JPS6174108A - Magnetic recording device for digital signals - Google Patents

Abstract

PURPOSE:To restore stably a data of PE waveform through the addition of a simple circuit by providing a gain control circuit of an output port of a PE waveform section in order to increase the peak value of a short period of a phase encoding (PE) waveform to be more than the peak value of a long period so as to correct the peak value change. CONSTITUTION:A waveform being at an H level is outputted only when the PE waveform is a short period from an output port 2 of a microcomputer 1 for PE waveform forming. The DC component of the PE waveform from the output port 3 is cut off by a capacitor 4, amplified by an operational amplifier 5 and its gain is decided by the synthesis of resistors 7 and 8. On the other hand, an analog switch 9 connected in series with a feedback resistor 8 is opened only during the short period of the PE waveform from the port 2 and the gain of the operational amplifier 5 is increased. Thus, the data of the PE waveform is restored stably through the addition of the analog switch 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording device such as a cassette tape recorder, and more particularly to an improvement in the method for recording digital signals.

Conventional configurations and their problems In recent years, with the spread of low-cost personal computers, inexpensive cassette tape recorders are often used as information recording devices. 24o due to the limit of the frequency characteristics of
It can only record about 100 bits/sac. Ph&se ICncoding, which is resistant to changes in tape running speed, is a method to improve the recording bit rate.
(hereinafter referred to as PK) is used.

FIG. 1 shows the relationship between the timing of original data and the PIC waveform. In other words, if the next data is still the same, it is inverted at the edge of the bit period and inverted again at the center of the bit period, but if the next data is different, it is not inverted at the edge of the bit period, and the next bit is LOW to the center of
, or the HIGH level is maintained and then inverted. It is well known that such a pE waveform can be easily created by controlling the output port using microcomputer software. FIG. 2 is an example of a flowchart of the software.

However, when the PICIC waveform created in this way is recorded and played back on a cassette tape recorder, if the bit period is set to a high speed of about 5 μS (8 bits/5ea), the PE waveform becomes short as shown in Figure 3. It is known that the peak value of the period part decreases. This is because, as shown in Figure 4, the frequency characteristics of the cassette tape recorder decrease in the high range when the recording level is high, so the harmonics of the long period (4KLIZ) rectangular wave of the PE waveform in Figure 3 are reproduced. However, the harmonics of the short period (8 Kflz) rectangular wave are attenuated. Therefore, when reading the original data from the recording and playback waveform shown in Figure 3, the method of applying a comparator at the level B and reading the period is used, but due to DC drift of the comparator, variations in the gain of the playback system, etc. There is a problem that the level tends to be relatively like the level /l/t) in Figure 3, and reading of the short period part becomes unstable, making it impossible to restore the original data.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems.
The purpose is to stabilize the restoration of PE waveform data by adding a simple circuit.

Structure of the Invention The present invention provides data input to the output port of a microcomputer for creating PE waveforms, in order to make the peak value of the short-period part of the PE waveform larger than the peak value of the long-period part.
A gain control circuit whose gain changes depending on the angle is provided to compensate for changes in peak value during recording and playback in advance.

Description of examples FIG. 6 shows an embodiment of the present invention.

1 is the microcomputer described in the conventional example, 2.3
is its output port, 4 is a coupling capacitor, 6 is an operational amplifier, 6, 7.8 are resistors that determine the gain of operational amplifier 5, 9 is an analog switch, and 10 is a voltage source for biasing the operational point of the operational amplifier. , 11 are output terminals of the operational amplifier 5.

The operation shown in FIG. 5 will be explained below. Microcomputer 1
As described in the prior art example, the PE waveform as shown in FIG. 6(a) is outputted to the output port 3 of FIG. 2 according to the flowchart of FIG. -Force output port 2 is shown in Figure 6 (Q
) is high only when the PE waveform has a short cycle)
A waveform that is at I level is output. (The timing of this output corresponds to when going through routes A and B in the flowchart in Figure 2, so it can be easily created using software.) The PE waveform at output port 3 in Figure 6 is a direct current It is cut and amplified by the operational amplifier 5, and its gain is determined by the combined value of the resistor 6 and the resistor 7.8.

However, an analog switch 9 controlled by the output port 2 of the microcomputer (waveform shown in FIG. 6 (0)) is connected in series to the feedback resistor 8, and when the control signal is at HIGH level, the analog switch 9 is connected in series. If a switch is selected that will open, the analog switch 9 will be open only during the short period of the PE waveform, and the gain of the operational amplifier 5 will increase, so the output 11 of the operational amplifier 6 will eventually become open.
A waveform as shown in FIG. 6(b) is output.

In other words, with the level /L/12 given by the voltage source 1o as the center, the long period period has an amplitude of 13, and the short period period has a large amplitude such as 14, so according to the frequency characteristics shown in Fig. 4. If the resistors 6 and 7°8 in Fig. 6 are appropriately selected, the peak value of the recording and playback waveform will be constant, and the original data can be played back stably even if there is DC drift of the comparator or variation in the gain of the playback system. I can do it.

Although an inverting operational amplifier is used for gain control in FIG. 6, a non-inverting operational amplifier may also be used.

It is also clear that the circuit can be configured with a tri-state buffer 15, 16, resistors 17, 18.19, capacitors 20, 21, and inverter 22, as shown in FIG. 7, without using an operational amplifier.

Effects of the Invention As described above, according to the present invention, data recording
Even if an inexpensive cassette tape recorder is used as the device, it is possible to stably restore and reproduce high-speed data by adjusting the peak value of the PE waveform before recording.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the Phase Encoding waveform, Figure 2 is a diagram showing an example of Phase Encoding waveform.
Flowchart of the microcomputer for waveform creation, Figure 3 shows the recording and playback waveform of Phase Encoding, Figure 4 shows the recording and playback frequency characteristics of the cassette tape recorder, Figure 5 is a circuit diagram of an embodiment of the present invention, and Figure 6 6 is an operation timing diagram, and FIG. 7 is a circuit diagram of another embodiment of the present invention. 1...Microcomputer, 2.3...
... Output port, 5... Operational amplifier, 6, 7.
8... Resistor, 9... Analog switch, 15.16... Tri-state buffer,
22...Inverter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3: Condolences: 4 Questions Shibu ζ” Story stain (hz) Figure 5: Figure 6

Claims (1)

[Claims] Phase is connected to one output port of the microcomputer.
means for simultaneously generating the encoding waveform and generating a control signal synchronized between the short periods of the phase encoding waveform at the other output port;
It comprises means for inputting the phase encoding waveform into a variable amplifier, means for controlling the gain of the variable amplifier with the control signal, and means for recording the output of the variable amplifier on a magnetic tape. Magnetic recording device for digital signals.