Method and apparatus for encoding and decoding an NRZI digital signal with low DC component and minimum low frequency components
US4626826A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 22, 1984 |
| Grant date | Dec 2, 1986 |
| Priority date | — |
| Expiry date | Oct 22, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B20/1426
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A converted digital signal is provided in an NRZI (non-return to zero, inverted) code with a zero DC component and with a maximum predetermined number of bits between level transitions in the signal. The base digital signal is divided into m-bit base words, each of which is then converted into an n bit converted code word to form a converted digital signal suitable for recording. The n-bit converted code word is selected from a plurality of primary combinations or code words having a DC component substantially equal to zero when NRZI-coded and a plurality of secondary combinations or code words having a DC component with an absolute value of two when NRZI-coded. A variance of the DSV (digital sum variation) of each primary combination when NRZI-coded and a polarity of the DC component of each secondary combination when NRZI-coded are altered in response to the DSV at the exit of the preceding converted digital signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.