KR100381020B1 - Rectangular Pulse Generator with constant duty cycle - Google Patents

Abstract

The present invention relates to a pulse generator for generating a square wave having a constant duty cycle independent of the strength of the input signal, the square wave pulse generator of the present invention and the short pulse swinging the frequency-modulated input signal to a constant intensity for a predetermined time An integrator for converting the signal into a low level signal, integrating the short pulse to generate an output signal having a positive slope, and integrating the low level signal lasting for a predetermined time to generate an output signal having a negative slope; And a comparator for generating a square wave pulse having a constant duty cycle by comparing a signal having a positive slope or a negative slope output through the integrator with a reference voltage.

Description

Rectangular pulse generator with constant duty cycle

The present invention relates to a pulse generator for converting a frequency-modulated signal such as amplitude shift keying (ASK) into a square wave for processing in a digital signal processor. The present invention relates to a square wave pulse generator having a constant duty cycle regardless of the magnitude of an input intensity. It is about.

1 is a circuit diagram of a conventional square wave pulse generator.

Referring to FIG. 1, a conventional square wave generator integrates an input signal having a frequency modulated sine wave form, such as an ASK, and converts an input signal into a signal having an envelope ripple component, and an output signal of the integrator 10. Is composed of a comparator 20 for generating a square wave pulse by comparing with the reference voltage Vref.

The comparator 20 is a comparator having hysteresis characteristics having two levels, that is, a high level reference voltage and a low level reference voltage, and first compares an input signal with a high level reference voltage Vref. If it is higher than the reference voltage, it is inverted to the low level and outputted. Due to the hysteresis characteristics, the reference voltage changes to a low level, and an input signal below the reference voltage of the low level is inverted to a high level and output.

Therefore, as shown in FIG. 2, the frequency-modulated signal A is input to convert the waveform B having a ripple component in the envelope through the integrator 10, and the signal B output through the integrator 10. ) Generates a square wave pulse signal D by comparing the two levels of the reference voltage Vref through the comparator 20 having hysteresis characteristics. The output signal D of the comparator 20 converted to the square wave as described above is transmitted to the digital signal processor of the next stage although not shown in the drawing.

However, the conventional square wave pulse generator as described above has a problem in that the duty cycle of the square wave output from the comparator 20 changes according to the strength of the frequency-modulated input signal input to the integrator 10.

That is, when the intensity of the input signal A is strong, the slope of the output waveform of the integrator 10 becomes steep as shown in FIG. 3, whereas when the intensity of the input signal B is weak, the integrator 10 is reduced. The slope of the output waveform is slowed down.

At this time, since the high and low reference voltages Vref of the comparator 20 having hysteresis characteristics are constant, the output signal of the integrator 10 having a steep slope becomes relatively long in the low level holding time. The output signal of the integrator 10 with a gentle slope becomes relatively long and maintains a high level.

Therefore, in the case where the strength of the input signal is strong, as shown in FIG. 3, the sustain period of the low level is relatively long, and the duty cycle is shortened. In contrast, in the case where the strength of the input signal is weak, as shown in FIG. As a result, the maintenance period of the high level was longer, resulting in a longer duty cycle.

An object of the present invention is to solve the problems of the prior art as described above, and an object of the present invention is to provide a pulse generator for generating a square wave having a constant duty cycle regardless of the strength of the input signal.

1 is a block diagram of a conventional square wave pulse generator,

2 is an operation waveform diagram of a conventional square wave pulse generator,

3 is a waveform diagram of a conventional square wave pulse generator in which the intensity of an input signal is strong;

4 is a waveform diagram of a conventional square wave pulse generator in which the intensity of an input signal is weak;

5 is a configuration diagram of a square wave pulse generator according to an embodiment of the present invention;

6 is a circuit configuration diagram of a short pulse generator in a square wave pulse generator according to an embodiment of the present invention;

7 is a circuit diagram of a linear pulse generator in a square wave pulse generator according to an embodiment of the present invention;

8 is an operation waveform diagram of a square wave pulse generator according to an embodiment of the present invention;

<Description of the symbols for the main parts of the drawings>

100: integrator 200: comparator

110: short pulse generator 120: linear pulse generator

61, 62: comparison means 63: output means

I1-I4: constant current source Q1-Q21: bipolar transistor

C1, C2: Capacitor R1: Resistance

In order to achieve the object of the present invention, the present invention is a square wave pulse generator for converting a frequency-modulated input signal into a square wave pulse, the short pulse swinging the input signal at a constant strength and a low level that lasts for a predetermined time An integrator for converting the signal into a signal, generating an output signal having a positive slope by integrating the short pulses, and generating an output signal having a negative slope by integrating the low level signal lasting for a predetermined time; A square wave pulse generator comprising a comparator for generating a square wave pulse having a constant duty cycle by comparing a signal having a positive slope or a negative slope output through the integrator with a reference voltage.

The integrator includes a short pulse generator for converting the frequency-modulated input signal into a short pulse swinging at a constant intensity and a low level signal lasting for a predetermined time; The linear pulse generator generates an output signal having a positive slope by integrating the short pulses generated from the short pulse generator, and generates an output signal having a negative slope by integrating the low level signal lasting for a predetermined time.

The short pulse generator comprises: first comparing means for comparing the input signal with a first reference voltage; Second comparing means for comparing the input signal with a second reference voltage; And output means for inputting the output signals of said first and second comparing means and generating them as said output signals.

The first comparing means includes first and second transistors for comparing means for comparing the input signal with a first reference voltage; And third and fourth transistors for current mirrors connected to the first and second transistors, wherein the second comparing means includes fifth and sixth transistors for comparing means for comparing the input signal with a second reference voltage. ; And a seventh and eighth transistors for current mirrors connected to the fifth and sixth transistors.

The output means comprises ninth and tenth transistors driven by output signals of the first and second comparing means, respectively, and when the input signal is greater than the first and second reference voltages, the output means swings at a constant intensity. A short pulse is generated as the output signal to the linear pulse generator, and when the input signal is less than the first and second reference voltages, a low level signal lasting for a predetermined time is generated as the output signal to the linear pulse generator. do.

The short pulse generator further includes first to third constant current sources for supplying a reference current to the first and second comparing means and the output means, respectively.

The linear pulse generator includes: a first transistor configured to output an output signal of the short pulse generator as an input signal; A first capacitor connected in parallel with the first transistor; A second transistor for providing a charging current to the first capacitor; A third transistor driven by the charging current of the first capacitor; Fourth and fifth transistors connected in parallel with the second transistor; A sixth transistor connected to the third transistor and a fourth transistor; A seventh transistor connected to the third transistor; An eighth and a ninth transistors connected to the third and seventh transistors, respectively; Tenth and eleventh transistors for current mirrors connected to the ninth transistors; The second capacitor is connected in parallel with the eleventh transistor.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the present invention through an embodiment of the present invention.

5 is a block diagram of a square wave pulse generator according to an embodiment of the present invention.

Referring to FIG. 5, the square wave pulse generator according to an embodiment of the present invention inputs a frequency-modulated input signal and limits the power to a constant intensity so that the short pulse swings at a constant intensity with respect to ground and lasts for a predetermined time. An integrator 100 generating a low level signal, integrating the short pulse to generate an output signal having a positive slope, and integrating the low level signal lasting for a predetermined time to generate an output signal having a negative slope; The comparator 200 generates a square wave pulse having a constant duty cycle by comparing a signal having a positive slope or a negative slope output through the integrator 100 with reference voltages Vref of two levels.

The integrator 100 converts a frequency-modulated input signal into a short pulse swinging at a constant strength, for example, 0.7 Vpp based on ground, and a low pulse signal lasting for a predetermined time. ) And an output signal having a positive slope by integrating the short pulses generated from the short pulse generator 110, and generating an output signal having a negative slope by integrating the low level signal lasting for a predetermined time. Pulse generator 120.

The comparator 200 is a comparator having hysteresis characteristics having two levels of reference voltages Vref.

FIG. 6 is a circuit diagram of the short pulse generator in the square wave pulse generator of FIG. 5.

The short pulse generator 110 may include a first comparator 61 for comparing an input signal with a first reference voltage V1, and comparing the input signal with a second reference voltage V2. And a second comparator 62 for outputting the output signals of the first and second comparators 61 and 62 to generate the output signals Out of the short pulse generator. .

The first comparator 61 is for a constant current source connected to the pnp transistors Q3 and Q4 and the pnp transistors Q3 and Q4 as comparison means for comparing the input signal Input and the first reference voltage V1. npn transistors Q7 and Q8.

The second comparator 62 is a current mirror connected to the pnp transistors Q5 and Q6 as comparison means for comparing the input signal Input and the second reference voltage V2, and the pnp transistors Q3 and Q4. Npn transistors Q9 and Q10.

The output means 63 is composed of npn transistors Q1 and Q2 which are driven by output signals of the first and second comparators 61 and 62, respectively, to generate a short pulse Out.

In addition, the short pulse generator 110 further includes a constant current source I1-I3 for supplying a reference current to the first and second comparators 61 and 62 and the output means 63, respectively.

The operation of the short pulse generator 110 having the configuration as described above is as follows.

The input signal Input is applied to the bases of the transistors Q4 and Q5 of the first and second comparators 61 and 62. When the input signal Input is below the first and second reference voltages V1 and V2, the transistors Q4 and Q5 are turned on, and the transistors Q3, Q7 and 8 and the transistors Q6, Q9 and 10 are both turned on. Is off.

Therefore, the reference voltages I2 and I3 flow through the bases of the transistors Q1 and Q2 of the output means 63 and operate in the saturation region. Therefore, the output signal out drops to the ground potential.

On the other hand, when the input signal Input is greater than or equal to the first and second reference voltages V1 and V2, the transistors Q4 and Q5 of the first and second comparators 61 and 62 are turned off and the transistors Q3 and Q7 and Q8 and transistors Q5, Q9 and Q10 are all turned on so that transistors Q1 and Q2 of output means 63 are turned off. Accordingly, the reference current I1 is provided to the linear pulse generator 120 as an output signal out.

Therefore, when the input signal Input is greater than or equal to the first and second reference voltages V1 and V2, the short pulse generator 110 outputs a signal whose intensity is 0.7 Vpp and is less than or equal to the reference voltages V1 and V2. In this case, since it outputs a ground level signal, it generates a short pulse swinging at 0.7Vpp relative to ground. In addition, when the low level input signal (Input) is maintained, the output signal (Out) is also maintained at the low level. Therefore, the short pulse generator generates a short pulse train swinging at 0.7 Vpp and a burst repeating the low. ) Generates a signal.

FIG. 7 illustrates a circuit diagram of the linear pulse generator in the square wave pulse generator of FIG. 5.

The linear pulse generator 120 includes an npn transistor Q11 having an output signal Output of the short pulse generator 110 as a base input signal, a capacitor C1 connected in parallel with the transistor Q11, and the capacitor. Pnp transistor Q15 for providing charging current to C1, pnp transistor Q12 driven by the charging current of capacitor C1, and pnp transistors Q14 and Q16 connected in parallel with transistor Q15. )

The linear pulse generator 120 also includes an npn transistor Q13 connected to the transistor Q12 and the transistor Q14, a pnp transistor Q19 connected to the transistor Q12, and the transistor Q12 and ( Pnp transistors Q17 and Q18 respectively connected to Q19, a current mirror npn transistors Q20 and Q21 connected to the transistor Q19, and a capacitor C2 connected in parallel with the transistor Q21.

The operation of the linear pulse generator 120 having the configuration as described above is as follows.

First, when the short pulse generator 110 generates an output signal Swinging at 0.7 Vpp, when the output signal Output is 0.7 Vpp, the reference voltage I1 is the linear pulse generator 120. It is provided as an input signal (Input) of. The reference voltage I1 is applied to the base of the transistor Q11 as an input signal of the linear pulse generator 120 so that the transistor Q11 operates in the saturation region. As the transistor Q11 operates in the saturation region, the base of the transistor Q12 drops to ground level.

As the base of transistor Q12 goes to ground level, transistor Q12 is turned off, transistors Q18, Q19, Q20, Q21 are turned off, and transistors Q13, Q14, Q15, Q16, Q17 are turned on. .

Accordingly, the current is charged in the capacitor C2 through the transistor Q16, and the current flowing through the transistor Q15 and the current charged in the capacitor C1 are discharged through the resistor R1 and the transistor Q11.

Next, when generating an output signal Swinging at 0.7Vpp from the short pulse generator 110, when the output signal is low level, the linear pulse generator 120 generates the short pulse generator of the low level. An output signal Output of 110 is input as an input signal.

The transistor Q11 is turned off by the low level input signal Input, so that the current flowing through the transistor Q15 is charged in the capacitor C1. A current is charged in the capacitor C1, but a low level signal applied from the short pulse generator 110 does not last long enough for the transistor Q12 to be sufficiently turned on.

Therefore, in the section of generating the short pulse swinging to 0.7Vpp from the short pulse generator 110, the discharge is not performed through the capacitor C2, but is continuously charged through the capacitor C2.

That is, when the short pulse swinging at 0.7 Vpp repeating the high level and the low level is input from the short pulse generator 110, the linear pulse generator 120 does not discharge through the capacitor C2. The charging is continued and a voltage having a positive slope is provided as an input signal of the comparator 200.

Meanwhile, when the low level output signal Output is continuously output from the short pulse generator 110 for a predetermined time, the low level output signal Output is the input signal of the linear pulse generator 120. Input is applied to the base of the transistor Q11.

The transistor Q11 is turned off by the low level input signal Input applied to the base, and the current flowing through the transistor Q15 is continuously charged in the capacitor C1. Transistor Q12 is turned on by continuous charging of capacitor C1 for a sufficient time.

As transistor Q12 is turned on, transistors Q13, Q14, Q15, and Q16 are turned off and charging of capacitor C1 is stopped. At this time, the transistors Q17, Q18, Q19, Q20, and Q21 are turned on so that the current charged in the capacitor C2 is discharged through the transistor Q21. Accordingly, the current charged in the capacitor C2 is discharged through the transistor Q21 so that a voltage having a negative slope is provided to the comparator 200 as an input signal.

Referring to the operation waveform diagram of FIG. 8, the operation of the square wave pulse generator of the present invention as shown in FIGS. 5 to 7 is as follows.

When a frequency-modulated input signal is applied to the integrator 100, the integrator 100 is shorted with a short pulse that is swinged by a certain intensity, for example, 0.7 Vpp, through the short pulse generator 110. Generate a low-level signal that lasts for time.

That is, the short pulse generator 110 compares the input signal (Input) with the first and second reference voltage (V1, V2) through the first and second comparators 61, 62, the input signal ( If the input is greater than or equal to the first and second reference voltages, a signal swinging to 0.7 Vpp based on the ground level is generated through the output means 63. If the input voltage is less than or equal to the reference voltages V1 and V2, a signal having the ground level Output In addition, when a low level input signal Input is applied for a predetermined time, the low level signal Output for a predetermined time is output through the output means 63.

The output signal of the short pulse generator 110 is provided as an input signal of the linear pulse generator 120 and integrated. When a short pulse swinging at 0.7 Vpp is input, a voltage signal having a positive slope is generated. When a low-level signal of time duration is inputted, a voltage signal having a negative slope is generated.

The comparator 200 generates a square wave pulse having a constant duty ratio from the signal input through the integrator 100 using hysteresis characteristics having two levels of reference voltages.

That is, when the output signal of the sadiri form having the positive and negative inclinations from the linear pulse generator 120 of the integrator 100 is provided as the input signal of the comparator 200, the comparator 200 receives the input. Compare the signal with the reference voltage.

As a result of the comparison, the output of the comparator 200 is inverted from the high level to the low level at the moment when the high reference voltage is less than the high, and the output of the comparator 200 is at the low level when the output voltage is higher than the reference voltage. Invert to high level at.

Accordingly, the comparator 200 generates a square wave pulse having a constant duty cycle with respect to the frequency modulated input signal by generating the square wave pulse regardless of the intensity of the input signal.

According to the square wave pulse generator of the present invention as described above, by limiting the strength of the frequency-modulated signal to a predetermined size and then converted to a square wave, there is an advantage that can generate a square wave having a constant duty cycle regardless of the input strength have.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (10)

In the square wave pulse generator for converting the frequency-modulated input signal into a square wave pulse, Converts the input signal into a short pulse swinging at a constant intensity and a low level signal lasting for a predetermined time, and integrates the short pulse to generate an output signal having a positive slope, and a low level signal lasting for a predetermined time An integrator for generating an output signal having a negative slope by integrating a; And And a comparator for generating a square wave pulse having a constant duty cycle by comparing a signal having a positive slope or a negative slope output through the integrator with a reference voltage. The method of claim 1, The integrator is A short pulse generator for converting the frequency-modulated input signal into a short pulse swinging at a constant intensity and a low level signal lasting for a predetermined time; And A linear pulse generator for generating an output signal having a positive slope by integrating the short pulse generated from the short pulse generator, and generating an output signal having a negative slope by integrating the low level signal lasting for a predetermined time Square wave pulse generator. The method of claim 2, The short pulse generator First comparing means for comparing the input signal with a first reference voltage; Second comparing means for comparing the input signal with a second reference voltage; And And output means for inputting the output signals of said first and second comparing means and generating them as said output signals. The method of claim 3, wherein The first comparing means First and second transistors for comparing means for comparing the input signal with a first reference voltage; And a third and fourth transistor for current mirrors connected to the first and second transistors. The method of claim 4, wherein The second comparing means Fifth and sixth transistors for comparing means for comparing the input signal with a second reference voltage; And a seventh and eighth transistors for current mirrors connected to the fifth and sixth transistors. The method of claim 5, The output means And a ninth and tenth transistor driven by an output signal of the first and second comparing means, respectively. The method of claim 6, The output means generates a signal having a predetermined intensity when the input signal is greater than or equal to the first and second reference voltages, and generates a signal of ground level when the input signal is less than or equal to the first and second reference voltages. The linear pulse generator generates a short pulse swinging at a constant intensity as an output signal, and the low level signal lasting for a predetermined time as the output signal when the input signal is at a low level for a predetermined time. Square wave pulse generator, characterized in that generated by. The method of claim 3, wherein And the short pulse generator further comprises first to third constant current sources for supplying a reference current to the first and second comparison means and the output means, respectively. The method of claim 2, The linear pulse generator A first transistor using the output signal of the short pulse generator as an input signal; A first capacitor connected in parallel with the first transistor; A second transistor for providing a charging current to the first capacitor; A third transistor driven by the charging current of the first capacitor; Fourth and fifth transistors connected in parallel with the second transistor; A sixth transistor connected to the third transistor and a fourth transistor; A seventh transistor connected to the third transistor; Eighth and ninth transistors connected to the third and seventh transistors, respectively; Tenth and eleventh transistors for current mirrors connected to the ninth transistors; And Square wave pulse generator, characterized in that consisting of a second capacitor connected in parallel with the eleventh transistor. The method of claim 1, The comparator is a square wave pulse generator, characterized in that the comparator having a hysteresis characteristic having two levels of reference voltage.