US4543564A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Interference suppression apparatus for a capacitive keyboard
Assignee: H.I.I.
•
Filing: 1982-03-26
•
Granted: 1985-09-24
•
Expires: 2002-03-26
Abstract
Abstract Apparatus for suppressing interference in a capacitive keyboard. Unconditioned operating signals from receiving lines are passed into a subtractor, which establishes the difference between the signal present on a reference line in the keyboard and supplies, at the output, a conditioned operating signal which is free from any unwanted electromagnetic component which may have entered the structure. In addition, in order to determine which of several keys is supplying the highest signal, operating signals corresponding to particular receiving lines are scanned in sequence to determine which has the highest amplitude. As the operating signal corresponding to each successive key is scanned, its voltage is compared with a previously-stored voltage for an earlier-scanned key. If a higher voltage is detected, the voltage and key address are stored in place of the previously-stored values.
Inventors
- 👤 Marcel Audoin
- 👤 Jean-Marc Fedeli
- 👤 Robert Poujois
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 04:50
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/96; H03K17/962; H03K17/9622; H03K2217/00; H03K2217/94; H03K2217/96; H03K2217/9607; H03K2217/960755; H03K2217/96077
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
161 words
An apparatus for the suppression of interference in a capacitive keyboard of the type including a series of sensitive keys on an outer surface accessible to a user, each key having a transmitting electrode excited by an alternating signal supplied by a transmitting line, and a receiving electrode selectively capacitively coupled to the transmitting electrode and connected to supply a receiving line, the receiving lines providing a corresponding set of unconditioned operating signals having amplitude variations dependent on the effect of the possible presence of the finger of a user on the sensitive key, said apparatus further comprising means for establishing the difference between the unconditioned operating signal from each receiving line and the signal from a reference line in the keyboard to supply a set of conditioned operating signals free from any unwanted electromagnetic component which has entered the keyboard, said means for establishing the difference including at least one subtractor into which signals from the receiving lines are passed.
Claim 2
Independent Claim
161 words
An apparatus for the suppression of interference in a capacitive keyboard of the type including a series of sensitive keys on an outer surface accessible to a user, each key having a transmitting electrode excited by an alternating signal supplied by a transmitting line, and a receiving electrode selectively capacitively coupled to the transmitting electrode and connected to supply a receiving line, the receiving lines providing a corresponding set of unconditioned operating signals having amplitude variations dependent on the effect of the possible presence of the finger of a user on the sensitive key, said apparatus further comprising means for establishing the difference between the unconditioned operating signal from each receiving line and the signal from a reference line in the keyboard to supply a set of conditioned operating signals free from any unwanted electromagnetic component which has entered the keyboard, said means for establishing the difference including at least one subtractor into which signals from the receiving lines are passed.
Claim 3
Dependent Claim
20 words
Apparatus according to claim 1, wherein the reference line for each receiving line is another one of the receiving lines.
Claim 4
Dependent Claim
31 words
An apparatus according to claim 1, wherein the reference line is the output of an averaging circuit which determines the mean of a plurality of signals collected on several receiving lines.
Claim 5
Dependent Claim
23 words
An apparatus according to claim 2, wherein the reference line for each receiving line is an adjacent receiving line of a matrix structure.
Claim 6
Dependent Claim
126 words
Apparatus in accordance with claim 1, wherein the capacitive keyboard includes: upper and lower insulating layers each having an outer face and an inner face, with the inner face of the upper insulating layer and the outer face of the lower insulating layer assembled to each other by adhesion; the outer face of the upper insulating layer carrying the sensitive keys and an earthed conductive shield surrouding the sensitive keys; the outer face of the lower insulating layer carrying the receiving electrodes and receiving lines, and carrying separating electrodes and supply lines for the separating electrodes; and the inner face of the lower insulating layer carrying the receiving electrodes and receiving lines, carrying separating electrodes, and carrying an earthed conductive shield separated by another insulating layer.
References Cited (Backward Citations)
DE2822847A1
Cited
FR2397696A1
Cited
US4145748A
Cited
US4257117A
Cited
US4211915A
Cited
US4305135A
Cited
US4291303A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-09-23 | 1989-03-25 | 1989-09-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-09-23 | 1993-03-25 | 1993-09-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-09-23 | 1997-03-25 | 1997-09-24 | $7700.00 | Window Closed / Lapsed |