Digital modulator and demodulator

Claim 2

A digital modulator for converting input data train to coded data train, comprising: grouping means for separating the input data train into data words each being composed of M bits; encoding means for converting each of the data words into a code word composed of N bits, where N>M, containing a specific number of '1' bits, said number being one of pre­determined numbers which are different at least 3 from one another; and transmitting means for outputting the code word in the form of a serial channel code.

Claim 3

A digital modulator as defined in Claim 1 wherein M is 8, N is 10, and the number of '1' bits contained in the cord word is 2 or 5.

Claim 4

A digital modulator as defined in Claim 2, wherein '1' bits in a cord word having two '1' bits are adjoined to each other.

Claim 5

A digital modulator as defined in Claim 1 wherein M is 8, N is 10, and the number of '1' bits contained in the cord word is 5 or 8.

Claim 6

A digital modulator as defined in Claim 4, wherein '0' bits in a cord word having eight '1' bits are adjoined to each other.

Claim 7

A digital modulator as defined in Claim 1, wherein M is 8, N is 10, and the number of '1' bits contained in the cord word is 1 or 5.

Claim 8

A digital modulator as defined in Claim 1, wherein M is 8, N is 10, and the number of '1' bits contained in the cord word is 5 or 9.

Claim 9

A digital modulator as defined in Claim 1, wherein M is 8, N is 10, and the number of '1' bits contained in the cord word is 2, 5 or 8; and wherein said encoding means converts some of the data words each to one of a code word having two '1' bits and a code word having eight '1' bits so as to reduce the DC component of the channel code, and con­verts the remaining data words each to a code word having five '1' bits.

Claim 10

A digital modulator as defined in Claim 8, wherein '1' bits in a code word having two '1' bits are adjoined to each other while '0' bits in a code word having eight '1' bits are adjoined to each other.

Claim 11

A digital modulator as defined in Claim 1, wherein M is 8, N is 10, and the number of '1' bits contained in the cord word is 1, 5 or 9; and wherein said encoding means converts some of the data words each to one of a code word having one '1' bit and a code word having nine '1' bits so as to reduce the DC component of the channel code, and con­verts the remaining data words each to a code word having five '1' bits.

Claim 12

A digital modulator as defined in Claim 1, wherein M is 8, N is 10, and said encoding means converts a data word which contains 3, 4 or 5 '1' bits into a code word by adding additional 2 bits to a specific position thereof, the additional 2 bits being designated as '1' and '1' when the data word contains 3 '1' bits, '1' and '0' when the data word contains 4 '1' bits, and '0' and '0' when the data word contains 5 '1' bits.

Claim 13

A demodulator for reproducing data words, each being composed of M bits from a channel signal formed of serial train of code words each being composed of N bits, where N > M, and containing a specific number of '1' bits, said number being one of predetermined numbers which are different at least 3 from one another, comprising: a plurality of voltage comparating means for waveform shaping the channel signal with their respective thresholds which are different from one another; counting means for separating an output of the voltage comparating means into N-bit words and counting the number of '1' bits contained in each N-bit word; maximum likelihood detecting means for identifying as a code word one having a maximum likelihood from N-bit words in each of which the number counted by the counting means corresponds to one of the predetermined numbers; and decoding means for decoding the code word identified by the maximum likelihood detecting means to recover a data word.

Claim 14

A demodulator for reproducing data words, each being composed of M bits from a channel signal formed of serial train of code words each being composed of N bits, where N > M, and containing a specific number of '1' bits, said number being one of predetermined numbers which are different at least 3 from one another, comprising: a plurality of voltage comparating means for waveform shaping the channel signal with their respective thresholds which are different from one another; counting means for separating an output of the voltage comparating means into N-bit words and counting the number of '1' bits contained in each N-bit word; maximum likelihood detecting means for identifying as a code word one having a maximum likelihood from N-bit words in each of which the number counted by the counting means corresponds to one of the predetermined numbers; and decoding means for decoding the code word identified by the maximum likelihood detecting means to recover a data word.

Claim 15

A decoder as defined in Claim 12, wherein the max­imum likelihood detecting means recognizes a threshold of the voltage comparating means which is most approximate to a reference value as a likelihood.

Claim 16

A demodulator for reproducing data words, each being composed of M bits from a channel signal formed of serial train of code words each being composed of N bits, where N > M, and containing a specific number of '1' bits, said number being one of predetermined numbers which are different at least 3 from one another, comprising: sample holding means for sampling the channel signal; analog to digital converter means for converting the sampled values into digital values; sorting means for arranging the digital values in the order of quantity; classifying means for designating the number of '1' bits in the code word as i when a difference between i-th value and i+1th value from the largest exceeds a specified value where i is one of said predetermined numbers and a large value is designated to corresponds to '1' while a small value to '0'; and code word reproducing means for reproducing a code word by recognizing i bits as '1' in the order from the largest likelihood in the digital values.

Claim 17

A demodulator for reproducing data words, each being composed of M bits from a channel signal formed of serial train of code words each being composed of N bits, where N > M, and containing a specific number of '1' bits, said number being one of predetermined numbers which are different at least 3 from one another, comprising: sample holding means for sampling the channel signal; analog to digital converter means for converting the sampled values into digital values; sorting means for arranging the digital values in the order of quantity; classifying means for designating the number of '1' bits in the code word as i when a difference between i-th value and i+1th value from the largest exceeds a specified value where i is one of said predetermined numbers and a large value is designated to corresponds to '1' while a small value to '0'; and code word reproducing means for reproducing a code word by recognizing i bits as '1' in the order from the largest likelihood in the digital values.