US4093965A
Expired / Lapsed
US
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Speed-switchable readback signal equalization and direct-current restoration
Assignee: Bell and Howell Co
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Filing: 1976-08-16
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Granted: 1978-06-06
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Expires: 1996-08-16
Abstract
Abstract Apparatus for recovering signals read back from a recording medium at different relative recording medium speeds have speed-switchable equipment for equalizing readback signals over frequency bands having different peak to-bandedge roll-off regions for different relative recording medium speeds. High-frequency equalization means in the speed-switchable equipment equalize readback signals in the peak-to-bandedge roll-off regions by providing speed-switchable frequency peaking characteristics and speed-switchable cut-off frequency characteristics and in company with each other shift the frequency peaking characteristics and cut-off frequency characteristics to the different peak-to-bandedge roll-off regions for different relative recording medium speeds.
Inventors
- 👤 David B. Gish
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:06
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/02; G11B5/027; G11B5/035
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
218 words
In apparatus for recovering signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: speed-switchable means for equalizing readback signals over frequency bands having different peak-to-bandedge roll-off regions for different relative recording medium speeds; and high-frequency equalization means in said speed-switchable means for equalizing readback signals in said peak-to-bandedge roll-off regions, including active low-pass filter means for providing speed-switchable frequency peaking characteristics and speed-switchable cut-off frequency characteristics and for shifting said frequency peaking characteristics and cut-off frequency characteristics in company with each other to said different peak-to-bandedge roll-off regions for different relative recording medium speeds; said active low-pass filter means including operational amplifier means having input means and output means, a speed-switchable RC network connected to said input and output means, and series-connected first and speed-switchable second resistor means, said first resistor means being connected between said input and output means, and said second resistor means being connected between said input means and a reference potential, with the ratio of the resistance, R 1 , of said first resistor means to the resistance, R 2 , of said second resistor means being such that R 1 /R 2 plus one is at least two; and said speed-switchable means including means for switching said speed-switchable RC network and second resistor means.
Claim 2
Dependent Claim
218 words
In apparatus for recovering signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: speed-switchable means for equalizing readback signals over frequency bands having different peak-to-bandedge roll-off regions for different relative recording medium speeds; and high-frequency equalization means in said speed-switchable means for equalizing readback signals in said peak-to-bandedge roll-off regions, including active low-pass filter means for providing speed-switchable frequency peaking characteristics and speed-switchable cut-off frequency characteristics and for shifting said frequency peaking characteristics and cut-off frequency characteristics in company with each other to said different peak-to-bandedge roll-off regions for different relative recording medium speeds; said active low-pass filter means including operational amplifier means having input means and output means, a speed-switchable RC network connected to said input and output means, and series-connected first and speed-switchable second resistor means, said first resistor means being connected between said input and output means, and said second resistor means being connected between said input means and a reference potential, with the ratio of the resistance, R 1 , of said first resistor means to the resistance, R 2 , of said second resistor means being such that R 1 /R 2 plus one is at least two; and said speed-switchable means including means for switching said speed-switchable RC network and second resistor means.
Claim 3
Dependent Claim
36 words
Apparatus as claimed in claim 1, wherein: said readback signals are subject to specific high-frequency compound losses; and said high-frequency equalization means include means for adjusting said frequency peaking characteristics to said specific high-frequency compound losses.
Claim 4
Dependent Claim
103 words
In apparatus for recovering signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: speed-switchable means for equalizing readback signals over frequency bands having different peak-to-bandedge roll-off regions for different relative recording medium speeds; and high-frequency equalization means in said speed-switchable means for equalizing readback signals in said peak-to-bandedge roll-off regions, including active low-pass filter means for providing speed-switchable frequency peaking characteristics and speed-switchable cut-off frequency characteristics and for shifting said frequency peaking characteristics and cut-off frequency characteristics in company with each other to said different peak-to-bandedge roll-off regions for different relative recording medium speeds.
Claim 5
Dependent Claim
103 words
In apparatus for recovering signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: speed-switchable means for equalizing readback signals over frequency bands having different peak-to-bandedge roll-off regions for different relative recording medium speeds; and high-frequency equalization means in said speed-switchable means for equalizing readback signals in said peak-to-bandedge roll-off regions, including active low-pass filter means for providing speed-switchable frequency peaking characteristics and speed-switchable cut-off frequency characteristics and for shifting said frequency peaking characteristics and cut-off frequency characteristics in company with each other to said different peak-to-bandedge roll-off regions for different relative recording medium speeds.
Claim 6
Dependent Claim
36 words
Apparatus as claimed in claim 3, wherein: said readback signals are subject to specific high-frequency compound losses; and said low-pass filter means include means for adjusting said frequency peaking characteristics to said specific high-frequency compound losses.
Claim 7
Dependent Claim
41 words
Apparatus as claimed in claim 3, wherein: said low-pass filter means include combined operating amplifier means and RC filter components; and said means for simultaneously shifting said peaking characteristics and cut-off frequency characteristics include means for switching said RC filter components.
Claim 8
Dependent Claim
43 words
Apparatus as claimed in claim 5, wherein: said readback signals are subject to specific high-frequency compound losses; and said low-pass filter means include means for adjusting said frequency peaking characteristics to said specific high-frequency compound losses by adjustment of said RC filter means.
Claim 9
Dependent Claim
193 words
In apparatus for recovering signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: speed-switchable means for equalizing readback signals over frequency bands having different peak-to-bandedge roll-off regions for different relative recording medium speeds; high-frequency equalization means in said speed-switchable means for equalizing readback signals in said peak-to-bandedge roll-off regions, including means for providing speed-switchable frequency peaking characteristics and speed-switchable cut-off frequency characteristics and for shifting said frequency peaking characteristics and cut-off frequency characteristics in company with each other to said different peak-to-bandedge roll-off regions for different relative recording medium speeds; and means connected to said high-frequency equalization means for direct-current restoration of equalized readback signals, including means for providing a first signal analogous to said equalized readback signals and asymmetrical in a first sense relative to a reference voltage, means for providing a second signal analogous to said equalized readback signals and asymmetrical in a second sense relative to a reference voltage, and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 10
Dependent Claim
193 words
In apparatus for recovering signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: speed-switchable means for equalizing readback signals over frequency bands having different peak-to-bandedge roll-off regions for different relative recording medium speeds; high-frequency equalization means in said speed-switchable means for equalizing readback signals in said peak-to-bandedge roll-off regions, including means for providing speed-switchable frequency peaking characteristics and speed-switchable cut-off frequency characteristics and for shifting said frequency peaking characteristics and cut-off frequency characteristics in company with each other to said different peak-to-bandedge roll-off regions for different relative recording medium speeds; and means connected to said high-frequency equalization means for direct-current restoration of equalized readback signals, including means for providing a first signal analogous to said equalized readback signals and asymmetrical in a first sense relative to a reference voltage, means for providing a second signal analogous to said equalized readback signals and asymmetrical in a second sense relative to a reference voltage, and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 11
Dependent Claim
115 words
In apparatus for recovering an alternating signal read back from a recording medium, the improvement comprising in combination: means for receiving said alternating readback signal; means connected to said receiving means for providing a first signal analogous to said received alternating readback signal and asymmetrical in a first sense relative to a reference voltage; means connected to said receiving means for providing a second signal analogous to said received alternating readback signal and asymmetrical in a second sense relative to a reference voltage; and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 12
Dependent Claim
115 words
In apparatus for recovering an alternating signal read back from a recording medium, the improvement comprising in combination: means for receiving said alternating readback signal; means connected to said receiving means for providing a first signal analogous to said received alternating readback signal and asymmetrical in a first sense relative to a reference voltage; means connected to said receiving means for providing a second signal analogous to said received alternating readback signal and asymmetrical in a second sense relative to a reference voltage; and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 13
Dependent Claim
122 words
In apparatus for recovering alternating signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: means for receiving said alternating readback signals; speed-switchable means connected to said receiving means for providing a first signal analogous to said received alternating readback signals and asymmetrical in a first sense relative to a reference voltage; speed-switchable means connected to said receiving means for providing a second signal analogous to said received alternating readback signals and asymmetrical in a second sense relative to a reference voltage; and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 14
Dependent Claim
122 words
In apparatus for recovering alternating signals read back from a recording medium at different relative recording medium speeds, the improvement comprising in combination: means for receiving said alternating readback signals; speed-switchable means connected to said receiving means for providing a first signal analogous to said received alternating readback signals and asymmetrical in a first sense relative to a reference voltage; speed-switchable means connected to said receiving means for providing a second signal analogous to said received alternating readback signals and asymmetrical in a second sense relative to a reference voltage; and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 15
Dependent Claim
65 words
Apparatus as claimed in claim 9, wherein: said speed-switchable first signal providing means include first means for clamping first excursions of said alternating signal above said direct-current reference voltage; said speed-switchable second signal providing means include second means for clamping second excursions of said alternating signal below said direct-current reference voltage; and said combining means include means for summing said clamped first and second excursions.
Claim 16
Dependent Claim
81 words
Apparatus as claimed in claim 10, wherein: said speed-switchable first signal providing means include first speed-switchable means connected to said first clamping means for providing a speed-switchable time constant; said speed-switchable second signal providing means include second speed-switchable means connected to said second clamping means for providing a speed-switchable time constant; and said apparatus include means connected to said first and second signal providing means for switching said first and second time constant providing means for different relative recording medium speeds.
Claim 17
Dependent Claim
105 words
Apparatus for direct-current restoration of an alternating signal, comprising in combination: means for receiving said alternating signal; means connected to said receiving means for providing a first signal analogous to said received alternating signal and asymmetrical in a first sense relative to a reference voltage; means connected to said receiving means for providing a second signal analogous to said received alternating signal and asymmetrical in a second sense relative to a reference voltage; and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 18
Dependent Claim
105 words
Apparatus for direct-current restoration of an alternating signal, comprising in combination: means for receiving said alternating signal; means connected to said receiving means for providing a first signal analogous to said received alternating signal and asymmetrical in a first sense relative to a reference voltage; means connected to said receiving means for providing a second signal analogous to said received alternating signal and asymmetrical in a second sense relative to a reference voltage; and means connected to said first and second signal providing means for combining said first and second signals and disposing said combined first and second signals symmetrically about a direct-current reference voltage.
Claim 19
Dependent Claim
63 words
Apparatus as claimed in claim 12, wherein: said first signal providing means include first means for clamping first excursions of said alternating signal above said direct-current reference voltage; said second signal providing means include second means for clamping second excursions of said alternating signal below said direct-current reference voltage; and said combining means include means for summing said clamped first and second excursions.
Claim 20
Independent Claim
79 words
A method of direct-current restoring an alternating signal, comprising in combination the steps of: providing a first signal analogous to said alternating signal and asymmetrical in a first sense relative to a reference voltage; providing a second signal analogous to said alternating signal and asymmetrical in a second sense relative to a reference voltage; providing a direct-current reference voltage; combining said first and second signals; and disposing said combined first and second signals symmetrically about said direct-current reference voltage.
Claim 21
Independent Claim
79 words
A method of direct-current restoring an alternating signal, comprising in combination the steps of: providing a first signal analogous to said alternating signal and asymmetrical in a first sense relative to a reference voltage; providing a second signal analogous to said alternating signal and asymmetrical in a second sense relative to a reference voltage; providing a direct-current reference voltage; combining said first and second signals; and disposing said combined first and second signals symmetrically about said direct-current reference voltage.
Claim 22
Dependent Claim
53 words
A method as claimed in claim 14, wherein: said first signal is provided by clamping first excursions of said alternating signal above said direct-current reference voltage; said second signal is provided by clamping second excursions of said alternating signal below said direct-current reference voltage; and said clamped first and second excursions are summed.
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) | 1981-06-05 | 1981-12-05 | 1982-06-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-06-05 | 1985-12-05 | 1986-06-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-06-05 | 1989-12-05 | 1990-06-06 | $7700.00 | Window Closed / Lapsed |