Telephonic communications – Line equalization or impedance matching
Reexamination Certificate
2005-08-02
2005-08-02
Harold, Jefferey F. (Department: 2644)
Telephonic communications
Line equalization or impedance matching
C379S394000
Reexamination Certificate
active
06925171
ABSTRACT:
A codifier/decodifier (CODEC) filter circuit (250) connected in a subscriber line interface circuit (202) includes a transmit section (264, 262, 260) for converting differential voltage audio transmit signals representing voice transmissions from the subscriber instrument (202) into encoded digital data for transmission to the digital switching network. A receive section (254, 252) coupled between the digital switching network and subscriber instrument (202) within CODEC (250) for converting encoded digital data representing voice signals switched through the digital switching network to differential voltage audio receive signals for transmission to the subscriber instrument (202). The subscriber loop and subscriber instrument (202) reflect the digital voltage audio signals to the transmit section (264, 262, 260). An impedance section (258, 256) within CODEC (250) connects between the transmit section (264, 262, 260) and the receive section (254, 252) and is disposed to provide an audio band feedback signal between the transmit section (264, 262, 260) and the receive section (254, 252) for synthesizing a source impedance for the subscriber line that matches the subscriber loop impedance. Impedance section (258, 256) includes an analog impedance scaling network (246) coupled between the transmit section (264, 262, 260) and receive section (254, 252). The impedance section (258, 256) also includes a programmable digital filter (258) coupled to the transmit section (264, 262, 260) having a transfer function equal to:in-line-formulae description="In-line Formulae" end="lead"?(R2T)(1+z−1)/(R1(T+2C2R2)(1+(T−2R2C2)/(T+2R2C2)z−1)in-line-formulae description="In-line Formulae" end="tail"?where R2is the second subscriber loop impedance, C2is the subscriber loop capacitance, R1is the first subscriber loop impedance, T is the sampling rate of the analog-to-digital converter and z is the frequency of the signal. Furthermore, a summer circuit (256) provides feedback between the programmable digital filter (258) and the receive section (254, 252) by summing the single-ended audio receive signals from the digital switching network with the audio band feedback signal output by the programmable digital filter (258).
REFERENCES:
patent: 4381561 (1983-04-01), Treiber
Hester Richard K.
Wang Minsheng
Brady III W. James
Harold Jefferey F.
Mosby April M.
Telecky , Jr. Frederick J.
Texas Instruments Incorporated
LandOfFree
Universal impedance matching network for the subscriber line... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Universal impedance matching network for the subscriber line..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Universal impedance matching network for the subscriber line... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3476061