Alan David Marshall

US Patent:

50900250, Feb 18, 1992

Filed:

Jul 24, 1990

Appl. No.:

7/558197

Inventors:

Alan C. Marshall - Framingham MA
Stuart P. MacEachern - Uxbridge MA
Howard C. Salwen - Newtonville MA

Assignee:

Proteon, Inc. - Westboro MA

International Classification:

H04L 2560

US Classification:

375 4

Abstract:

An improved local area network node of the type described in ANSI/IEEE Standard 802. 5, including a receiver-demodulator having an input connectable to the ring and having a received data output and a received clock output, an elasticity buffer connected to the received data output, a modulator for modulating the output of the buffer in accordance with a signal at a clocking input of the modulator, and a phase-locked loop interposed between the received clock output of the demodulator and the clocking input of the modulator, the loop including a voltage-controlled oscillator, a phase detector and a filter connected for providing a control-voltage to the oscillator.

US Patent:

51329263, Jul 21, 1992

Filed:

Sep 21, 1990

Appl. No.:

7/586415

Inventors:

Stuart P. MacEachern - Uxbridge MA
Alan C. Marshall - Framingham MA
Howard C. Salwen - Newtonville MA

Assignee:

Proteon, Inc. - Westboro MA

International Classification:

G06G 702
H03H 730
H04L 700
H03D 324

US Classification:

364825

Abstract:

An improved local area network ring node of the type described in ANSI/IEEE Standard 802. 5, including a receiver having an input connectable to the ring, a phase-locked loop circuit for extracting a clock frequency from the receiver output and including a phase detector for generating a phase error signal, and a data demodulator connected for demodulating at the extracted clock frequency the data in the receiver output. The improvement lies in the provision of a filter for deriving a control signal from the outputs of the data demodulator and the phase detector and an adaptive equalizer for reducing the effect of jitter in signals applied to the receiver input from the network, the equalizer comprising a filter network including a voltage variable impedance so connected as to vary responsively to the control signal.