-frequency signal;
multiplying said orthogonal components of said first final intermediate-frequency signal each by a factor composed of a constant term and a second harmonic of the carrier frequency of said first final intermediate-frequency signal, to generate orthogonal components of a second final intermediate-frequency signal;
synchrodyning a first of the orthogonal components of said second final intermediate-frequency signal to recover, as a real first baseband signal, said first of the orthogonal components of said modulating signal;
and
synchrodyning a second of the orthogonal components of said second final intermediate-frequency signal to recover, as a real second baseband signal, said second of the orthogonal components of said modulating signal.

4 more elements

Apparatus for inclusion within a radio receiver after front-end circuitry for receiving a complex-amplitude-modulation signal as transmitted by a transmitter to said radio receiver, converting said complex-amplitude-modulation signal to a penultimate intermediate-frequency signal, and amplifying the power in said penultimate intermediate-frequency signal compared to the complex-amplitude-modulation signal received by said radio receiver;

said apparatus comprising:
signal generation circuitry for generating a first pair of equal-amplitude heterodyning signals separated in frequency by twice the carrier frequency of a first final intermediate-frequency signal and for generating a second pair of equal-amplitude heterodyning signals separated in frequency by twice the carrier frequency of said final intermediate-frequency signal, which said second pair of equal-amplitude heterodyning signals are in quadrature phasing with said first pair of equal-amplitude heterodyning signals of like frequencies;
a first mixer for heterodyning said penultimate intermediate-frequency signal with said first pair of equal-amplitude heterodyning signals to generate said first final intermediate-frequency signal;
a second mixer for heterodyning said penultimate intermediate-frequency signal with said second pair of equal-amplitude heterodyning signals to generate a second final intermediate-frequency signal;
first synchronous detection circuitry for synchrodyning said first final intermediate-frequency signal to recover, as a real first baseband signal, a first component of modulating signal used in said transmitter for generating said complex-amplitude-modulation signal;
and
second synchronous detection circuitry for synchrodyning said second final intermediate-frequency signal to recover, as a real second baseband signal, a second component of said modulating signal used in said transmitter for generating said complex-amplitude-modulation signal, said first and second components of said modulating signal being mutually orthogonal to each other.

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said apparatus comprising:
controlled oscillator circuitry for generating oscillations supplied in first and second phases that are adjustable in response to a control signal, but are in a prescribed quadrature relationship respective to each other;
a first mixer for heterodyning said penultimate intermediate-frequency signal with said oscillations supplied in said first phase by said controlled oscillator circuitry, thereby to generate a first final intermediate-frequency signal;
a second mixer for heterodyning said penultimate intermediate-frequency signal with said oscillations supplied in said second phase by said controlled oscillator circuitry, thereby to generate a second final intermediate-frequency signal;
circuitry for multiplying said first and said second final intermediate-frequency signals each by a factor composed of a constant term and a second harmonic of the carrier frequency of said first final intermediate-frequency signal, to generate a third final intermediate-frequency signal as the product of said first final intermediate-frequency signal multiplied by said factor, and, to generate a fourth final intermediate-frequency signal as the product of said second final intermediate-frequency signal multiplied by said factor;
first synchronous detection circuitry for synchrodyning said third final intermediate-frequency signal to recover, as a real first baseband signal, a first component of modulating signal used in said transmitter for generating said complex-amplitude-modulation signal;
and
second synchronous detection circuitry for synchrodyning said fourth final intermediate-frequency signal to recover, as a real second baseband signal, a second component of said modulating signal used in said transmitter for generating said complex-amplitude-modulation signal, said first and second components of said modulating signal being mutually orthogonal to each other.

5 more elements

Dependencies are inferred from the claim text.

Dual-carrier heterodyne for separating orthogonal components of complex amplitude-modulation signals

Life of this patent

Dual-carrier heterodyne for separating orthogonal components of complex amplitude-modulation signals

Life of this patent

Abstract

Claims32