Data processing: measuring – calibrating – or testing – Calibration or correction system – Circuit tuning
Reexamination Certificate
2000-09-26
2004-08-24
West, Jeffrey R. (Department: 2857)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Circuit tuning
C702S060000, C702S075000, C702S085000
Reexamination Certificate
active
06782335
ABSTRACT:
TECHNICAL FIELD
The present invention relates to cable modem networks, and more particularly to input power estimation methods that compensate for variations in tuner gain characteristics.
BACKGROUND ART
Digital modems are increasingly being used by consumers as cable modem network service providers obtain additional subscribers. Cable modem devices designed for the mass-market are designed to be affordable to as many consumers as possible. However, low-cost, high production devices manufactured for the mass consumer market often exhibit variations and irregularities in their operating characteristics, such as gain non-linearities, frequency ripple and temperature effects. These variations make it difficult to measure the radio frequency (RF) input power to the cable modem accurately.
Currently known calibration solutions do not address variations in the tuner gain and intermediate frequency (IF) amplifier gain in the tuner of the cable modem as the frequency and power level of the input signal changes. Further, any calibration method that applies the same parameters globally to all cable modem devices does not consider the fact that individual devices may exhibit slightly different operating characteristics and may have different irregularities. These variations may adversely affect the cable modem's performance if not adequately addressed via an accurate input RF power determination.
Although it is theoretically possible to use the cable modem to calculate data that will compensate for variations in tuner gain characteristics, this would require incorporating additional calculation circuitry into the cable modem, increasing the cable modem's complexity and generating a device that is likely to be too expensive for the mass consumer market.
There is a need for a simple method and system to correct for variations and irregularities that are commonly encountered in low-cost, high volume cable modems when estimating input power to the cable modem.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method for estimating input power to a cable modem device having a tuner and a modem. The method includes generating a look-up table that contains look-up values used to compute an estimated input power to the modem's receiver. The look-up table is stored in the modem for reference. The method includes inputting a plurality of calibration signals having known input frequencies and known input power levels into the device's receiver, recording a calibration point corresponding to each of the calibration signals in a calibration matrix, and interpolating the calibration points in said calibration matrix to generate the look-up table values.
A cable modem device according to the claimed invention has the look-up table stored in the modem, preferably as 8-bit data. During modem operation, the modem checks the frequency of an input signal received by the modem's receiver, checks an accumulated value of an integrator, checks the look-up table for the look-up value corresponding to the frequency and accumulated integrator value, and uses the look-up value to determine an estimated input power. Because the look-up table values are derived from the cable modem device's actual operating characteristics, the input power estimate will reflect any variations or irregularities in the specific device being used.
REFERENCES:
patent: 4531089 (1985-07-01), Ishizuka et al.
patent: 4829380 (1989-05-01), Iadipaolo
patent: 5027376 (1991-06-01), Friedman et al.
patent: 5048054 (1991-09-01), Eyuboglu et al.
patent: 5129098 (1992-07-01), McGirr et al.
patent: 5265151 (1993-11-01), Goldstein
patent: 5315380 (1994-05-01), Ingraham et al.
patent: 5339109 (1994-08-01), Hong
patent: 5452473 (1995-09-01), Weiland et al.
patent: 5465205 (1995-11-01), Kamiya
patent: 5469115 (1995-11-01), Peterzell et al.
patent: 5722056 (1998-02-01), Horowitz et al.
patent: 5764546 (1998-06-01), Bryant et al.
patent: 5793815 (1998-08-01), Goodnow et al.
patent: 6072902 (2000-06-01), Myers
patent: 6118811 (2000-09-01), Narumi et al.
patent: 6131023 (2000-10-01), Matsuura
patent: 6148047 (2000-11-01), Mohindra
patent: 6240551 (2001-05-01), Webb et al.
patent: 6285960 (2001-09-01), Fung et al.
patent: 6539128 (2003-03-01), Lee et al.
patent: 6606615 (2003-08-01), Jennings et al.
patent: 04267613 (1992-09-01), None
IBM Technical Disclosure Bulletin No. NN9312505, vol. 36, Issue 12, Dec. 1993.*
International Preliminary Examination Report, dated Jan. 17, 2002.
Grossman Michael Andrew
Lynaugh Kevin
Zeng Yong Huang
General Instrument Corporation
Kananen Ronald P.
Nichols Steven L.
Rader & Fishman & Grauer, PLLC
West Jeffrey R.
LandOfFree
Method and system for estimating input power in a cable... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and system for estimating input power in a cable..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and system for estimating input power in a cable... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3331875