JPH0628329B2 - Harmonic remover - Google Patents

Description

TECHNICAL FIELD The present invention relates to a harmonic elimination device, and more particularly to a harmonic elimination device for eliminating low-order harmonics.

2. Description of the Related Art In a conventional facsimile apparatus or the like, a low-pass filter (hereinafter abbreviated as LPF) is used to remove harmonic components from the output of a modulator. However, in many devices such as facsimile machines, the modulated output signal is often a binary signal, which is expensive to remove the third harmonic component.
The LPF had to be dedicated to that frequency.

The present invention is made in view of the above-mentioned problems,
An object of the present invention is to provide a simple and inexpensive harmonic wave removing device that can remove high frequency components from a binary signal in advance, and more specifically, a binary first signal having a frequency within a frequency band of a telephone line. A facsimile means for outputting a pulse signal and a binary first pulse signal output from the facsimile means are applied to a time constant circuit composed of a resistor and a capacitor, and an output waveform of the time constant circuit is applied by a waveform shaping circuit. A delay unit that outputs a second pulse signal that is a delayed signal of the first pulse signal by converting it into a binary pulse signal, and the first pulse signal and the second pulse signal are added to each other to obtain the second pulse signal. Adder means for outputting an addition signal obtained by subtracting low-order harmonic components of one pulse signal, and high-order harmonics contained in the addition signal are removed, and a sine wave is output to output a sine wave circuit. And to provide a harmonic elimination device, characterized in that it comprises a low-pass filter for outputting a sine wave component excluding the low-order harmonic components of said first pulse signal within a few bands.

EXAMPLES The present invention will be described in detail below based on examples shown in the drawings.

First, an embodiment of the harmonic wave removing device of the present invention will be described.

In the figure, reference numeral a indicates an input signal line, and a binary signal input from the input signal line a is input to a time constant circuit 1 composed of a capacitor C1 and a resistor R1. The output signal line b of the time constant circuit 1 is connected to the waveform shaping circuit 2 such as a comparator.

Further, the binary signal input from the input signal line a is also input to the buffer amplifier 4. The output signal of the buffer amplifier 4 and the output signal of the waveform shaping circuit 2 (signal line
c) is input to the inverting input terminal of the operational amplifier Q1 via the resistors R2 and R3, respectively. However, the signal on the output signal line c of the waveform shaping circuit 2 is delayed from the input binary signal, and the output signal of the buffer up 4 is an output signal having the same voltage as the input binary signal.

The non-inverting input terminal of the comparator 91 is grounded,
Further, the output signal thereof is fed back to the inverting input via the resistor R4, and constitutes an adder 3 for adding the signals input via the resistors R2 and R3.

The output signal line d of the adder 3 configured as described above is connected to the LPF 5 via the capacitor C2, and the output signal passing through this LPF is output via the signal line e.

Next, the operation of the above configuration will be described with reference to the waveform charts of FIGS.

The waveforms shown in FIGS. 2 (a) to 2 (e) are the waveforms when the signal lines a to e of FIG. 1 are operating. Now, when a binary signal as shown in FIG. 2 (a) is applied to the signal line a, this waveform is delayed by the time constant circuit 1 and the signal line b
Then, a waveform as shown in FIG.

The signal on the signal line b passes through the waveform shaping circuit 2 to obtain a delayed binary signal as shown in FIG. 2 (c).

The waveform of the signal line c is added to the output signal of the buffer amplifier 4 (the same voltage and the same waveform as the signal of the signal line a) in the adder 3, and is added to the signal line d by an appropriate amplification factor, as shown in FIG. A signal from which the third harmonic component is removed as shown is obtained.

Further, by passing the signal on the signal line d through the LPF 5, higher harmonics can be removed, and a sine wave having a single frequency component as shown in FIG. 2 (e) can be obtained on the signal line e. it can.

As described above, the third harmonic component can be removed without using an expensive filter circuit, which is useful for reducing the cost of the system to which it is applied.

Although the adder is used in the embodiment shown in FIG. 1, the same effect can be obtained by replacing the adder with a subtractor.

In addition, the waveform shaping circuit having the above-described configuration can accurately measure
A comparator may be used to remove the second harmonic component.

The configuration shown above is a circuit for removing the third-order harmonic component. However, if a plurality of combinations of the time constant circuit and the waveform shaping circuit are provided, higher-order higher-order harmonic components of the fifth or higher order can be obtained. Can be removed.

Effect As is clear from the above description, according to the present invention, the low-order harmonic component is removed by delaying the input pulse signal, adding it to the pulse of the original signal, and passing it through a low-pass filter. , It is possible to prevent the low-order harmonic components of a facsimile signal using a telephone line having a relatively low frequency band of 300 Hz to 3400 Hz from being erroneously recognized as another facsimile signal.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the circuit configuration of the harmonic elimination device of the present invention, and FIGS. 2 (a) to (e) are waveform diagrams showing the signal waveforms of the respective signal lines in FIG. is there. 1 ... Time constant circuit, 2 ... Waveform shaping circuit 3 ... Adder, 4 ... Buffer amplifier 5 ... LPF, C1, C2 ... Capacitor Q1 ... Operational amplifier, R1-R4 ... Resistors.

Claims (1)

[Claims] 1. A facsimile means for outputting a binary first pulse signal having a frequency within a frequency band of a telephone line, and a binary first pulse signal output from the facsimile means with a resistor and a capacitor. A delay means for outputting a second pulse signal, which is a delay signal of the first pulse signal, by applying it to a time constant circuit and converting the output waveform of the time constant circuit into a binary pulse signal by a waveform shaping circuit. An addition unit that adds the first pulse signal and the second pulse signal to output an addition signal obtained by subtracting a low-order harmonic component of the first pulse signal, and a high-order signal included in the addition signal. And a low-pass filter that outputs a sine wave by removing the higher harmonics of the first pulse signal and outputs a sine wave component other than the low-order harmonic component of the first pulse signal in the frequency band of the telephone line. Harmonic rejection apparatus.