JPS58220215A - Digital modulating method - Google Patents

Abstract

PURPOSE:To realize self-clocking, by dividing the data bits to every 4 bits to convert them into code words of 8 bits to 16 combinations of data bits and then applying NRZI modulation to the series of code words. CONSTITUTION:The data bits are divided to every 4 bits and then converted into code words P1-P8 of 8 bits to 16 combinatons of data bits as shown in a table. Then NRZI modulation is applied to the series of code words. At least >=2 bits 0 are included between the bit 1 and 1 of the code series, and the number of bits 0 is reduced down to <=11 at most. Thus the minimum magnetization inverting interval is set as Tmin=1.5T compared with the conventional interval T along with the maximum magnetization interval Tmax=6T and the detecting window width Tw=0.5T respectively. This process increases the linear bit density and realizes the self-clocking.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital modulation method, and particularly to a digital conversion method based on a 4-8 conversion method for converting 4 data bits into an 8-bit code word, and its purpose is to improve the SPM method. The object of the present invention is to provide a digital modulation method that has performance similar to that of the present invention and can be easily processed using general-purpose circuits.

In general, digital magnetic recording has the characteristics of being able to economically record a large amount of information and to store it stably for a long period of time. An alternative modulation method for information signals is RZ (Return to Zero).

RB (Return to Bias), N R
Z (Non-Return to Zero),
N RZ I (Non-Return to Zero
I).

F M (Frequency Modulation
), P R (PhaseEncoding),
M F M (Modified Frequency)
y Modulation).

Various proposals have been made, such as M2FM (Mociified MFM). On the other hand, recently, various new modulation methods other than these 1 have been proposed. For example, 415
M N RZ I (Modified Non-R
eternto Zero I), 3P
M (3Po5ition Modulation)
.

Z M (Zero Modulation) f
What is x? Furthermore, recently, new modulation methods other than those mentioned above have been considered due to high-density transition, but in digital magnetic recording, detection window width Tw, minimum magnetization, and reversal interval Tm1
It is said that a modulation method with a large density ratio (D R ) of n or the linear bit density to the maximum magnetization reversal density is desirable.

The present invention was made in view of these demands,
This provides a modulation system with a large DR ratio of 1.5 and performance completely equivalent to the 3PM system described above.

The present invention will be described in detail below with reference to drawings of embodiments.

FIG. 1 is a conversion table for the 3PM method. The SPM method converts 3-bit data into a 6-bit code word,
This code word sequence is modulated with NRZI. The code word is characterized in that at least two bits II o 11 are inserted between bit l111+ and the next bit "1", but the 6th bit P5 of the chronologically older code word is 1.
1'', and the 1st bit P1 of the code word that follows is 1.
”, bit 61
bit 6o” that falls between 11111 and 11111
Since the condition that the minimum consecutive number of is 2 is violated,
In this case, the 5th bit P5 of the old codeword and the 1st bit P1 of the following codeword are inverted to bit 0'', and the 6th bit P6 of the old codeword is inverted to bit l'1''. There are special rules. Furthermore, if the 5th bit P5 of a code word is l1111 and the 1st bit P1 of the next code word is 1'', the minimum inversion interval will be T, so in this case, the above Ps and P+ are Both bits are inverted to ``0'', and the 6th bit P6, which is always ``0'', is inverted to 1'' to maintain the anti-i interval at 1.57.Furthermore, this SPM method also has a sign Bit °゛1” of word sequence
The maximum number of bits (O') that can fit between the bit '°1' and
The codewords are selected like er and naurine.

On the other hand, FIG. 2 shows the 4-8 conversion FEM-1 (
Four to Eight Modulation
) conversion table. This method converts 4-bit data into an 8-bit code word, and converts the code word sequence into N
It is modulated by RZI. As shown in Figure 3a, the code word should contain at least two digits (O) between bit 1'' and the next bit °°1'', and no more than 11 digits at most. It is characterized by the added restrictions, but as shown in Figure 3, the 7th bit P7 of the chronologically older codeword is "1", and the 1st bit P1 of the following codeword is "1". If a sequence of code words such as 1111+ occurs, the conditions of this method will be violated as in 3PM, so in this case, the 7th bit P of the old code word
7 and the 1st bit P1 of the code word that follows it as pit o”
The 8th bit P8 of the old code word is changed to bit ″′1.
”, and has exactly the same performance as 3PM.

Figure 4 shows the ratio of recording current waveforms between the FEM-1 method and the conventional modulation method, in which (7) is the data, (a) is the waveform by the NRZI method, and (a) is (2) is a waveform based on the FM system, (3) is a waveform based on the 3PM system, and (force) is a waveform based on the FEM~1 system. Note that in FIG. 1, T indicates the bit period.

In the case of the MFM method, which is currently most commonly used in large-capacity magnetic flux devices, the magnetization reversal interval is T, 1.5T.
, 2T, and the minimum magnetization reversal interval Tm1n l
dT. For modulation methods other than MFM, T
The min is T for NRZI and 0.5T for FM. As described above, in most conventional modulation systems, the minimum magnetization reversal interval is T or less, and therefore the DR is 1 or less. On the other hand, in sPM and FEM-1 of this method, the minimum magnetization reversal interval T min is 1.5T, and D R = 1
．． It is 5. Therefore, if the minimum magnetization reversal interval is made the same as that of MFM, the linear bit density can be increased by 1.5 times. The advantage of this FEM-1 method over the 3PM method is that most general-purpose logic ICs currently on the market are in units of 4 or 8 bits, and the 3-6
The 4-8 conversion of this FEM-1 is easier to process than the conversion.

Table 5 shows a comparison of various modulation methods for reference.

As explained above, according to the present invention, the minimum magnetization reversal interval is 1.5T, the maximum magnetization reversal interval is 6T, the detection window widths o, s'r
A digital modulation method for high-density recording that is easy to self-clock can be provided.

[Brief explanation of the drawing]

Fig. 1 is a conversion table diagram of the 3PM method, Fig. 2 is a conversion table diagram of FEM-1 in the digital modulation method of the present invention, and Fig. 3 is a case where the maximum magnetization reversal interval occurs in FEM-1 and application of special rules. A diagram to illustrate an example,
FIG. 4 is a comparison diagram of recording current waveforms between FEM-1 and conventional modulation methods, and FIG. 6 is a comparison diagram of various modulation methods. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) A digital modulation method for high-density recording, in which data bits are divided into 4-bit units, and 8-bit code words (P+, Pz , Ps. P4 , Ps , Pa , P7 , Pa ) and the data time series group as ■ 00000100 ■ 0ooO10o. ■ 00010000 ■ 00100000 ■ oloOooOo ■ 0o01oo1゜■ 1oo10o10 ■ 00100100 ■ olooloOo [phase] 1oo10oo0 2 pages @ 10000010 @ 00100010 0 oloooOo l. ■ 01000100 @ 10000100 ■ 10001000 A digital modulation method characterized by correlating data strings and then modulating with NRZI. (2) The 7th bit P7 and the 8th bit P8 of the chronologically older codeword and the 1st bit P1 of the chronologically newer codeword in the codeword sequence pattern at the codeword-to-codeword concatenation part
becomes '1o1', the 8th bit P8 is inverted to bit '1', and the 7th bit P7 and the 1st bit P1
2. The digital modulation method according to claim 1, wherein the digital modulation method is inverted to bit llo''. (3) A patent characterized in that the codeword sequence contains at least two or more pits, tos, and "O"s between bits "1" and bits "1", and the number is within 11 capes at most. 37.-1 The digital modulation method according to claim 1 or 2.