JPS5892964A - Apparatus for measuring amplitude frequency characteristic of waveform - Google Patents

Abstract

PURPOSE:To reduce the measuring time with a simple circuitry by enabling the reading out of a relative frequency deviation at a high accuracy in the combination of a waveform converter and a detector. CONSTITUTION:A waveform converter 1 which converts into individual full- waveforms a waveform to be measured made by amplitude modulation of six different frequencies separately, for example, a multi-burst waveform is composed of waveform separators 1a and 1b and a waveform synthesizer 1c. The waveform separator 1a and 1b are composed of a first clip circuit for detecting the waveform of positive polarity from the muli-burst waveform and a second clip circuit for detecting the waveform of negative polarity from the multi-burst waveform. The waveform synthesizer 1c comprising a differential amplifier receiving and synthesizes a half-waveform separated positive and negative in the polarity with the waveform separators 1a and 1b and outputs full-waveforms each having a frequency component double in the frequency thereof. A detector 2 comprising a low pass filter detects (n) average components proportional to the amplitude of the respective full waves from output waveforms of the waveform synthesizers 1a and 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a method for measuring the amplitude-frequency characteristics of a television broadcast line using a pressure waveform in which n different frequencies, such as a multi-burst waveform, are amplitude-modulated. This invention relates to a characteristic measuring device.

Conventionally, for example, n different frequencies, such as the multiburst waveform shown in FIG. 2(a), each have an amplitude of
When measuring the amplitude-frequency characteristics of a television line or the like using the generated waveform, the multi-burst waveform was directly observed with an oscilloscope and the frequency characteristics were determined by relative comparison of the amplitudes.

In addition, to further improve measurement accuracy, we expanded the multiburst waveform and compared the peaks at the top and bottom of each frequency waveform.

However, the multi-burst waveform transmitted via a television line etc. is affected by non-linear distortion of the line etc., and the average value of the superimposed sine wave of the multi-burst waveform fluctuates.
The amplitude of the waveform is often asymmetrical with respect to the average value of the regular superimposed sine wave, especially in the high range of several MHz or more.

In such cases, the method of enlarging the waveforms and relatively comparing the peaks of each waveform in order to improve measurement accuracy has not been able to measure the amplitude frequency characteristics of the actual transmission line with high measurement accuracy.

Therefore, when observing such a multiburst waveform with an oscilloscope, a relative comparison of the total amplitude of the waveform must be performed. TL11 was a national disaster.

In addition, when measuring automatically without direct observation, there is a method of envelope detection for each frequency, A-D conversion, and digital processing, but a detector with a different detection time constant for each frequency is used. , the circuit configuration becomes large-scale.・Also, since the detector uses an active element, there are problems such as being easily affected by temperature changes.

This invention was made in view of the above problems, and
Convert the measured waveform tube into a full-wave waveform in which each of the different frequencies has an amplitude fM, detect n average value components proportional to the amplitude of each full wave, and detect the n average value components proportional to the amplitude of each full wave. The present invention provides a waveform amplitude frequency characteristic measuring device that detects the amplitude frequency characteristic of the waveform to be measured from the level of the waveform.

This invention will be explained below. FIG. 1 shows a block diagram of a first embodiment of the present invention. In this diagram,
The waveform converter 1 converts a measured waveform whose amplitude is modulated at six different frequencies, such as a multi-burst waveform, into a full-wave waveform, and includes a waveform separator 1a,
lb and a waveform synthesizer 1c.

The waveform separator 1a, lb u consists of a first clipping circuit that detects a positive polarity waveform from the multi-burst waveform and a second clipping circuit that detects a negative polarity waveform from the multi-burst waveform.

The waveform synthesizer 1c is composed of a differential amplifier, etc., and receives and synthesizes the half-wave waveforms separated into positive and negative by the waveform separators 1a and lb, and synthesizes the half-wave waveforms, each having a frequency component twice the frequency. Output the waveform of the wave.

The detector 2 is composed of low-pass filters and detects n average value components proportional to the amplitudes of the respective full waves from the output waveforms of the waveform synthesizers 1a and lb. The sampling holder 3 samples and holds the levels of the n average value components output from the detector 2, respectively.

The A/D converter 4 converts the signal held by the sampling holder 3 into a digital signal. The arithmetic device 5 is an A-D converter 4
. . , and calculates the amplitude value of each of the multi-burst waveforms. The display 6 digitally displays the amplitude value calculated by the calculation device 5.

Next, its operation will be explained.

A multi-burst waveform as shown in FIG. 2(a) is applied to the input terminal 7 from the system under test. Multiburst waveform #-j: has six different frequencies, each of which is amplitude modulated as shown in FIG. 2(b).

This multi-burst waveform is added to the waveform separators 1a and lb, and the ml clip circuit 1a and the second clip circuit 1
Positive polarity based on the average value A (Fig. 2 (C))
and negative polarity (Fig. 2 (・)). Figure 2(d)
shows the waveform of a positive polarity half wave of one separated frequency, and FIG. 2 <t>ta shows the waveform of a negative polarity half wave. The half-wave waveforms separated into positive and negative waves by the waveform separators 1a and lb (Fig. 2(e) and (a)) are synthesized by the waveform synthesizer 1c,
A full-wave waveform shown in FIG. 2(g), each having frequency components twice the frequency described above, is output. FIG. 2(h) shows the waveform of the full wave at low frequencies, and the dotted line is the average value component. Also, Figure 2 U) shows the waveform of the full wave when the high frequency waveform 4 (width 0) shown in Figure 2 (&) becomes unpaired due to the influence of non-linear distortion in the line, etc. show.

Full wave waveform output from waveform synthesizer 1c (Figure 2-)
) is a detector 2 composed of a low-pass filter, which detects six average value components proportional to the amplitude of each full wave, as shown in FIG. 2 (axis). That is, if we consider the full wave of low frequency when it is not affected by non-linear distortion as shown in FIG. 3, the expansion equation of this waveform is as follows. Therefore, when the signal is passed through a low-pass filter with a cut of 2ωt, only the negative component remains, and the output signal of the Rohm π-s filter becomes e(ωt)=−E. This indicates the average of the sine wave, so the low-pass filter may be any filter that can remove the lowest frequency 2ωt component. The same holds true for asymmetric full-wave waveforms in the high range. In this way, the peak values of the six average value components detected by the detector 2 faithfully reflect the amplitude frequency characteristics of the measured waveform.

The levels of the six average value components detected by the detector 2 are digitally processed by a sampling holder 31, a digital converter 4, and an arithmetic unit 5. The amplitude values of each of the digitally processed multi-bursts are digitally displayed on a display 6.

FIG. 4 shows a block diagram of a second embodiment of the present invention.1. '2:7 is the same as in FIG.

Detector 2f detects 6 zero average value components (second
The level in Figure (k) is directly observed using a direct observation device 8 such as an oscilloscope, and relative deviations are measured.

As explained above, the present invention is capable of converting a waveform to be measured in which n different frequencies are amplitude-modulated into a full-wave waveform, respectively, from the output waveform of a waveform converter and a # converter. Since it is equipped with a detector for detecting n average value components proportional to the amplitude of be able to. Furthermore, when automatically measuring by digital processing, it is only necessary to take in one sampling data for each frequency, which simplifies the circuit configuration. Furthermore, since there are fewer sampling points, it has the advantage of shortening the measurement time.

Note that the waveform converter and the detector are not limited to the embodiments described above, and can be modified and implemented without changing the gist.

[Brief explanation of the drawing]

Fig. 1 shows a first embodiment of the invention, Fig. 2 shows a waveform diagram for explaining the invention in detail, Fig. 3 shows a waveform diagram of all waves, and Fig. 4 shows a second embodiment of the invention. be. 1 is a waveform converter, 2 is a detector, 3 is a sampling holder, 4 is an A-D converter, 5 is an arithmetic unit, and 6 is a display. Patent applicant Anritsu Electric Co., Ltd.

Claims (4)

[Claims] (1) A waveform converter for converting the waveform to be measured whose amplitude is modulated at n different frequencies into a full-wave waveform; a detector for detecting n average value components, and detecting the amplitude frequency characteristic of the waveform to be measured from the level of the n average value components. Frequency bony device. (2) The waveform converter includes a waveform separator for separating the amplitude of the measured waveform into positive and negative polarities, and receives and synthesizes the half-wave waveforms separated into positive and negative polarities by the waveform separator. 2. A waveform amplitude frequency characteristic device according to claim 1, further comprising a waveform synthesizer for outputting a full-wave waveform. (3) a waveform converter for converting the waveform under measurement whose n different frequencies are amplitude-modulated into full-wave waveforms; the output waveform of the waveform converter is proportional to the amplitude of each full-wave; a detector for detecting the n average value components; a sampling holder for sampling and holding the levels of the n average value components output from the detector;
an A-Df converter for converting the signal held in the holder into a digital signal; and an operation for receiving the output of the A-D converter and calculating the value of the amplitude of each of the waveforms to be measured. A waveform amplitude frequency characteristic measuring device comprising: (4) The waveform converter includes a waveform separator for separating the amplitude of the measured waveform into positive and negative polarities, and receives and synthesizes the half-wave waveforms separated into positive and negative polarities by the waveform separator. 4. A waveform amplitude frequency/number characteristic device according to claim 3, further comprising a waveform synthesizer for outputting a full-wave waveform.