Coded data generation or conversion – Digital code to digital code converters – To or from minimum d.c. level codes
Patent
1997-01-30
2000-07-04
Young, Brian
Coded data generation or conversion
Digital code to digital code converters
To or from minimum d.c. level codes
341 59, 341 73, 341 74, 341 94, 341106, H03M 500
Patent
active
06084535&
ABSTRACT:
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.
REFERENCES:
patent: 5198813 (1993-03-01), Isozaki
patent: 5491479 (1996-02-01), Wilkinson
Carew Isaiah A.
Karabed Razmik
Nazari Nersi
Popplewell Andrew
Mitel Semiconductor Americas Inc.
Young Brian
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