EP0163313A2
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EP
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Method and apparatus for spectral dispersion of the radiated energy from a digital system
Assignee: Tektronix Inc
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Filing: 1985-05-30
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Granted: —
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Expires: 2005-05-30
Abstract
Abstract O Method and apparatus are disclosed for dispersing the electromagnetic energy radiated from a digital system to minimize the EMI and RFI emanating from such a system. To accomplish this, one approach of the present invention includes a VCO which is modulated by a band-limited signal to provide a system clock signal which has a broader spectral signature than the traditional precise crystal controlled oscillator traditionally utilized in digital systems. In addition, an optional feedback stage is disclosed for compensating for frequency drift of the VCO with time. This includes a precision crystal controlled oscillator operating at substantially the same frequency as the unmodulated VCO. This signal is then continuously compared with the modulated output signal of the VCO to generate a compensation signal which in turn is combined with the modulation signal to minimize the long-term errors and thus minimize the long-term drift of the modulated clock signal. Another approach disclosed is to modulate the amplitude of the bus voltage being provided for the digital system.
Inventors
- 👤 Richard F. Crall
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 05:57
CPC Classifications
H; H04; H04B; H04B15/00; H04B15/02; H04B15/04; H03; H03B; H03B29/00; H03L; H03L7/00; H03L7/06; H04B2215/00; H04B2215/064
Claims Analysis
Total Claims: 40
Claim 1
Independent Claim
39 words
A method of generating a digital system master clock signal comprising the steps of: a. generating a clock signal of a selected center frequency and amplitude; and b. modulating the clock signal of step a. within a limited band.
Claim 2
Independent Claim
39 words
A method of generating a digital system master clock signal comprising the steps of: a. generating a clock signal of a selected center frequency and amplitude; and b. modulating the clock signal of step a. within a limited band.
Claim 3
Dependent Claim
16 words
A method as in claim 1 wherein the modulation type of step b. is frequency modulation.
Claim 4
Dependent Claim
16 words
A method as in claim 1 wherein the modulation type of step b. is phase modulation.
Claim 5
Dependent Claim
16 words
A method as in claim 1 wherein the modulation type of step b. is amplitude modulation.
Claim 6
Dependent Claim
17 words
A method as in claim 1 wherein the modulation type of step b. is pulse width modulation.
Claim 7
Dependent Claim
17 words
A method as in claim 1 wherein the modulation type of step b. utilizes a cyclical signal.
Claim 8
Dependent Claim
14 words
A method as in claim 6 wherein the cyclical signal is a pseudo-random signal.
Claim 9
Dependent Claim
19 words
A method as in claim 1 wherein the modulation type of step b. utilizes a band limited random signal.
Claim 10
Dependent Claim
91 words
A method as in claim 1 further including the steps of: c. generating a precision frequency signal having a center frequency with substantially a fixed relationship to the center frequency of step a.; d. generating a compensation signal from the signal from step c. and the resultant signal of steps a. and b.; and e. modifying the signal of step b. in response to the signal of step d. to correct the accumulated error of the resultant signal of steps a. and b. with respect to the signal of step c.
Claim 11
Dependent Claim
53 words
A method as in claim 9 wherein step d. includes the steps of: f. counting the cycles of the generated signal of step c.: g. counting the cycles of the resultant signal of steps a. and b.: and h. comparing the counts of steps f. and g. and generating the compensation signal therefrom.
Claim 12
Dependent Claim
33 words
A method as in claim 9 wherein the center frequency of the precision frequency signal of step c. is substantially the same as the center frequency of the clock signal of step a.
Claim 13
Dependent Claim
46 words
A method as in claim 9 wherein the center requency of the precision frequency signal of step c. is k times the center frequency of the clock signal of step a., k being any positive factor including fractions less than and greater than the numeral 1.
Claim 14
Dependent Claim
28 words
A method as in claim 9 wherein the counting of steps c. and d. is modified to account for the factor k difference of the two frequency signals.
Claim 15
Dependent Claim
25 words
A method as in claim 10 wherein the comparing step h. is modified to account for he factor k difference of the two frequency signals.
Claim 16
Dependent Claim
41 words
A method as in claim 9 wherein step e. includes the step of: i. converting the signal of step h. to an analog signal; and j. summing the modulation signal of step b. with the analog compensation signal of step i.
Claim 17
Dependent Claim
34 words
Apparatus for generating a digital system master clock signal comprising: means for generating a clock signal of a selected center frequency and amplitude; and means for modulating the clock signal within a limited band.
Claim 18
Dependent Claim
34 words
Apparatus for generating a digital system master clock signal comprising: means for generating a clock signal of a selected center frequency and amplitude; and means for modulating the clock signal within a limited band.
Claim 19
Dependent Claim
13 words
Apparatus as in claim 16 wherein the type of modulation is frequency modulation.
Claim 20
Dependent Claim
13 words
Apparatus as in claim 16 wherein the type of modulation is phase modulation.
Claim 21
Dependent Claim
13 words
Apparatus as in claim 16 wherein the type of modulation is amplitude modulation.
Claim 22
Dependent Claim
14 words
Apparatus as in claim 16 wherein the type of modulation is pulse width modulation.
Claim 23
Dependent Claim
11 words
Apparatus as in claim 16 wherein the modulation signal is cyclical.
Claim 24
Dependent Claim
14 words
Apparatus as in claim 16 wherein the cyclical signal is a pseudo random signal.
Claim 25
Dependent Claim
15 words
Apparatus as in claim 16 wherein the modulation signal is a band limited random signal.
Claim 26
Dependent Claim
77 words
Apparatus as in claim 16 further including: means for generating a precision frequency signal having a center frequency with substantially a fixed relationship with the center frequency of the clock signal; means for generating a compensation signal from the precision frequency signal and the modulated clock signal: and means for modifying the modulation signal in response to the compensation signal to correct the accumulated error of the modulated clock signal with respect to the precision frequency signal.
Claim 27
Dependent Claim
56 words
Apparatus as in claim 24 wherein the means for generating a compensation signal includes: means for counting the cycles of the precision frequency signal; means for counting the cycles of the modulated clock signal; and means for comparing the counts of the precision frequency signal and the modulated clock signal and generating the compensation signal therefrom.
Claim 28
Dependent Claim
27 words
Apparatus as in claim 24 wherein the center frequency of the precision frequency signal is substantially the same as the center frequency of the modulated clock signal.
Claim 29
Dependent Claim
39 words
Apparatus as in claims 24 wherein the center frequency of the precision frequency signal is-k times the center frequency of the modulated clock signal, k being any positive factor including fractions less than and greater than the numeral 1.
Claim 30
Dependent Claim
24 words
Apparatus as in claim 24 wherein the two counting means are modified to account for the factor k difference of the two frequency signals.
Claim 31
Dependent Claim
23 words
Apparatus as in claim 25 wherein the comparison means is modified to account for the factor k difference of the two frequency signals.
Claim 32
Dependent Claim
37 words
Apparatus as in claim 24 wherein the modification means includes: means for converting the resultant comparison signal from the comparison means to an analog signal; and means for summing the modulation signal with the analog comparison signal.
Claim 33
Dependent Claim
25 words
Apparatus as in claim 16 wherein: said generating means includes a voltage controlled oscillator; and said modulating means includes a band-limited random noise signal generator.
Claim 34
Dependent Claim
17 words
Apparatus as in claim 24 wherein said precision frequency signal generating means includes a crystal controlled oscillator.
Claim 35
Dependent Claim
42 words
Apparatus as in claim 16 wherein said modulating means includes: means for producing a pulse width modulation signal; and signal generator means for generting a selected signal for application to the pulse width modulation means to determine the width of said pulses.
Claim 36
Dependent Claim
13 words
Apparatus as in claim 33 wherein said generator means generates a cyclical signal.
Claim 37
Dependent Claim
15 words
Apparatus as in claim 33 wherein said generator means generates a band limited random signal.
Claim 38
Independent Claim
36 words
A method of generating a digital system bus voltage signal comprising the steps of: a. generating a bus voltage of a selected amplitude; and b. modulating the bus voltage of step a. within a limited range.
Claim 39
Independent Claim
36 words
A method of generating a digital system bus voltage signal comprising the steps of: a. generating a bus voltage of a selected amplitude; and b. modulating the bus voltage of step a. within a limited range.
Claim 40
Dependent Claim
80 words
A method as in claim 36 further including the steps of: c. integrating the modulated bus voltage signal: d. generating a compensation signal from the integrated modulated bus voltage signal and a fixed reference voltage having substantially the same value as the b.s voltage of step a.; and e. modifying the signal of step b. in response to the signal of step d. to correct the accumulated error of the modulated bus voltage with respect to the fixed reference voltage.
References Cited (Backward Citations)
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