Transceiver for transmitting and receiving voice and data signals includes a voice signal driver configured to operate in idle or working operating modes, during which it has a high or low output impedances respectively. A data signal driver drives an analog data transmission signal via a channel to the subscriber. A data reception circuit that converts a received analog data reception signal into digital reception data includes a multiplication circuit for multiplying the digital reception data by compensation coefficients selected to compensate for channel distortions, an identification circuit connected to the channel for providing an identification signal indicative of whether the subscriber terminal is on or off-hook, and a control circuit to select the operating mode in response to the identification signal and to determine compensation coefficients to compensate for a change in the channel resulting from a change in the output impedance of the voice signal driver.
1. A transceiver for transmitting and receiving voice signals and data signals, said transceiver comprising:
a voice signal driver configured to operate in an operating mode selected from
an idle-operating mode, during which the voice signal driver has a high output impedance, and
a working operating-mode, during which the voice signal driver has a low output impedance and is configured to drive an analog transmission voice signal, via a transmission channel, to a subscriber terminal;
a data signal driver for driving an analog data transmission signal via the transmission channel to the subscriber terminal; and
a data reception circuit configured to convert a received analog data reception signal into digital reception data, the data reception circuit including
a multiplication circuit for multiplying the digital reception data by adjustable channel distortion compensation coefficients selected to compensate for channel distortions of the transmission channel,
an identification circuit connected to the transmission channel, the identification circuit being configured to output an identification signal indicative of whether the subscriber terminal is taken off-hook or placed on-hook, and
a control circuit configured
to select the operating mode of the voice signal driver in response to the identification signal by switching the voice signal driver into the working operating-mode when the subscriber terminal is taken off-hook and switching the voice signal driver into the idle operating-mode when the subscriber terminal is placed on-hook, and
to set the channel distortion compensation coefficients to compensate for a change in the transmission channel resulting from a change in the output impedance of the voice signal driver.
2. The transceiver as claimed in claim 1 , wherein the data signals are modulated by a discrete modulation method.
3. The transceiver as claimed in claim 1 , wherein the control circuit is configured to apply a channel distortion coefficient set on the basis of the operating mode of the voice signal driver.
4. The transceiver of claim 3 , wherein the control circuit is configured
to apply a first set of channel distortion compensation coefficients to the multiplication circuit when the voice signal driver operates in the idle operating-mode, and
to apply a second set of channel distortion compensation coefficient to the multiplication circuit in the working operating-mode.
5. The transceiver as claimed in claim 1 , wherein the control circuit is configured to define a set of channel distortion compensation coefficients that include complex-valued coefficients.
6. The transceiver as claimed in claim 4 , wherein the control circuit is configured to offset the channel distortion compensation coefficients of the first and second sets by a constant complex value.
7. The transceiver as claimed in claim 4 , wherein the control circuit further comprises a calculation unit for calculating the coefficients of the second set of channel distortion compensation coefficients as a function of the coefficients of the first set of channel distortion compensation coefficients.
8. The transceiver as claimed in claim 4 , wherein the control circuit further comprises a memory unit for storing the coefficients of the first and second sets of channel distortion compensation coefficients.
9. The transceiver as claimed in claim 1 , wherein further comprising a switching device for selectively connecting and disconnecting the identification circuit from the transmission channel in response to a signal from the control circuit.
10. The transceiver of claim 9 , wherein the control circuit is configured to disconnect the identification circuit from the transmission channel when the subscriber terminal is taken off-hook and to connect the identification circuit to the transmission channel when the subscriber terminal is placed on-hook.
11. The transceiver as claimed in claim 1 , wherein the transmission channel comprises a telephone subscriber line.
12. The transceiver as claimed in claim 1 , wherein the data signals comprise multi-tone signals.
13. The transceiver as claimed in claim 1 , further comprising:
a coder, connected upstream from the data signal driver, for coding the digital transmission data to be transmitted,
an IFFT transformation calculation circuit, connected upstream from the data signal driver, for IFFT transformation of the digital transmission data, and
a digital/analog converter, connected upstream from the data signal driver, for converting the transformed digital transmission data into the analog data transmission signal.
14. The transceiver as claimed in claim 1 , further comprising
an analog/digital converter, connected upstream from the multiplication circuit, for converting the analog data reception signal into digital reception data,
a digital FIR filter having adjustable filter coefficients and being connected upstream from the multiplication circuit, and
an FFT transformation calculation circuit, connected upstream from the multiplication circuit, for FFT transformation of the filtered digital reception data.
15. The transceiver as claimed in claim 1 , further comprising a decoder and a decision circuit, both connected downstream from the multiplication circuit, for decoding the digital reception data.
16. The transceiver as claimed in claim 4 , wherein the control circuit is configured to determine the coefficients of the first set by characterizing the transmission channel during an initialization period for initializing the transceiver.
17. The transceiver as claimed in claim 1 , wherein the transceiver is an xDSL transceiver.