Directional receiver coupling arrangement with frequency selectivity and gain control for DSL
9 Assignments
0 Petitions
Accused Products
Abstract
A directional coupler for a modem has a high common mode noise rejection characteristic with low transmit signal leakage, and reduced distortion of components mixed with a received signal. A primary filter network is connected to a communications circuit. The primary filter network has an output connected to an input of an amplifier. A feedback network is connected between the input and output of the amplifier. The primary filter network, the amplifier and the feedback network are arranged to provide a virtual ground at the input of the amplifier, and a filter characteristic which attenuates frequencies in the transmit signal band. The advantage is reduced component count while providing excellent transmit signal rejection and reducing received signal distortion.
15 Citations
39 Claims
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1-18. -18. Cancelled
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19. A modem comprising:
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a) a communications circuit for coupling a signal source of the modem to a telecommunications network, the communications circuit comprising a signal line adapted to simultaneously carry a transmit (Tx) signal and a receive (Rx) signal and a compensation network connected to the signal line for balancing an impedance of the signal line; and
b) a directional coupler for coupling a signal receiver of the modem to the communications circuit, the directional coupler circuit comprising;
i) a primary network connected to the communications circuit, the primary network being tuned to attenuate frequencies in a frequency band of the Tx signal, and having a respective primary network output;
ii) an amplifier having a respective amplifier input connected to the primary network output, and a respective amplifier output connected to the receiver; and
iii) a feedback network tuned to attenuate frequencies in a frequency band of the Tx signal, and connected between the amplifier input and the amplifier output;
wherein the primary network, the amplifier, and feedback network are arranged to provide a virtual ground at the amplifier input. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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Specification