US3808529A
Expired / Lapsed
US
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Method and apparatus for analyzing random signals
Assignee: United States Department of the Navy
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Filing: 1973-06-22
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Granted: 1974-04-30
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Expires: 1993-06-22
Abstract
Abstract Apparatus for analyzing random signals so as to determine whether a signal less random than white noise is present. Signals within a desired frequency band are modulated with a pair of quadraturely-phased reference signals which have a frequency preferably equal to the lower frequency of this band. The lower side bands produced when a periodic signal z(t) of constant angular velocity omega is present are Hilbert transforms of each other. These signals, x(t) and jx(t) which equal cosine omega (t) and sine omega (t), are examined so as to determine, for example, the number of times per second that x(t) changes from a positive to a negative condition while x(t) is positive. This number of wrong way zero axis crossings provides a general indication of the degree of randomness of the periodic signal. Alternatively, the number of wrong way crossings of x(t) that occur for a calculated number of right way crossings are also counted.
Inventors
- 👤 R Rowlands
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 03:43
CPC Classifications
G; G01; G01R; G01R29/00; G01R29/26
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
101 words
Apparatus for analyzing random signals so as to determine whether a signal z(t), which is less random than white noise, is present comprising, means for developing from said random signals a pair of signals x(t) and x(t) which are the real and imaginary parts of the complex signal z(t) and correspond to cos omega (t) and sin omega (t), respectively; and means for indicating the number of times per unit time that one of said pair of signals crosses a zero axis in a wrong direction, said number of times being indicative of the degree of randomness of said periodic signal.
Claim 2
Dependent Claim
101 words
Apparatus for analyzing random signals so as to determine whether a signal z(t), which is less random than white noise, is present comprising, means for developing from said random signals a pair of signals x(t) and x(t) which are the real and imaginary parts of the complex signal z(t) and correspond to cos omega (t) and sin omega (t), respectively; and means for indicating the number of times per unit time that one of said pair of signals crosses a zero axis in a wrong direction, said number of times being indicative of the degree of randomness of said periodic signal.
Claim 3
Dependent Claim
36 words
In an arrangement as defined iN claim 1 wherein said unit time corresponds to the time required for said one signal to cross the same zero axis a calculated number of times in a right direction.
Claim 4
Dependent Claim
141 words
In a method for analyzing random signals occuring within a pre-selected frequency band so as to determine whether a signal less random than white noise is present, the steps of modulating said random signals with a pair of quadraturely-phased reference signals having a frequency equal to the lower limit of said band, the lower side bands produced when a periodic signal z(t) of constant angular velocity, omega , is present corresponding to x(t) and jx(t) and being equal to cos omega (t) and sin omega (t), respectively; and counting the number of times per unit time that x(t) crosses the zero axis from a positive to a negative condition while x(t) is positive, the count so obtained being indicative of the number of wrong zero axis crossings of the vector z(t) and, consequently, the degree of randomness of said periodic signal.
Claim 5
Dependent Claim
141 words
In a method for analyzing random signals occuring within a pre-selected frequency band so as to determine whether a signal less random than white noise is present, the steps of modulating said random signals with a pair of quadraturely-phased reference signals having a frequency equal to the lower limit of said band, the lower side bands produced when a periodic signal z(t) of constant angular velocity, omega , is present corresponding to x(t) and jx(t) and being equal to cos omega (t) and sin omega (t), respectively; and counting the number of times per unit time that x(t) crosses the zero axis from a positive to a negative condition while x(t) is positive, the count so obtained being indicative of the number of wrong zero axis crossings of the vector z(t) and, consequently, the degree of randomness of said periodic signal.
Claim 6
Dependent Claim
72 words
In a method as defined in claim 3 wherein the number of times per unit time that x(t) crosses the zero axis and changes from a negative to a positive condition while x(t) is negative is also counted; and wherein the two counts so obtained are averaged to provide an indication of the randomness of said periodic signal, the degree of randomness being inversely proportional to the magnitude of said average count.
Claim 7
Dependent Claim
150 words
Apparatus for analyzing random signals so as to determine whether within a pre-selected frequency band a signal less random than white noise is present comprising, means for modulating said random signals which are within said pre-selected frequency band with a pair of quadraturely-phased reference signals whose frequency is related to the lower limit of said band; means for filtering said modulated signals so as to extract the lower side bands which are produced when a periodic signal z(t) of constant angular velocity, omega , is present, said side bands corresponding to x(t) and jx(t) and being equal to cos omega (t) and sin omega (t), respectively; and means for counting the number of times per unit time that x(t) crosses the zero axis from a positive to a negative condition while x(t) is positive, the count so obtained being inversely proportional to the degree of randomness of said periodic signal.
Claim 8
Dependent Claim
150 words
Apparatus for analyzing random signals so as to determine whether within a pre-selected frequency band a signal less random than white noise is present comprising, means for modulating said random signals which are within said pre-selected frequency band with a pair of quadraturely-phased reference signals whose frequency is related to the lower limit of said band; means for filtering said modulated signals so as to extract the lower side bands which are produced when a periodic signal z(t) of constant angular velocity, omega , is present, said side bands corresponding to x(t) and jx(t) and being equal to cos omega (t) and sin omega (t), respectively; and means for counting the number of times per unit time that x(t) crosses the zero axis from a positive to a negative condition while x(t) is positive, the count so obtained being inversely proportional to the degree of randomness of said periodic signal.
Claim 9
Dependent Claim
52 words
In an arrangement as defined in claim 5 means for counting the number of times per unit time that x(t) crosses the zero axis from a negative to a positive condition while x(t) is negative, the count so obtained also being inversely proportional to the degree of randomness of said periodic signal.
Claim 10
Dependent Claim
50 words
In an arrangement as defined in claim 5 means for counting the number of times that x(t) crosses the zero axis and changes from a positive to a negative condition for a predetermined number of times that it crosses the same zero axis from a negative to a positive condition.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-04-29 | 1977-10-29 | 1978-04-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-04-29 | 1981-10-29 | 1982-04-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-04-29 | 1985-10-29 | 1986-04-30 | $7700.00 | Window Closed / Lapsed |