JPS6011484B2 - signal converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal conversion device that converts a rectangular wave into a sine wave.

Currently, there is a standard called the Kansas City Standard as one of the movements to standardize data recording methods for recording data from microcomputers onto audio cassette tapes.

This means that the data “1” becomes 2400 days and “0” becomes 1 day.
After converting to 200 day 2 square waves, each is converted to 2400
It modulates into HZ and 1200Hz sine waves and records them serially on an audio cassette tape. However, some modulation circuits combine the above two types of rectangular waves outside of a common low-pass filter and convert them into a sine wave, but when the period of the rectangular wave changes, the phase shifts and the 1200Hz and There is a drawback that the output level of the 2400Hz sine wave is different. In addition to this, 12
There is a filter that uses two obijo passing filters of 00Hz and 2400 days 2, but what this and the above example have in common is that the rectangular wave is directly supplied to the filter, so its harmonics are Wave components were generated, which caused malfunctions. SUMMARY OF THE INVENTION Therefore, the present invention provides a signal conversion device that does not cause a phase shift and is not affected by harmonic components of a rectangular wave.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 1, 1 is a microcomputer, and 2 is a pulse generation circuit, which converts data "0" and "1" from the microcomputer to 2400Hz and 1200Hz, respectively.
This converts it into a HZ rectangular wave. 3 is a first triangular wave generation circuit, which includes an operational amplifier 4 and a resistor 5...8.
It consists of capacitors 9 and 10 and an analog switch 11.

Reference numeral 12 denotes an inverter constituting the second triangular wave generation circuit, which includes an operational amplifier 13, resistors 14, 15, 16, and a condenser 17.

18 is a limiter, resistor 19, capacitor 20, 2
1 and diodes 22 and 23.

Reference numeral 24 denotes an amplifier circuit, which includes a reduction operational amplifier 25 and resistors 26, 27, and 28, and together with the limiter 18 constitutes a conversion circuit.

Reference numerals 29 and 30 indicate analog switches, which constitute first and second control circuits, respectively, and both of which also constitute a synthesis circuit.

31 is an inverter, 32 is a capacitor, 33 and 34 are resistors, and 35 is a magnetic head.

Next, the operation will be explained.

Data “1” and “0” from microcomputer 1
occurs, 2400HZ and 1200H, which are the converted pulses shown in FIG. 2B, are output from the terminal 2a of the conversion circuit 2, respectively.
Z rectangular wave P. , P2 are generated, and from the terminal 2b, pulses P3, P with a period of 1/2 of each of those shown in FIG. 2C are generated.
It is designed so that 4 occurs. First, when data "1" occurs, the analog switch 11 opens, and as shown in FIG.
The pulse P3 is supplied from the capacitor 9 to the operational amplifier 4 via this, and the voltage at the apex shown by ◯ in FIG. On the other hand, the triangular wave P5 is converted into a second wave by the inverter 12.
As shown in FIG. Since the analog switches 29 and 30 are alternately opened and closed by the rectangular wave P shown in FIG. 2B from the pulse generating circuit 2, the respective outputs are generated by the rectangular wave P shown in FIG. 2B. Every other triangular wave P5 like F,
P6 occurs. Therefore, the limiter 18 uses the triangular wave P5. A triangular wave P, (FIG. 2H) which is a composite of P6 is supplied. In this limiter 18, the peak portion of the triangular wave is removed, and the triangular wave is converted into a rounded trapezoidal wave (FIG. 2, 1) by the nonlinear characteristics of the diodes 22 and 23. This trapezoidal wave is fed to the amplifier circuit 24, the high frequency is cut by the frequency characteristics of the operational amplifier 25, and an approximate triangular wave is generated as shown in FIG. . Then, it is recorded on an audio cassette tape (not shown). Next, when data "0" is generated from the microcomputer 1, the analog switch 11 is closed, so that the pulse P4 in FIG. The signal is supplied to an operational amplifier 4.

Therefore, the gain is reduced by the amount passed through the resistor 6, and the operational amplifier 4 generates a triangular wave P8 with a gentler slope than the triangular wave P5, as shown in FIG. 2D. The amplitude of this triangular wave P8 is set to be the same as that of the triangular wave P5. The triangular wave P8 is supplied to the analog switch 29, inverted by the inverter 12, and supplied to the analog switch 301. Analog switch 29, 3
Since the river is alternately opened and closed by the rectangular wave P4 in Figure 2 C, each output has triangular waves P9 and P in Figure 2 G and F.
,. occurs. These are combined and recorded on an audio cassette tape from the amplifier circuit 24 via the magnetic head 35 in the same manner as described above. Although the above embodiment describes the case where digital data is converted into a sine wave and recorded on an audio cassette tape, the invention is not limited to this. It can also be applied to

As detailed above, according to the present invention, a rectangular pulse to be converted is converted into a first triangular wave having a period half that period and a second triangular wave which is an inversion of the first triangular wave, and every other triangular wave is removed. After that, they are combined and converted into a sine wave, so a sine wave with no phase shift can be obtained.

Moreover, unlike the conventional method, since there is no filter involved, there is no adverse effect caused by harmonic components of the pulse to be converted.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, and FIG. 2 is a tie chart for explaining the operation. 3...First triangular wave generation circuit, 12...
- Second triangular wave generation circuit, 29, 30...analog switch, 18...conversion circuit. Figure 1 Figure 2

Claims (1)

[Claims] 1 A pulse generation circuit that generates a rectangular pulse to be converted and a pulse with a half period of the pulse to be converted;
a first triangular wave generating circuit that generates a triangular wave, a second triangular wave generating circuit that generates a second triangular wave that is an inversion of the first triangular wave, and a first control circuit that passes every other first triangular wave. , a second control circuit that passes a second triangular wave corresponding to the first triangular wave removed by the first control circuit; Signal conversion consisting of a synthesis circuit that synthesizes a triangular wave with a second triangular wave to generate a triangular wave with a period twice that of the first triangular wave and the second triangular wave, and a conversion circuit that converts the triangular wave from this synthesis circuit into a sine wave. Device.