Patent US4937839A successfully refreshed from Google Patents.
US4937839A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Frequency multiplexed full duplex 4800 bps modem
Assignee: HYCOM Inc 16841 ARMSTRONG AVENUE IRVINE CALIFORNIA 92714 A Corp OF CA
•
Filing: 1988-07-25
•
Granted: 1990-06-26
•
Expires: 2008-07-25
Abstract
Abstract 4800 B/S full duplex operation of a frequency-multiplexing modem over the switched telephone network without cancellation is made possible by combining 900-baud, 32-state operation with a combination of analog filtering and raised cosine digital filtering and stop bit robbing.
Inventors
- 👤 David M. Motley
- 👤 John F. Stockman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 12:32
CPC Classifications
H; H04; H04L; H04L5/00; H04L5/14; H04L5/143
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
107 words
A method of operating a communicating pair of frequency-multiplexing V.22 bis sending and receiving modems having a substantially 7200 Hz sample rate over the switched telephone network at a full duplex nominal 4800 B/S data rate without echo cancellation, comprising the steps of: (a) transmitting a data signal from the sending modem at substantially 900 baud in a 32-state constellation; (b) pre-filtering the received signal in the receiving modem through an analog filter; (c) further filtering said signal in the receiving modem through a digital raised cosine filter; and (d) robbing sufficient stop bits in the sending modem to increase the data throughput rate beyond 4800 B/S.
Claim 2
Independent Claim
107 words
A method of operating a communicating pair of frequency-multiplexing V.22 bis sending and receiving modems having a substantially 7200 Hz sample rate over the switched telephone network at a full duplex nominal 4800 B/S data rate without echo cancellation, comprising the steps of: (a) transmitting a data signal from the sending modem at substantially 900 baud in a 32-state constellation; (b) pre-filtering the received signal in the receiving modem through an analog filter; (c) further filtering said signal in the receiving modem through a digital raised cosine filter; and (d) robbing sufficient stop bits in the sending modem to increase the data throughput rate beyond 4800 B/S.
Claim 3
Dependent Claim
22 words
The method of claim 1, in which said raised cosine filter is substantially a 1050 baud, 16.7% oversampled raised cosine 32-tap filter.
Claim 4
Dependent Claim
24 words
The method of claim 1, in which the lower channel frequency is substantially 1000 Hz, and the higher channel frequency is substantially 2500 Hz.
Claim 5
Dependent Claim
28 words
The method of claim 1, in which the combined filtering action of said analog and said digital filter is in excess of 60 dB at all signal frequencies.
Claim 6
Dependent Claim
19 words
The method of claim 1, in which said stop bit robbing involves robbing 4 out of 5 stop bits.
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) | 1993-06-25 | 1993-12-25 | 1994-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-06-25 | 1997-12-25 | 1998-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-06-25 | 2001-12-25 | 2002-06-26 | $7700.00 | Window Closed / Lapsed |