Patent EA-000985-B1 (EA)
Title: Apparatus and method for demodulating multi-level signal
Inventor: SATO SATOSHI
IPC: H04L25/06
Filed: 1996-10-29
Abstract: 1. A multi-level signal demodulation apparatus comprising: means for converting an input analog signal having a multi-level to a digital signal; means for discriminating the level of the digital signal by comparing the digital signal with multiple threshold data corresponding to the multi-level of the input analog signal; means for averaging first digital signals corresponding to a first level of the multi-level of the input analog signal; means for averaging second digital signals corresponding to a second level of the multi-level of the input analog signal; means for adjusting one of the means from said means for averaging first signal and said means for averaging second signal based on the averaged first digital signal and averaged second digital signal and adjusting said means for discriminating base on the newest averaged first digital signal and averaged second digital signal which is obtained by actuating the means for averaging the signal which is discriminated by said discriminating means the level of the digital signal. 2. A multi-level signal demodulation apparatus according to claim 1, wherein said adjusting means comprises means for correcting the multiple threshold data based on the newest averaged first digital signal and averaged second digital signal obtained by actuating the means for averaging the signal. 3. A multi-level signal demodulation apparatus according to claim 1, wherein said adjusting means comprises means for normalizing the digital signal prior to comparing the digital signal with multiple threshold data based on the newest averaged first digital signal and averaged second digital signal obtained by actuating the means for averaging the signal. 4. A multi-level signal demodulation apparatus comprising: means for converting an input analog signal having a multi-level to a digital signal; means for discriminating the level of the digital signal by comparing the digital signal with multiple threshold data corresponding to the multi-level of the input analog signal, and outputting a signal corresponding to a demodulated analog signal; and  means for correcting the multiple threshold data based on a previous digital signal discriminated as a first level and a previous digital signal discriminated as a second level when said discriminating means discriminates the level of the digital signal as the first level or the second level. 5. The apparatus according to claim 4, wherein said correcting means corrects the multiple threshold data based on an average of previous digital signals discriminated as the first level and an average of previous digital signals discriminated as the second level. 6. The apparatus according to claim 4, wherein said correcting means comprises: first and second memories respectively corresponding to the first and second levels, said memories operating in a first-in, first-out (FIFO) manner and respectively storing plural digital signals; means for storing the digital signals into said first or second memories when said discriminating means discriminates the level of the digital signal as the first or second level; means for respectively averaging the digital signals stored in said first and second memories; and means for calculating the multiple threshold data based on average values of the signals stored in said first and second memories. 7. The apparatus according to claim 6, further comprising means for presetting plural digital initial signals into said first and second memories. 8. The apparatus according to claim 4, wherein said first and second levels are minimum and maximum levels. 9. A method of demodulating a multi-level signal, comprises the steps of: converting an input analog signal having a multi-level to a digital signal; discriminating the level of the digital signal by comparing the digital signal with multiple threshold data corresponding to the multi-level of the input analog signal, and outputting a signal corresponding to a demodulated analog signal; and  correcting the multiple threshold data based on a previous digital signal discriminated as a first level and a previous digital signal discriminated as a second level when said step of discriminating discriminates the level of the digital signal as the first level or the second level. 10. The method according to claim 9, wherein said step of correcting corrects the multiple threshold data based on an average of previous digital signals discriminated as the first level and an average of previous digital signals discriminated as the second level. 11. The method according to claim 9, wherein said step of correcting, comprises: storing plural digital signals in first and second memories respectively corresponding to the first and second levels when said step of discriminating discriminates the level of the digital signal as the first or second level, said memories operating in a first-in, first-out (FIFO) manner; respectively averaging the digital signals stored in said first and second memories; and calculating the multiple threshold data based on average values of the signals stored in said first and second memories. 12. The method according to claim 11, further comprises the step of presetting plural digital initial signals into said first and second memories. 13. The method according to claim 9, wherein said first and second levels are minimum and maximum levels. 14. A multi-level signal demodulation apparatus comprises:  means for converting an input analog signal having a multi-level to a digital signal;  means for normalizing the digital signal such that digital signals having a same level are within a predetermined range, the first input of which is connected to the means for converting an input analog signal having a multi-level to a digital signal; means for discriminating the level of the normalized digital signal and outputting a signal corresponding to a demodulated analog signal having an input connected to the means for normalizing the digital signal, the first output for outputting of the output signal and a second output for transmitting digital data discriminated as the first or second levels and said means can discriminate the level of the normalized digital signal by comparing the digital signal with multiple threshold data; means for correcting a range of normalized values of said normalizing means, the input of which is connected to the second output of said means for discriminating the level of the normalized digital signal and forming the output signal, and output of which is connected to the second input of the means for normalizing of the digital signal for correcting of the normalized values of the means for normalizing based on the previous digital signal discriminated by the means for discriminating of level of the normalized digital signal and forming of the output signal as the first level, and the previous digital signal discriminated by the means for discriminating of level of the normalized digital signal and forming of the output signal as the second level. 15. The apparatus according to claim 14, wherein said normalizing means normalizes the digital signal with a scale having a first value which is an average of previous digital signals discriminated as the first level and a second value which is an average of previous digital signals discriminated as the second level. 16. The apparatus according to claim 14, wherein said normalizing means comprises:  first and second memories respectively corresponding to the first and second levels, said memories respectively storing plural digital signals; and  means for normalizing the digital signal with a scale having a first value which is an average of the digital signals stored in said first memory and a second value which is an average of the digital signals stored in said second memory. 17. The apparatus according to claim 16, further comprises means for presetting plural digital initial signals into said first and second memories. 18. The apparatus according to claim 16, wherein said correcting means comprises means for storing the digital signal into said first or second memory when said discriminating means discriminates the level of the digital signal as the first or second level in a first-in, first-out (FIFO) manner. 19. The apparatus according to claim 14, wherein said normalizing means comprises:  a first memory for storing an accumulated value of N digital signals discriminated as the first level by said discriminating means, wherein N is an integer;  a second memory for storing an accumulated value of N digital signals discriminated as the second level by said discriminating means; and  means for normalizing the digital signal with a scale having a first value which is 1/N of the accumulated value of the digital signals stored in said first memory and a second value which is 1/N of the accumulated value of the digital signals stored in said second memory. 20. The apparatus according to claim 19, further comprises means for presetting plural digital initial signals into said first and second memories. 21. The apparatus according to claim 19, wherein said correcting means comprises means for updating the accumulated value of said first or second memory by changing the digital signal output from said converting means to a sum of (N-1)/N of the accumulated value stored in said first or second memory and the digital signal output from said converting means when said discriminating means discriminates the level of the digital signal as the first level or the second level. 22. The apparatus according to claim 14, wherein said first and second levels are minimum and maximum levels. 23. The apparatus according to claim 14, further comprises means for correcting the multiple threshold data based on the normalized digital signal output from said normalizing means. 24. The apparatus according to claim 14, further comprises means for correcting the multiple threshold data based on the normalized digital signal outpu