JPS6113303B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit whose purpose is to reduce noise by passing a signal on which noise is superimposed through a band limiting circuit, thereby receiving a more accurate signal. More specifically, the present invention relates to a circuit for reading binary signals recorded on a magnetic recording medium, such as a magnetic storage device such as a magnetic tape, a magnetic disk, or a magnetic drum.

FIG. 1 is a block diagram showing an example of the prior art. In FIG. 1, a signal on which noise is superimposed from a signal source 1 is amplified to a certain level by an amplifier circuit 21 that constitutes a signal waveform reproducing circuit 2, and a band limiting circuit 22 removes noise outside the signal band. and enters the waveform processing circuit 3. The waveform processing circuit 3 checks whether there are any errors in the input signal, and if there are errors, receives the same signal again. In the band limiting circuit in such a receiving circuit, the important points are how effectively to remove noise superimposed on the signal and how to transmit the signal waveform with little distortion. In order to remove noise, it is better that the band of the band-limiting circuit is narrow, and conversely, in order to transmit the signal waveform with less distortion, it is better that the band of the band-limiting circuit is wide.

Furthermore, there are two types of bands: one determined by the amplitude characteristic and the other determined by the phase characteristic, and which one to emphasize depends on the type of waveform to be transmitted. For this reason, determining the band of the band limiting circuit has been a difficult task of finding an optimal compromise.

An object of the present invention is to effectively remove noise from a signal waveform on which noise is superimposed.

The present invention is characterized in that band limiting circuits with different bands are used when receiving the same signal again.

FIG. 2 shows an embodiment of the present invention.

The signal waveform on which noise has been superimposed is amplified by the amplifier circuit 21, and then first passes through the band limiting circuit 22 and then enters the waveform processing circuit 3 by the switching circuit 4. The frequency-amplitude characteristic of the band limiting circuit 22 is shown by characteristic 1 (solid line) in FIG. In addition, the frequency-phase delay characteristics are
This is shown by characteristic 1 (solid line) in the figure. If an error occurs as a result of processing the signal on the first path, the switching circuit 4 inputs the signal to the waveform processing circuit 3 via the band limiting circuit 23. The frequency-amplitude characteristic of the band limiting circuit 23 is shown in characteristic 2 (broken line) in FIG. Further, the frequency-phase characteristic is shown in characteristic 2 (broken line) in FIG.

As shown in FIGS. 3 and 4, the band limiting circuit 2
In No. 2, the amplitude characteristic is flat over a wide band, but the phase delay characteristic is unstable near the cutoff frequency c. On the other hand, the band limiting circuit 23 has poor amplitude characteristics but flat phase delay characteristics. By using two band limiting circuits, both of which have advantages and disadvantages, even if one of them receives incorrectly, the other one can receive correctly.

Note that the switching between the band limiting circuits 22 and 23 may be performed alternately, or, for example, one may retry n times and then the other may retry m times until reception is achieved correctly. Good too. Furthermore, the characteristics of the band-limiting circuit can be determined by taking arbitrary characteristics.
It becomes possible to select the optimal combination according to the characteristics of the signal to be received and the noise prevention noise. Furthermore, it is also possible to provide three or more band limiting circuits and conduct trials for each.

According to the present invention, it is possible to remove noise from a signal more effectively than before.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a conventional system, Fig. 2 is a block diagram of an embodiment of the present invention, Figs.
The figure is a frequency characteristic diagram showing the characteristics of the block in FIG. 2. 1...Signal line, 2...Signal waveform reproducing circuit, 3...
... Waveform processing circuit, 4 ... Switching circuit, 21 ... Amplification circuit, 22, 23 ... Bandwidth limiting circuit.

Claims (1)

[Claims] 1. Connecting means for supplying an input signal to a plurality of band limiting circuits having different band characteristics, and selecting an output signal of another band limiting circuit when an error is detected in the output signal of one band limiting circuit. A signal reproducing circuit characterized in that it is provided with a switching means for switching so as to perform a switching operation. 2. The signal reproducing circuit according to claim 1, wherein the switching means is activated when the same signal as the input signal in which the error was detected is applied again.