US4791577A — Frequency shift for removing spurious spectral co…

Claim 1

Independent Claim 182 words

Apparatus for suppressing distortion components in the output produced by a spectrum analyzer in response to an input signal, comprising: a first mixer circuit for receiving the input signal and producing a first IF signal having a spectral distribution shifted in frequency from that of the input signal by an amount f LO ; a second mixer circuit for receiving the same input signal and producing a second IF signal having a spectral distribution shifted from that of the input signal by an amount f LO +Δf; first and second spectrum analyzers for receiving the first and second IF signals, respectively, and producing first and second spectrum output signals which represent spectral components of the first and second IF signals, respectively; and output signal processing means for comparing the spectral components in the first and second spectrum output signals and for suppressing any components in the first spectrum output signal which do not also appear in the second spectrum output signal as components that are offset in frequency by the amount Δf from their respective counterparts in the first spectrum output signal.

Claim 2

Dependent Claim 182 words

Apparatus for suppressing distortion components in the output produced by a spectrum analyzer in response to an input signal, comprising: a first mixer circuit for receiving the input signal and producing a first IF signal having a spectral distribution shifted in frequency from that of the input signal by an amount f LO ; a second mixer circuit for receiving the same input signal and producing a second IF signal having a spectral distribution shifted from that of the input signal by an amount f LO +Δf; first and second spectrum analyzers for receiving the first and second IF signals, respectively, and producing first and second spectrum output signals which represent spectral components of the first and second IF signals, respectively; and output signal processing means for comparing the spectral components in the first and second spectrum output signals and for suppressing any components in the first spectrum output signal which do not also appear in the second spectrum output signal as components that are offset in frequency by the amount Δf from their respective counterparts in the first spectrum output signal.

Claim 3

Dependent Claim 32 words

Apparatus as defined in claim 1, wherein: the spectrum analyzers are discrete Fourier transform (DFT) processors, each producing a stream of output signals representing the spectral components of the respective IF signals.

Claim 4

Dependent Claim 73 words

Apparatus as defined in claim 2, wherein: the times of occurrence of the output signals in each stream of output signals are indicative of the frequencies of the spectral components; and the output signal processing means includes delay means connected in the output of the second DFT processor, to shift the output stream of that processor by a time offset equivalent of Δf, to facilitate comparison between the two streams of output signals.

Claim 5

Dependent Claim 70 words

Apparatus as defined in claim 3, wherein the output signal processing means further includes: a comparator circuit for comparing the first output stream and the time-delayed second output stream, and generating output signals indicative of the result of the comparison; and switching means responsive to the output signals from the comparator circuit, for disabling output from the apparatus upon the failure of the comparator circuit to detect matching input signals.

Claim 6

Dependent Claim 57 words

Apparatus as defined in claim 4, wherein: the switching means includes a multiplexor controlled by the output of the compartor circuit and having a first in put derived from the first DFT processor selected when the comparator cirucit indicates a match, and a second input of a null signal selected when the comparator circuit indicates a non-match.

Claim 7

Dependent Claim 46 words

Apparatus as defined in claim 4, wherein: the comparator circuit includes two input threshold circuits to provide outputs when the inputs exceed a preselected threshold valve; and an AND gate connected to receive the outputs of the threshold circuits, and to provide a comparator circuit output.

Claim 8

Dependent Claim 145 words

Apparatus for suppressing distortion components in the output produced by a spectrum analyzer in response to an input signal, comprising: mixing means, for producing from the input signal first and second derived signals, of which the corresponding spectral components are separated from each other by a frequency offset Δf; first and second spectrum analyzers for receiving the first and second derived signals, respectively, and producing first and second spectrum output signals which represent the spectral components of the first and second derived signals, respectively; and output signal processing means for comparing the spectral components in the first and second spectrum output signals and for suppressing any components in the first spectrum output signal which do not also appear in the second spectrum output signal as components that are offset in frequency by the amount Δf from their respective counterparts in the first spectrum output signal.

Claim 9

Dependent Claim 145 words

Apparatus for suppressing distortion components in the output produced by a spectrum analyzer in response to an input signal, comprising: mixing means, for producing from the input signal first and second derived signals, of which the corresponding spectral components are separated from each other by a frequency offset Δf; first and second spectrum analyzers for receiving the first and second derived signals, respectively, and producing first and second spectrum output signals which represent the spectral components of the first and second derived signals, respectively; and output signal processing means for comparing the spectral components in the first and second spectrum output signals and for suppressing any components in the first spectrum output signal which do not also appear in the second spectrum output signal as components that are offset in frequency by the amount Δf from their respective counterparts in the first spectrum output signal.

Claim 10

Dependent Claim 32 words

Apparatus as defined in claim 7, wherein: the spectrum analyzers are discrete Fourier transform (DFT) processors, each producing a stream of output signals representing the spectral components of the respective derived signals.

Claim 11

Dependent Claim 73 words

Apparatus as defined in claim 8, wherein: the times of occurrence of the output signals in each stream of output signals are indicative of the frequencies of the spectral components; and the output signal processing means includes delay means connected in the output of the second DFT processor, to shift the output stream of that processor by a time offset equivalent of Δf, to facilitate comparison between the two streams of output signals.

Claim 12

Dependent Claim 70 words

Apparatus as defined in claim 9, wherein the output signal processing means further includes: a comparator circuit for comparing the first out-put stream and the time-delayed second output stream, and generating output signals indicative of the result of the comparison; and switching means responsive to the output signals from the comparator circuit, for disabling output from the apparatus upon the failure of the comparator circuit to detect matching input signals.

Claim 13

Dependent Claim 56 words

Apparatus as defined in claim 10, wherein: the switching means includes a multiplexor controlled by the output of the comparator circuit and having a first input derived from the first DFT processor selected when the comparator circuit indicates a match, and a second input of a null signal selected when the comparator circuit indicates a non-match.

Claim 14

Dependent Claim 46 words

Apparatus as defined in claim 10, wherein: the comparator circuit includes two input threshold circuits to provide outputs when the inputs exceed a preselected threshold valve; and an AND gate connected to receive the outputs of the threshold circuits, and to provide a comparator circuit output.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-12-13	1992-06-13	1992-12-13	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-12-13	1996-06-13	1996-12-13	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-12-13	2000-06-13	2000-12-13	$7700.00	Window Closed / Lapsed

Frequency shift for removing spurious spectral components from spectrum analyzer output

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