Analogue echo filter
First Claim
1. An analog echo filter for an echo damping path of a modem, which is located between a transmit path and a receive path, in which case the modem can be supplied with an analog transmit signal, which is transmitted in full-duplex via a transmission line, via the transmit path, with the modem having an analog hybrid circuit for separating and combining the transmit signal and a received signal which can be output via the receive path, and having an active analog filter, whose transfer function is adjustable,wherein a passive analog input filter is provided for input balancing of the echo damping path and for adjusting a terminating impedance for the analog hybrid circuit;
- the transfer function of the active analog filter can be switched between a first-order transfer function and a second-order transfer function;
the active analog filter has three operational amplifiers, which are connected in series; and
the second operational amplifier in the series circuit can be bridged by switches in order to switch the active analog filter from a second-order transfer function to a first-order transfer function.
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Accused Products
Abstract
The invention relates to an analog echo filter for a modem, to which an analog transmit signal is supplied. According to the invention, a passive analog input filter and an active analog filter, whose transfer function is adjustable, are provided. The transfer function of the active analog filter can preferably be switched between a first-order transfer function and a second-order transfer function.
18 Citations
3 Claims
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1. An analog echo filter for an echo damping path of a modem, which is located between a transmit path and a receive path, in which case the modem can be supplied with an analog transmit signal, which is transmitted in full-duplex via a transmission line, via the transmit path, with the modem having an analog hybrid circuit for separating and combining the transmit signal and a received signal which can be output via the receive path, and having an active analog filter, whose transfer function is adjustable,
wherein a passive analog input filter is provided for input balancing of the echo damping path and for adjusting a terminating impedance for the analog hybrid circuit; -
the transfer function of the active analog filter can be switched between a first-order transfer function and a second-order transfer function;
the active analog filter has three operational amplifiers, which are connected in series; and
the second operational amplifier in the series circuit can be bridged by switches in order to switch the active analog filter from a second-order transfer function to a first-order transfer function. - View Dependent Claims (2, 3)
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Specification
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- Resources
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Current AssigneeMaxlinear Incorporated
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Original AssigneeInfineon Technologies AG
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InventorsTenen, Aner, Hauptmann, Joerg, Pecourt, Frederic
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Primary Examiner(s)VO, DON NGUYEN
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Application NumberUS09/890,751Time in Patent Office2,055 DaysField of Search375/219, 375/222, 375/223, 375/285, 375/257, 375/258, 370/276, 370/282, 370/285, 370/286, 370/289, 370/290, 379/3, 379/406.01, 379/406.05US Class Current375/222CPC Class CodesH04B 3/23 using a replica of transmit...
