JPS5924394B2 - Even order strain detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting strain, and more particularly to a device for detecting the magnitude and polarity of even-order strain.

In recent years, with the development of electronic technology, various signals have been transmitted.

In this case, the signal transmission system includes a transistor amplifier with an inappropriate bias, a light emitting/receiving device (photocoupler) for optical communication,
It often includes elements or circuits with nonlinear characteristics, such as recording and reproducing devices using magnetism and light, and circuits using diodes. When a signal is transmitted through a transmission system having such nonlinear characteristics, the transmission signal, which should originally be a sine wave, may be erroneously transmitted due to even-order distortion. Conventionally, in order to detect the occurrence of such distortion, an expensive measuring device such as an oscilloscope or spectrum analyzer was connected to the signal system, and by observing the measuring device, even numbers that could cause erroneous transmission were detected. Such measuring instruments were used to discover where distortion occurs and to adjust transmission systems to eliminate it.

However, the above-mentioned method requires an expensive measuring instrument to detect even-order distortion, and requires constant observation by a measurer.

Furthermore, since the observer must read the data himself and perform control (adjustment) as a countermeasure based on the read data, it has various drawbacks such as being unsuitable for automation. In view of the above points, the present invention has been made to solve such problems and eliminate such drawbacks, and its purpose is to provide an even-order strain detection device that can automatically detect even-order distortions. Our goal is to provide the following.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The even-order strain detection device according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an even-order strain detection device according to the present invention, in which input terminal 1
A signal under test whose even-order distortion is to be detected is applied to the band pass filter 2 via the bandpass filter 2. Here, the signal under test is, for example, a frequency modulated signal. Furthermore, it is assumed that the band pass filter 2 passes most of the sideband waves of this frequency-modulated signal and does not pass direct current. The frequency-modulated signal that has passed through the band bus filter 2 further passes through a limiter 3, and its output is branched, with one side being sent to a clamp circuit 4 and one to a low-pass filter 5.
is applied in series to one input terminal of the differential amplifier 6. The other branched output from the limiter 3 is applied to the other input terminal of the differential amplifier 6 via an inverting amplifier 7, a clamp circuit 8, and a low-pass filter 9 in series.
Here, it is assumed that the limiter 3 provides a certain output voltage Va for input voltages that are even slightly positive, and provides another constant output voltage Vb for input voltages that are even slightly negative. However, such a limiter 3 in which Va>Vb can be realized by a known circuit using a diode and an amplifier. It is assumed that both the clamp circuit 4 and the clamp circuit 8 clamp the lower end of the input voltage waveform to 0V.

Further, it is assumed that both the low-pass filter 5 and the low-pass filter 9 have cutoff frequencies sufficiently lower than the modulation frequency of the frequency modulation signal applied to the input terminal 1. The differential amplifier 6 supplies a voltage obtained by subtracting the voltage of the second input B from the voltage of the first input A to the output terminal 11 as an output. Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to FIGS. 2 and 3 showing waveforms at various parts.

First, when a frequency-modulated signal under test with no harmonic distortion is applied to the input terminal 1, the output signal of the filter 2 becomes a waveform P as shown in Fig. 2A, and the center line of the waveform P The voltage at Q becomes zero (0). The output signal of bandpass filter 2 is then applied to limiter 3,
The output of this limiter 3 becomes a square wave shown in FIG. 2B.
Since the signal to be measured does not contain any harmonic distortion, the square wave has a duty factor of 0.5 due to the action of the limiter 3. That is, the period in which the output is Va and the period in which the output is B are both equal if averaged over a long period of time. Therefore, the output of the clamp circuit 4, which receives the output of the limiter 3, has the waveform shown in FIG. 2C due to the action of the clamp circuit 4. On the other hand, the output of the limiter 3 becomes as shown in FIG. 2D due to the action of the clamp circuit 8 inputted via the inverting amplifier 7. FIG. 2D is obtained by inverting the polarity of the waveform shown in FIG. 2C and clamping the lower end to zero (0). Next, the outputs of the low-pass filter 5 and the low-pass filter 9, which receive the outputs of the clamp circuit 4 and the clamp circuit 8, respectively, are connected to the second filter.
It is equal to the average value of the waveforms shown in Figures C and D, but since the duty factor is 0.5, both −f(Va
-Vb). Therefore, the output of the differential amplifier 6 becomes zero. That is, if the input waveform at input terminal 1 is a sine wave without distortion, the voltage at output terminal 11 will be zero.
Next, it is assumed that a signal under measurement that has undergone even-order distortion is applied to terminal 1 by a nonlinear element, such as a transistor amplifier with inappropriate bias.

Since the waveform passed through such an element generally has a rise time and a fall time that are approximately equal to K, the waveform R becomes a waveform R in which the lower half of a sine wave is condensed, as illustrated in FIG. 3A. At this time, the average value S deviates in the positive direction from the average value u of the waveform T when no distortion is applied, as shown in FIG. occurs. FIG. 3B shows the output voltage waveform of the limiter 3 when the voltage at the input terminal 1 has the waveform R shown in FIG. 3A. Then, if the duty factor of waveform R is m, then m<
It is 0.5. Figure 3 C and D are limiter 3, respectively.
These are the output waveforms of the clamp circuit 4 and the clamp circuit 8 which input the output voltage of , and the average value of the waveform shown in FIG. The value is (1-m)(VaVb). Therefore, the output of the low-pass filter 5 is more negative than the output voltage of the low-pass filter 9, so the output voltage of the differential amplifier 6 is (2
m1) (Va-Vb), which shows a negative value. Next, when a waveform with the upper side of the waveform congested as shown in FIG. 3E is supplied to input terminal 1, contrary to FIG. , this distortion occurs when the polarity of the nonlinearity is reversed. In such a case, the average value of the waveform shown in Fig. 3E is shifted in the positive direction compared to the sine wave, so the output waveform of the limiter 3 is as shown in Fig. 3F.
The duty factor m of this waveform is as shown in
is more dog-like than 0.5. Therefore, by the operation of the clamp circuit 4 and the clamp circuit 8, the low-pass filter 5 and the low-pass filter 9, and the differential amplifier 6,
The value of the output voltage is (2m1) (Va-Vb), which is a positive value. In the above embodiments, the input waveform has symmetrical distortion;
That is, it does not respond to odd-order distortions, but in frequency modulated signals, such distortions are usually not harmful, and such responsiveness does not pose a problem.

Further, in the embodiments of the present invention, the case where the input signal is frequency modulated has been described, but the present invention can also be used in amplitude modulation as long as the degree of modulation is not 100%. Further, the present invention is not limited to transmission systems, but can be applied to all cases where positive and negative symmetrical waveforms are handled. As explained above, when the signal applied to input terminal 1 is a sine wave without distortion, the voltage at output terminal 11 is zero, but due to the nonlinearity of the transmission system, the voltage may change in the positive or negative direction of the waveform. When a signal subjected to such distortion is applied, a voltage corresponding to the degree and polarity of the distortion is sent to the output terminal 11. Therefore, the voltage at the output terminal 11 can be used to determine, for example, the magnitude and polarity of even-order distortion in the transmission system, which is extremely useful for monitoring distortion in the transmission system. Therefore, it can be constructed at a lower cost than conventional spectrum analyzers, and the polarity and amount of distortion can be read. Furthermore, according to the present invention, since the amount and polarity of strain can be obtained as a voltage value, it can be used for automatic recording and automatic processing, and can be used to automatically detect strain in the transmission system by feeding back to the source of the strain. It has various excellent effects such as being able to be controlled so as to be small in size.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of an even-order strain detection device according to the present invention, Fig. 2 is a waveform diagram of various parts when a distortion-free waveform is applied to the circuit shown in Fig. 1, and Fig. 3 is FIG. 2 is a waveform diagram of various parts when a waveform with even-order distortion is added to the circuit shown in FIG. 1; 2...Band pass filter, 3...
Limiter, 4, 8... Clamp circuit, 5, 9...
...Low pass filter, 6 ... Differential amplifier, 7 ... Inverting amplifier, 11 ... Output terminal.

Claims (1)

[Claims] 1 A first circuit that outputs two types of voltage as the signal under test becomes more positive or negative than its average level, and a voltage that is the polarity of the output voltage sent from this first circuit. a second circuit for output; a third and fourth circuit for obtaining a voltage obtained by clamping the upper end or the lower end of the output voltage to a common voltage from the output voltage of the first and second circuits; A differential amplifier includes first and second low-pass filters connected to the output terminals of the fourth circuit, respectively, and the output voltages of the first and second low-pass filters as first and second inputs, respectively. Equipped with a drawer,
An even-order distortion detection device characterized in that a voltage signal corresponding to the polarity and magnitude of distortion is extracted from the output end of the differential amplifier.