SIGNAL ANALYSIS OF MULTIPLICATIVELY RELATED FREQUENCY COMPONENTS IN A COMPLEX SIGNAL

• US 3,731,188 A
• Filed: 04/19/1971
• Issued: 05/01/1973
• Est. Priority Date: 04/19/1971
• Status: Expired due to Term

• Current Assignee: Tracor Aerospace, Inc.
• Original Assignee: Spurgeon E. Smith
• Inventors: Smith, Spurgeon E.
• Primary Examiner(s): Smith, Alfred E.
• Application Number:
  US05/135,090
• Time in Patent Office: 743 Days
• Field of Search: 324/77 179/1SA 328/140,166,167
• US Class Current: 324/76.31
• CPC Class Codes: G01R 23/00 Arrangements for measuring frequencies; Arrangements for analysing frequency spectra

Abstract

Apparatus including a plurality of frequency-tunable filters controlled by a frequency synthesizer in turn controlled by a variable oscillator for examining a complex signal at frequency '"'"''"'"''"'"''"'"'bins'"'"''"'"''"'"''"'"' which are multiplicatively related, the amplitudes of the signals in these bins yielding quality information about the complex signal when compared to predetermined amounts known to be indicative of quality.

Claims

1. Apparatus for determining the frequency components to be found in a complex signal, the frequency components having a multiplicative relationship to each other, comprising a plurality of synchronous filters, the center frequency of each of said synchronous filters being adjustably determined by the frequency of an applied reference signal, the complex signal being applied to each of said filters for determining the existence of a signal in the passband thereof, a frequency synthesizer for producing a plurality of output signals, the frequencies of which are multiplicatively related to each other, said output signals being connected respectively as the applied reference signals to said plurality of synchronous filters, a variable oscillator connected as the input to said frequency synthesizer, a frequency change of said oscillator causing the frequencies of the signal outputs from said synthesizer to change, and means connected to said filters for indicating the amplitude of the frequency components passed by said synchronous filters.

2. Apparatus as described in claim 1, and including frequency control means connected to said variable oscillator, the frequency control setting thereof having a predetermined passband center frequency selection relationship with each of said synchronous filters.

3. Apparatus as described in claim 1, wherein said indicating means for each filter includes an amplitude averager.

4. Apparatus as described in claim 1, wherein said indicating means includes a separate circuit connected to each filter, comprising rectifier means for development of an average amplitude for the signal passed by said filter, and metering means connected to said rectifier means for visually presenting said amplitude.

5. Apparatus for determining the frequency components to be found in a comPlex signal, the frequency components having a multiplicative relationship to each other, comprising a plurality of synchronous filters, the center frequency of each of said synchronous filters being adjustably determined by the frequency of an applied reference signal, the complex signal being applied to each of said filters for determining the existence of a signal in the passband thereof, a frequency synthesizer for producing a plurality of output signals, the frequencies of which are multiplicatively related to each other, said output signals being connected respectively as the applied reference signals to said plurality of synchronous filters, a variable oscillator connected as the input to said frequency synthesizer, a frequency change of said oscillator causing the frequencies of the signal outputs from said synthesizer to change;

a separate amplitude averager circuit connected to the output of each of said filters, a threshold level detector circuit connected to each of said amplitude averager circuits, each threshold level detector circuit producing an output when the amplitude averager circuit produces a signal having an amplitude in excess of the threshold level, the threshold level for each of said threshold level detector circuits being independently adjustable, and means connected to said threshold detector circuits for indicating the frequency components passed by said synchronous filters that produce an average amplitude in excess of the threshold level settings of said threshold level detector circuits.

6. Apparatus for determining the satisfactory performance of a physical system producing a signal having a complex signal spectrum, the spectrum indicating satisfactory performance when frequencies having a known multiplicative and amplitude relationship to each other are within predetermined limits, comprising a plurality of synchronous filters, the center frequency of each of said synchronous filters being adjustably determined by the frequency of an applied reference signal, the signal having the complex signal spectrum being applied to each of said filters for determining the existence of a signal in the passband thereof, a frequency synthesizer for producing a plurality of output signals, the frequencies of which are multiplicatively related to each other in the predetermined relationship, said output signals being connected respectively as the applied reference signals to said plurality of synchronous filters, a variable oscillator connected as the input to said frequency synthesizer, a frequency change of said oscillator causing the frequencies of the signal outputs from said synthesizer to change, a separate amplitude averager circuit connected to the output of each of said filters, a threshold level detector circuit connected to each of said amplitude averager circuits, each threshold level detector circuit producing an output when the amplitude averager circuit produces a signal having an amplitude in excess of the threshold level, the threshold level for each of said threshold level detector circuits being independently adjustable in accordance with the predetermined relationship, and AND circuit means connected to each of said threshold level detector circuits, an output therefrom evidencing satisfactory performance of the physical system.

7. Apparatus for determining the unsatisfactory performance of a physical system producing a signal having a complex signal spectrum, the spectrum indicating unsatisfactory performance when frequencies having a known multiplicative and amplitude relationship to each other are within predetermined limits, comprising a plurality of synchronous filters, the center frequency of each of said synchronous filters being adjustably determined by the frequency of an applied reference signal, the signal having the complex signal spectrum being applied to each of said filters for determining the existence of a signal in the passband thereof, a frequency Synthesizer for producing a plurality of output signals, the frequencies of which are multiplicatively related to each other in the predetermined relationship, said output signals being connected respectively as the applied reference signals to said plurality of synchronous filters, a variable oscillator connected as the input to said frequency synthesizer, a frequency change of said oscillator causing the frequencies of the signal outputs from said synthesizer to change, a separate amplitude averager circuit connected to the output of each of said filters, a threshold level detector circuit connected to each of said amplitude averager circuits, each threshold level detector circuit producing an output when the amplitude averager circuit produces a signal having an amplitude in excess of the threshold level, the threshold level for each of said threshold level detector circuits being independently adjustable in accordance with the predetermined relationship, and AND circuit means connected to each of said threshold level detector circuits, an output therefrom evidencing unsatisfactory performance of the physical system.

8. Apparatus for determining the satisfactory performance of a physical system producing a signal having a complex signal spectrum, the spectrum indicating satisfactory performance when frequencies having a known multiplicative and amplitude relationship to each other are within predetermined limits, comprising a plurality of synchronous filters, the center frequency of each of said synchronous filters being adjustable determined by the frequency of an applied reference signal, the signal having the complex signal spectrum being applied to each of said filters for determining the existence of a signal in the passband thereof, a frequency synthesizer for producing a plurality of output signals, the frequencies of which are multiplicatively related to each other in the predetermined relationship, said output signals being connected respectively as the applied reference signals to said plurality of synchronous filters, a variable oscillator connected as the input to said frequency synthesizer, a frequency change of said oscillator causing the frequencies of the signal outputs from said synthesizer to change, a separate amplitude averager circuit connected to the output of each of said filters, a threshold level detector circuit connected to each of said amplitude averager circuits, each threshold level detector circuit producing an output when the amplitude averager circuit produces a signal having an amplitude in excess of the threshold level, the threshold level for each of said threshold level detector circuits being independently adjustable in accordance with the predetermined relationship, and accumulator means connected to each of said threshold level detector circuits, an output above a predetermined amount indicating satisfactory performance.

9. Apparatus for determining the unsatisfactory performance of a physical system producing a signal having a complex signal spectrum, the spectrum indicating unsatisfactory performance when frequencies having a known multiplicative and amplitude relationship to each other are within predetermined limits, comprising a plurality of synchronous filters, the center frequency of each of said synchronous filters being adjustable determined by the frequency of an applied reference signal, the signal having the complex signal spectrum being applied to each of said filters for determining the existence of a signal in the passband thereof, a frequency synthesizer for producing a plurality of output signals, the frequencies of which are multiplicatively related to each other in the predetermined relationship, said output signals being connected respectively as the applied reference signals to said plurality of synchronous filters, a variable oscillator connected as the input to said frequency synthesizer, a frequency change of said oscillator causing the Frequencies of the signal outputs from said synthesizer to change, a separate amplitude averager circuit connected to the output of each of said filters, a threshold level detector circuit connected to each of said amplitude averager circuits, each threshold level detector circuit producing an output when the amplitude averager circuit produces a signal having an amplitude in excess of the threshold level, the threshold level for each of said threshold level detector circuits being independently adjustable in accordance with the predetermined relationship, and accumulator means connected to each of said threshold level detector circuits, an output above a predetermined amount indicating unsatisfactory performance.

10. Apparatus for analyzing a complex signal, frequency components therein having a predetermined frequency multiplicative relationship to each other and a predetermined proportionate amplitude relationship to each other, comprising a plurality of synchronous filters, the center frequency of each of said synchronous filters being adjustably determined by the frequency of an applied reference signal, the signal having the complex signal spectrum being applied to each of said filters for determining the existence of a signal in the passband thereof, a frequency synthesizer for producing a plurality of output signals, the frequencies of which are multiplicatively related to each other in the predetermined relationship, said output signals being connected respectively as the applied reference signals to said plurality of synch-ronous filters, a variable oscillator connected as the input to said fre-quency synthesizer, a frequency change of said oscillator causing the frequencies of the signal outputs from said synthesizer to change, a separate amplitude averager circuit connected to the output of each of said filters, a gain circuit connected to each of said separate amplitude averager circuits to increase the gain of the signal therefrom by the predetermined proportionate amount with respect to the other of said gain circuits to produce a substantially equal output amplitude for each of said gain circuits. a threshold level detector circuit connected to each of said gain circuits, each threshold level detector circuit producing an output when the gain circuit produces an amplitude in excess of the threshold level, and means connected to said threshold detector circuits for indicating the frequency-multiplicatively related signals passed by said synchronous filters that produce an average amplitude in excess of the predetermined proportionate amplitude amounts.

11. Apparatus for determining whether the frequency components found in a complex signal are closer in related overall amplitude values to a first group of related amplitudes or to a second group of related amplitudes, comprising a plurality of filters, one each for isolating the frequency components found in the complex signal, a first set of amplitude gain means, one connected to each of said filters, for raising the amplitudes to the values of the first group, a second set of amplitude gain means, one connected to each of said filters, for raising the amplitudes to the values of the second group, first combining means connected to each of said first set of amplitude gain means for producing a first output, said first output being equal to a predetermined value when the amplitudes of said frequency components are equal to said first group of related amplitudes, and second combining means connected to each of said second set of amplitude gain means for producing a second output, said second output being equal to a predetermined value when the amplitudes of said frequency components are equal to said second group of related amplitudes.

12. Apparatus as described in claim 11, wherein said first combining means is an adder, the square of each of said gains means in said first set produces an output for the related amplitude of sAid first group of related amplitudes such that the output from said first combining means is equal to a predetermined amount, said second combining means is an adder, and the square of each of said gains means in said second set produces an output for the related amplitude of said second group of related amplitudes such that the output from said second combining means is equal to said predetermined amount, the ratio of the outputs from said first and second combining means being an indication of which of said first and second groups of related amplitudes the amplitudes of the isolated frequency components of said complex signal most resemble, a ratio of one indicating equal similarity to both groups, a ratio greater than one indicating a comparative similarity to one of said groups and a ratio less than one indicating a comparative similarity to the other of said groups.