US 4,584,690 AGranted

Alternate Mark Invert (AMI) transceiver with switchable detection and digital precompensation

AssigneeDavid Systems, Inc.

InventorsLuca Cafiero, Mario Mazzola, Massimo Prati

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Abstract

A high-speed digital transceiver is provided for use in a PBX environment comprising twisted-pair wire cables interconnecting like transceivers, each transceiver being operative to exchange voice, data and control information in a packetized format over a common twisted-pair cable. Specifically, each transceiver communicates packetized pulse code modulated information in pure Alternate Mark Inverted (AMI) coding, that is, without the introduction of bipolar violation pulses to provide timing. Frame synchronization is acquired on the first pulse by the use of a digital circuit deriving synchronization from a local high-speed clock. The use of a high-speed clock-driven digital circuit for synchronization acquisition eliminates the need for a phase-locked loop synchronization scheme and its concomitant finite acquisition delay. In addition, a receiving section employs a threshold selecting circuit which switches or makes thresholds in response to an expectation of the absence any bipolar violation in the transmitted signal. The effect of intersymbol interference are further minimized by provision of digital precompensation in the transmitted signal to maximize the slew rate between consecutive pulses. The precompensation scheme is based on a knowledge of the bit pattern and the amount of energy contained in a sequence of bits.

Claims8

Dependent claims

An apparatus for transmission and reception of digital data over a bandlimited channel comprising:

means for generating and transmitting a pure alternate mark invert pulse code (pure AMIPC, signal from a digital message signal, said pure AMIPC signal being free of bipolar violations;
and
means for receiving a signal representative of said pure AMIPC signal, said receiving means including means defining a first threshold and a second threshold, said first threshold for identifying positive polarity pulses of said pure AMIPC signal, and said second threshold for identifying negative polarity pulses of said pure AMIPC signal, said first threshold and said second threshold being substantially equal in amplitude, first detecting means coupled to said threshold defining means for only detecting a signal of an amplitude greater than said first threshold, second detecting means coupled to said threshold defining means for only detecting a signal of an amplitude greater than said second threshold, means for simultaneously enabling said first detecting means and said second detecting means until receipt of a first representative signal of arbitrary polarity, said enabling means also for disabling said first detecting means upon receipt of a representative signal of positive polarity until receipt of a representative signal of negative polarity and for disabling said second detecting means upon receipt of a representative signal of negative polarity until receipt of a representative signal of positive polarity and timing means, for establishing a pulse duration of a reconstructed pulse for each said representative signal of positive polarity and negative polarity, said pulse duration being independent of duration of said representative signal in order to minimize effects of intersymbol interference.

Dependencies are inferred from the claim text.