JPS6321572A - Electric length measurement - Google Patents

Abstract

PURPOSE:To measure a deviation in the electric length between high frequency coaxial cables accurately, by determining a difference in the electric length between the cables from intersections between the vertical lines formed by vertically aligning points as value measured at two or three measuring frequencies and an axis of abscissa scale. CONSTITUTION:When measuring the electric length between high frequency axial cables, several phases are measured in a range of 180 deg. at the prescribed frequency t0, at a half of the frequency f0, a quarter of the frequency f0/2 and the frequency f0/4. The results of the measurement are presented with an angle on the axis of ordinate in a range of 180 deg. and a cable length lambda on the axis of abscissa. The results thus presented are plotted on normal phase variation curves Pf0, Pf0/2 and Pf0/4 obtained separately at the measuring frequencies of f0, f0/2 and f0/4 which are recorded on a paper. A difference in the electric length between the cables is determined from intersections between vertical lines formed by points vertically aligning as value measured at three measuring frequency points f0, f0/2 and f0/4 and an axis of abscissa scale.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrical length measuring method, and particularly to an electrical length measuring method for reliably measuring the electrical length deviation between a plurality of high-frequency coaxial cables. .

[Prior Art] Conventionally, there was no way to measure the electrical length of a high-frequency coaxial cable other than to estimate it by this calculation, but the inventors proposed the n:A method.
3i, but we have established a measurement method for normal phase, reverse phase, plus and minus 1λ. That is, standing waves are measured at two types of frequencies.

[Problem to be Solved by the Invention 1] Although there was no method for accurately measuring the nλ difference in the above-mentioned prior art, there are now many cases where it is required to match the absolute electrical lengths between cables. In particular, for the purpose of precisely controlling the directivity of the antenna, it is necessary to precisely adjust the electrical length in order to reduce the frequency characteristics. In order to make adjustments, we first had to measure, but there was no accurate method.

The electrical length of a cable is an inevitable accumulation of minute changes caused by manufacturing tolerances of the cable. This accumulation is measured as a wavelength shortening rate, and there are variations between production lots, between drums even in the same lot, and even in the same drum in the longitudinal direction, which is an important problem in applications that require control of electrical length deviation. In Figure 6, the vertical axis shows the electrical length difference (λ
) and the cable length (λ) is plotted on the horizontal axis to show the electrical length deviation of the high frequency coaxial cable. In the figure, λt is the wavelength shortening rate of the cable, Δ is λ1, and 8 is the wavelength shortening rate deviation of the cable. As shown in the figure, when the deviation is 1% (in the case where △ is λ1 in the figure), there is a deviation in the electrical length depending on the cable length and frequency, as shown in the table below. Even if the cables are aligned, there will be differences in electrical length.

The present invention has been made in view of the above points, and it is an object of the present invention to provide an electrical length measuring method that makes it possible to reliably measure the electrical length deviation between high frequency coaxial cables.

[Means for solving the problem] The above purpose is to measure the electrical length of multiple high-frequency coaxial cables by measuring the specified frequency and the frequency of 1/n (n is an integer) of this specified frequency for each of them. Measure the phase at multiple points in the range of plus and minus 180 degrees, take the angle in the range of plus and minus 180 degrees on the vertical axis, take the cable 5 (λ) on the horizontal axis, and measure each measurement result. Plot the normal phase curve of the frequency on the curve of the recording paper on which it was recorded, and calculate the distance between the cables from the intersection point of the perpendicular line of the point where the values measured at two or three measurement frequencies coincide vertically and the horizontal axis scale. This is achieved by determining the electrical length difference.

[Function] In addition to phase measurement at the specified frequency, phase measurement is performed at a frequency 1,/n of the specified frequency. Measured value -180° on the vertical axis
An angle scale is provided from O0 to +180°, the cable length (λ) is plotted on the horizontal axis, and graph paper is prepared on which the normal phase change is written. Then, write the measurement points measured at the above-mentioned frequencies that can be measured with a phase of plus and minus 180 degrees on graph paper, and mark the perpendicular line of the point where the values measured at each measurement frequency match vertically and the horizontal axis scale. Since the electrical length difference between the cables is determined from the intersection of the two cables, the electrical length difference between the cables can be determined accurately.

[Example] The present invention will be described below based on the illustrated example. An embodiment of the present invention is shown in FIGS. 1-5.

In this embodiment, when measuring the electrical length of a high frequency coaxial cable, the specified frequency f and this specified frequency f are used for each. 1/2, 1/4 frequency f/2, fo/4
Measure the phase at multiple points in the range of plus and minus 180 degrees with
And the normal phase change III line P of each measurement frequency fo, fo/2, fo/4
(f), P (fo/2), P (f./4)
Curves P (fo), P (f
o/2), P (f./4), respectively, and the intersection of the perpendicular line of the point where the values measured at the three measurement frequencies f, f/2, and fo/4 match vertically and the horizontal scale The electrical length difference between the cables was calculated from By doing this, the respective measurement frequencies f, f
/2, fo/4, and the perpendicular line of the point where the measured values vertically coincide with each other and plotted on the respective normal phase change curves P(fo), P(f/2), P(f./4). The electrical length difference between the cables can be accurately determined from the intersection of and the horizontal axis scale (see Figure 1).
In this way, it is possible to obtain an electrical length measuring method that makes it possible to reliably measure the electrical length deviation between high frequency coaxial cables.

That is, in FIGS. 3 to 5, the frequency is f. , f/2,
This is a plot of the phase measurement results of two cables at fo/4, with one cable having the reference length O0 and the deviation of the other cable being plotted. FIG. 3 shows the specified frequency f. The measured value at point b is the speed value, but since only the measured values within the range of plus and minus 180'aJ are given, the first shift of measurement corresponds to any of the plotted points a, C, and d. It is unclear whether Therefore, as shown in FIG. 4, the specified frequency r.

1/2 frequency f. When measuring at /2, the measured values are plotted at two points, 8 points and 0 points. One of these two is the speed value, and the other is the dummy point. To confirm this, as shown in Figure 5, 1/
4 frequency. /4, the measured value is plotted at point d as shown in the figure, and the position of the speed value is at the measured value plot point of f, f/2, fo/4 as shown in Figure 1. This is the point where . That is, at the specified frequency fo, point b of points a, b, c, and d, and at fo/2, eight points, B and 0, and f. /4 indicates that the cable length (λ) corresponding to point d is longer than the reference cable. As described above, according to this embodiment, the measurement accuracy is poor in the conventional measurement method, and it takes time to confirm the measurement value by using various measurement methods, but the measurement can be performed in less than 1/4 of the time. Additionally, the operator can take measurements without feeling anxious. Furthermore, the deviation can be confirmed without measuring the wavelength shortening rate.

In addition, commercially available phase measuring instruments measure plus and minus 180 degrees.
Therefore, even though the value exceeding this range is the value of the next repetition, the measured value is the same and it is impossible to distinguish between the previous repetition or the next repetition. In order to make this distinction, we use the fact that the measurement range is plus and minus 180 degrees, and by changing the frequency, we overlap those that are repeated several times and those that are repeated only once. The position is determined based on the measured value of one repetition.

The frequency that is 1/0 of the specified frequency is determined by the cable length, frequency, and wavelength shortening rate.Since the wavelength shortening rate of cables is usually controlled at about plus or minus 1%, U l- Electrical length difference 10 at IF
It is preferable to measure by changing the frequency up to one repetition, which can measure up to about λ.

In addition, although this example is a manual measurement using a phase measuring device and a special graph, it is possible to combine the phase measuring device and a microcomputer, store the graph creation, and automatically measure the graphs for each measurement frequency and the measured values. It is possible to make vessels.

[Effects of the Invention] As described above, the present invention enables the electrical length deviation between high-frequency coaxial cables to be reliably measured, and the electrical length deviation between the high-frequency coaxial cables to be reliably measured. A measurement method can be obtained.

[Brief explanation of the drawing]

FIG. 1 shows f according to an embodiment of the electrical length measuring method of the present invention.
, fo/2, f0/4 A characteristic diagram showing graph paper for measured values and examples of measured values; FIG. 2 also shows f, f according to one embodiment.
A characteristic diagram showing a graph paper for o/2 o'clock measured values and an example of measured values, FIG. 3 is also f according to one embodiment. FIG. 4 is a characteristic diagram showing a graph paper for measured values and an example of measured values. /Characteristic diagram showing graph paper for measured value at 2 o'clock and example of measured value, FIG. 5 is a characteristic diagram showing example of graph paper for fixed value for measurement at fo/4 o'clock according to one embodiment, FIG. High frequency coaxial cable cable length (λ) and electrical length difference (
λ). Ill12111 1fλ 12 "λ Oo,zf:I-
ojλtzra 1Download Me Kanochi 7゛・Confirmation(λ) Sweet M3 Right (Go 7-・Shukutakidot) Engraving of drawing (no change in content) So 4Figure 1 3 5 10 3080 1(to
360500 1000 KF Length (Entry) Procedure Amendment (Method) 6゜8゜2 Name of Invention Electrical Length Measurement Method 3 Name of Person Who Makes Correction (512) Hitachi Cable Co., Ltd. Wawasha Hiroharu Hashimoto 4 Agent Address: 100
Figure 6 of the drawing to be revised for 2-1-2 Marunouchi, Chiyoda-ku, Tokyo. The details of the amendment are as shown in the attached sheet. Attached document catalog correction drawing (Figure 6) 1 or more copies

Claims (1)

[Claims] (1) When measuring the electrical length of multiple high-frequency coaxial cables, the specified frequency and the frequency of 1/n (n is an integer) of this specified frequency are plus or minus 18
Measure the phase in the range of 0° at multiple points, take the angle in the range of plus and minus 180° on the vertical axis, take the cable length (λ) on the horizontal axis, and calculate the normal of each of the above measurement frequencies. Plot the phase change curves on each of the curves of the recording paper on which the recording was made, and calculate the distance between the cables from the intersection of the perpendicular line of the point where the values measured at the two or three measurement frequencies match vertically and the horizontal axis scale. An electrical length measuring method characterized by determining an electrical length difference.