System for transmitting, receiving and decoding multilevel signals

Claim 2

Apparatus for transmitting a multilevel signal having a given number of levels over a transmission line having input and output terminals, said apparatus comprising: a. transmission means coupled to the input terminal of the transmission line, said transmission means including reference means for providing a reference level signal having a fewer number of defined levels than the given number and inserting means for inserting the reference level signal in a train of the multilevel signals at predetermined time intervals and for transmitting the train of the multilevel signals and inserted reference level signal; and b. receiving means coupled to the output terminal of the transmission line, said receiving means including detection means for receiving transmitted multilevel signals and reference level signal and for detecting the intersymbol interference imposed by the transmission line on the reference level signal due to the adjacent multilevel signals, and adjustment means responsive to the detected intersymbol interference for correcting the intersymbol interference imposed upon the multilevel signal.

Claim 3

Apparatus as claimed in claim 1, wherein said adjustment means includes a transversal filter.

Claim 4

adjustment means responsive to the detected intersymbol interference for correcting the intersymbol interference imposed upon the second train of the multilevel signals.

Claim 5

adjustment means responsive to the detected intersymbol interference for correcting the intersymbol interference imposed upon the second train of the multilevel signals.

Claim 6

inserting means for inserting the reference level signals in a first train of the multilevel signals at a predetermined time interval and for transmitting the thus formed second train of multilevel signals and inserted reference level signal along the transmission line; and b. receiving means coupled to the output terminal of the transmission line, said receiving means including:

Claim 7

inserting means for inserting the reference level signals in a first train of the multilevel signals at a predetermined time interval and for transmitting the thus formed second train of multilevel signals and inserted reference level signal along the transmission line; and b. receiving means coupled to the output terminal of the transmission line, said receiving means including:

Claim 8

Apparatus as claimed in claim 2, wherein said transversal filter is of the zero-forcing type.

Claim 9

Apparatus as claimed in claim 2, wherein said transversal filter is of the mean-square type.

Claim 10

Apparatus as claimed in claim 1, wherein said transmission means includes: storage means; clock means for generating a first, repetitive clock signal at intervals of T/m, where T is a predetermined interval of time and m is a predetermined integer and for generating a second, repetitive clock signal at an interval of T/(m+1); storing means responsive to the first clock signal for storing in said storage means a train of the multilevel signals; reference means responsive to the second clock signal for retrieving from said storage means a train of the multilevel signals and for providing the reference level signal; and inserting means for inserting at time intervals of T the reference level signal into the train of multilevel signals retrieved from said storage means and for transmitting the train of the multilevel signals and inserted reference level signal.

Claim 11

Apparatus as claimed in claim 1, wherein the levels of the multilevel signals to be transmitted are representative of a binary number of n bits where n is a predetermined integer, said transmission means including means for providing a reference level signal of a selected magnitude at a transition point of a binary digit of a selected position of the n bits.

Claim 12

Apparatus as claimed in claim 6, wherein detection means for detecting the train of the transmitted multilevel signals and the injected reference level signal to provide an output signal representing in binary number form the most significant digit of the n bits and for detecting the polarity of the error of the transmitted reference level signal with respect to a predetermined level to provide an output signal representing in binary number form said selected position.

Claim 13

Apparatus as claimed in claim 7, wherein said detection means comprises: SHIFT register means having a predetermined position; means for sequentially storing in said shift register means the binary output signals representative of the transmitted reference level signal and the multilevel signals transmitted before and after the transmitted reference level signal; storage means for receiving and storing the error polarity binary signal; calculation means responsive to the shifting of the error polarity binary signal to said predetermined position in said shift register means for calculating the exclusive ''''ORs'''' of the binary output signals representative of the transmitted multilevel signals and the error polarity binary signal representative of the transmitted reference level signal error to provide correction signals for diminishing the intersymbol interference imposed on the transmitted multilevel signal.

Claim 14

Apparatus as claimed in claim 8, wherein there is included equalizer means comprising a delay line having a plurality of output taps, a plurality of adjustable attenuators coupled to corresponding output taps of said delay line, said attenuators being coupled to receive the correction signals for adjusting the attenuators to substantially reduce the intersymbol interference imposed upon the transmitted multilevel signals.

Claim 15

Apparatus as claimed in claim 1, wherein said receiving means includes: delay means for sequentially receiving the transmitted reference level signal and the transmitted multilevel signals and having a main output signal tap and a plurality of echo output taps; a plurality of adjustable attenuator means coupled to corresponding taps of said delay means, each of said attenuator means having an output terminal; adding means coupled to each output terminal of said attenuator means for adding the output signals thereof to provide a composite signal; a multilevel decoding circuit coupled to receive the composite signal for providing polarity bit signals indicative of the transmitted multilevel signals and the reference level signal and error polarity bit signals indicative of the error polarity of the reference level signal with respect to a predetermined level; first and second shift registers for receiving and storing polarity bit signals indicative of the transmitted multilevel signals and the error polarity bit signal of the reference level signal, respectively; said first shift register having a number of stages corresponding to the number of said attenuators, said second shift register having a number of stages corresponding to said main signal tap and said echo taps; a plurality of calculating circuits responsive to the shifting of the error polarity bit signal of the reference level signal to the output terminal of said second shift register, for calculating the exclusive ''''ORs'''' of the polarity bit signals of the multilevel signals as stored in the various stages of said first shift register and the error polarity bit signal of the reference signal appearing at the output terminal of said second shift register; and a plurality of integrating circuits coupled to the corresponding calculating circuits for providing integrated output signals to be applied to the corresponding attenuator means.

Claim 18

The method as claimed in claim 11, wherein there is further included the steps of: storing the received, second train of multilevel signals including the reference level signals and a predetermined number of the multilevel signals preceding and following the transmitted reference level signal; and the correcting step, including adjusting the levels of the subsequently received signals in accordance with the intersymbol interference imposed upon the transmitted reference level signal in a direction to decrease the imposed intersymbol interference.

Claim 19

Apparatus for receiving and transmitting a multilevel signal having a given number of levels over a transmission line having input and output terminals, said apparatus comprising: a. transmission means coupled to the input terminal of the transmission line, said transmission means including:

Claim 20

Apparatus for receiving and transmitting a multilevel signal having a given number of levels over a transmission line having input and output terminals, said apparatus comprising: a. transmission means coupled to the input terminal of the transmission line, said transmission means including:

Claim 21

Apparatus for transmitting and receiving multilevel signals having a given number of levels over a transmission line having input and output terminals, the levels of the multilevel signals corresponding to a binary number of n bits, where n is a predetermined integer, said apparatus comprising: a. transmission means coupled to the input terminal of the transmission line, said transmission means including reference means for providing a reference level signal having a fewer number of defined levels than the given number, at least one level being set at a magnitude corresponding to a transition point of a binary digit of a selected position of the n bits, and inserting means for inserting the reference level signal in a train of multilevel signals at predetermined time intervals and for transmitting the train of the multilevel signals and the inserted reference level signal over the transmission line; and b. receiving means coupled to the output of the transmission line, said receiving means including detection means for receiving the transmitted multilevel signals and reference level signal and for detecting the intersymbol interference imposed by the transmission line on the reference level signal due to the adjacent multilevel signals, and adjustment means responsive to the detected intersymbol interference for correcting intersymbol interference imposed upon the multilevel signals.

Claim 22

Apparatus for transmitting and receiving multilevel signals having a given number of levels over a transmission line having input and output terminals, the levels of the multilevel signals corresponding to a binary number of n bits, where n is a predetermined integer, said apparatus comprising: a. transmission means coupled to the input terminal of the transmission line, said transmission means including reference means for providing a reference level signal having a fewer number of defined levels than the given number, at least one level being set at a magnitude corresponding to a transition point of a binary digit of a selected position of the n bits, and inserting means for inserting the reference level signal in a train of multilevel signals at predetermined time intervals and for transmitting the train of the multilevel signals and the inserted reference level signal over the transmission line; and b. receiving means coupled to the output of the transmission line, said receiving means including detection means for receiving the transmitted multilevel signals and reference level signal and for detecting the intersymbol interference imposed by the transmission line on the reference level signal due to the adjacent multilevel signals, and adjustment means responsive to the detected intersymbol interference for correcting intersymbol interference imposed upon the multilevel signals.

Claim 23

Apparatus as claimed in claim 14, wherein said detection means includes means for decoding the multilevel signals into binary signals of n bits.

Claim 24

Apparatus as claimed in claim 14, wherein said detection means compares the received multilevel and reference signals with respect to a reference signal having a level of a magnitude corresponding to the transition point of the binarY digit of the selected position for decoding the multilevel signals into corresponding binary signals of n bits and for providing first and second manifestations indicating respectively that each of the received reference level signals is above or below the reference signal level, said adjusting means responsive to the first and second manifestations for adjusting the levels of the received multilevel signals.

Claim 25

Apparatus as claimed in claim 16, wherein said adjusting means includes a delay line having a plurality of taps, a plurality of attenuating means, each associated with one of said taps, and integrating means for integrating the first and second manifestations to adjust the setting of each of said attenuating means.

Claim 26

Apparatus as claimed in claim 17, wherein said detection means provides the first and second manifestations, said adjusting means including logic means for providing the exclusive OR of the first and second manifestations, for adjusting said plurality of attenuating means.