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A system comprises an encoder, a precoder, a PRML channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies encoding such that the code string after p

A system comprises an encoder, a precoder, a PRML channel, a detector, and a decoder. An input signal is received by the encoder. The encoder generates a code string by adding one or more bits and outputs the code string to the precoder. The encoder applies encoding such that the code string after passing through the precoder has a Hamming distance greater than one to eliminate error events with a small distance at the output of the PRML channel. The present invention also provides codes that after precoding have Hamming distance of 2 and 0 mod 3 number of ones. These codes when used over a PRML channel in an interleaved manner preclude +/-( . . . 010-10 . . . ) error events and error events +/-( . . . 01000-10 . . . ). The code string also has a predetermined minimum number of ones at the output of the PRML channel to help derive a clock from the input signal. The encoder provides a "systematic" encoding scheme in which for many code strings the encoded bits are the same as the input bits used to generate the encoded bits. This systematic approach of the present invention provides an encoder that is easy to implement because a majority of the bits directly "feed through" and non-trivial logic circuits are only needed to generate the control bits. The systematic encoding also dictates a decoder that is likewise easy to construct and can be implemented in a circuit that simply discards the control bit. The encoder preferably comprises a serial-to-parallel converter, a code generator, and a parallel-to-serial converter. The code generator produces a rate 16/18 or 16/17 code. The present invention also includes a method that is directed to encoding bit strings and comprises the steps of: 1) converting the input strings to input bits, and 2) adding at least one bit to produce an encoded string with many ones and a Hamming distance greater than one after precoding.

대표청구항 ▼

[ What is claimed is:] [1.] An encoder for coding an input signal in a communications system having a precoder, a partial response channel, a detector, and a decoder, the coded input signal having a Hamming distance of at least two at the output of the precoder for enhanced channel performance and a

[ What is claimed is:] [1.] An encoder for coding an input signal in a communications system having a precoder, a partial response channel, a detector, and a decoder, the coded input signal having a Hamming distance of at least two at the output of the precoder for enhanced channel performance and a predetermined minimum number of ones at the output of the partial response channel for providing clock information, the encoder comprising:a serial-to-parallel converter having an input and a plurality of outputs for converting a serial string into parallel bits, the input of the serial-to-parallel converter coupled to receive the input signal;a code generator having a plurality of inputs and outputs for producing a first code bit using the equation v.sub.6 =cs.sym.v.sub.1 .sym.v.sub.2 .sym.v.sub.5 .sym.v.sub.9 .sym.v.sub.10 .sym.v.sub.13 .sym.v.sub.14 .sym.v.sub.17 .sym.v.sub.18, and a second code bit having a value based on the number of binary ones present in the input signal, the inputs of the code generator coupled to at least one of the plurality of outputs of the serial-to-parallel converter; anda parallel-to-serial converter having a plurality of inputs and an output for generating a serial string from parallel bits, the plurality of inputs of the parallel-to-serial converter coupled to at least one of the plurality of outputs of the code generator.