JP3593408B2 - Digital reception signal time width adjustment device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a digital received signal time width adjusting device that improves a duty ratio of a received digital signal.
[0002]
[Prior art]
Conventionally, when transmitting a digital signal composed of a plurality of pulse signals, the waveform of the pulse signal may change due to the influence of the capacitance component and the inductance component of the transmission line. For example, when a pulse signal P1 having a time width T as shown in FIG. 3A is transmitted from the transmission side, the signal is transformed into P2 in FIG. 3B by the transmission line. The waveform of the pulse signal P2 thus modified is reproduced on the receiving side by a Schmitt trigger circuit or the like.
[0003]
The Schmitt trigger circuit has a characteristic of outputting a pulse waveform output signal that rises when the input level exceeds a predetermined value (L1) and ends when the input level falls below a predetermined value (L2). ing. At this time, the relationship L1> L2 is usually set so that a malfunction does not occur even if noise or the like is superimposed on the pulse signal received on the receiving side.
[0004]
When the pulse signal P2 is input to the Schmitt trigger circuit having the above characteristics, a pulse signal P3 having a time width t is reproduced as shown in FIG. In this case, if the waveform of the received pulse signal P2 changes, the time width t of the reproduced pulse signal P3 differs from the time width T of the pulse signal P1 sent from the transmission side, and the duty ratio May change.
[0005]
[Problems to be solved by the invention]
When the time width t of the pulse signal P3 reproduced as described above is different from the time width T of the pulse signal P1 sent from the transmission side, and the duty ratio changes, a digital signal composed of a plurality of pulse signals is converted. It cannot be detected correctly.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks, and to provide a digital received signal time width adjusting device capable of adjusting a pulse width of a received digital signal so as not to cause a difference in a duty ratio. And
[0007]
[Means for Solving the Problems]
The present invention has a characteristic of outputting an output signal starting at a point when an input signal exceeds a predetermined first level and terminating at an point when the input signal falls below a predetermined second level. Waveform reproducing means for reproducing the waveform of the pulse signal sent from the apparatus, signal width measuring means for measuring the width of the output signal output from the waveform reproducing means, and the output signal measured by the signal width measuring means width and said comparing the width of the pulse signal fed from the sender, the time of the digital received signal and comparator means for outputting a control signal for adjusting at least one of the first level and the second level In the width adjusting device, the waveform reproducing means may include a semiconductor element having an input terminal, an output terminal, and a ground terminal, and a plurality of semiconductor elements having an input terminal to which an input signal is input and a number connected between the input terminals. And having a diode.
[0010]
Further, the present invention has a characteristic of outputting an output signal whose start point is when the input signal exceeds a predetermined first level and whose end point is when the input signal falls below a predetermined second level, and Waveform reproducing means for reproducing the waveform of the pulse signal sent from the transmission source, signal width measuring means for measuring the width of the output signal output from the waveform reproducing means, and the signal width measured by the signal width measuring means. A digital reception signal comprising: comparison means for comparing a width of an output signal with a width of a pulse signal sent from the transmission source and outputting a control signal for adjusting at least one of the first level and the second level. in time width adjustment device, the waveform reproduction means, an input terminal and an output terminal, and a semiconductor device having a ground terminal, a first resistor connected between the input terminal and the power supply terminal, said input terminal contacting A second resistor connected between the first resistor and the second resistor, the diode having an adjustable number of diodes connected between an input terminal for inputting an input signal and the input terminal; At least one is a variable resistor.
[0011]
According to the configuration described above, the start end of the pulse signal output from the waveform reproducing unit, for example, the rising timing can be adjusted by changing the value of the variable resistor connected to the input terminal of the semiconductor element. By changing the number of diodes connected between the input terminals of the semiconductor element, the end of the pulse signal output from the waveform reproducing means, for example, the falling timing, can be adjusted, and the time width of the output pulse signal can be adjusted. . Therefore, the duty ratio can be adjusted so that the time width of the reproduced digital signal is the same as the time width of the digital signal sent from the transmission side, and the received digital signal can be detected correctly.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to FIG.
[0013]
Reference numeral 11 denotes a transmitting side, and reference numeral 12 denotes a receiving side. A digital signal composed of a plurality of pulse signals is transmitted from the transmitter 111 on the transmitting side 11. The digital signal is transmitted to the receiving side 12 via the transmission line L. At this time, the waveform of the pulse signal constituting the digital signal changes depending on the capacitance component and the inductance component of the transmission line L, and is received by the receiving side 12.
[0014]
In addition, one of the pulse signals of the transmitting side 11 constituting the digital signal is indicated by, for example, P1, the modified pulse signal received by the receiving side 12 is indicated by, for example, P2, and the time width of the pulse signal P1 is set. Indicated by T.
[0015]
The receiving side 12 includes a waveform reproducing circuit 121, a signal width measuring circuit 122, a pulse signal generating circuit 123, a comparing circuit 124, and the like. The received digital signal is input to the waveform reproducing circuit 121. The waveform reproducing circuit 121 outputs, for example, an output signal having a waveform that rises when the level of the input signal exceeds a predetermined value (L1) and ends when the level falls below the predetermined value (L2), for example. A circuit, for example, a Schmitt trigger circuit. At this time, for example, a pulse signal P3 having a time width t is reproduced from the waveform reproducing circuit 121.
[0016]
The reproduced pulse signal P3 is sent to the signal width measurement circuit 122. The pulse signal p1, p2, p3,... Having a short cycle is supplied from the pulse signal generation circuit 123 to the signal width measurement circuit 122, and the pulse signals p1, p2 counted during the time width t of the pulse signal P3. , P3,..., The time width t is measured.
[0017]
The time information of the time width t measured by the signal width measurement circuit 122 is sent to the comparison circuit 124. The time information of the time width T of the pulse signal P1 is sent from the transmission side 11 to the comparison circuit 124, and the time width T is compared with the time width t in the comparison circuit 124. Then, a control signal corresponding to the difference between the two time widths (Δt = T to t) is generated. The control signal generated by the comparison circuit 124 is sent to the waveform reproduction circuit 121, and the level is adjusted so that the time width t becomes equal to the time width T, for example, by changing the level (L1, L2) at which the pulse signal is reproduced.
[0018]
Here, an example of the waveform reproduction circuit 121 will be described with reference to FIG.
[0019]
IN is an input terminal to which a digital signal is input. The input terminal IN is connected to the diode D1, the switches SW1, SW2, and the base B of the transistor Q1. Note that diodes D2 and D3 are connected in parallel to the switches SW1 and SW2, respectively. The base B of the transistor Q1 is connected to the power supply terminal ET through the variable resistor VR1, and the emitter E is connected to the ground terminal GD through the variable resistor VR2. The output signal output to the collector C of the transistor Q1 is amplified by an amplifier surrounded by a frame 21, is inverted in polarity by an inverting unit surrounded by a frame 22, and is output to an output terminal OUT. Note that the transistors constituting the amplifier 21 and the inverting unit 22 are represented by Q, the resistance is represented by R, and the diode is represented by D.
[0020]
According to the above configuration, when the magnitude of the input signal input to the input terminal IN exceeds a predetermined level (for example, L1) determined by the values of the variable resistors VR1 and VR2, the transistor Q is turned on. The magnitude of the input signal input to the input terminal IN is a predetermined level (for example, L2... L2 is the value of the variable resistor VR1 and the variable resistor VR2, and the value of the diode connected between the base B of the transistor Q1 and the input terminal IN). It turns off when the voltage drops below the forward voltage drop, that is, the number of diodes.
[0021]
In this case, the collector C voltage increases when the transistor Q1 is off, and decreases when the transistor Q1 is on. Then, such a change in the collector C voltage is inverted by the inverting unit, and the pulse signal P3 in FIG. 1 is output to the output terminal OUT.
[0022]
When the time width of the pulse signal output to the output terminal OUT is changed, for example, when the time width of the pulse signal is increased, the values of the variable resistors VR1 and VR2 are adjusted to turn on the transistor Q1. Lower the level L1 of the input signal, or lower the level L2 of the input signal at which the transistor Q is turned off by increasing the number of diodes D1 to D3 connected between the input terminal IN and the base B of the transistor Q1. Done. The number of diodes to be connected is adjusted by opening and closing the switches SW1 and SW2. When the time width of the pulse signal is shortened, the opposite control is performed.
[0023]
According to the above-described configuration, the starting point of the pulse signal output by changing the values of the variable resistors VR1 and VR2, for example, the rising timing, is connected between the input terminal IN and the base B of the transistor Q1. By changing the number of diodes, the end of the pulse signal, for example, the fall timing, can be adjusted, and the time width of the output pulse signal can be adjusted. Therefore, the duty ratio can be adjusted so that the time width t of the reproduced digital signal is the same as the time width T of the digital signal sent from the transmission side. If a digital signal is received with the duty ratio adjusted as described above, the received digital signal can be correctly detected.
[0024]
It should be noted that the rise and fall of the digital signal used in the above-described embodiment mean the start and end of the pulse digital signal, and do not always correspond to the rise and fall of the signal level. Further, the level L1 of the input signal at which the transistor Q1 turns on is set higher than the level L2 of the input signal at which the transistor Q1 turns off. However, the magnitude relation between the level L1 and the level L2 may be opposite or equal.
[0025]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the time width adjustment apparatus of the digital reception signal which can adjust the pulse width of the received digital signal can be implement | achieved.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention.
FIG. 2 is a circuit diagram showing an example of a waveform reproduction circuit according to the present invention.
FIG. 3 is a waveform diagram illustrating a conventional example.
[Explanation of symbols]
11: transmitting side 12 ... receiving side 111 ... transmitter 121 ... waveform reproducing circuit 122 ... signal width measuring circuit 123 ... pulse signal generating circuit 124 ... comparing circuit

Claims (2)

It has the characteristic of outputting an output signal starting from when the input signal exceeds a predetermined first level and terminating when the input signal falls below a predetermined second level, and is sent from a transmission source. Waveform reproducing means for reproducing the waveform of the pulse signal, a signal width measuring means for measuring the width of the output signal output from the waveform reproducing means, and a width of the output signal measured by the signal width measuring means. A comparison unit that compares the width of the pulse signal sent from the transmission source and outputs a control signal that adjusts at least one of the first level and the second level . A semiconductor element having an input terminal, an output terminal, and a ground terminal; and a plurality of diodes whose number connected between an input terminal to which an input signal is input and the input terminal can be adjusted. Time width adjustment device of the digital reception signal, characterized in that it comprises a. It has the characteristic of outputting an output signal starting from when the input signal exceeds a predetermined first level and terminating when the input signal falls below a predetermined second level, and is sent from a transmission source. Waveform reproducing means for reproducing the waveform of the pulse signal, a signal width measuring means for measuring the width of the output signal output from the waveform reproducing means, and a width of the output signal measured by the signal width measuring means. A comparison unit that compares the width of the pulse signal sent from the transmission source and outputs a control signal that adjusts at least one of the first level and the second level. the waveform reproduction means, an input terminal and an output terminal, and a semiconductor device having a ground terminal, a first resistor connected between said input terminal and a power supply terminal, which is connected between ground and the input terminal And second resistors, and a plurality of diodes number can be adjusted to the input signal is connected to an input terminal for inputting between said input terminal, said first resistor or said second at least one of the variable resistance of the resistor A time width adjusting device for a digital reception signal, characterized in that:

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