Signal quality measurement using full-complex FM detector
AssigneeVisteon Global Technologies, Inc.
InventorJ. William Whikehart
Life of this patent
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Abstract
A signal quality indicator for frequency modulated or phase modulated communication signals is obtained using a full-complex detector. The noise detector looks at the actual signal of interest and not other outside indicators such as high frequency content. Signal quality is measured accurately and efficiently. The resulting measure is used to control subsequent processing such as stereo blend, noise blanking, diversity antenna switching, and others in an FM radio receiver.
Claims12
A method of determining signal quality in a communications receiver, comprising the steps of:
- obtaining a complex modulated signal including an in-phase modulated signal I(t) and a quadrature-phase modulated signal Q(t);
- and
- demodulating said in-phase modulated signal and said quadrature-phase modulated signal using a full complex detector to generate a in-phase demodulated signal and a quadrature-phase demodulated signal, wherein said in-phase demodulated signal includes noise, and wherein a power level of said in-phase demodulated signal provides a measure of noise in said quadrature-phase demodulated signal.
Apparatus for processing a modulated signal comprising;
- a complex mixer for converting said modulated signal into a complex modulated signal including an in-phase modulated signal I(t) and a quadrature-phase modulated signal Q (t);
- a full complex detector demodulating said in-phase modulated signal and said quadrature-phase modulated signal to generate a in-phase demodulated signal and an quadrature-phase demodulated signal;
- a reproduction circuit receiving said quadrature-phase demodulated signal for reproducing information contained in said modulated signal;
- and
- a noise circuit coupled to said full complex detector and said reproduction circuit, said noise circuit modifying said reproduced information in response to said in-phase demodulated signal.
An FM receiver comprising:
- an intermediate frequency stage for providing an intermediate frequency (IF) signal including a frequency modulated information signal;
- a complex mixer coupled to said intermediate frequency stage and generating an in-phase modulated signal I(t) and a quadrature-phase modulated signal Q(t);
- a full complex detector demodulating said in-phase modulated signal and said quadrature-phase modulated signal to generate an in-phase demodulated signal and a quadrature-phase demodulated signal;
- an audio processor receiving said quadrature-phase demodulated signal for controlling reproduction of said frequency modulated information signal;
- and
- a noise reduction circuit receiving said in-phase demodulated signal and coupled to said audio processor for modifying said reproduction of said frequency modulated information signal in response to said in-phase demodulated signal.
Dependencies are inferred from the claim text.