Invalidity dossier
US 5809085
Apparatus and method for detecting and discriminating various signal types in the presence of impulse distortions
Current assignee: Motorola Mobility LLC
Added 9/23/2026, 5:16:42 PM
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Patent summary
Title, assignee, inventors, filing/issue dates, abstract, and a plain-language overview of the claims.
Patent Overview — US 5,809,085 A
Title: Apparatus and method for detecting and discriminating various signal types in the presence of impulse distortions
Patent number / application: US 5,809,085 A; Application US 08/496,048
Dates: Priority and filing date 1995-06-28; granted/publication date 1998-09-15; anticipated expiration 2015-06-28 (status listed as "Expired - Lifetime")
Inventors: Richard L. Goodson; Mickey C. Rushing; Gary D. Hunt; Lee T. Gusler, Jr.
Original assignee: Motorola, Inc. Current assignee listed as Motorola Mobility LLC and Arris Enterprises LLC.
Purpose: The invention detects amplitude-modulated signals, such as the ITU V.8 "ANSam" answer-back tone (a 2100 Hz sine wave with 180-degree phase reversals every 450 ms, amplitude-modulated by a 15 Hz sine wave at 20 percent modulation index), and discriminates it from the ITU V.25 "ANS" tone. The stated problem is that phase reversals and network transients appear as impulse distortions, causing filter ringing/overshoot, long recovery times, and false ANSam detections. The stated goal is reliable detection at low SNR (e.g., 6 dB) and low receive levels (e.g., -43 dBm) with minimal complexity and response time.
Plain-language scope (from the excerpt): A DCE/modem receives an analog signal via a DAA and A/D converter; a DSP (e.g., Motorola M56002) with a microprocessor (e.g., M68302) processes it. The invention applies a non-linear filtering technique using a "dynamic soft limiter" to dynamically reduce impulse distortions at varying power and amplitude levels, rather than synchronizing to phase reversals as in prior approaches. Figure 4 shows functional components; Figures 5A–5C show ANSam, band-pass-filtered, and limited signals; Figure 6 shows the dynamic soft limit component; Figure 7 shows the method flow.
Source: https://patents.google.com/patent/US5809085/en
What the excerpt does not establish: The excerpt is partial (it ends mid-sentence in the Figure 3 description) and omits the claims, detailed circuit descriptions, and the Figure 6/7 details. It therefore does not establish the specific claim language, exact limiter implementation, or measured performance results. Dates and legal status are expressly assumptions per the source, not legal conclusions.
Generated 10/1/2026, 9:43:42 PM
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PTAB challenges
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Assignment history
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Prior art
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Derivative works
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