JPS58220211A - Digital modulating method - Google Patents

Abstract

PURPOSE:To realize self-clocking, by dividing data bits to every 4 bits to convert these bits into code words of 9 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-P9 of 9 bits to 16 combinations of these bits. Then NRZI modulation is applied to the code word series, and at least >=2 bits 0 are included between the bit 1 and 1 of the code word series. At the same time, the number of bits 0 is reduced down to <=9 at most. Thus the minimum magnetization inverting interval is set as Tmin=1.33T compared with the conventional interval T along with the maximum magnetization inverting interval Tmax=4.44 and a product of 0.59T<2> of Tmin and the detecting window width. 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 more particularly to a digital modulation method based on a 4-9 conversion method for converting 4 data bits into 9 bit code words.

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. The information value go modulation method for this purpose is RZ (Return to Zero).

RB (Rturn to Bias), NRZ (N
On Return.

Zero), N RZ I (Non-Retur)
n to Zero I).

F M (Frequency Modulation
), P R (phaseICncoding), M
FM (Modified Frequency Mod
ration), M2FM (Modified MF
Various proposals have been made, including M). On the other hand, recently, various new modulation methods other than these have been proposed. For example 41
5MNRZI (Modified Non-Retu
rn to Zer.

I), 3PM (3Position Modulat)
ion), Z M (Zero Modulation)
n) etc. Furthermore, recently, with increasing density, new modulation methods other than those mentioned above are being considered, but in digital magnetic recording, detection window width TW, minimum magnetization reversal interval Tw
It is said that a modulation method with a large ratio DR (Devsity Ratio) of in or linear bit density to the maximum magnetization reversal density is desirable. Furthermore, the ease of increasing the density is often expressed as the product of the minimum magnetization reversal interval Twin and the detection window width Tw.

The present invention was made in view of these demands, and the minimum magnetization reversal interval Tm1n is 12/9T (=1.33T).
This provides a modulation method in which the product of magnetization reversal interval Tm1n and detection window width 'rw is 4B/81 T'' (Q59T2), which is larger than 0.5 T2 of MFM.

Hereinafter, the present invention will be described in detail with reference to drawings of embodiments.

In the MF and M methods, bit "1" corresponds to inversion, and bit "0" corresponds to no inversion. Furthermore, like FM, the inverse 6-v inversion is performed at the boundaries between bits, but only at the boundaries between bit "0" and pit 0". This modulation method uses the minimum magnetization reversal interval T
win is larger than T and FM o,s T, detection window width T
The w is also 0.5T, which is comparable to FM, and it also has features such as easy self-clocking.

On the other hand, FIG. 1 shows the 4-9 conversion FNM (Fo
ur to N1ne Modulation) conversion table. This method converts 4-bit data into a 9-bit code word, and modulates the code word sequence with NRZI. The code word is limited so that at least two or more bits "O" are inserted between a bit "1" and the next bit "1", and there are no more than nine bits, as shown in Figure 2a. The characteristic is that the 8th bit P8 of the chronologically older code word is "1", and the 1st bit P1 of the code word that follows it is "1". If such a sequence of code words occurs, the conditions of this method are violated, so in this case, the 8th bit P of the old code word
8 and the 1st pin point Pl of the following code word are inverted to 6 bits "0", and the 9th bit P9 of the old code word is inverted to bit "1'°". Magnetization reversal interval Twin: 133T, maximum magnetization reversal interval Tmax'; 4.44T, detection window width TW=0.4
It has the characteristics of 4T. Therefore, if the MFM method and the minimum magnetization reversal interval Twin are the same, the line focus density can be increased to 16
It can be multiplied by 33 times.

Figure 3 shows a comparison of recording current waveforms between the FNM method and the conventional modulation method.
The waveform by the iNRZI method, (ri) is the waveform by the FM method, (field is the waveform by the MFM method, (o) is the waveform by the 3PM method, and (force) is the waveform by the FNM method. In the figure, T is the bit. It shows the cycle.

In the case of the MFM method, which is currently most commonly used in large-capacity magnetic disk drives, the magnetization reversal interval is T, 1.5T.
, 2T, and the minimum magnetization reversal interval C1n is T. In the case of a modulation method other than the MFM method, NRZI is used as Twin, T and FM is 045T. On the other hand, the maximum magnetization reversal interval Tmax is 7 pages for NRZI, T for FM, and 2T for MFM.

In addition, in the sPM method, the minimum magnetization reversal interval Tllll1n is 1.
6T, and the maximum magnetization reversal interval Tmax is 6T. Therefore, in the present FNM method, the minimum magnetization reversal interval Tm1n is 1°33T, which is improved from T in the MFM method, and the maximum magnetization reversal interval Tmax is 4.44T, which is better than 6T in the 3PM method. Further, FIG. 4 shows a comparison of various modulation methods.

As explained above, according to the present invention, the minimum magnetization reversal interval T win is 1.33T, which is larger than T in the MFM method.
The maximum magnetization reversal interval Tmax is 4.44T, which is smaller than 6T of the 3PM method, and the product of the minimum magnetization reversal interval Twin, which indicates the ease of high density, and the detection window width Tw is 0.59T.
2 and MFM method (7) 0.6T2 yo 1) It is possible to provide a modulation method that is large and also capable of self-clocking.

[Brief explanation of drawings]

Figure 1 is an FNM conversion table diagram in the digital modulation method of the present invention. Figure 2 is a diagram for explaining the case where the maximum magnetization reversal interval occurs in iFNM and an example of application of special rules. Figure 3 is a diagram showing FNM and conventional modulation. FIG. 4 is a comparison diagram of recording current waveforms of various modulation methods. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 4T79 x 10 = 4.44T 2 to 4T/9 = 0.89T Pregnancy

Claims (3)

[Claims] (1) A digital modulation method for high-density recording, in which data bits are divided into 4-bit units, and a 9-bit code word (F'l 'P2P3P4 Ps P6 P
7 Ps P9 ) and the data time sequence group as ■ 000010000 ■ 000100000 ■ 000010010 ■ 01001001 0 ■ 1001001 00 ■ 1 00100010 ■ 000100010 ■ 001 0001 00 ■ 01000 1 000 [Phase] 1 oOol ooO0 2 pages 0001ooO01゜＠ olooooool . @ 100000010 ■ oloooo 100 [phase] 100000100 @ 100001000 A digital modulation method characterized by making these data strings correspond and then modulating with NRZI. (2) The 8th bit P8 and the 9th bit P9 of the chronologically older codeword and the 1st bit P1 of the chronologically newer codeword in the codeword series pattern at the codeword-to-codeword concatenation part
is 101, the 9th bit P9 is set to
1'', the 8th bit P8 and the 1st bit P1
2. The digital modulation method according to claim 1, wherein the digital modulation method is inverted to bit "O". (3) Bit “1'' and bit II 11 of codeword sequence
The digital modulation method according to claim 1 or 2, characterized in that the third page is configured to include at least two or more, and at most nine or less, 'IIoII'. .