System and method for phase equalization
AssigneeLevel One Communications, Inc.
InventorHiroshi Takatori
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Abstract
A phase equalizer in the receiver portion of a bi-directional communication system is disclosed equalizer for reducing precursor intersymbol interference without any substantial degradation in signal to noise ratio. The phase equalizer is implemented as a switched capacitor filter having a clock (switch) rate at least four times the data baud rate and a z-transfer function T(z) of a form: ##EQU1## wherein G, A, and B are fixed but adjustable coefficients.
Claims5
A switched capacitor filter circuit for reducing precursor intersymbol interference in a digital subscriber loop, the circuit comprising:
- (a) input means for accepting received data pulses;
- (b) filter means, coupled to the input means, for modifying phase and amplitude characteristics of the received data pulses to create phase and amplitude modified pulses, the filter means comprising a plurality of capacitor and switch pairs coupled to an amplifier to provide a z-transfer function T(z) of a form:
- ##EQU6## wherein G, A and B are fixed but adjustable coefficients;
- and (c) output means, coupled to the filter means, for outputting the phase and amplitude modified pulses.
A switched capacitor filter circuit for reducing precursor intersymbol interference comprising:
- (a) input means for accepting an input 2B1Q (Two Binary One Quaternary) pulse;
- (b) sampled-data means, coupled to the input means, for modifying phase and amplitude characteristics of the input 2B1Q pulse to create a modified output 2B1Q signal, and the sampled-data means comprising an operational amplifier, with at least four capacitor and switch pairs coupled thereon, for providing a z-domain transfer function of a form:
- ##EQU7## (c) output means, coupled to the sampled-data means, for outputting the modified output 2B1Q pulse.
A method for reducing precursor intersymbol interference in a digital subscriber loop having a proximal and a distal end, the method comprising the steps of:
- (a) accepting pulses sent from the distal end of the loop;
- (b) filtering the pulses to modify phase and magnitude characteristics thereof by applying the pulses through a switched capacitor filter having a z-transfer function T(z) of a form:
- ##EQU8## (c) outputting the filtered pulses in an ISDN 2B1Q format.
A method for reducing precursor intersymbol interference in an U-interface ISDN receiver, comprising the steps of:
- (a) accepting 2B1Q (Two Binary One Quaternary) pulses;
- (b) modifying magnitude and phase characteristics of the 2B1Q pulses through a switched capacitor filter according to a z-domain transfer function T(z):
- ##EQU9## (c) outputting the modified 2B1Q pulses.
Dependencies are inferred from the claim text.