US5068875A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Adaptive loop gain phase filter
Assignee: International Business Machines Corp
•
Filing: 1989-09-01
•
Granted: 1991-11-26
•
Expires: 2009-09-01
Abstract
Abstract The adaptive loop gain phase filter of the invention utilizes an averaged value of the phase error at each baud time instead of the phase error for generating the value of the frequency shift. Such an averaged value is obtained by accumulating in accumulator ACCU2 (34) the phase error at each baud time after multiplying it by a factor K O , and is provided either very M baud time when a counter (38) preset at M reaches O, or if the contents of accumulator (34) reach a predetermined limit value. The value of the frequency shift which is accumulated in accumulator ACCU1 (14) is every accurate and enables the phase disturbance such as line breaks and phase hits to be overcome.
Inventors
- 👤 Michel Quintin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 19:14
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/32; H04L27/34; H04L27/38; H04L27/3818
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
268 words
Adaptive loop gain phase filter in a combined amplitude-and-phase-modulation modem wherein a shift of the frequency of the signal carrier creates a phase error that requires a phase correction of the received signal at each baud time, said filter comprising: first accumulating means (34) for providing at baud time n+1, an averaged value of said phase error, from the phase error at baud time n+1 multiplied by a first factor K 0 : detecting means (46) connected to said first accumulating means for detecting when the contents of said accumulating means reach a predetermined limit value; counting means (38) for providing a periodic pulse ever M baud time; gating means (36) connected to said first accumulating means, to said counting means and to said detecting means for outputting the content of said accumulating means in response to either the detection by said detecting means of said predetermined limit value, or to said periodic pulse provided by said counting means; second accumulating means (14) connected to said gating means for providing the value of the frequency shift in response to said averaged value of said phase error multiplied by a second factor (K 1 ) when said gating means are enabled; and summing means (20) connected to said second accumulating means for providing the phase correction to be applied to the received signal at baud time n+1 in response to said value of frequency shift multiplied by a third factor (K 2 , said phase error at baud time n+1 multiplied by a fourth factor (K 3 ) and the value of the phase correction at baud time n.
Claim 2
Dependent Claim
268 words
Adaptive loop gain phase filter in a combined amplitude-and-phase-modulation modem wherein a shift of the frequency of the signal carrier creates a phase error that requires a phase correction of the received signal at each baud time, said filter comprising: first accumulating means (34) for providing at baud time n+1, an averaged value of said phase error, from the phase error at baud time n+1 multiplied by a first factor K 0 : detecting means (46) connected to said first accumulating means for detecting when the contents of said accumulating means reach a predetermined limit value; counting means (38) for providing a periodic pulse ever M baud time; gating means (36) connected to said first accumulating means, to said counting means and to said detecting means for outputting the content of said accumulating means in response to either the detection by said detecting means of said predetermined limit value, or to said periodic pulse provided by said counting means; second accumulating means (14) connected to said gating means for providing the value of the frequency shift in response to said averaged value of said phase error multiplied by a second factor (K 1 ) when said gating means are enabled; and summing means (20) connected to said second accumulating means for providing the phase correction to be applied to the received signal at baud time n+1 in response to said value of frequency shift multiplied by a third factor (K 2 , said phase error at baud time n+1 multiplied by a fourth factor (K 3 ) and the value of the phase correction at baud time n.
Claim 3
Dependent Claim
55 words
Phase filter according to claim 1 wherein said counting means (38) comprise a counter which is preset to a value M and decremented at each baud time, a gating pulse being provided when the contents of said counter reach 0 for enabling said gating means (36) and presetting again said counter to the value M.
Claim 4
Dependent Claim
23 words
Phase filter according to claim 1 or 2 wherein M is of the order of 1000 and factor K 1 is around 1/1000.
Claim 5
Dependent Claim
12 words
Phase filter according to claim 3 wherein factor K 0 is 1/16.
Claim 6
Dependent Claim
58 words
Phase filter according to claim 4 wherein, when the modem starts operating in data mode, factor K 1 is decreased from an initial value such as 1/2 to its final value while M is increased from an initial value such as 100 to its final value, thereby allowing to acquire more quickly the steady state of the modem.
Claim 7
Dependent Claim
136 words
Method of compensating a phase hit in a combined amplitude-and-phase-modulation modem comprising a phase filter providing a very accurate value of the frequency shift, said method comprising the steps of: saving the value of frequency shift last computed just prior to the occurrence of a phase hit; detecting a phase hit; phase rotating the received signal by a slowly incremented angle to determine the value of the phase correction for which the mean-square error presents a minimum; computing the phase correction during the phase rotating by using the value of the frequency shift being saved, so that said phase correction is continually determined as if no phase hit has occurred; and adding to said continually determined value of the phase correction, the value of said slowly incremented angle for which the mean-square error presented a minimum.
Claim 8
Dependent Claim
136 words
Method of compensating a phase hit in a combined amplitude-and-phase-modulation modem comprising a phase filter providing a very accurate value of the frequency shift, said method comprising the steps of: saving the value of frequency shift last computed just prior to the occurrence of a phase hit; detecting a phase hit; phase rotating the received signal by a slowly incremented angle to determine the value of the phase correction for which the mean-square error presents a minimum; computing the phase correction during the phase rotating by using the value of the frequency shift being saved, so that said phase correction is continually determined as if no phase hit has occurred; and adding to said continually determined value of the phase correction, the value of said slowly incremented angle for which the mean-square error presented a minimum.
References Cited (Backward Citations)
US4394760A
Cited
US4386430A
Cited
US4580275A
Cited
US4701873A
Cited
US4773034A
Cited
US4789952A
Cited
US4847864A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-11-25 | 1995-05-27 | 1995-11-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-11-25 | 1999-05-27 | 1999-11-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-11-25 | 2003-05-27 | 2003-11-26 | $7700.00 | Window Closed / Lapsed |