JPH02141017A - Transmitter-receiver using pulse transformer - Google Patents

Abstract

PURPOSE:To improve margin against the deterioration of an S/N caused by undershooting and to expand the selectivity of a pulse transformer by providing a time constant circuit which smoothes the rise of input pulses in the front stage of a drive circuit. CONSTITUTION:A time constant circuit 3 is provided in the front stage of the drive circuit 2 of a transformer 1 of a transmitter using the pulse transformer. The circuit 3 is constituted of a diode D, resistance R, and capacity C and smoothes the rise of input pulses to the drive circuit when the pulse transformer is driven. When the fall of the signals to the transformer 1 is smoothed in such way, occurrence of undershooting is reduced and the selectivity of the pulse transformer is expanded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a transmitting/receiving device using a pulse transformer used on a pulse transmission path, and particularly to a drive circuit that reduces the adverse effects of undershoot.

86 Summary of the Invention The present invention provides a time constant circuit, which is disposed before a pulse transformer drive circuit and smooths the rise of the input pulse to the drive circuit, in a pulse transformer transmitting/receiving device used on a pulse transmission path. In addition, in a receiver using a pulse transformer, a timer is installed after the pulse transformer to lock the output pulse, thereby reducing the margin against deterioration of the S/N ratio due to undershoot, etc. The present invention discloses techniques for improving the selectivity of pulse transformers, mitigating their adverse effects, and expanding the selectivity of pulse transformers.

C8 Conventional technology A pulse transformer is a transformer that faithfully transmits the pulse waveform. Pulses have a wide range of frequency spectra and phase shifts are likely to occur. It is said that the capacity must be designed to be sufficiently small.

FIG. 5(a) is a circuit diagram of a pulse transformer drive circuit of a transmitter using a general pulse transformer, and FIG. 5(b) is a waveform diagram of an output example thereof, which is a transmission called bipolar transmission. It is a method.

Since the Vce end of the transformer shown in Figure 5(a) is drawn out from the center of the primary side, the square wave input from the two input ends is treated as a pulse with opposite polarities as shown in Figure 5(b).
) Outputs the waveform shown in

FIG. 6 is a circuit diagram showing an example of a receiving device that receives signals from a transmission path using a pulse transformer. Further, FIG. 7 is a circuit diagram showing an example of a transmitting/receiving device in a transmission line using a pulse transformer. A receiving device using a pulse transformer has two comparators A and B arranged in parallel.
A square wave is output from these comparators A and B.

D9 Problems to be Solved by the Invention However, in a transformer such as a pulse transformer, the waveform actually output from the above drive circuit does not pass direct current, so even when driven with a square wave, the waveform actually output from the above drive circuit is as shown in FIG. 5(b). The correct square wave as shown in FIG. 5(c) is not obtained, and distortions such as droop and undershoot occur as shown in FIG. 5(c).

Furthermore, when the pulse transformer on the receiving side receives a signal with distortion such as droop or undershoot as described above, undershoot is detected if the threshold level of the comparator is low, as shown in FIG. 8(a), for example. An erroneous output as shown in FIG. 8(b) occurs. Furthermore, when noise resistance is considered, if noise or the like is superimposed on the undershoot as shown in FIG. 8(c), malfunctions are more likely to occur. These undershoots become larger when a plurality of transmission devices are connected to one transmission path as shown in FIG.

The present invention was created in view of these problems, and
It is an object of the present invention to provide a transmitting/receiving device using a pulse transformer that improves the margin against deterioration of the S/N ratio due to undershoot etc., reduces its adverse effects, and expands the selectivity of the pulse transformer.

E9 Means for Solving the Problems Means for solving the above problems in the present invention are provided in a pulse transformer drive circuit of a transmitting device used on a pulse transmission path, and are arranged in a curved part of the drive circuit. A time constant circuit is provided to smooth the rise of the input pulse.

Furthermore, a timer for locking the output pulse is provided at the downstream stage of the pulse transformer of the receiving device.

F1 action When driving a pulse transformer, the present invention reduces undershoot by smoothing the rise of the input pulse to the drive circuit and smoothing the fall of the signal to the transformer, and also starts a timer in the receiving device. By locking the output signal, the undershoot is reduced, the adverse effects of the undershoot are reduced, and the selectivity of the pulse transformer is expanded.

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

FIG. 1 is a circuit diagram showing an embodiment of a driving circuit for a transmitter using a pulse transformer according to the present invention.

In the figure, a time constant circuit 3 is disposed before the drive circuit 2 of the transformer I. The time constant circuit 3 is composed of a diode D, a resistor R, and a capacitor C.
) When a rectangular pulse as shown in ) is input, the drive circuit 2
When the output falls, diode D becomes conductive, so it falls sharply, but when it rises, diode D ceases to conduct, so the output falls smoothly as shown in Figure 2 (b), due to the time constant of resistor R and capacitor C. stand up. and,
This signal is inverted by the drive circuit 2, and the signal sent from the transformer 1 to the transmission line falls gently as shown in FIG. 2(c). Although only one of the input terminals of the transformer 3 has been described above, the same applies to the other input terminal.

FIG. 3 is a circuit diagram showing an embodiment of the receiving device of the present invention. In the same figure, the primary side of the pulse transformer 4 is connected to the transmission line, both ends of the secondary side of the pulse transformer 4 are connected to comparators (A) 5 and (B) 6, and their neutral point is connected to the ground GNO. The signals are detected by comparing each output with the voltage Vcc, but after that, timers (A) 7 and (B) 8 are connected to the AND gate (A).
9 and (B) 10, so that even if an erroneous input occurs, it will not be output to the output side. FIG. 4 is a waveform diagram showing the timing, and the present embodiment will be described below with reference to FIGS. 3 and 4.

For example, when a pulse signal with period T including undershoot is input from the transmission line as shown in FIG. 4, the comparators (A) and (B) output square waves with erroneous inputs. However, when the first output of the comparator (A) is input to the AND gate (A), the timer (
Since B) is not activated, its output passes through the gate (A) as it is and also activates the timer (A).

When the timer (A) is activated -, the comparator (A)
) remains low for a predetermined period of time less than the period T even if the output of
is output and input to the AND gate (B), so the AND gate (B) does not output any output during that time, and therefore, erroneous inputs are not output from the AND gate (B). The timer (A) returns to High after a predetermined period of time, and when the comparator (B) has a normal input, the signal passes through the AND gate (B) as is. This output in turn starts the timer (B) and similarly eliminates the erroneous input to the comparator (A). In this way, in this embodiment, the timers (A) and (B) are activated to extend the human power for a predetermined period of time, and the AND gates (A) and (B) are used to remove the erroneous human power, allowing only normal signals to pass. let still,
It is assumed that the timer extension time does not exceed the period T.

By using the circuit of the present invention, it is possible to prevent the performance of a pulse transformer from being limited by undershoot, etc., expand its selectivity, and also prevent deterioration of the S/N ratio due to undershoot, etc. Improve margins.

Furthermore, when a large number of pulse transformers are connected to one transmission line, there is also the effect of reducing the increase in undershoot caused by parallel connection, increasing the flexibility of use.

Effects of the H0 Invention As stated above, according to the present invention, a pulse transformer is used which improves the margin against deterioration of the S/N ratio due to undertunedness, reduces its negative effects, and expands the selectivity of the pulse transformer. A transmitting/receiving device can be provided.

[Brief explanation of the drawing]

1 and 3 are circuit diagrams of an embodiment of the present invention, FIGS. 2 and 4 are waveform diagrams thereof, and FIGS. 5 to 9 are explanatory diagrams of a conventional example. 1.4...Pulse transformer, 2...Drive circuit, 3.
・・Time constant circuit, 5.6・・Comparator, 7.8・
...Timer, 9, 10...and gate. 2 people outside, 3 time constant circuit Figure 1 ND Circuit diagram of another embodiment of the present invention Figure 3 Figure 2 Figure 4 M-work Figure 5

Claims (2)

[Claims] (1) A pulse transformer-based transmitting device used on a pulse transmission path, characterized in that a time constant circuit for smoothing the rise of the input pulse to the drive circuit is disposed in the preceding stage of the drive circuit. A transmitting device using a transformer. (2) In a receiving device that is used on a pulse transmission path and receives a pulse signal with a pulse transformer and outputs a pulse signal with two comparators, an AND gate is provided after each of the comparators, and an AND gate is provided on the output side of each of these AND gates. A receiving device using a pulse transformer, characterized in that a timer is provided for locking each other's outputs, and the timer is set to a time that does not exceed the pulse signal period.